JPH1022976A - Spread spectrum communication equipment - Google Patents

Abstract

(57) [Summary] A sufficient attenuation cannot be obtained with a single-stage attenuator circuit, and a receivable signal power cannot be set to a sufficiently large value. Increasing the degree of attenuation by increasing the number of attenuator circuits increases the passage loss, causes a problem in operation when the received signal power is small, and complicates the circuit. A connection between an antenna terminal, a transmission system circuit, and a reception system circuit is controlled by a transmission / reception switching circuit in response to transmission / reception. The switching operation is also controlled by the gain control voltage output from the gain control circuit 33, and the received signal amplitude detection circuit 331 detects excessive input signal power that cannot be absorbed by the operation of the variable gain circuit and the attenuator circuit 312 of the reception circuit 311. In this case, the transmission / reception switching circuit 2 connecting the antenna terminal 1 and the reception circuit 311 is disconnected by the gain control voltage generated by the gain control voltage generation circuit 332.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus for transmitting and receiving data using a spread spectrum communication system.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional example of a spread spectrum communication apparatus. 1 in the figure is an antenna terminal,
2 is a transmission / reception switching circuit, 312 is an attenuator circuit,
311 is a reception circuit, 41 is a transmission circuit, 32 is a demodulation circuit,
42 is a modulation circuit, 5 is an interface circuit, 6 is an external connection terminal, 331 is a reception signal amplitude detection circuit, and 332 is a gain control voltage generation circuit.

The operation at the time of transmission will be described. During transmission, the transmission / reception switching circuit 2 uses the transmission / reception switching signal
1 and the antenna terminal 1 are connected.
Since the transmission signal amplitude output from the transmission circuit 41 is larger than the signal amplitude received by the spread spectrum communication apparatus during normal use, if a transmission signal having this large amplitude is input to the reception circuit 311. An irreparable effect on the receiving circuit 311 is considered. The transmission / reception switching circuit 2 also has a function of preventing a strong transmission signal output from the transmission circuit 41 from leaking into the reception circuit 311. To avoid this problem, it is conceivable to prepare a dedicated antenna for transmission and reception, but this is not common because the scale of the device increases.

The transmission data input from the terminal 6 is transmitted as a transmission signal through the interface circuit 5 to the modulation circuit 42.
Is input to The modulation circuit 42 performs spread spectrum modulation on the transmission signal and outputs the signal to the transmission circuit 41. The transmission signal is adjusted in transmission frequency, transmission power, occupied frequency bandwidth, and the like by the transmission circuit 41, and is output from the antenna terminal 1 through the transmission / reception switching circuit 2.

Next, the operation at the time of reception will be described. At the time of reception, the transmission / reception switching circuit transmits the antenna terminal 1 and the attenuator
Are connected. That is, the received signal subjected to spread spectrum modulation input from the antenna terminal 1 passes through the attenuator circuit 312 and is received by the receiving circuit 3.
11 is input. In the receiving circuit 311, the demodulation circuit 32
The received signal is output to the demodulation circuit 32 by adjusting the frequency and the signal amplitude of the received signal so that the operation of demodulating the spread spectrum modulation in is performed stably. The demodulation circuit 32 receives the received signal and demodulates the spread spectrum modulation. The interface circuit 5 outputs the received signal from the terminal 6 as received data.

In order to stably perform the demodulation operation in the demodulation circuit 32, the gain of the reception circuit 311 is automatically controlled so that the amplitude of the reception signal input to the demodulation circuit 32 is kept constant. Hereinafter, the automatic gain control method will be described. The automatic gain control function includes a reception signal amplitude detection circuit 331.
Then, a signal corresponding to the received signal amplitude from the signal amplitude in the demodulation circuit 32 is supplied to the gain control voltage generating circuit 332, and the gain control voltage generating circuit 332 generates a gain control voltage corresponding to the signal output from the received signal amplitude detecting circuit 331. Then, the signal is supplied to the variable gain circuit in the receiving circuit 311 and the attenuator circuit 312 placed before the receiving circuit 311. The gain of the variable gain circuit is controlled in accordance with the gain control voltage.
11 serves to keep the output amplitude constant. If the amplitude of the signal input to the receiving circuit 311 is too large to be controlled by the variable gain circuit, the attenuator circuit 311
The attenuator circuit 312 suppresses the amplitude of the reception signal input to the reception circuit 311 by the gain control voltage input to the reception circuit 12. As a result, the amplitude of the received signal input to the reception circuit 311 is attenuated, and the amplitude of the signal input to the demodulation circuit 32 is kept constant by the variable gain circuit in the reception circuit 311.

