Abstract: A coupled interference cancellation system (CICS) for canceling retransmission-antenna-to-receiving-antenna (coupled) interference signals. The system is connected to a bidirectional, over-the-air repeater for a wideband digital cellular communication system. For each repeater direction, the CICS injects one or more modulated pilot signals at the retransmission antenna input which are emitted along with the communications signal. The portion of the repeater output signal that is coupled to the receiving antenna is indicated by the properties of the pilot signals that are detected at the repeater's receiving antenna. The detected quadrature components of the pilot signals are used to generate a cancellation signal by vector modulation and delay of a sample of the retransmission antenna input. The cancellation signal is applied at the receiving antenna output to subtract the coupled interference.

Abstract: A radio communications transceiver which operates to transmit radio signals via a transmit antenna and receive radio signals via a receive antenna, wherein said transmit and receive antennas are disposed to provide at least a substantial amount of radio signal isolation therebetween. The radio communications transceiver further includes a cancellation device comprising a first coupler coupled to the transmit antenna and arranged to extract a sample of the transmit signal, a second coupler coupled to the receiver antenna and arranged to extract a sample of the received signal, a correlator fed on first and second inputs with the transmit and the received signal samples respectively, the correlator operating to generate an error signal representative of a correlation of the transmit and received radio signals, which error signal is fed to a modulator which operates to modulate the transmit signal sample, consequent upon the error signal.

Abstract: A full-duplex radio transceiver, in which cancellation of transmission signals in the receive path is achieved by sampling the transmission signals, and controllably adjusting the gain and phase of the sampled signal, before subtracting the adjusted signal from the received signals in order to minimise the component of the transmission signals appearing in the received signals. Processing is done in a DSP at or near baseband.

Abstract: The invention concerns a communications system including at least one transmit antenna near at least one receive antenna, transmission producing signals in the receive frequency band. The system includes a transmit neutralizing circuit for supplying a correction signal for eliminating only interfering signals whose frequency is in the receive signal frequency band. The transmit neutralizing circuit is on the input side of an amplifier and comprises means for evaluating, in the wanted receive frequency band, a limited number of parameters of the power amplifier feeding the transmit antenna, this evaluation of parameters being effected on the basis of the input and output signals of the amplifier. The circuit also evaluates the signals causing the interference prior to the input of the amplifier; this evaluation of the interfering signals is based on the calculated parameters and the signal at the input of the amplifier. Application to transmission systems on ships or spacecraft.

Abstract: An isolation improvement circuit for a dual-polarization antenna, the dual-polarization antenna consisting of both a transmitter and receiver antenna for simultaneously transmitting a transmission signal and receiving a receiver signal, in which the transmitter and receiver antennas are configured so as to be mutually orthogonal either by physical or electrical orientation in order to reduce how much of the transmitter signal is picked up by the receiver antenna. The isolation improvement circuit reduces the level of transmitter signal appearing at the output port of the receiver antenna by providing a time-delayed transmission signal that destructively interferes with the transmitter signal picked up by the receiver element.

Abstract: A communication network consisting of two types of links. A first link is one in which a source-transmitted signal is cancelled at the receiver associated with the transmitter, so that the desired received signals can be extracted from a composite received signal, the composite received signal consisting of the source-transmitted signal relayed from the relay station along with the desired received signals from one or more other users, plus additive noise. The other link is one in which no cancellation is performed on the received composite signal.

Abstract: A booster system for transmitting a received wave after amplifying it comprises a receiving antenna section, a carrier combining section, a transmitting section, a transmitting antenna section and a parameter control section. The carrier combining section multiplies a canceling signal by a cancel parameter to obtain a replica signal, then combines it with a received signal in at least one of the radio frequency band, the intermediate frequency band and the base band, and derives a combined base band signal from the combined signal. The transmitting section generates a send signal and a canceling signal by using a signal demodulated through the demodulation of the combined base band signal. Based on the combined base band signal and the canceling signal, the parameter control section determines a canceling parameter such that the power of the combined base band signal is reduced, the parameter being provided to the carrier combining section.

Abstract: Intermediate frequency Fif output from a first frequency mixer passes through IF filter which attenuates a noise level at a frequency of a difference between receiving frequency Frx and output frequency FL2 from a second local oscillator to a level such that the a transmitting noise produces no receiving sensitivity suppression, whereby the intermediate frequency becomes one that possesses a sufficiently low noise level compared to a sensitivity level of a receiver. After the intermediated frequency is converted to a transmitting frequency by a second frequency mixer, in the intermediate frequency which increases its noise level by a gain obtained by the circuit components disposed behind first frequency mixer, a receiving band noise is removed by a transmitting filter having an attenuation amount at a receiving band equal to the gain obtained by the circuit component disposed behind the first frequency mixer.

