WO2001076109A1

WO2001076109A1 - Tdma power measurement

Info

Publication number: WO2001076109A1
Application number: PCT/US2000/008950
Authority: WO
Inventors: Andrew E. Bowyer
Original assignee: Wavetek Wandel Goltermann, Inc.
Priority date: 2000-03-31
Filing date: 2000-04-01
Publication date: 2001-10-11

Abstract

A method for measuring a TDMA signal that includes TDMA bursts that may vary in burst bit structure, burst lengths, and burst rates. An exemplary method of the present invention includes the step of generating a first segment power signal that is representative of a first resolution segment of the TDMA signal. Another step of the method includes sampling the first segment power signal to obtain a first plurality of samples. Yet another step of the method includes identifying a first sample of the first plurality of samples that corresponds to a leading edge of a first TDMA burst of the plurality of TDMA bursts. The method also includes the step of obtaining a first trace vector comprising a first predetermined number of samples of the first plurality of samples that follow the first sample. The method further includes the step of updating based upon the first trace vector, a first average trace vector comprising a first plurality of average samples. Moreover, the method includes the step of determining based upon a first average sample of the first average trace vector, a first TDMA measurement value for the TDMA signal that is representative of signal power of the TDMA carrier signal.

Description

TDMA POWER MEASUREMENT

Field of Invention

The present invention relates generally to time division multiplexing access (TDMA) communications, and more particularly to method and apparatus of obtaining a power measurement of TDMA bursts.

Background of the Invention

Community Antenna Television ("CATN") systems are used in a widespread manner for the transmission and distribution of television signals to end users, or subscribers. In general, CATV systems comprise a headend facility and a distribution network. The headend facility obtains television signals associated with a plurality of CATN channels and generates a broadband CATV signal therefrom. The distribution network then delivers the CATN broadband signal to television receivers located within the residences and business establishments of subscribers.

Two-way CATN networks have been implemented in order to provide subscribers with advanced CATV services such as broadband Internet access via cable modems, interactive TV, and telephony. In order to provide these advance CATV services to a large number of subscribers without requiring a separate communication channel for each subscriber, CATV franchises implement some of these services with time division multiplexing access (TDMA) resource allocation schemes in order to allocate a shared communication channel among several subscribers. For example, TDMA resource allocation has been used by several CATV franchises to provide broadband Internet access to subscribers. In particular, many CATV franchises have implemented broadband Internet access with two frequency channels. A first frequency channel is used to transmit data from the CATV franchise downstream to subscribers and a second frequency channel is used to transmit data upstream from the subscribers to the CATV franchise. These frequency channels which carry digital signals in the CATV system are referred to herein simply as digital channels.

In order to enable multiple subscribers to use the same upstream digital channel, the subscribers transmit data upon the upstream digital channel via TDMA signals that include TDMA bursts and idle periods. Each TDMA bursts corresponds to a period in which a cable modem is transmitting a TDMA carrier signal and modulated data, and each idle period corresponds to a period in which the cable modem is not transmitting the TDMA carrier signal and modulated data. By configuring the subscriber's cable modems such that only one cable modem is transmitting a TDMA burst at any given time, multiple subscribers may transmit data via the same upstream digital channel.

While TDMA signals enable multiple subscribers to utilize the same upstream digital channel, obtaining accurate power measurements of a TDMA signal is difficult due to the nature of the TDMA signal. Ideally, a power measurement of an RF signal is a measurement of the RF carrier signal. However, as stated above, the TDMA carrier signal is not present during idle periods. Accordingly, in order to obtain an accurate power measurement of a TDMA signal, the power measurement must account for the fact that TDMA signal includes idle periods in which no TDMA carrier signal is present.

One known measurement apparatus for measuring TDMA signals is disclosed in U.S. Patent No. 5,303,262 to Johnson. The Johnson measurement apparatus includes a DSP circuit that generates a timing reference value that is used to identify analog measurements of the TDMA signal that are relevant to a TDMA burst of the TDMA signal and from which a measurement for the TDMA signal may be obtained. In particular, the DSP circuit performs extensive processing of the TDMA signal in order to obtain a least-squares estimate of the data clock used by the transmitter generating the TDMA signal. From this least-squares estimate of the transmitter's data clock and a known structure of the TDMA signal, the DSP circuit is able to generate a timing reference value that identifies an analog measurement corresponding to the first useful bit of a TDMA burst. Based upon the identification of the first useful bit of the TDMA burst, the Johnson measurement apparatus is operable to identify additional analog measurements relevant to the TDMA burst and from which a measurement for the TDMA signal may be obtained.

Besides requiring extensive processing, the measurement apparatus of Johnson is highly dependent upon a known structure of the TDMA bursts. In particular, the measurement apparatus of Johnson relies on a certain bit length and bit structure of the TDMA bursts in order to identify analog measurements that are relevant to a TDMA burst. However, many CATV franchises have implemented broadband Internet services such that TDMA bursts generated by the subscriber cable modems may vary greatly in bit length and bit structure. As a result, TDMA bursts may range from 10 microseconds to 200 microseconds. Accordingly, due to the varying structure of the TDMA bursts, the Johnson measurement apparatus would not produce reliable measurements in many CATV environments.

Moreover, as of yet, no one standard has been set for cable modem communications. As a result, TDMA signals generated by cable modems of one CATV franchises may have a different burst bit structure, a different burst length (e.g. 20 microseconds), a different burst rate (e.g. a TDMA burst every 50 microseconds) than TDMA signals generated by cable modems of another CATV franchise. Furthermore, a CATV franchise may implement the cable modems such that the cable modems generate TDMA signals having varying burst lengths and burst rates. Accordingly, there is a need for a measurement device and method that may obtain power measurements of TDMA signals having different burst bit structures, bursts lengths, and burst rates.

Summary of the Invention

The present invention fulfills the above needs, as well as others, by providing apparatus and methods for obtaining a signal power measurement of a TDMA signal that includes TDMA bursts that may vary in burst bit structure, burst lengths, and burst rates. An exemplary method of the present invention includes the step of generating a first segment power signal that is representative of a first resolution segment of the TDMA signal. Another step of the method includes sampling the first segment power signal to obtain a first plurality of samples which temporally represent signal power of the first resolution segment. Yet another step of the method includes identifying a first sample of the first plurality of samples that corresponds to a leading edge of a first TDMA burst of the plurality of TDMA bursts. The method also includes the step of obtaining a first trace vector comprising a first predetermined number of samples of the first plurality of samples that follow the first sample. The method further includes the step of updating based upon the first trace vector, a first average trace vector comprising a first plurality of average samples. Moreover, the method includes the step of determining based upon a first average sample of the first average trace vector, a first TDMA measurement value for the TDMA signal that is representative of signal power of the TDMA carrier signal.

The present invention further includes various apparatus for carrying out the above method. For example, one apparatus according to the present invention includes a receiver, a power measurement device coupled to the receiver, an analog to digital (A/D) converter coupled to the power measurement device, and a controller coupled to the A/D converter. The receiver is operable to receive the TDMA signal, and generate a first IF signal that is representative of a first resolution segment of the TDMA signal. The power measurement device is operable to receive the first IF signal, and generate a first segment power signal from the first IF signal that is representative of the first resolution segment. Moreover, the A/D converter is operable to sample the first segment power signal in order to produce a first plurality of samples that temporally represents the first resolution segment.

The controller is operable to detect a leading edge of a first TDMA burst of the plurality of TDMA bursts based upon the first plurality of samples, and obtain from the first plurality of samples, a first sample that corresponds to a first temporal offset from the leading edge of the first TDMA burst. Furthermore, the controller is operable to determine based upon the first sample, a first TDMA measurement value for the TDMA signal that is representative of signal power of the TDMA carrier signal.

The above features and advantages, as well as others, will become more readily apparent to those of ordinary skill in the art by reference to the following detailed description and accompanying drawings.

Brief Description of the Drawings

FIG. 1 shows a block diagram of a community antenna television system ("CATV") environment in the present invention may be utilized;

FIG. 2 shows time division multiplexing access (TDMA) signals used by the CATV environment of FIG. 1; FIG. 3 illustrates frequency characteristics of the TDMA signals;

FIG. 4 shows in a block diagram of a measurement device for measuring TDMA signals;

FIG. 5. illustrates the measurement device of FIG. 4 in greater detail;

FIG. 6. shows a flowchart of a first TDMA power measurement method implemented by the measurement device of FIG. 4; and

FIG. 7 shows a flowchart of a second TDMA power measurement method implemented by the measurement device of FIG. 4.