A patent relating to the automatic gain control method is disclosed in
There is 1-33025 publication.

[0008]

In the above configuration, the upper limit of the signal amplitude that can be input to the present device is determined by the attenuator circuit 3.
It is determined by the maximum attenuation of 12 and it is impossible to receive a received signal exceeding this upper limit. In the worst case, it is conceivable that if a reception signal exceeding the upper limit value is continuously input to the receiving circuit 311, the receiving circuit 311 may be irreparably affected.

In order to avoid this, the attenuator circuit 31
2 may be configured in multiple stages, but in this case, the complexity of the circuit and the input signal amplitude are reduced by the attenuator circuit 31.
This method also has a drawback because the characteristics are degraded when a received signal having an amplitude that does not cause the 2 does not operate.

[0010]

In order to solve the above problem, according to the present invention, the gain control voltage output from the gain control voltage generation circuit 322 is also supplied to the transmission / reception switching circuit 2,
When a large-amplitude reception signal that cannot be suppressed by the attenuator circuit 312 is input, the reception control signal is output to the attenuator circuit 312 when the transmission / reception switching circuit 2 is connected to the transmission circuit 41 by the gain control voltage. The configuration is such that the amplitude is strongly suppressed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention. In FIG. 1, 3 is a demodulation circuit, and 4 is a modulation circuit.

Hereinafter, the operation of the embodiment shown in FIG. 1 will be described in detail. When the spread spectrum communication apparatus transmits data, the transmission / reception switching circuit 2 receives the transmission / reception switching signal and connects the modulation circuit 4 to the antenna terminal 1 and, as described in the conventional example, transmits data input from the terminal 6 to the interface. The signal passes through the circuit 5 and is further subjected to spread spectrum modulation by the modulation circuit 4 to adjust the transmission frequency, transmission power, occupied frequency bandwidth, etc., and output from the antenna terminal 1 through the transmission / reception switching circuit 2. The demodulation circuit 3 may use an element that is easily affected by the large amplitude signal. In this state, the demodulation circuit 3 is disconnected from the modulation circuit 5 and the antenna terminal 1 by the transmission / reception switching circuit 2. Since the large-amplitude signal output from the modulation circuit 5 leaks into the demodulation circuit 3 only with a sufficiently small amplitude, the demodulation circuit 3 is not affected by the transmission signal.

At the time of reception, the transmission / reception switching circuit 2 receives the transmission / reception switching signal and connects the antenna terminal 1 to the demodulation circuit 3. The received signal input from the antenna terminal 1 is input to the demodulation circuit 3 through the transmission / reception switching circuit 2. The reception signal is adjusted in frequency and signal amplitude by the demodulation circuit 3, demodulated in spread spectrum modulation, and output from the terminal 6 through the interface circuit 5 as reception data. When the amplitude of the received input signal is large, if the large amplitude received signal is directly input to the demodulation circuit 3, a stable demodulation operation may not be performed. In order to prevent this problem, the demodulation circuit is provided with a gain control means, which controls the operation of the transmission / reception switching circuit 2. That is, when a large-amplitude signal that makes the demodulation operation of the demodulation circuit 3 unstable becomes received, the transmission / reception switching circuit 2 is switched to a state in which the antenna terminal 1 and the modulation circuit 4 are connected by the gain control means. As a result, the amplitude of the received signal input to the demodulation circuit 3 is suppressed, and a stable demodulation operation is realized. When the transmission / reception switching circuit is always in a state of connecting the antenna terminal 1 and the modulation circuit 4, when the received signal amplitude is a normal amplitude that does not make the demodulation operation of the demodulation circuit 3 unstable, the demodulation circuit 3 Since the input signal amplitude becomes small and the demodulation operation becomes unstable, the transmission / reception switching circuit 2 connects the antenna terminal 1 and the demodulation circuit 3 during normal reception.

FIG. 2 is a block diagram showing a second embodiment of the present invention, in which 31 is a receiving circuit, 32 is a demodulating circuit, 33
Is a gain control circuit, 41 is a transmission circuit, and 42 is a modulation circuit.