Abstract: The invention is a repeater for a telecommunications transmission system such as a CDMA wireless system. The repeater reduces leakage by using a feedback signal whose amplitude and phase are adjusted in response to the amplitude and phase of a sampled input signal when a switch turns off the normal output of the repeater for a short period of time. In one embodiment, a pilot signal is transmitted during this time period so that the sampled input is the leakage signal. In another embodiment, the sampled input is the normal transmission signal received during the time period.

Abstract: Adaptive apparatus for eliminating interference from a received signal provided on a transmission line caused by radio transceivers includes a plurality of frequency tunable filters tuned to the operating frequency of a corresponding transmitter. The transmitter signal of each transmitter is provided to a corresponding filter. The filter eliminates the non-essential transmission of harmonics, intermodulation and wideband noise of the transmission signal. The adaptive apparatus includes a plurality of cancellation devices wherein each cancellation device receives a sample of each filtered transmission signal and the received signal. The received signal includes an error portion generated by the transmitters and a non-error portion corresponding to the signal received by the antenna. Each cancellation device compares the corresponding sampled transmission signal with the sample of the received signal.

Abstract: Apparatus for simultaneously receiving a plurality of AM signals of widely differing strengths on a set of carrier frequencies and for re-broadcasting the AM signals at equalized strengths at either the original carrier frequencies or at a set of carrier frequencies that are offset from the original from the received frequencies by a constant difference. Regardless of whether the re-broadcast carriers are offset, the system includes provision for interrupting the re-broadcast signals by an audio message of general interest or public safety.

Abstract: A method and apparatus system for cancelling a leak-through signal component generated by an interfering transmitter from a received/leak-through signal comprising a multiplier for multiplying the received/leak-through signal by a reference signal provided from the interfering transmitter. The system further includes an integrator for integrating the output of the multiplier to generate an estimate of the gain and phase of the leak-through signal component. A gain and phase adjustor, responsive to the generated gain and phase estimates, is also included for adjusting the gain and phase of the reference signal to generate a cancellation signal that is a substantially gain and phase matched estimate of the leak-through signal. The generated cancellation signal is then subtracted from the received/leak-through signal to substantially cancel the leak-through signal component.

Abstract: A radio relay system including a water-proof conductor housing on which is located a pair of antennas, one antenna being used for transmitting and receiving radio carrier wave signals of a first and a second frequency, respectively, while the other antenna is used for transmitting and receiving radio carrier wave signals of a third and a fourth frequency, respectively. A skirt for each of the antennas is located adjacent the antennas on the housing, one skirt has a length equal to a quarter of the wavelength of the first frequency while the other skirt has a length equal to a quarter wavelength of the third frequency.

Abstract: Linking of radio paging transmitters is accomplished through the utilization of TDM transmission on the same channel as that assigned to the paging service, thus eliminating the necessity of a separate channel for linkage of the remote transmitting sites to a central originating location. For data transmission, real time data is broadcast via a direct RF link to buffer storage at each of the remote transmitting sites, with the data being read out to each of the paging transmitters from the local buffers in a phase-adjusted synchronized fashion under control of sync signals generated at and broadcast from the central originating location. The data transmission rate from the central originating location to the remote sites may be made significantly higher than the radio paging data rate in order to minimize link time to minimize linkage overhead by reducing the amount of time the channel is used for linkage as opposed to paging.

Abstract: A cellular communication system booster has plural narrowband and wideband channels each having down mixers, local oscillators, IF filters, and amplifiers for amplifying communication signals. On a narrowband channel preferably not in use, and preferably in a time-multiplexed manner, a reference signal of known signal strength is substituted at the output amplifier in lieu of a normal communications signal. When this amplified reference signal is broadcast at the output antenna a portion of the signal is feed back to the input antenna due to imperfect isolation between the antennas. This feedback signal is measured by a Radio Signal Strength Indicator (RSSI) circuit at the point of its receipt into the IF filter of the narrowband channel. The measured signal strength serves as a measurement of signal isolation/feedback between the antennas.

Abstract: A system for stabilization of the coupling value between the transmitted radio signals resulting from cross polar discrimination, using the transmit power level control in radio link systems formed of several radio channels using multilevel QAM modulation. A first control signal is derived for each RF channel and a second control signal is derived for the adjacent channels. The first and second control signal are then combined to derive threshold signals. The threshold signals are multiplexed with station identification signals and this multiplexed signal is multiplexed with other service signals. The twice multiplexed signal is then inserted in the frame of a main information signal. The signal is demultiplexed to derive a remote transmit power control signal. The atmospheric precipitation condition is evaluated through statistical control of the bit error rate. A local transmit power control signal is derived.

