+

WO1988006387A1 - Recepteur permettant la reception de liaison descendante de satellite de communications - Google Patents

Recepteur permettant la reception de liaison descendante de satellite de communications Download PDF

Info

Publication number
WO1988006387A1
WO1988006387A1 PCT/US1987/000347 US8700347W WO8806387A1 WO 1988006387 A1 WO1988006387 A1 WO 1988006387A1 US 8700347 W US8700347 W US 8700347W WO 8806387 A1 WO8806387 A1 WO 8806387A1
Authority
WO
WIPO (PCT)
Prior art keywords
receiver
carrier
output
signal
phase
Prior art date
Application number
PCT/US1987/000347
Other languages
English (en)
Inventor
Milton H. Brockman
Original Assignee
Brockman Milton H
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Brockman Milton H filed Critical Brockman Milton H
Priority to PCT/US1987/000347 priority Critical patent/WO1988006387A1/fr
Publication of WO1988006387A1 publication Critical patent/WO1988006387A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
    • H04B7/084—Equal gain combining, only phase adjustments

Definitions

  • the transmission of audio broadcast signal s is another area in which satel lites are utilized.
  • a single satellite transponder has the capability of relaying dozens of independent audio sources.
  • 10 dBW carriers leased from satellite common carriers, networks with nationwide coverage have been established that provide news and special programming of events through local radio stations.
  • Regional broadcasters are also p lanning that by leasing a 10 dBW carrier , they can bypass local terrestrial station-to-transmitter links. Up-link antennas 5 meters in diameter and down-link antennas as smal l as 3 meters (9.85 ft.) are used.
  • Sa te l l ite communications is providing more and more relief to long-haul communications circuits; i.e., coaxial cable. Uplinking is possible from any location with relatively little power.
  • the critical element in a satellite link is the transponder power needed to perform these communications modes in all weather and under al l conditions of loading.
  • Video Conferencing for example, implementing data compression techniques to trade off minimal picture degradation for greatly reduced data rates, is contemplated.
  • An alternative to video compression is limited motion and freeze frame video.
  • the use of statistical multiplexing and digital speech interpolation techniques can more than double a transponder's voice handling capacity.
  • SSB can significantly increase the capacity of transponders already in orbit.
  • each voice circuit allows for a satellite transponder power per channel lower than for uncompanded FM.
  • an FM based system with 36 MHz of bandwidth can handle 2,800 one-way voice channels; companded SSB can boost the transponder's capability to 7,200 voice channels.
  • DBS direct broadcast service
  • the K u band offers the prospect of an integrated home entertainment and information system that surpasses the performance of terrestrial and cable technologies combined.
  • the signal-to- noise ratio achievable at the DBS delivery point depends on a suitable antenna and a low-noise temperature down converter as wel l as on the antenna's polarization, pointing error, and gain.
  • antenna gain is directly related to the dish size.
  • the dish antennas do not have to be mounted on the roof ; they can be small enough to be concealed under the roof in an average dwel ling or office building, reducing or eliminating moisture and weather effects which can cause attenuation at u band.
  • the novel receiver employs a combination of principles governing the reception of weak signals and the combining of outputs of antennas and receiver arrays, as well as signal processing for digital and analog signals.
  • the prior art is represented by applicant's prior patent No.
  • the present invention defines receiver implementations for equal or unequal aperture antennas, in combination with other novel features described herein, to obtain carrier sensitivity improvement that is greater than the ratio of total antenna array aperture to main receiver aperture, and provides a correlated demodulated output signal that represents the total antenna array aperture.
  • the unequal aperture case in which antennas of unequal size may be used is des- cribed with reference to performance characteristics of the same system, but it is another embodiment.
  • This invention provides a high sensitivity receiver for electromagnetic radiation reception particularly in the C-band, S-band, X-band and K band which are the bands now in use or planned to be utilized for transmission of commercial communications services and home entertainment and data services.
  • the novel receiver lends itself to reception of several different modes of transmission and program encryp- tion or scrambling, and is amenable to tracking any signal having a lower power level inserted carrier, or a pilot signal such as is used in FM or single sideband. Any type of modulation on the signal or signals that is in turn phase modulated onto a phase stable microwave or RF carrier with a residual carrier whose level is a few percent of the total signal power, can be received and provided to the user for demodulation and detection or presentation.