Hereinafter, the operation of this embodiment will be described in detail. The operation at the time of transmission will be described. The modulation circuit 42 performs spread spectrum modulation, and the transmission circuit 41 shapes a transmission waveform. That is, the transmission data input from the terminal 6 is output from the interface circuit 5, is subjected to spread spectrum modulation by the modulation circuit 42, and the transmission circuit 41 adjusts the transmission frequency, transmission power, occupied frequency bandwidth, etc. The signal is output from the antenna terminal 1 through the switching circuit 2.

Next, the operation at the time of reception will be described. The reception signal input from the antenna terminal 1 is input to the reception circuit 31 through the transmission / reception switching circuit 2. The received signal is adjusted in frequency and signal amplitude by a receiving circuit 31, further demodulated by spread spectrum modulation by a demodulating circuit 32, and output as received data from a terminal 6 through an interface circuit 5. In order for the demodulation circuit 32 to perform the demodulation operation stably, the signal amplitude input to the demodulation circuit 32 needs to be constant. For the automatic gain control operation to realize this, the gain control circuit 33 detects the signal amplitude in the demodulation circuit 32 and outputs a control signal according to the signal amplitude. This control signal controls the gain of the variable gain circuit in the receiving circuit 31, and increases the gain of the variable gain circuit when the amplitude of the received signal input to the receiving circuit 31 is small. When the signal amplitude is large, the gain of the variable gain circuit is reduced to keep the signal amplitude input to the demodulation circuit 32 constant.

If the amplitude of the received signal is larger and cannot be controlled by the operation of the variable gain circuit in the receiving circuit 31,
Alternatively, if there is a possibility that irreparably affecting the receiving circuit 31 if the large-amplitude received signal is directly input to the receiving circuit 31, the reception switching circuit 2 is also controlled by the control signal output from the gain control circuit 33. Then, the connection between the antenna terminal 1 and the receiving circuit 31 in the transmission / reception switching circuit 2 is disconnected, and the antenna terminal 1 and the transmitting circuit 41 are connected. At this time, since the received signal having a sufficiently suppressed amplitude is input to the receiving circuit 31, the amplitude of the signal input to the demodulation circuit 32 is kept constant by the gain control operation by the variable gain circuit in the receiving circuit 31. . As for other operations, the same operations as those in the embodiment shown in FIG. 1 are performed.

According to this embodiment, the gain of the variable gain circuit in the reception circuit 31 and the operation of the transmission / reception switching circuit 2 are controlled by the control signal output from the gain adjustment circuit 33, and the demodulation circuit 32
, The amplitude of the received signal inputted is kept constant, and a more stable demodulation operation is realized as compared with the effect of the embodiment shown in FIG.

FIG. 3 is a block diagram showing a third embodiment of the present invention. In FIG.
Is a gain adjustment voltage generation circuit.

Hereinafter, the operation of this embodiment will be described in detail. In the present embodiment, the gain control circuit 33 includes a reception signal amplitude detection circuit 331 and a gain adjustment voltage generation circuit 332. The reception signal amplitude detection circuit 311 detects the signal amplitude in the demodulation circuit 32, and outputs a signal corresponding to the reception signal amplitude to the gain control voltage generation circuit 332,
Gain control voltage generation circuit 332 receives this signal and outputs a gain control voltage. This gain control voltage is supplied to the receiving circuit 31
The gain of the variable gain circuit is controlled, and the gain of the variable gain circuit is increased when the amplitude of the received signal input to the receiving circuit 31 is small, and the variable gain is adjusted when the amplitude of the received signal input to the receiving circuit 31 is large. By reducing the gain of the circuit, the signal amplitude input to the demodulation circuit 32 is kept constant.

When the amplitude of the received signal is larger and cannot be controlled by the operation of the variable gain circuit in the receiving circuit 31,
Alternatively, if there is a possibility that irreparably affecting the receiving circuit 31 if the large-amplitude received signal is input to the receiving circuit 31 as it is, the transmission / reception switching circuit 2 is controlled by the gain control voltage. The connection between the antenna terminal 1 and the receiving circuit 31 is disconnected, and the antenna terminal 1 and the transmitting circuit 41 are connected. At this time, since the received signal having a sufficiently suppressed amplitude is input to the receiving circuit 31, the amplitude of the signal input to the demodulating circuit 32 is kept constant by the gain control operation by the variable gain circuit in the receiving circuit 31, A stable demodulation operation is realized. As for other operations, the same operations as those in the embodiment shown in FIG. 1 are performed.