Detailed Description

Shown in FIG. 1 is a diagram of a CATV system 10 which utilizes time division multiplexing access (TDMA) communications to provide cable modem services to subscribers 40. The CATV system 10 includes a headend facility 20, a CATV distribution network 30, and subscribers 40. The CATV distribution network 30 generally provides a communications network for transferring RF signals both from the headend facility 20 to the subscribers 40 and from the subscribers 40 to the headend facility 20. In particular, the CATV distribution network 30 includes splitter 31 and nodes 32_l5 32₂ ... 32_N through which downstream signals to the subscribers 40 are transmitted from the headend facility 20. Furthermore, the CATV distribution network 30 may include various other elements such as optical transmitters, optical receivers, optical fibers, coaxial cable, bidirectional amplifiers, taps, and terminators which are not shown. It should be appreciated that the CATV distribution network 30 is merely exemplary and that the present invention may be practiced upon other network topographies and other network environments such as cellular and satellite communications.

The headend facility 20, which is operably coupled to the CATV distribution network 30, includes a standard television services headend 22, an advanced services headend 24, and a signal combiner 28. The standard television services headend 22 is coupled to the CATV distribution network 30 via the signal combiner 28. Moreover, as is well known in the art, the standard services headend 22 receives a plurality of television signals, such as from satellite receivers (not shown) and antennas (not shown) located at the headend facility 20 and converts these television signals to appropriate frequencies for transmission over the CATV distribution network 30 to subscribers 40. In this regard, the standard services headend 22 may be able to handle 78 channels. Each of the 78 channels includes a unique carrier or channel frequency which in United States cable systems lies within the 5 MHz to 890 MHz frequency band. Moreover, in United States cable systems, the CATV channel frequencies are typically separated by 6 MHz or integer multiples thereof.

The advanced services headend 24 is coupled to the CATV distribution network via the signal combiner 28 in order to transmit advanced CATV service signals to the subscribers 40. Moreover, the advanced services headend 24 is coupled to the nodes 31_l5 31 ... 3l_N in order to receive upstream signals from the subscribers 40. The advanced services headend 24 is a device well known to those of ordinary skill in the art that provides several advanced control services such as telephony services, cable modem services, digital video services, and interactive TV services.

More specifically, the exemplary embodiment of the advanced services headend 24 disclosed herein utilizes two digital channels to provide cable modem services to the subscribers 40. The advanced services headend 24 utilizes a first digital channel to transmit data downstream to the subscribers 40, and a second digital channel to receive data from the subscribers 40. In order to allow a subscriber 40 to send data upstream to the advanced CATV headend 24 without interfering with data being sent upstream by another subscriber 40, an allocation scheme is used for allocating the upstream digital channel to the subscribers 40. A common allocation scheme used to allocate the upstream digital channel to the subscribers 40 is TDMA.

An exemplary composite TDMA signal 42 is depicted in FIG. 2. The composite TDMA signal 42 includes a first TDMA signal 42A originated from a first cable modem of a first subscriber 40 A and a second TDMA signal 42B originated from a second cable modem of a second subscriber 40B. As depicted, the composite TDMA signal 42 includes a plurality of TDMA bursts 44 in which data is transmitted and a plurality of idle periods 46 in which no data is transmitted. More specifically, each TDMA burst 44 includes a TDMA carrier signal having a digital channel frequency Ec upon which data is modulated. In the exemplary embodiment described herein, the data is modulated using Pseudo Random Bit Sequence (PRBS) modulation which appears to be random noise within a bandwidth that is much less than the bandwidth of the TDMA burst 44. Furthermore, each idle period 46 symbolizes a period of time in which the digital channel associated with the TDMA carrier signal is unused. In other words, each idle period 46 symbolizes a period of time in which no TDMA carrier signal is being produced by the first cable modem and the second cable modem.

As depicted in FIG 2, the first TDMA signal 42A includes several TDMA bursts 44A in which the first cable modem of the first subscriber 40A transfers data upstream to the advanced services headend 24. Moreover, the first TDMA signal 42 A includes several idle periods 46A in which the first cable modem is not transmitting data upstream to the advance services headend 24. The second cable modem of the second subscriber 40B may transmit data to the advance services headend 24 during the idle periods 46 A of the first TDMA signal 42A. For example, FIG. 2 illustrates a second TDMA signal 42B originating from the second cable modem of the second subscriber 40B. The second TDMA signal 42B includes TDMA bursts 44B which occur during the idle periods 46A of the first TDMA signal 42A. Moreover, the second TDMA signal 42B includes idle periods 46B in which the TDMA bursts 42A of the first TDMA signal 42A may be transmitted. The non-overlapping nature of the first TDMA signal 42A and the second TDMA signal 42B is better illustrated by the composite TDMA signal 42. As illustrated by the composite TDMA signal 42, the TDMA bursts 44A of the first TDMA signal 42A do not overlap with the TDMA bursts 44B of the second TDMA signal 42B thereby enabling the first cable modem and second cable modem to communicate with the advanced services headend 24 via a single upstream digital channel. It should be appreciated by those skilled in the art that the TDMA signals 42, 42A, and 42B are merely exemplary and that TDMA may be used to allocate a digital channel amongst more communication devices.

CATV providers commonly perform diagnostic tests on the CATV system 10 in order to maintain a level of service demanded by subscribers 40. For example, after installing a cable modem for a subscriber 40, a technician typically tests the cable modem to ensure that the installed cable modem is working properly. One test that the technician may perform is an average power measurement of a TDMA signal applied to the CATV distribution network 30 by the cable modem. The average power measurement of the TDMA signal is essentially a measurement of the average power of the TDMA carrier signal generated by the cable modem during TDMA bursts. As stated above, each TDMA burst essentially comprises an RF carrier signal modulated by a Pseudo Random Bit Sequence (PRBS). As a result of the PRBS modulation of the TDMA carrier signal, the TDMA signal has a channel bandwidth BWc that is defined by the PRBS modulation.

A frequency response of the TDMA signal is illustrated in FIG. 3. As illustrated in FIG. 3, the channel bandwidth BWc of the TDMA signal is centered about the channel frequency Ec of the TDMA carrier signal. The channel bandwidth BWc represents the occupied power bandwidth of the TDMA signal and is dependent upon the modulation of the TDMA signal and other characteristics of the TDMA signal transmitter. Various known techniques exists for determining the channel bandwidth BWc of the TDMA signal. For example, TDMA signals may be analyzed to determine the 99% occupied power bandwidth for the TDMA signals.

FIG. 3 also illustrates that the channel bandwidth BWc of the TDMA signal may be divided into a set of resolution segments RBW₀, RBW], ... RBWN which span the channel bandwidth BW . As will be discussed in more detail below, the exemplary embodiment of the present invention obtains a total average power value P_T for the TDMA signal from either an average power measurement value P_mWχ for a single resolution segment RBWx or from a set of average power measurement values P_mWtι , P_MW^ , ... P_mWN for the resolution segment set RBWo, RBWj, ... RBW_M- It is noted that the exemplary embodiment of the present invention uses average power measurement values P_{mw ,} to obtain the total average power value Er for the TDMA signal because averaging techniques reduce the adverse effects that random noise and PRBS modulation have on the resulting measurement values.

Referring again to the calculation of total average power value Er in accordance with the present invention, it is noted that the total average power value Er for the TDMA signal may be obtained from equation (1) which extrapolates the total average power value E-r for the TDMA signal from the obtained average power measurement value E^ for a single resolution segment RBWx of the TDMA signal.

f BW \

Alternatively, the total average power value Er for the TDMA signal may be determined from equation (2) which linearly sums the set of average power measurement values P_mWt , P_mw , ... P_mw obtained for a set of resolution segments RBWo, RBWi, ...

RBWN, that span the channel bandwidth BWc of the TDMA signal.

N ^PI>BW„ (2) E^ lOlog∑lO ¹⁰

The above two techniques of obtaining a total average power value Er for a TDMA signal both require that the average power measurement values P_{llBW ,} or P_mw be obtained from the TDMA carrier signal. Since the TDMA carrier signal is only present during TDMA bursts, both of the above techniques require obtaining average power measurement value(s) P_mVλ from the TDMA bursts, and then determining the total average power value P_τ for the

TDMA signal from the obtained average power measurement value(s) P_{mw ,} associated with the TDMA bursts.