  • This mode of transmission allows the use of the most sensitive receiving system; i.e., the phase coherent system espoused in this invention.
  • the lower power level inserted carrier or pilot signal cases will provide a less sensitive system than the phase modulated system, for the same received signal level conditions.
  • This high sensitivity, high dynamic range receiving system which utilizes a plurality of smaller antennas in lieu of a large antenna, has a carrier sensitivity better than, and a demodulated signal-to-noise ratio equal to, the larger antenna and single receiver having an equal effective area.
  • the receiver uses a phase stable fixed frequency local oscillator signal for the first heterodyne mixer so that all branches of the receiver including the main receiver and branch receivers 1 through N have first IF signal outputs that are at the same fixed frequency, except for the frequency diversity embodiment to be described later.
  • These signals are at a low level and are amplified in a first IF amplifier in the main receiver and N branch receivers, and are applied to a heterodyne mixer in the main receiver which receives a local oscillator signal controlled by a first phase locked loop.
  • This phase locked local oscillator signal is distributed to the N branch receivers and applied to the second heterodyne mixer of each receiver.
  • the main receiver and the branch receivers include a third heterodyne mixer and a third IF ampl ifier.
  • the local oscil lator signal appl ied to the third heterodyne mixer in each branch receiver is control led by a phase locked loop in each branch receiver.
  • the local oscillator applied to the third heterodyne mixer in the main receiver is a fixed phase stable frequency.
  • the outputs of the main receiver and the N branch receivers at the third IF amplifier output are fed to a carrier summing junction where the carrier signals are combined in phase to yield a carrier sensitivity greater than a single receiver and large aperture antenna with equal effective area.
  • a separate wide bandwidth third IF amplifier and phase detector in the main receiver and each branch receiver provide coherent demodulation of the signal. All receiver signals are coherently summed in a separate summing junction to provide the data spectrum output to the user.
  • the modulation group delay of each branch receiver is matched to the corresponding main receiver group delay to optimize the signal-to-noise ratio of the correlated modulation output signal.
  • a digital implementation of the receiver allows the carrier phase locked loop bandwidth of the summed receiver system to be automatically adjusted in accordance with the carrier predetection signal-to-noise ratio such that the receiver can accommodate the signal-to-noise ratio degradation due, for example, to atmospheric effects.
  • the receiver is tuned to the carrier frequency of the satel lite service by setting the frequency of the first local oscillator signal at the first heterodyne mixer.
  • the first local oscil lator frequency is set to receive any one of the several transmissions provided by the satellite service by selecting the matching phase stable fixed frequency source.
  • This first local oscil lator signal is set either manually or by remote control and provides the first IF output signal when heterodyned with the tuning reference frequency.
  • Fixed frequency phase stable references are mixed with a phase locked loop signal to provide the local oscil lator signal controlled by a carrier first phase locked loop, to the second heterodyne mixer in the main receiver and to the second heterodyne mixers in the N branch receiver channels (except for frequency diversity reception).
  • This heterodyne process provides the second IF output signal in the main and N branch receivers.
  • the carrier third IF is summed with the N branch receiver carrier third IFs to provide coherently summed, carriers plus carrier loop predetection receiver noise of the main receiver and the N branch receivers.
  • the bandpass limited output of the summed main receiver carrier third IF amplifier is analog-to-digital (A/D) converted and compared in phase with the quadrature phase of the coherent A/D converted detector reference frequency, sampled every T- ⁇ time interval and averaged over each Ti to provide a measure of the phase error (in digital form) in the phase locked loop for each T ⁇ .
  • the time between samples Tn is a function of the received signal level.
  • This averaged measure of phase error for each T ⁇ in digital form is applied to a software tracking filter whose output causes a numerically controlled oscillator to change phase , and when mixed with the main receiver fixed reference frequencies, provides phase lock with the received carrier frequency.
  • Analog techniques can also be used to accomplish the same functions.
  • a different phase stable fixed frequency oscillator, or frequency synthesizer if frequency agility is required would be used for each N branch receiver in place of the second fixed frequency reference used in the main receiver to provide a second local oscillator frequency offset in each of the N branch receivers' second local oscil lator to match the frequency offset relative to the main receiver of each of the diverse received frequencies. See Figure 4 for a block diagram of the receiver.