According to the present embodiment, the reception signal amplitude detection circuit 331 receives a signal output according to the signal amplitude in the demodulation circuit 32, and uses the gain control voltage generated by the gain control voltage generation circuit 332 to output the signal to the reception circuit 31. The gain of the variable gain circuit and the operation of the transmission / reception switching circuit 2 are controlled.
As a result, the amplitude of the received signal input to the demodulation circuit 32 is kept constant, and the gain control operation is performed more stably as compared with the effect of the embodiment shown in FIG.
Thus, a more stable demodulation operation is realized.

FIG. 4 is a block diagram showing a fourth embodiment of the present invention, wherein 311 is a receiving circuit, and 312 is an attenuator circuit.

Hereinafter, the operation of this embodiment will be described in detail. In the present embodiment, an attenuator circuit 312 is provided at a stage preceding the receiving circuit 311 and the gain control voltage generating circuit 32
The gain control voltage output from the control circuit 2 controls the attenuator circuit 312 in addition to the variable gain circuit in the reception circuit 311 and the transmission / reception switching circuit 2. Hereinafter, the operation at the time of reception will be described in detail.

In order for the demodulation circuit 32 to stably perform the demodulation operation, the amplitude of the signal input to the demodulation circuit 32 must be constant. For the automatic gain control operation to realize this, the reception signal amplitude detection circuit 331 detects the signal amplitude in the demodulation circuit 32 and outputs a signal corresponding to the reception signal amplitude to the gain control voltage generation circuit 332. Gain control voltage generation circuit 332 receives this signal and outputs a gain control voltage. This gain control voltage controls the gain of the variable gain circuit in the receiving circuit 311, and increases the gain of the variable gain circuit when the amplitude of the received signal input to the receiving circuit 311 is small, and is input to the receiving circuit 311. If the received signal amplitude is large, reduce the gain of the variable gain circuit,
The amplitude of the signal input to the demodulation circuit 32 is kept constant.

When the amplitude of the received signal is even larger and cannot be controlled by the operation of the variable gain circuit in the receiving circuit 311, or when the received signal with the large amplitude is
If there is a possibility that irreparable effects may be exerted on the receiving circuit 311 by inputting it to 1, the attenuator circuit 312 is controlled by the gain control voltage to attenuate the amplitude of the signal input to the receiving circuit 311. The signal amplitude input to the demodulation circuit 32 is kept constant by the variable gain circuit in the reception circuit 311. Further, when a received signal having an excessive amplitude that cannot be suppressed only by the attenuation operation of the attenuator circuit 312 is input, the gain control voltage also controls the transmission / reception switching circuit 2, and the antenna terminal 1 and the attenuator circuit in the transmission / reception switching circuit 2 The connection with 312 is disconnected, and the antenna terminal 1 and the transmission circuit 41 are connected. At this time,
Since a received signal having a sufficiently suppressed amplitude is input to the attenuator circuit 312, the signal amplitude input to the demodulation circuit 32 is maintained constant by the gain control operation of the variable gain circuit in the reception circuit 311. Attenuator circuit 3
A stable demodulation operation can be realized even when a received signal having an excessive amplitude that cannot be suppressed by only the 12 attenuating operations is input. Other operations are the same as those of the embodiment shown in FIG.

According to this embodiment, the gain of the variable gain circuit in the receiving circuit 311, the operation of the attenuator circuit 312, and the operation of the transmission / reception switching circuit 2 are determined by the gain control voltage generated by the gain control voltage generating circuit 332. Controlled. As a result, even when a signal having a larger amplitude is received as compared with the embodiment shown in FIG. 3, it is possible to keep the amplitude of the received signal input to the demodulation circuit 32 constant. In addition to the effects shown in the illustrated embodiment, higher performance of the function can be achieved.

In the embodiment, the case where the transmission / reception switching circuit 2 is constituted by a semiconductor switch will be described. When a large amplitude reception signal is detected during reception and the transmission / reception switching circuit 2 is in a state where the antenna terminal 1 and the modulation circuit 4 are connected, if the transmission / reception switching circuit 2 is configured by a semiconductor switch, the demodulation circuit 3 Can supply a sufficiently suppressed reception signal, and can improve the performance of the present spectrum communication device.