A general block diagram of a measurement device 60 suitable for obtaining average power measurement values P_mWχ of a TDMA signal and determining a total average power value Er for the TDMA signal therefrom is illustrated in FIG 4. Referring to FIG. 4, the measurement device 60 includes an RF input connector 68, an RF receiver 70, a power measurement device 72, an analog-to-digital (A/D) converter 74, a controller 76, a display 78, and a user input device 80. The RF input connector 68 is operable to receive a broadband RF signal that includes a digital channel having a channel frequency Ec (e.g., 26 MHz) for carrying TDMA signals. The RF receiver 70 is coupled to the RF input connector 68 in order to receive the broadband RF signal. In other words, the RF receiver 70 is operable to the digital channel and generate a broadband IF signal having a portion centered about an IF frequency FJ_F (e.g. 10.7 MHz) that is representative of the digital channel and the TDMA signals transmitted over the digital channel.

The power measurement device 72 is coupled to the RF receiver 70 in order to receive the broadband IF signal from the RF receiver 70. The power measurement device 72 is operable to generate a resolution segment power signal that is representative of a single resolution segment RBWx of the TDMA signal. The power measurement device 72 may suitably be any device operable to generate an analog signal representation of the power of a resolution segment RBWx of the input IF signal. For example, the power measurement device 72 may include a log amp detector and associated filters that in combination generate an analog signal representation of the power of a resolution segment RBWx of the input IF signal.

The A/D converter 74 is coupled to the power measurement device 72 in order to receive the segment power signal. In general, the A/D converter 74 is operable to sample the segment power signal in order to produce a stream of digital samples dx that are representative of the segment power signal. More specifically, the A/D converter 74 is operable to sample the segment power signal at a sampling rate such as 1 MHz in order to produce a stream of 8 bit samples dx at a rate of 1 million samples a second.

The controller 76 is coupled to the RF receiver 70 in order to provide the RF receiver 70 with control signals that cause the RF receiver 70 to tune to a particular frequency identified by the control signals. The controller 76 is further coupled to the A/D converter 74 in order to receive the digital samples dx produced by the A D converter 74. As will be discussed in more detail with reference to FIG. 6 and FIG. 7, the controller 76 is operable to process the received digital samples dx and produce a total average power value Er for the TDMA signal. More specifically, the controller 76 is operable to detect leading edges of TDMA bursts in order to identify digital samples d_x that correspond to TDMA carrier signal. From the identified digital samples dx, the controller 76 is operable to determine a total average power value Er for the TDMA signal. The display 78 is coupled to the controller 76 in order to receive control signals which cause the display 78 to display total average power values Er obtained by the controller 76.

Moreover, in a preferred embodiment, the display 78 is further operable to graphically display average signal traces comprising (i) averaged digital samples ax representative of average power measurement values P_{mw .} of resolution segments RBWx, and (ii) averaged digital samples ax representative of the average noise level of the digital channel in which the TDMA signal is being transmitted. Furthermore, in a preferred embodiment, the display 78 is operable to graphically display a cursor or marker which may be used to identify a particular averaged digital sample or a digital sample offset for use in obtaining a total average power value Er for the TDMA signal.

The display 78 preferably comprises an electronic display device such as an LED display, a liquid crystal (LCD) display, or a cathode ray tube or the like. In a preferred embodiment, the display 78 comprises a LCD display to facilitate the construction of a highly portable measurement system. LCD displays are advantageous for portable devices because of their relatively low power consumption and weight.

The user input device 80 is coupled to the controller 76 in order to provide the controller 76 with signals representative of user input. Via the user input device 80, a user of the measurement device 60 may configure the measurement device 60 to perform a particular measurement. Moreover, the user may provide the measurement device 60 with various parameters to be used during the measurement process. In a preferred embodiment of the present invention, the user input device 80 is implemented with a keypad which includes keys that may be actuated and upon actuation cause signals to be transmitted to the controller 76 that identify which key of the keypad was actuated. It is noted that the user input device 80 may be implemented with other known input devices such as pointing devices and touch screens.

Referring to FIG. 5 there is shown a more detailed circuit diagram of the measurement device 60 of FIG 5. As illustrated, the measurement device 60 includes the RF input connector 68, the RF receiver 70, the power measurement device 72, the A/D converter 74, the controller 76, the display 78, the user input device 80, and a digital to analog converter (DAC) 82.

Illustratively, the controller 76 is a microcontroller that includes program memory for storing firmware routines for the controller 76 and data memory for storing data generated by the controller 76. In the exemplary embodiment, the controller 76 is implemented with conventional circuitry, such as a MC68331 microcontroller manufactured by Motorola, Inc., Motorola, Microcontroller Product Group, 6501 William Cannon Drive West, Oakhill, Tex 78735, and outputs 84, 86, 88, 90, 92 and 94 and data inputs 96 are implemented with appropriate inputs and outputs of the microcontroller. Moreover, the microcontroller illustratively includes a bus interface 98 to which the user input device 80 and the display 78 are operatively coupled.

The oscillator frequency control outputs 84 are coupled to a first oscillator controller 100 which in turn is coupled to a first voltage controlled oscillator (VCO) 102. The oscillator frequency control outputs 86 are coupled to a second oscillator controller 104 which in turn is coupled to a second voltage controlled oscillator 106. The oscillator frequency control data outputs 88 are coupled to a third oscillator controller 108 which in turn is coupled to a third voltage controlled oscillator 110.

The first oscillator controller 100 and the first voltage controlled oscillator 102 comprise a programmable phase-lock-loop circuit which is programmed via the oscillator frequency control outputs 84 of the controller 76. Similarly, the second oscillator controller 104 and the second voltage controlled oscillator 106 comprise a programmable phase-lock- loop circuit which is programmed via the oscillator frequency control outputs 86 of the controller 76. Likewise, the third oscillator controller 108 and the third voltage controlled oscillator 110 comprise a programmable phase-lock-loop circuit which is programmed via oscillator frequency control outputs 88 of the controller 76.

The RF receiver 70 includes a switchable low pass filter 112 with a 50 MHz cutoff frequency, an RX attenuator 114, an RX attenuator controller 116, a first RX mixer 118, a buffer amplifier 120, a 1574.5 MHz band pass filter 122 with a 15 MHz pass band, a buffer amplifier 124, a second RX mixer 126, a buffer amplifier 128, a 83.5 MHz band pass filter 130 with a 4 MHz pass band, a buffer amplifier 132, a third RX mixer 134, a buffer amplifier 136, and a buffer amplifier 138. The low pass filter 112 is coupled to the RF input connector 68. The RX attenuator controller 116 has an input coupled to the RX attenuator controller output 90 of the controller 76 and an output coupled to the RX attenuator 114. The first VCO oscillator 102 has its output also coupled through the buffer amplifier

120 to a local oscillator input of the first RX mixer 118. An IF output of first RX mixer 118 is coupled through the 1574.5 MHz band-pass filter 122 and a buffer amplifier 124 to a RF input of the second RX mixer 126. The second VCO 106 has its output also coupled though a buffer amplifier 128 to a local oscillator input of the second RX mixer 126. An IF output of the second RX mixer 126 is coupled though a buffer amplifier 132 to an RF input of the third RX mixer 134. The third VCO 110 has its output coupled though a buffer amplifier 136 to a local oscillator input of the third RX mixer 134. An IF output of the third RX mixer 134 is coupled via the buffer amplifier 138 to the power measurement device 72.

The power measurement device 72 includes a switched resolution bandwidth (R-BW) filter 140 having a programmable pass band of 30 KHz, 280 KHz, or 2 MHz, a 12 MHz low pass filter 142, a programmable gain amplifier (PGA) 144, a log amp detector 146, and a video bandwidth (VBW) filter 148. In a preferred embodiment of the present invention, the 2 MHz pass band of the RBW filter 140 is actually implement with a 10 MHz high pass filter which in combination with the 12 MHz low pass filter 142 effectively produce a 2 MHz pass band. An input of the switched RBW filter 140 is coupled to the IF output of the third RX mixer 134 via the buffer amplifier 138. Moreover, a control input of the switched RBW filter 140 is coupled to the control output 88 of the controller 76. The input of the PGA 144 is coupled to the output of the switched RBW filter 140 via the 12 MHz low pass filter 142. The control input of the PGA 144 is coupled to an output of the DAC 82. The data inputs of the DAC 82 are coupled to the data outputs 94 of the controller 76.