  • the architecture of the summed receiver system lends itself wel l to encryption of program material by frequency diversity either singly or in combination with other scrambling or encoding techniques.
  • frequency diversity a television transmission or other data, particularly imaging data, are split up among the several receivers, each operating at a separate frequency making up the summed system and are reassembled by keyed decoding functions with the key being changeable and known only to the subscribers. Since the carrier signals are coherently summed and demodulated, they can each carry discrete segments of the modulation.
  • the frequency diversity encryption method is adaptable to the widely used aerospace , general ly post-detection, encoding methods that are fully developed.
  • receiver system of this invention includes pseudonoise coding and interleaved Reed- Solomon coding, as wel l as the simpler multiplexing algorithms.
  • the proper encoding algorithm can produce improved data since error correction, data compression and dropout compensation can be employed.
  • Another aspect of the receiver system of this invention is its adaptability to frequency reuse; i.e., transmitting and receiving separate information on orthogonal polarizations of the same signal.
  • the six channels of the receiver are split up into three antennas each with orthogonal polarization output ports. In this manner, six different carriers can be used for frequency diversity with each antenna having a polarization diversity capability, enabling further possibilities for secure communications.
  • the novel receiver is uniquely adaptable to all the modes of satellite transmission that are in use or planned for the near future.
  • Figure 1 is a conceptual drawing of the receiver installation illustrating the equal or unequal aperture antennas and the remotely located elements of the novel receiving system as well as the operator and display elements.
  • Figure 2 is a schematic block diagram of the receiver showing the essential elements of the receiver including the front end, the receiver channels, the summing methods for the carrier and the modulation spectrums when taken in combination with Figure 3 which shows the digital controller.
  • Figure 3 is a block diagram of the digital controller which applies to both Figures 2 and 4 for controlling the bandwidth of the phase locked loop local oscillator.
  • Figure 4 is a schematic block diagram of the frequency diversity embodiment of the receiver, illustrating also the polarization diversity and frequency reuse capabilities of the receiver.
  • Figure 5 is a graph showing the effect on the carrier margin of widening the noise bandwidth of the branch receiver third IFs for equal apertures in preventing loss of phase lock at very low signal levels.
  • Figure 6 is a graph showing the effect of increasing the carrier margin by combining the outputs of a plurality of- equal aperture antennas and their receiver channels.
  • Figure 7 is a graph showing the effect on the carrier margin of widening the noise bandwidth of the branch receiver third IFs for unequal apertures in preventing loss of phase lock at very low levels.
  • Figure 8 is a graph showing the effect of increasing the carrier margin by combining the outputs of a plurality of unequal aperture antennas and their receiver channels.
  • the receiver embodiments to be described in the following have in common the use of equal or unequal aperture antennas, each having a separate receiver channel with the channels being summed after the third IF amplifiers in each of N receiver channels.
  • the signal carriers are summed in this system in such a manner that the signals are coherentl additive while the noise is summed in an rms fashion.
  • the point o summing is after the predetection IF amplifiers for the carriers whil the modulation spectrums are summed in another junction at baseband.
  • only one branch receiver A of N possible branches is shown because the branch receivers are identical except for possible differences in group delays, and differences in configuration for frequency and polarization diversity implementations.
  • the antenna paraboloids for the receiver include the main receiver antenna and branch receiver antennas 11 through 15.
  • the distance between the main antenna and the branch antennas is dependent upon the antenna enclosure, or if the space is unlimited for antenna installation, the branch antennas can be located for spatial diversity to compensate for fading due to atmospheric propagation effects.
  • the paraboloids are nominally a few feet i diameter providing convenient light weight packages that can be easily handled by one man for installation in the upper story of a residence or office building where they can be concealed and protected from the environment.
  • Low voltage DC is provided for powering the wideband amplifiers at the base of the antenna.
  • Coaxial lines 16 connect the antennas' amplifiers to the summing receiver at a location that could be hundreds of feet away.
  • Delay line loops in the coaxial cables provide for tailoring the group delays in the branch antennas relative to the main receiver as a rough approximation.
  • Phase shifters in the receiver channels perform the vernier group delay adjustments. Once set, the group delays in each receiver channel remain the same.