In the above description, the transmission / reception switching circuit 2 has only two states: a state in which the modulation circuit 4 and the antenna terminal 1 are connected, and a state in which the antenna terminal 1 and the demodulation circuit 3 are connected. As mentioned above, even if the transmission / reception switching circuit 2 has a configuration in which two states change continuously using, for example, a variable resistor, there is no problem in the operation of the present invention.

[0031]

According to the present invention, even when a large-amplitude received signal that cannot be controlled by the gain control of the variable gain circuit and the attenuator circuit 312 in the receiving circuit 311 is received,
The reception signal is attenuated by the transmission / reception switching circuit 2, and a large demodulation signal is not input to the reception circuit 311, so that the demodulation circuit 32 can perform a stable demodulation operation. This eliminates the need for an additional circuit for achieving a stable operation, makes it possible to set the upper limit of the receivable signal amplitude to a higher value, and achieves higher performance and simplification of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a spread spectrum communication apparatus according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the spread spectrum communication apparatus according to the present invention.

FIG. 3 is a block diagram showing a third embodiment of the spread spectrum communication apparatus according to the present invention.

FIG. 4 is a block diagram showing a fourth embodiment of the spread spectrum communication apparatus according to the present invention.

FIG. 5 is a block diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Antenna connection terminal, 2 ... Transmission / reception switching circuit, 3 ... Receiving circuit, 4 ... Modulation circuit, 5 ... Interface circuit, 6 ... Connection terminal, 31 ... Demodulation circuit, 32 ... Demodulation circuit, 33 ... Gain control circuit, 41 ... Transmission circuit, 42: modulation circuit, 311: reception circuit, 312: attenuator circuit, 331: reception signal amplitude detection circuit, 332: gain control voltage generation circuit.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Minoru Mogi 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture

Claims (7)

[Claims] 1. A spread spectrum communication apparatus, comprising: at least an antenna terminal, a modulation circuit, a demodulation circuit, and a connection between data input / output to / from the spread spectrum communication apparatus, the modulation circuit, and the demodulation circuit. A transmission / reception switching circuit for switching connection between an antenna terminal and a reception circuit, or between a transmission circuit and an antenna terminal according to reception and transmission, and the demodulation circuit includes a gain control unit. 5. The spread spectrum communication apparatus according to claim 1, wherein the transmission / reception switching circuit is controlled by a transmission / reception switching signal and the gain control means. 2. The modulation circuit according to claim 1, wherein the modulation circuit performs a spread spectrum modulation, and frequency-converts a transmission signal output from the modulation circuit to a frequency suitable for transmission.
And, a demodulation circuit configured to demodulate the spread spectrum modulation, and the received signal is frequency-converted to a frequency suitable for demodulation of the spread spectrum modulation signal in the demodulation circuit. A spread spectrum communication apparatus comprising a receiving circuit for shaping a waveform and gain control means, wherein the gain control means controls a gain of the receiving circuit and the transmission / reception switching circuit. 3. The gain control means according to claim 1, wherein said gain control means detects an amplitude of a reception signal input to a reception circuit from a signal in said demodulation circuit, and converts a signal corresponding to the amplitude of the reception signal into a gain. A reception signal amplitude detection circuit that outputs to a control voltage generation circuit, and a gain control voltage generation circuit that receives a signal output from the reception signal amplitude detection circuit and generates a gain control voltage. A spread spectrum communication apparatus in which a gain of a receiving circuit and the transmission / reception switching circuit are controlled. 4. A spread spectrum communication apparatus according to claim 1, wherein said receiving circuit comprises a variable gain circuit controlled by said gain control means and an attenuator circuit controlled by said gain control means. 5. The spread-spectrum communication according to claim 1, wherein, when receiving, the transmission / reception switching circuit switches to a transmission side by the gain control means when an amplitude of a reception signal exceeds a set value. apparatus. 6. The method of claim 1, 2, 3, 4, or 5,
The transmission / reception switching circuit is a spread spectrum communication device including a semiconductor switch. 7. The method according to claim 1, wherein
The transmission / reception switching circuit is a spread spectrum communication apparatus in which switching between a transmission state and a reception state changes continuously.