An output of the PGA 144 is coupled to an input of the log amp detector 146. An output of the log amp detector 105 is coupled to an input of the VBW filter 148. An output of the VBW filter 148 is coupled to an input of the A/D converter 74. Data outputs of the A/D converter 74 are coupled to the data inputs 96 of the controller 76.

The RF receiver 70 is a super heterodyne receiver. The signal from RF input connector 68 is first filtered by low pass filter 112. The filtered signal is then passed through the programmable RX attenuator 114 which is used to lower the signal level in the event that the received signal level is too high and is over driving the RF receiver 70. The attenuated signal is then mixed by the first RX mixer 118 with the frequency to which the first VCO 142 is tuned in order to generate at the IF output of the first RX mixer 118 the first IF signal of the RF receiver 104, which is nominally 1574.5 MHz. The first IF signal is then filtered by the band-pass filter 122 to remove any IF images and mixed by the second RX mixer 126 with the second VCO 106 to produce the second IF signal (nominally 83.5 MHz) of the RF receiver 70. The second IF signal is filtered by the band-pass filter 130 and mixed with the third VCO 110 by the third RX mixer 134 to produce the third IF signal (nominally 10.7 MHz) of RF receiver 104. The third VCO 110 can be programmed by the controller 76 in 10 KHz increments to any frequency between 72.3 MHz and 73.3 MHz.

The third IF signal of RF receiver 70 is filtered by the switched RBW filter 140 and then passed through the 12 MHz low pass filter 142 to the PGA 144. The output of the PGA 144 is provided to the log amp detector 146 which generates a DC voltage that is representative of the signal level of the output of the PGA 144 and the RF signal received by the RF input connector 68. The output of the log amp detector 146 is digitized by the A/D converter 74 and this digitized value is read by the controller 76. The controller 76 uses the digitized value read from A/D converter 74 to determine how much gain to program into the PGA 144 via the DAC 82 so as to provide a signal to the A D converter 74 having a sufficient magnitude so that accurate level measurements can be made.

Referring now to FIG. 6, there is shown a measurement method 600 for obtaining average power measurement values P_mVχ for resolution segments RBWx of a TDMA signal and generating a total average power value Er for the TDMA signal therefrom. As illustrated in FIG. 6, the power measurement method 600 begins in step 602 with the measurement device 60 being coupled to the cable distribution network 30 in order to receive a broadband RF signal that includes a TDMA signal to be measured. In a preferred embodiment, a technician couples the RF input connector 68 to the distribution network 30 such that the RF input connector 68 is likely to receive TDMA signals from a single TDMA transmitting source such as a single cable modem. For example, a technician may couple the RF input connector 68 to a subscriber's cable drop box in order to receive TDMA signals from the subscriber's cable modem.

After coupling the measurement device 60 to the distribution network 30, the measurement device 60 receives input via the user input device 80 that configures the measurement device 60 to perform a TDMA power measurement. A preferred embodiment of the measurement device 60 is operable to perform several different types of measurements. Accordingly, the measurement device 60 in step 604 receives user input via the user input device 80 which places the measurement device 60 into a TDMA power measurement mode. Moreover, in a preferred embodiment, the measurement device 60 receives input that defines a channel frequency Ec, a measurement bandwidth BWM, and a resolution bandwidth BWR. Essentially, the channel frequency Fc defines a digital channel within which the TDMA signal is transmitted, the measurement bandwidth BW_M defines the bandwidth centered about the channel frequency Ec to be measured, and the resolution bandwidth BW_R defines the bandwidth of each resolution segment RBWx to be measured.

Then, controller 76 in step 605 initializes a counter J and an average trace vector V. In an exemplary embodiment of the present invention, the controller 76 in step 605 sets the counter J equal to the value of zero. Moreover, the controller 76 sets each average sample ax of the average trace vector V equal to zero. In an exemplary embodiment, the average trace vector V includes 240 average samples ax. Accordingly, in the exemplary embodiment, the controller 76 sets each of the 240 average samples aj, 02, ... α^o equal to zero. After initializing the counter J, the controller 76 in an exemplary embodiment generates control signals in step 606 which cause the RF receiver 70 to tune to the channel frequency Ec (e.g. 26 MHz). More specifically, the controller 76 transmits control signals to the first oscillator controller 100, the second oscillator controller 104, and the third oscillator controller 108 which cause the receiver 70 to shift the channel frequency Ec portion of the broadband RF signal received from the RF input connector 68 to the third IF frequency of 10.7 MHz. In other words, the control signals cause the RF receiver 70 to generate a broadband IF signal in which the digital channel portion of the broadband RF signal identified by the channel frequency E is centered about the IF frequency of 10.7 MHz. Assuming that the broadband RF signal includes a TDMA signal at the channel frequency Ec, the resulting IF signal includes the TDMA signal at the IF frequency Fip.

The power measurement device 72 in step 608 generates a segment power signal that represents the power of a resolution segment RBWx of the TDMA signal. More specifically, the switched RBW filter 140 of the power measurement device 72 band pass filters the IF signal with the programmed resolution bandwidth BW_R. AS a result of band pass filtering the IF signal, the switched RBW filter 140 generates a filtered IF signal that is representative of the desired resolution segment RBWx of the TDMA signal. Then, the log amp detector 146 receives the filtered IF signal from the switched RBW filter 140 and generates a power signal that is representative signal power of the desired resolution segment RBW_X of the TDMA signal. Finally, the VBW filter 148 low pass filters the power signal with in order to generate the segment power signal which is representative of the signal power of the TDMA carrier signal within the resolution bandwidth BW_R. The A/D converter 74 in step 610 samples the segment power signal at a sampling rate of 1 MHz to produce a series of digital samples dx that are representative of the segment power signal. In a preferred embodiment, the A/D converter 74 continuously samples the segment power signal in step 610 to produce a series of 8 bit digital samples at a rate of 1 million samples a second. Moreover, since the segment power signal is representative of a TDMA signal that includes both TDMA bursts and idle periods, the series of digital samples dx produced by the A/D converter 74 includes both (i) digital samples dx representative of TDMA bursts in which a TDMA carrier signal is present, and (ii) digital samples dx representative of idle periods in which no TDMA carrier signal is present. The controller 76 in step 612 determines from the digital samples dx which digital samples dx correspond to TDMA bursts and therefore to periods in which the TDMA carrier signal is being transmitted. Jn particular, the controller 76 detects the leading edge of a TDMA burst in order to determine which digital samples dx correspond to periods in which the TDMA carrier signal is being transmitted. In a preferred embodiment, the controller 76 detects the leading edge by determining that a certain number N of successive digital samples dx are greater than a threshold level T. For example, the controller 76 may detect the leading edge of a TDMA burst by determining that two digital samples dx and dχ+ι in a row are greater than a threshold level T of 5 dBmV.

In response to detecting the leading edge of a TDMA burst, the controller 76 in step 614 updates an average trace vector V with a trace vector that includes a predetermined number M of digital samples dx. More specifically, the controller 76 averages the digital samples dx of the newly obtained trace vector with the average samples ax of the average trace vector V to obtain an updated average trace vector V that includes a predetermined number M of updated average samples a 'x. For example, the controller 76, in a preferred embodiment, obtains a trace vector including the 240 digital samples di, d₂, ds, ... d₂₄o after the digital samples dx corresponding to the detected leading edge, and averages each digital sample dx of the newly obtained trace vector with a corresponding average sample ax of the average trace vector V. As a result of performing the above operations, the controller 76 obtains an updated average trace vector V having 240 average samples a'j, a '₂, a' ₃, ... a' ₂₄₀. In the exemplary embodiment described herein, the controller 76 calculates each average sample a 'x of the updated average trace vector V based upon equation (3): where J is equal to the present value of the counter J. It should be noted that an exemplary embodiment initializes the counter J to zero thereby causing the first obtained trace vector to be stored as the updated average trace vector V. In step 616, the controller 76 causes a graphical representation of the updated average trace vector V to be displayed by the display 78. In an exemplary embodiment, a user may define a time span (e.g. 1 millisecond) of the TDMA signal to be displayed and analyzed. Since in the exemplary embodiment, the A D converter 74 samples at a constant rate of 1 million samples per second or 1 sample per a microsecond, the controller 76 in the exemplary embodiment either (i) alters the predetermined number M of digital samples dx included in the trace vector, or (ii) decimates the digital samples dχ received from the A/D converter 74 so as to arrive at trace vector and an average trace vector V that span the user defined time span. More specifically, in the exemplary embodiment, the controller 76 defines the trace vector and the average trace vector V to include (i) 240 samples if the time span is greater than or equal to 240 microseconds (i.e. 240 samples * sampling rate of the A D converter 74), and (ii) less than 240 samples if the time span is less than 240 microseconds.