  • the receiver package in this embodiment is a five branch channel and one main channel receiver having fixed frequency selection for tuning control.
  • an appropriate display device or terminal and peripheral device 21 is operated from the six channel receiver.
  • FIG. 2 shows the conceptual block diagram of the main channel and one branch channel. All of the branch channels are essentially the same as the A channel.
  • the wideband amplifiers at the antennas 23 provide sufficient bandwidth to accommodate the desired reception band. These amplifiers are designed to be low noise within the state of the art. Any signal in the frequency range is applied as one input to the first heterodyne mixer 24.
  • the other input to the mixers 24 is the first local oscillator signal which is a source 25 of fixed frequency phase stable signals, manually or remotely settable for receiver tuning.
  • the output of the first mixers 24 are applied to first IF amplifiers 26. These amplifiers furnish the first intermediate frequency outputs from the antenna area for each receiver channel. These signals are applied to second mixers 27 in the receiver package located remotely from the antenna area for each receiver channel.
  • the second heterodyne mixers 27, 27A through N have a local oscillator which coherently tracks the phase of the received carrier at the first IF frequency with a carrier tracking loop in the main receiver.
  • This tracking loop includes the third IF filters 29, the carrier summing junction 30 and the third IF amplifier 31 in the main receiver.
  • this amplifier has a limited output and a linear output.
  • the linear output is applied to a coherent amplitude detector and AGC circuits which operate in a conventional manner.
  • the limited output provides a carrier component which varies with received carrier level which in turn, provides change in closed loop tracking bandwidth with change in signal level as described herein.
  • the reference signals shown are all standards for frequency and are phase stable within the state of the art for high quality equipment. Refer to Figure 3.
  • the bandpass limited output of the summed main receiver third IF amplifier 31 is analog-to-digital (A/D) converted and compared in phase with the quadrature phase of the coherent A/D converted second reference frequency in detector 32, sampled every time interval Ti and averaged over each Ti time interval to provide a measure of the phase error in digital form in the phase locked loop for each T ⁇ .
  • the time between samples T ⁇ is a function of the receiver signal level.
  • This average measure of phase error for each T- ⁇ time interval is applied to a software or firmware tracking filter whose output causes a numerically controlled oscillator (NC0) 34 to change phase.
  • NCO with D/A provides phase lock with the received carrier frequency.
  • the bandpass limited carrier third IF output i.e., summed coherent carrier plus receiver noise
  • the time interval between samples Ti is controlled by the carrier component S c ⁇ of the bandpass limited third IF output with the time between samples T- ⁇ decreasing as S c ⁇ increases.
  • the carrier component S_ ⁇ is represented by the average value of S_ ⁇ + noise, a digital value, which results from digital detection of the A/D converted bandpass limited output of the main receiver carrier third IF amplifier, with the in-phase A/D converted detection second reference frequency for the main receiver phase locked loop.
  • the average value of S c + N provides a specified value T ⁇ which in conjunction with other loop parameters, determines the design point closed loop bandwidth of the main receiver carrier phase locked loop.
  • T ⁇ the design point closed loop bandwidth of the main receiver carrier phase locked loop.
  • the N branch receivers utilize similar techniques to provide in each branch receiver a local oscillator controlled by a carrier phase locked loop to the third heterodyne mixer with fixed frequency phase stable references and set to the same frequency as reference frequency 1 in the main receiver to achieve phase lock and track out any differential phase effects.
  • the S c ⁇ + N is provided by detecting the limited output of the third IF amplifier with the reference frequency, in detector 35.
  • the average value is applied to the sample and average 36 which controls the value T j ⁇ which is inversely proportional to the carrier component S_
  • T j ⁇ which is inversely proportional to the carrier component S_
  • the computation delay 37 provides a delay and controls the time for each T j when the phase of the NCO in the main receiver is changed.
  • demodulator signal spectrum summing which occurs after the third mixer, emanating from the second IF distribution amplifier and IF filter, followed by a third IF amplifier and phase detector, the output of which is the demodulated signal spectrum.
  • These outputs from the main receiver and the N branch receivers are coherently summed in a signal summer 41.
  • This summing circuit provides a demodulated signal at a carrier margin enhanced over what would be available relative to the signal to noise ratio of a single antenna and receiver system having the same aperture area.
  • Figure 4 shows an embodiment of the invention for frequency diversity, frequency reuse for bandwidth conservation by transmitting information on orthogonal components of the same frequency carrier, and a polarization diversity mode of operation.
  • the architecture of the receiver is substantially the same as the receiver of Figure 2 except that in the main receiver the phase locked receiver controller output is applied to a first mixer 42 which receives a fixed frequency reference that is of a high frequency so that the sum of the two inputs to the mixer 42 is equal to the local oscillator frequency desired to tune the second mixer 43 to heterodyne with the output signal from the first IF output amplifier emanating from the antenna area to produce the second IF signal which is coherently detected as described for Figure 2.
  • each receiver operates at a different frequency, yet they remain coherent with the main receiver system by virtue of the fact that the main receiver controller phase locked loop output is applied to a mixer 44 which also receives a phase stable fixed frequency reference so that the output of the mixer 44 is a frequency offset from the main receiver frequency and differing from the input signal from the first IF amplifier of the branch receiver, emanating from the antenna area, by the second IF frequency.
  • the bandpass filters 45 and 46 establish the bandwidth limit and select the proper frequency output of the mixers 42 and 44.
  • each branch receiver to operate at a different frequency while maintaining phase coherence with the main carrier signal and enables summing of the third IFs which are at the same frequency to provide the advantages previously described for the summed receiver configuration.
  • the demodu ⁇ lated signal spectrum from each receiver is applied to a modulation summing circuit as in the embodiment of Figures 2 and 3. It is apparent that since the modulation spectrums can be summed, different segments of the modulation can be transmitted on separate carriers received by separate receivers. These separate carriers can further be encoded with the same or separate codes and decoded after the summing circuit 41, Figure 3. Thus, a two dimensional encoding or scrambling system is provided for secure communications.
  • each antenna can employ an orthomode feed 51 such that the main receiver channel can receive the signal from one of the orthogonal polarization ports while a branch receiver can receive orthogonal polarization signals from the other.
  • two of the branch receivers can receive the signals from orthogonal polarization ports of the second antenna.
  • This technique can be expanded to a third antenna with orthogonal polarization ports and two additional branch receivers.
  • This configuration is also advantageous for secure communications wherein segments of the data spectrum can be multiplexed on orthogonal polarizations of the carrier according to an algorithm.
  • the combination of frequency diversity as described earlier and polarization diversity is possible wherein a carrier frequency of left circular polarization and another carrier offset therefrom can have right circular polarization, both carriers containing modulation or encoding segments thereof, can be combined in the receiver of Figure 4 and Figure 3, thereby providing two additional dimensions for encoding or encryption algorithms.
  • A. single equivalent antenna with its receiver would have twice the area which provides 3 dB more carrier margin than the main receiver with its smaller antenna.
  • the equal aperture array has 6.6 dB more carrier margin than the main receiver alone with its antenna. Consequently, the improvement or "enhancement" in carrier margin for two equal aperture antennas with their receivers is 6.6 minus 3 or 3.6 dB relative to a single equivalent area antenna with its receiver as shown in Figure 6.
  • This relative carrier margin improvement increases slightly for a main receiver and two branch receivers (3 antennas) arrayed and decreases to 2.6 dB improvement for 6 antennas with their receivers arrayed.
  • the plot shows hat with the main receiver and one branch receiver coherently summed, and the bandwidth of the branch receiver third IF filter 9 times the bandwidth of the main receiver third IF filter, the gain in carrier margin is 4.64 db at low carrier levels, and cycle slipping for coherently summed receivers will not occur at a carrier level which represents an initial 5.5db carrier margin for the main receiver alone. This represents a basic difference over the prior art in which this principle was not recognized and not utilized.
  • the improvement or "enhancement” in carrier margin for the two antenna array is 4.64 minus 1.34 or 3.3 relative to a single equivalent area antenna with its receiver as shown in Figure 8.
  • This relative carrier margin improvement increases slightly for a main receiver and two branch receivers (3 antennas) arrayed and decreases to 2.4 db improvement for 6 antennas with their receivers arrayed.
  • novel receiver embodiments show paraboloidal antennas, other types can be used ; e.g., disk-on-rod, offset, shaped reflector, without departing from the teachings of the invention.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radio Transmission System (AREA)