For example, if the user defined time span is 480 microseconds, then the controller 76 in the exemplary embodiment would discard (i.e. decimate) every other digital sample dx received from the A D converter 74, and use the remaining 240 digital samples dx after the detected leading edge for updating the average trace vector V having 240 average samples ax. In this manner, the resulting 240 samples of the trace vector and average trace vector V would span the user defined time span of 480 microseconds. Similarly, if the user defined time span is 120 microseconds, then the controller 76 in the exemplary embodiment would (i) set the predetermined number M equal to 120, and (ii) use the 120 digital samples dx after the detected leading edge for updating the average trace vector V having 120 average samples oχ. It should be those skilled in the art that the controller 76 could alternatively be implemented to adjust the sampling rate of the A/D converter 74 or use a combination of adjusting the sampling rate, decimation rate, and the number of samples included in the trace vector and the average trace vector Vto achieve the desired time span. After causing a graphical representation of the updated average trace vector V to be displayed, the controller 76 in step 618 obtains from the update average trace vector V an average sample a 'χ that is representative of the average power measurement value P_mw of the resolution segment RBWx. In environments where TDMA bursts are likely to vary in length (e.g. from 10 microseconds to 200 microseconds), the average trace vector is likely to include average samples ax which correspond to idle portions which occur after the completion of the detected TDMA burst. As a result, in one embodiment of the present invention, the controller 76 analyzes the average trace vector V in order to obtain an average sample ax to use for the average power measurement value P_mw, . More specifically, the controller 76 in this embodiment utilizes the largest average sample ax of the average trace vector V for the average power measurement value P_mw. . By using the largest average sample ax, the controller 76 is ensured to obtain an average power measurement value P_{mw ,} for the resolution segment REJ- ^that corresponds to the TDMA carrier signal.

Alternatively, in another embodiment of the present invention, the controller 76 obtains a predetermined average sample a 'x from the updated average trace vector V for the average power measurement value P_mw . . For example, in an exemplary embodiment of the present invention, the average power measurement value P_{mw ,} is set equal to the 7^th average sample ay of the average trace vector V. If the shortest TDMA burst is 20 microseconds long, the A/D converter 74 generates digital samples dx at a rate of 1 per microsecond, and the first average sample α; corresponds roughly with leading edges of TDMA bursts, then the 7^th average sample ₇ corresponds approximately to a 7 microsecond temporal offset from leading edges of TDMA bursts. It is noted that a 7 microsecond temporal offset from the leading edges of the TDMA bursts in this environment is within the 20 microsecond minimum length of the TDMA bursts. Accordingly, selecting the 7^th average sample a of the average trace vector V in such an environment should produce an average power measurement value P_mW which corresponds to the TDMA bursts and the TDMA carrier signal.

In yet another embodiment, the controller 76 receives user input via the user input device 80 which indicates a particular average sample ax of the average trace vector V. More specifically, a user of the measurement device 60 may determine from the displayed graphical representation of the average trace vector Kthe portion of the graph attributable to the TDMA bursts and presence of the TDMA carrier signal. For example, the user in a preferred embodiment may position a graphical cursor via the user input device 80 in order to indicate to the controller 76 a particular average sample ax of the average trace vector V to use as the average power measurement value P_mw, for the resolution segment RBWx. More specifically, in a preferred embodiment of the measurement device 60, the controller 76 converts the position of the graphical cursor to a vector offset / which identifies the position of an average sample ax within the average trace vector V. Based upon the vector offset I, the controller 76 may obtain the average sample ax identified by the vector offset / and use the obtained average sample ax for the average power measurement value P_mWχ . For example, if the cursor indicates a vector offset / of 10, then the controller 76 utilizes the tenth average sample ajo of the average trace vector Ffor the average power measurement value P_{mw .}. After obtaining the average power measurement value P_mWγ , the controller 76 in step

620 determines a total average power value Er for the TDMA signal based upon the obtained average power measurement value P_mw . . More specifically, the controller 76 extrapolates the total average power value Er utilizing above equation (1) which is presented again for convenience:

where P_RBWχ represents the obtained the average power measurement value for the resolution segment RBWx, BWc represents the channel bandwidth of the TDMA signal, and BW_R represents the bandwidth of the resolution segment being measured. In a preferred embodiment, the channel bandwidth BWc of the TDMA signal, and the bandwidth BW_R of the resolution segment are provided by the user in step 602.

It should be appreciated that the measurement device 60 may be implemented with a fixed channel bandwidth BWc and a fixed resolution bandwidth BW_R thereby enabling the total average power value P_τ for the TDMA signal to be calculated from equation (4):

(4) r_τ = "_RBWχ + C where C is a constant equal to 10*log(-5 WC/BW_R). It should further be appreciated that the measurement device 60 may be implemented to support a fixed number of resolution bandwidths BW_R and a fixed number of channel bandwidths BW_C thereby enabling a separate constant C to be pre-calculated for each supported combination of resolution bandwidth BW_R and channel bandwidth BWc. In step 622, the controller 76 causes the obtained total average power value Er for the TDMA signal to be displayed on the display 78.

After causing the obtained total average power value E for the TDMA signal to be displayed, the controller 76 in step 624 updates the counter J and returns to step 612 in order obtain a new total average power value E for the TDMA signal. In an exemplary embodiment, the controller 76 increments the counter J by one and returns to step 612. By returning to step 612, the controller 76 (i) detects another TDMA burst, obtains another trace vector in response to detecting the TDMA burst, (ii) updates the average trace vector with the newly obtained trace vector, (iii) obtains a new average power measurement value RBWx from the updated average trace vector V, and (iv) determines a new total average power value Er from the newly obtained average power measurement value RBWx.

Referring now to FIGS. 7, there is shown a flowchart for a second TDMA power measurement method 700 implemented by the measurement device 60. The measurement device 60 in the second TDMA power measurement essentially obtains a total average power value Er for the TDMA signal from a set of average power measurement values P_mw , P_mw ,

... P_mw that span the channel bandwidth BWc of the TDMA signal. Similar to step 602 of the TDMA power measurement method 600, the power measurement method 700 begins in step 702 with the measurement device 60 being coupled to the cable distribution network 30 in order to receive a broadband RF signal that includes a TDMA signal to be measured. After coupling the measurement device 60 to the distribution network 30, the measurement device 60 receives input via the user input device 80 that configures the measurement device 60 to perform a TDMA power measurement. In particular, the controller 76 in step 704 receives user input which defines a channel frequency Ec, a measurement bandwidth BWM, and a resolution bandwidth BWR. Essentially, the channel frequency F_c defines a digital channel within which the TDMA signal is transmitted, the measurement bandwidth BWM defines the bandwidth centered about the channel frequency Fc to be measured, and the resolution bandwidth BWR defines the bandwidth of each resolution segment RBWx to be measured.

From the supplied input, the controller 76 in step 706 determines a start frequency FSTART, a stop frequency FSTOP, and a frequency increment FJ_NC- In particular, the controller 76 calculates the start frequency FSTART , the stop frequency FSTOP, and the frequency increment Fmc based upon equations (5), (6) and (7): BW M

(5) r START ^~ --

2 BW M,

(6) 'STOP ^~ ^c ^"*^"

2 (7) F_INC = BW_R

After obtaining the above parameters, the controller 76 in step 708 sets a test frequency F_TEST equal to the start frequency F_START and causes the switched RBW filter 140 to switch to the resolution bandwidth BWR identified in step 704. Accordingly, the controller 76 transmits control signals to the switched RBW filter 140 which cause the RBW filter 140 to switch to the filter having the pass band equal to the supplied resolution bandwidth BWR.