Abstract

Un récepteur (20) utilisant un ensemble de petites antennes paraboliques (10-15) au lieu d'une seule et grande antenne couvrant la même surface, chaque antenne reliée à un canal récepteur hétérodyne séparé à phase cohérente comprend un canal principal et des canaux secondaires, les canaux étant additionnés pour fournir un signal oscillateur local porteur à verrouillage de phase qui est distribué à tous les canaux produisant des signaux FI cohérents en phase dans tous les canaux. Ceux-ci sont additionnés pour augmenter la marge en dB de porteur par rapport au seuil de sensibilité, du système combinant les canaux récepteurs, à un niveau plus élevé que celui de l'antenne unique couvrant une surface équivalente avec son unique récepteur. La tendance au glissage de fréquence à proximité du seuil est encore réduite en utilisant dans les FI des filtres de prédétection de bruit de bande passante qui sont plus larges dans les récepteurs secondaires que dans le récepteur principal. Les spectres de modulation des canaux récepteurs sont démodulés et additionnés pour donner un rapport signal/bruit de sortie apparenté à la somme des zones effectives de l'ensemble d'antennes plus petites. Un contrôleur numérique de bande passante à verrouillage de phase règle la sensibilité du système de canaux combinés au niveau du signal reçu augmentant la portée dynamique du système. L'architecture de canal séparé du récepteur permet de protéger les techniques de communication incluant le codage des différentes fréquences, le codage de différentes polarisations, la réutilisation de fréquences et l'imbrication et le multiplexage de segments de flux de données.
PCT/US1987/000347 1987-02-11 1987-02-11 Recepteur permettant la reception de liaison descendante de satellite de communications WO1988006387A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/US1987/000347 WO1988006387A1 (fr) 1987-02-11 1987-02-11 Recepteur permettant la reception de liaison descendante de satellite de communications

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1987/000347 WO1988006387A1 (fr) 1987-02-11 1987-02-11 Recepteur permettant la reception de liaison descendante de satellite de communications

Publications (1)

Publication Number Publication Date
WO1988006387A1 true WO1988006387A1 (fr) 1988-08-25