Then, controller 76 in step 709 initializes a set of counters Jo, Ji, ... JN and a set of average trace vectors V°, V¹, ... ¹. In an exemplary embodiment of the present invention, the measurement device 60 includes a separate counter χ for each resolution segment RBWx of the set of resolution segments RBWo, RBW], ... RBWM- Accordingly, the controller 76 in step 707 sets the each count Iχ of the set of counters Jo, J_/, ... J_# equal to the value of zero. Moreover, the controller 76 sets each average sample a_x ^γ of the average trace vectors V^γ equal to zero. In an exemplary embodiment, the measurement device 60 utilizes a separate average trace vector V^γ having 240 average samples

, ... aζ₄₀ for each resolution segment RBWy of the set of resolution segments RBWo, RBW], ... RBW_N- Accordingly, in the exemplary embodiment, the controller 76 sets each of the 240 average samples

, a^γ , ... a₂₄₀ for each separate average trace vector V equal to zero. Then, the controller 76 in step 710 generates control signals which cause the RF receiver 70 to tune to the test frequency F_TEST- More specifically, the controller 76 transmits control signals to the first oscillator controller 100, the second oscillator controller 104, and the third oscillator controller 108 which cause the receiver 70 to shift the test frequency F_TES_T portion of the broadband RF signal received from the RF input connector 68 to the third IF frequency of 10.7 MHz. Assuming that the broadband RF signal includes a resolution segment RBWy of the TDMA signal at the test frequency F_TES_T, the resulting IF signal includes the resolution segment RBWy of the TDMA signal at the IF frequency of 10.7 MHz.

The power measurement device 72 in step 712 generates a segment power signal that represents the power of the resolution segment RBW_Y of the TDMA signal that corresponds to the test frequency FT_EST- More specifically, the switched RBW filter 140 of the power measurement device 72 band pass filters the IF signal with the programmed resolution bandwidth BWR. AS a result of band pass filtering the IF signal, the switched RBW filter 140 generates a filtered IF signal that is representative of the desired resolution segment RBWy of the TDMA signal. Then, the log amp detector 146 receives the filtered IF signal from the switched RBW filter 140 and generates a power signal that is representative signal power of the desired resolution segment RBWy of the TDMA signal. Finally, the VBW filter 148 low pass filters the power signal in order to generate the segment power signal which represents of the signal power of the TDMA carrier signal within desired resolution segment RBWy.

The A/D converter 74 in step 714 continuously samples the segment power signal at a rate of 1 MHz in order to produce a series of digital samples dx that are representative of the segment power signal. Moreover, since the segment power signal is representative of a TDMA signal that includes both TDMA bursts and idle periods, the series of digital samples dx produced by the A/D converter 74 includes both (i) digital samples dx representative of TDMA bursts in which a TDMA carrier signal is present, and (ii) digital samples dx representative of idle periods in which no TDMA carrier signal is present.

In a manner similar to step 612 of method 600, the controller 76 in step 716 determines from the digital samples dx which digital samples dx correspond to TDMA bursts and therefore to periods in which the TDMA carrier signal is being transmitted. In particular, the controller 76 detects the leading edge of a TDMA burst in order to determine which digital samples dx correspond to periods in which the TDMA carrier signal is being transmitted. In a preferred embodiment, the controller 76 detects the leading edge by determining that a certain number N of successive digital samples dx are greater than a threshold level T.

In response to detecting the leading edge of a TDMA burst, the controller 76 in step 718 updates an average trace vector V^γ associated with the resolution segment RBWy with a trace vector that includes a predetermined number M of digital samples dx. More specifically, the controller 76 averages the digital samples dx of the newly obtained trace vector with the average samples a_x of the average trace vector V^γ to obtain an updated average trace vector V that includes a predetermined number M of updated average samples

. For example, the controller 76, in a preferred embodiment, obtains a trace vector including the 240 digital samples di, d2, ds, ... d₂₄ after the digital samples dx corresponding to the detected leading edge, and averages each digital sample dx of the newly obtained trace vector with a v V corresponding average sample a_x of the average trace vector V . As a result of performing the above operations, the controller 76 obtains an updated average trace vector V having 240 average samples ' ,

, ... a'^Y _2W for the resolution segment RBWy. In the exemplary embodiment described herein, the controller 76 calculates each average sample a'^Y _x of the updated average trace vector V'^Y based upon equation (8):

where Jy is equal to the present value of the counter associated with the average trace vector Vy for the resolution segment RBWy. It should be noted that an exemplary embodiment initializes the counter Jy to zero thereby causing the first obtained trace vector for a given resolution segment RBWy to be stored as the updated average trace vector V'^Y for the resolution segment RBWy.

After updating the average trace vector V^Y for the resolution segment RBWy, the controller 76 in step 720 updates the test frequency F_TEST- In particular, the controller 76 in step 720 increments the test frequency FTE_ST by the frequency increment FJMC- The controller 76 then determines in step 722 whether each average trace vector V^Y for the set of average trace vectors V°, V', ... ¹ has been updated. In particular, the controller 76 determines whether the updated test frequency FTE_ST is greater than the stop frequency F_ST_OP- If the updated test frequency FTEST is not greater than the stop frequency FS_TO_P, then the controller 76 determines that each average trace vector V^Y of the set of average trace vectors V°, V¹, ... has not been updated. Accordingly, the controller 76 returns to step 710 in order to update the average trace vector V^Y for the resolution segment RBWy of the TDMA signal corresponding to the updated test frequency F_TES_T- Conversely, if the updated test frequency FTEST is greater than the stop frequency FS_TO_P, then the controller 76 determines that each average trace vector V^Y of the set of average trace vectors V°, V¹, ... V¹ has been updated. As a result, the controller 76 proceeds to step 724 in order to obtain average power measurement values E _o , P_mW , ... P_mWι) for the resolution segment set RE W₀, RBWj, ...

RBWN that spans the channel bandwidth BWc-

The controller 76 then in step 723 obtains from each updated average trace vector V'^Y an average sample a'^Y _x that is representative of an average power measurement value P_mw for the respective resolution segment RBWy. In environments where TDMA bursts are likely to vary in length (e.g. from 10 microseconds to 200 microseconds), the each average trace vector V^γ is likely to include average samples a_x which correspond to idle portions which occur after the completion of the detected TDMA burst. As a result, in one embodiment of the present invention, the controller 76 analyzes each average trace vector V in order to obtain an average sample a_x to use for the respective average power measurement value P_mw . More specifically, the controller 76 in this embodiment utilizes the largest average v V sample a_x of the average trace vector V for the respective average power measurement value P_mw, . By using the largest average sample a_x , the controller 76 is ensured to obtain an average power measurement value P_mw, for the respective resolution segment RBWy that corresponds to the TDMA carrier signal.

Alternatively, in another embodiment of the present invention, the controller 76 obtains a predetermined average sample a'_x from each updated average trace vector V'^γ for the respective average power measurement value P_mw, . For example, in an exemplary embodiment of the present invention, each average power measurement value P_mw. is set equal to the 7' average sample a^γ of each respective average trace vector V^γ. If the shortest TDMA burst is 20 microseconds long, the A/D converter 74 generates digital samples dx at a rate of 1 per microsecond, and each first average sample

corresponds roughly with leading edges of TDMA bursts, then each 7^th average sample a^γ corresponds approximately to a 7 microsecond temporal offset from leading edges of TDMA bursts. It is noted that a 7 microsecond temporal offset from the leading edges of the TDMA bursts in this environment is within the 20 microsecond minimum length of the TDMA bursts. Accordingly, selecting the 7^th average sample a^γ of each average trace vector V^γ in such an environment should produce an average power measurement value P_mw, for each respective resolution segment

RBWy that corresponds to the TDMA bursts and the TDMA carrier signal. In yet another embodiment, the controller 76 (i) causes a graphical representation of the average trace vectors V^γ to be displayed on the display 78, and (ii) receives user input via the user input device 80 which indicates a particular average sample ax of the average trace vector V. More specifically, the controller 76 in an exemplary embodiment causes a single average trace vector J^ of the set of average trace vectors V°, V¹, ... Ϋ¹ to be displayed. Then, the controller 76 receives user input via the user input device 80 that identifies a portion of the displayed graphical representation attributable to the TDMA bursts and presence of the TDMA carrier signal. For example, the user in a preferred embodiment may position a graphical cursor via the user input device 80 in order to indicate to the controller 76 a v V particular average sample α_x of the average trace vector V to use as the average power measurement value P_mWγ for the resolution segment RBWy.

More specifically, in a preferred embodiment of the measurement device 60, the controller 76 converts the position of the graphical cursor to a vector offset /which identifies the position of an average sample α_x within the average trace vector V^Y. Based upon the vector offset /, the controller 76 may obtain from each average trace vector V¹, V², ... the average sample α identified by the vector offset / and use the obtained average samples α for the average power measurement value P_mWii , P_mw , •■ • _RBWN • F°^r example, if the cursor indicates a vector offset I of 10, then the controller 76 utilizes the tenth average sample ₀ of each average trace vector V°, V¹, ... ^ for the average power measurement value P_mw ,

*RBW_X > ^{■ ■ ■ •}

It is noted that other methods of graphically displaying the average trace vectors V¹, V², ... V^ may be used. For example, a composite average trace vector may be calculated from the average trace vectors V°, V¹, ... ¹ which in essence is an average of the average trace vectors V°, V¹ , ... ¹. The controller 76 may then cause the composite average trace vector to be displayed in order to receive user input that identifies a proper temporal offset I. Other techniques for presenting the user with the average trace vectors V°, V¹, ... P^ should be readily apparent to those skilled in the art in light of the disclosure herein.

The controller 76 in step 724 determines a total average power value Er from the average power measurement values P_mWα , P_m!Vt , ... E^,^ for the resolution segment set RBWo, RBWi, ... RBWN- In particular, the controller 76 linearly sums the average power measurement values P_mW[) , P_RBW^ • ■ • ?ww_N f°^r the resolution segments RBWo, RBW/, ...

RBWN that span the channel bandwidth BWc. This calculation is represented by equation (2) which is presented again for convenience:

N ^χ° n'„

(2) E_τ = 101og l0 ¹⁰ n=0 where P_mw represents the average power measurement value for the resolution segment RBWo corresponding to the start frequency F_STA_RT, P_RBWN represents the average power measurement value for the resolution segment RBW_N corresponding to the stop frequency F_STOP, and P_mw , P_mWl , ■ ■■ P_mw_N represent the average power measurement values for the resolution segments corresponding to frequencies FSTART + Ewe, FSTART + *Ew . • • • FSTART + (N-l) * Fj_Nc, respectively.

The controller 76 then in step 726 displays the obtained total average power value Er for the TDMA signal.

The controller 76 then in step 728 sets the test frequency F_TEST equal to the start frequency F_START and returns to step 710 in order update the total average power value Er for the TDMA signal. In particular, the controller 76 in re-executing steps 710-726 updates the average power measurement values P_mVa , P_mWχ , ... P_mWN for the resolution segments

RBWo, RBWI, - R W_N that span the channel bandwidth BW_C of the TDMA signal. Moreover, the controller 76 updates the set of average trace vectors V°, V¹, ... Ϋ¹ with a newly obtained trace vectors for the resolution segment RBWo, RBWo, ■ ■ ■ RBW_N- From the updated average trace vectors V'°, V'¹, ... V'^N, the controller 76 obtains new average power measurement values P_mWa , P_mw , ... P_mw for the resolution segments RBWo, RBWi, •••

RBW_N, and determines a new total average power value Er for the TDMA signal from the obtained average power measurement values P^^ , P_mw , ... P_mw . While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description is to be considered as exemplary and not restrictive in character, it being understood that only an exemplary embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected. For example, while exemplary embodiments have been disclosed with average trace vectors V, it should be appreciated that features of the present invention may be practiced without average trace vectors V. In particular, instead of using average trace vectors V, the present invention may be implemented to continually update a stored average power measurement value P_{mw .} with digital samples dx that correspond to a set temporal offset I from each detected leading edge of a TDMA burst. Moreover, while the described exemplary embodiments have certain advantages over power art device in measuring TDMA signals, the exemplary embodiments may also obtain accurate power measurements of frequency division multiplexing access (FDMA) signals and code division multiplexing access (CDMA) signals. FDMA signals and CDMA signals would trigger acquisition of new trace vectors and updating of the average trace vector V on an essentially constant basis due to the continuous nature of FDMA signals and CDMA signals. The resulting total average power value Er obtained by the exemplary embodiments, however, would be accurate for these signals.

Claims

What is claimed is:

1. A method of measuring a TDMA signal comprising a plurality of TDMA bursts modulated upon a TDMA carrier signal, comprising the steps of: a) detecting a leading edge of a first TDMA burst of said plurality of TDMA bursts; b) obtaining for a first resolution segment of said TDMA signal, a first segment power measurement value which corresponds to a first temporal offset from said leading edge of said first TDMA burst; and c) determining based upon said first segment power measurement value, a first TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

2. The method of claim 1, further comprising the steps of: d) detecting a leading edge of a second TDMA burst of said plurality of TDMA bursts; e) obtaining for a second resolution segment of said TDMA signal, a second segment power measurement value which corresponds to a second temporal offset from said leading edge of said second TDMA burst; and f) determining based upon said first segment power measurement value and said second segment power measurement value, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

3. The method of claim 1, further comprising the steps of: d) detecting a leading edge of a second TDMA burst of said plurality of TDMA bursts; e) obtaining for a second resolution segment of said TDMA signal that corresponds to a different resolution segment of said TDMA signal than said first resolution segment, a second segment power measurement value which corresponds to a second temporal offset from said leading edge of said second TDMA burst; and f) determining based upon said first segment power measurement value and said second segment power measurement value, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

4. The method of claim 1, further comprising the steps of: d) detecting a leading edge of a second TDMA burst of said plurality of TDMA bursts; e) obtaining for a second resolution segment of said TDMA signal, a second segment power measurement value which corresponds to a second temporal offset from said leading edge of said second TDMA burst which is equivalent to said first temporal offset; and f) determining based upon said first segment power measurement value and said second segment power measurement value, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

5. The method of claim 1, further comprising the steps of: d) detecting a leading edge of a second TDMA burst of said plurality of TDMA bursts; e) obtaining for a second resolution segment of said TDMA signal, a second segment power measurement value which corresponds to a second temporal offset from said leading edge of said second TDMA burst, wherein step c) further comprises the steps of cl) determining an average power measurement value based at least in part upon said first segment power measurement value and said second segment power measurement value, and c2) determining said first TDMA measurement value for said TDMA signal based said average power measurement value.

6. The method of claim 1, further comprising the steps of: d) receiving user input that defines said first temporal offset from said leading edge of said first TDMA burst.

7. The method of claim 1, further comprising the steps of: d) displaying a graphical representation of said TDMA signal; e) receiving user input that identifies a portion of said graphical representation corresponding to said first TDMA burst in order to define said first temporal offset from said leading edge of said first TDMA burst.

8. A method of measuring a TDMA signal comprising a plurality of TDMA bursts modulated upon a TDMA carrier signal, comprising the steps of: a) generating a first segment power signal that is representative of a first resolution segment of said TDMA signal; b) sampling said first segment power signal to obtain a first plurality of samples which temporally represent signal power of said first resolution segment; c) detecting a leading edge of a first TDMA burst of said plurality of TDMA bursts based upon said first plurality of samples; d) obtaining from said first plurality of samples, a first sample that corresponds to a first temporal offset from said leading edge of said first TDMA burst; and e) determining based upon said first sample, a first TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

9. The method of claim 8, further comprising the steps of: f) detecting a leading edge of a second TDMA burst of said plurality of TDMA bursts based upon said first plurality of samples; g) obtaining from said first plurality of samples, a second sample that corresponds to a second temporal offset from said leading edge of said second TDMA burst; and h) determining based upon said second sample, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

10. The method of claim 8, wherein step c) further comprises the step of identifying a second sample of said first plurality of samples that corresponds to said leading edge of said first TDMA burst, and step d) further comprises the step of selecting said first sample from said first plurality of samples such that said first sample corresponds to a predetermined number of samples after said second sample.

11. The method of claim 8, further comprising the steps of: f) receiving user input that defines said first temporal offset from said leading edge of said first TDMA burst.

12. The method of claim 8, further comprising the steps of: f) displaying a graphical representation of said first segment power signal; g) receiving user input that identifies a portion of said graphical representation corresponding to said first TDMA burst in order to define said first temporal offset from said leading edge of said first TDMA burst.

13. The method of claim 8, further comprising the step of: f) analyzing said first segment power signal in order to determine said first temporal offset from said leading edge of said first TDMA burst such that said first temporal offset corresponds to said first TDMA burst.