Family

ID=22202288

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1987/000347 WO1988006387A1 (fr) 1987-02-11 1987-02-11 Recepteur permettant la reception de liaison descendante de satellite de communications

Country Status (1)

Country Link
WO (1) WO1988006387A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8213485B2 (en) 1996-05-28 2012-07-03 Qualcomm Incorporated High rate CDMA wireless communication system using variable sized channel codes
CN114815691A (zh) * 2022-04-20 2022-07-29 上海航天测控通信研究所 一种抗振型双路射频收发数字处理装置

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838342A (en) * 1967-02-27 1974-09-24 Philips Corp A switched frequency communications system with automatic phase and amplitude compensation
US4186347A (en) * 1978-10-31 1980-01-29 Nasa Radio frequency arraying method for receivers

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3838342A (en) * 1967-02-27 1974-09-24 Philips Corp A switched frequency communications system with automatic phase and amplitude compensation
US4186347A (en) * 1978-10-31 1980-01-29 Nasa Radio frequency arraying method for receivers

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
TDA Progress Report 42-76, October - December 1983, M.H. BROCKMAN, "Enhanced Radio Frequency Carrier Margin Improvement for an Array of Receiving Systems with Unequal Predetection Signal-To-Noise Ratio", (see pages 170-188). *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8213485B2 (en) 1996-05-28 2012-07-03 Qualcomm Incorporated High rate CDMA wireless communication system using variable sized channel codes
US8588277B2 (en) 1996-05-28 2013-11-19 Qualcomm Incorporated High data rate CDMA wireless communication system using variable sized channel codes
CN114815691A (zh) * 2022-04-20 2022-07-29 上海航天测控通信研究所 一种抗振型双路射频收发数字处理装置

Similar Documents

Publication Publication Date Title
US4956864A (en) Receiver for communications satellite down-link reception
US5319673A (en) Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites
EP0407263B1 (fr) Système de réception de signaux t.v. retransmis par satellites
US6600730B1 (en) System for distribution of satellite signals from separate multiple satellites on a single cable line
US6510317B1 (en) Satellite digital audio radio service tuner architecture for reception of satellite and terrestrial signals
JP3889885B2 (ja) ミリ波送信装置、ミリ波受信装置、ミリ波送受信システム及び電子機器
US7697911B2 (en) Single path architecture with digital automatic gain control for SDARS receivers
US7447171B2 (en) Antenna diversity system
HUT78099A (hu) Előtétegység közvetlen televízió műsorsugárzás vevőrendszeréhez
US8418210B2 (en) Satellite television system ground station having wideband multi-channel LNB converter/transmitter architecture with controlled uplink transmission
US5999137A (en) Integrated antenna system for satellite terrestrial television reception
US20090262787A1 (en) Method and Apparatus for Providing Satellite Television and Other Data to Mobile Antennas
JPH1056391A (ja) 衛星又はマルチチャンネル多点配信システム局を介して送信されたプログラムの受信装置
WO1988006387A1 (fr) Recepteur permettant la reception de liaison descendante de satellite de communications
KR100502496B1 (ko) 위성 방송 지상 중계 장치
JP3180396B2 (ja) アンテナ調整方法
US20100183050A1 (en) Method and Apparatus for Providing Satellite Television and Other Data to Mobile Antennas
KR100629004B1 (ko) 튜너
Feher et al. PSK combiners for fading microwave channels
KR970007605B1 (ko) 두대의 저가정지 위성을 이용하는 라디오 주파수 방송시스템 및 그 방법
McClannan et al. A satellite system for CATV
Imahori Uplink Terminals
Kubota et al. International transmission of HDTV signals
LANGHANS et al. Optimized TV and radio transmission parameters for satellite distribution at C band
Dorofeev et al. Satellite Tv Distribution System" Moscow"

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): DE GB JP KP

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): FR

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

点击 这是indexloc提供的php浏览器服务，不要输入任何密码和下载