14. A method of measuring a TDMA signal comprising a plurality of TDMA bursts modulated upon a TDMA carrier signal, comprising the steps of: a) generating a first segment power signal that is representative of a first resolution segment of said TDMA signal; b) sampling said first segment power signal to obtain a first plurality of samples which temporally represent signal power of said first resolution segment; c) identifying a first sample of said first plurality of samples that corresponds to a leading edge of a first TDMA burst of said plurality of TDMA bursts; d) obtaining a first trace vector comprising a first predetermined number of samples of said first plurality of samples that follow said first sample; e) updating based upon said first trace vector, a first average trace vector comprising a first plurality of average samples; and f) determining based upon a first average sample of said first average trace vector, a first TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

15. A device for measuring a TDMA signal comprising a plurality of TDMA bursts modulated upon a TDMA carrier signal, comprising: a receiver operable to (i) receive said TDMA signal, and (ii) generate a first IF signal that is representative of a first resolution segment of said TDMA signal; a power measurement device coupled to said receiver and operable to (i) receive said first IF signal, and (ii) generate a first segment power signal from said first IF signal that is representative of said first resolution segment; an analog to digital (A/D) converter coupled to said power measurement device and operable to sample said first segment power signal in order to produce a first plurality of samples that temporally represents said first resolution segment; and a controller coupled to said A/D converter and operable to (i) detect a leading edge of a first TDMA burst of said plurality of TDMA bursts based upon said first plurality of samples, (ii) obtain from said first plurality of samples, a first sample that corresponds to a first temporal offset from said leading edge of said first TDMA burst, and (iii) determine based upon said first sample, a first TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

16. The device of claim 15, wherein said controller is further operable to:

(iv) detect a leading edge of a second TDMA burst of said plurality of TDMA bursts based upon said first plurality of samples, (v) obtain from said first plurality of samples, a second sample that corresponds to a second temporal offset from said leading edge of said second TDMA burst, and (vi) determine based upon said second sample, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA signal.

17. The device of claim 15, wherein said receiver is further operable to (iii) generate a second IF signal representative of a second resolution segment of said TDMA signal that is different than said first resolution segment, said power measurement device is further operable to (iii) receive said second IF signal, and (iv) generate a second segment power signal from said second IF signal that is representative of said second resolution segment, said A/D converter is further operable to sample said second segment power signal in order to produce a second plurality of samples that temporally represents said second resolution segment, and said controller is further operable to (iv) detect a leading edge of a second TDMA burst of said plurality of TDMA bursts based upon said second plurality of samples, (v) obtain from said second plurality of samples, a second sample that corresponds to a second temporal offset from said leading edge of said second TDMA burst, and (vi) determine based upon said first sample and said second sample, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

18. The device of claim 15, wherein said receiver is further operable to (iii) generate a second IF signal that is representative of a second resolution segment of said TDMA signal, said power measurement device is further operable to (iii) receive said second IF signal, and (iv) generate a second segment power signal from said second IF signal that is representative of said second resolution segment, said A/D converter is further operable to sample said second segment power signal in order to produce a second plurality of samples that temporally represents said second resolution segment, and said controller is further operable to (iv) detect a leading edge of a second TDMA burst of said plurality of TDMA bursts based upon said second plurality of samples, (v) obtain from said second plurality of samples, a second sample that corresponds to a second temporal offset from said leading edge of said second TDMA burst which is equivalent to said first temporal offset, and (vi) determine based upon said first sample and said second sample, a second TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

19. The device of claim 15, wherein said receiver is further operable to (iii) generate a second IF signal that is representative of a second resolution segment of said TDMA signal, said power measurement device is further operable to (iii) receive said second IF signal, and (iv) generate a second segment power signal from said second IF signal that is representative of said second resolution segment, said A/D converter is further operable to sample said second segment power signal in order to produce a second plurality of samples that temporally represents said second resolution segment, and said controller is further operable to (iv) detect a leading edge of a second TDMA burst of said plurality of TDMA bursts based upon said second plurality of samples, (v) obtain from said second plurality of samples, a second sample that corresponds to a second temporal offset from said leading edge of said second TDMA burst which is equivalent to said first temporal offset, (vi) determine an average sample value based upon said first sample and said second sample, and (vii) determine said first power measurement value for said TDMA signal based said average sample value.

20. The device of claim 15, wherein said controller is further operable to:

(iv) identify a second sample of said first plurality of samples that corresponds to said leading edge of said first TDMA burst, and (v) select said first sample from said first plurality of samples such that said first sample corresponds to a predetermined number of samples after said second sample.

21. The device of claim 15, further comprising a user input device coupled to said controller and operable to (i) receive user input, and (ii) transmit signals to said controller that are representative of said user input, wherein said controller is further operable to (iv) receive signals from said user input device that define said first temporal offset from said leading edge of said first TDMA burst.

22. The device of claim 15, further comprising a user input device coupled to said controller and operable to (i) receive user input, and (ii) transmit signals to said controller that are representative of said user input; and a display coupled to said controller and operable to display a graphical representation of said first segment power signal in response to signals received from said controller, wherein said controller is further operable to (iv) generate signals which cause said display to display said graphical representation of said first segment power signal, and (v) receive signals from said user input device that identify a portion of said graphical representation corresponding to said first TDMA burst in order to define said first temporal offset from said leading edge of said first TDMA burst.

23. The device of claim 22, wherein said display is selected from a group of portable displays comprising light emitting diode displays and liquid crystal displays.

24. The device of claim 15, wherein said controller is further operable to (iv) analyze said first plurality of samples in order to obtain said first sample such that said first sample corresponds to said first TDMA burst.

25. The device of claim 15, wherein said power measurement device comprises: a resolution bandwidth filter coupled to said receiver and operable to band pass filter said IF signal to produce a filtered first IF signal that is representative of said first resolution segment of said TDMA signal; a power detector coupled to said resolution bandwidth filter and operable to generate a power signal that is representative of said filtered IF signal; and a video bandwidth filter coupled to said power detector and operable to filter said power signal in order to produce said first segment power signal.

26. A device for measuring a TDMA signal comprising a plurality of TDMA bursts modulated upon a TDMA carrier signal, comprising: a receiver operable to (i) receive said TDMA signal, and (ii) generate a first IF signal that is representative of a first resolution segment of said TDMA signal; a power measurement device coupled to said receiver and operable to (i) receive said first IF signal, and (ii) generate a first segment power signal from said first IF signal that is representative of said first resolution segment; an analog to digital (A/D) converter coupled to said power measurement device and operable to sample said first segment power signal in order to produce a first plurality of samples that temporally represents said first resolution segment; and a controller coupled to said A/D converter and operable to (i) identify a first sample of said first plurality of samples that corresponds to a leading edge of a first TDMA burst of said plurality of TDMA burst, (ii) obtain a first trace vector comprising a first predetermined number of samples of said first plurality of samples that follow said first sample, (iii) update based upon said first trace vector, a first average trace vector comprising a first plurality of average samples, and (iv) determine based upon a first average sample of said first average trace vector, a first TDMA measurement value for said TDMA signal that is representative of signal power of said TDMA carrier signal.

27. The device of claim 26, wherein said controller is further operable to (v) obtain said first average sample from said first average trace vector such that said first average sample corresponds to a first temporal offset from said first sample of said first trace vector.

28. The device of claim 26, wherein said controller is further operable to (v) identify a second sample of said first plurality of samples that corresponds to a leading edge of a second TDMA burst of said plurality of TDMA bursts, (vi) obtain a second trace vector comprising a second predetermined number of samples of said first plurality of samples that follow said second sample, and (vii) update said first average trace vector based upon said second trace vector prior to determining said first TDMA measurement value for said TDMA signal.

29. The device of claim 26, further comprising a user input device coupled to said controller and operable to (i) receive user input, and (ii) transmit signals to said controller that are representative of said user input; and a display coupled to said controller and operable to display a graphical representation of said first average trace vector in response to signals received from said controller, wherein said controller is further operable to (v) generate signals which cause said display to display said graphical representation of said first average trace vector, and (vi) receive signals from aid user input device which identify a portion of said graphical representation associated with TDMA bursts of said TDMA signal in order to identify said first average sample of said first trace vector.

30. The device of claim 26, wherein said controller is further operable to (v) analyze said first average trace vector in order to obtain said first average sample such that said first average sample corresponds to said first TDMA burst.

31. The device of claim 26, further comprising: a user input device coupled to said controller and operable to (i) receive user input, and (ii) transmit signals to said controller that are representative of said user input; and a display coupled to said controller and operable to display a graphical representation of said first average trace vector in response to signals received from said controller, wherein said controller is further operable to (v) generate signal which cause said display to display said graphical representation of said first average trace vector, (vi) receive signals from said user input device which identify a portion of said graphical representation associated with idle periods of said TDMA signal in order to identify a second average sample of said first average trace vector representative of idle periods of said TDMA signal, and (vii) determine based upon said second average sample, a noise measurement value for said TDMA signal that is representative of signal noise of said TDMA signal.