Abstract: A one frequency repeater includes a receiver for receiving a reception signal through a receiving antenna, a variable frequency characteristic filter for generating a signal for cancelling an interference signal caused by leakage of a transmission signal into a receiving antenna, an adder for adding the interference signal and the reception signal, a demodulator for demodulating an output signal from the adder, a data converter for converting an output signal from the modulator, a modulator for modulating a carrier according to an output from the data converter, and a transmitter for transmitting from a transmitting antenna an output signal modulated by the modulator. The variable frequency characteristic filter receives the signal modulated by the modulator, is controlled in response to a control signal including the output from the data converter, and supplies the interference cancellation signal to the adder.

Abstract: The system for measuring the spillover signal from a transmitter to a receiver in a same frequency repeater or a booster has a frequency conversion device which slightly offsets the transmission frequency from the reception frequency, and a signal detector which measures the offset frequency component in the reception signal. The offset frequency is around 100 Hz, which is higher than the fading frequency, and low enough not to affect the operation of receivers. The measured spillover level is used to control the gain of the repeater, and/or to cancel the spillover signal, so that the repeater has the maximum gain without suffering from oscillation.

Abstract: Apparatus for isolating a radar receiver from a radar transmitter in a continuous wave, single antenna radar system where a circulator connects transmitter, receiver, and antenna. The apparatus includes a reactive element which reflects back through the circulator a portion of a transmission signal provided from the transmitter through the circulator to the antenna. The reflected transmission signal portion is equal in magnitude and opposite in phase to a leakage portion of the transmission signal transmitted by the circulator from the transmitter to the receiver. The reflected and leakage signal portions cancel in the circulator to enhance the isolation of the receiver.

Abstract: A digital microwave radio repeater using the same carrier frequency for the transmitter and the receiver carriers for improving the frequency utilization efficiency. The transmitter-to-receiver interference signal is cancelled by producing an estimated-interference signal of the interference signal from the digital baseband signal by the use of a transversal filter and by subtracting the estimated-interference signal from the received signal. The estimated-interference signal is also produced by frequency shifting a digital modulated signal in the transmitter. The transmitter carrier frequency is locked to the receiver carrier frequency by the use of a phase-locking technique, so that the interference signal is reduced.

Abstract: An electronic process and device are provided for decoupling a receiving antenna situated in the immediate vicinity of a transmitting antenna transmitting a frequency modulated interfering signal.The process consists in superimposing on each of the signals for the static control of variable attenuators, disposed in a regulation loop for cancelling out the interfering signal received by the antenna, a signal whose amplitude is proportional, at all times, to the difference between the carrier frequency of the interfering signal and the instantaneous value of its modulation signal .phi.'.sub.B (t).

Abstract: An apparatus for minimizing the spillover signal from the transmitter to the receiver in a same frequency repeater includes a mechanism for generating a receiver first injection signal carrying the modulation component of the transmitter signal, and a first mixer for mixing the received signals and the first injection signal to produce a first IF signal having one unmodulated IF component signal and another modulated IF component signal. A correlation and cancellation circuit is utilized to cancel the unmodulated IF component signal. A mechanism is provided for generating a second injection signal which carries the modulation component of the transmitter signal. A second mixer mixes the first IF signal and the second injection signal to produce a second IF signal such that the modulation component of the spillover signal is substantially cancelled.

Abstract: A single channel, or push-to-talk transceiver includes a switch-controlled Gunn oscillator for generating the carrier frequency during transmission and a continuously operating local oscillator for demodulation of a received signal in the receive mode. When the push-to-talk switch is depressed, the transmit oscillator is energized and leakage signals cross the circulator to the receiver portion of the transceiver. An RF AFC loop between the transmitter and receiver portions includes a low-pass filter at the preamplifier output which serves as a simple slope discriminator. This output is detected and used to close an electronic servo loop. Once closed, this servo loop locks the transmit oscillator frequency relative to the local oscillator thereby preventing frequency drift during warm-up.

Abstract: Disclosed is an in-band, non-sampling, real time VHF radio relay or signal epeater for use in two-way, multi-hop remote sensor data links. Each signal repeater comprises a transceiver which includes interference cancellation circuits for preventing the high level signal produced by the radio repeater's transmitter section from desensitizing the low noise RF amplifier circuitry incorporated in the front end of the radio repeater's receiver section. Such apparatus is utilized to implement a remote sensor data collection network consisting of a plurality of subject radio repeaters and several sensors normally arranged in groups. The data which flows over the relay network can either originate at the sensors and flow to a read out station or it may originate at the read out station and flow to the sensors. Sensor originated information may be either digital or analog, or both, while read-out station originated information is digital only. The relay operates with either analog or digitally-modulated signals.

Abstract: A same-frequency repeater used in a system that has at least one other same-frequency repeater is protected against oscillation resulting from feedback of signals broadcast by the same-frequency repeater, either directly or after reception and rebroadcast by another same-frequency repeater. A tag is added to the signal to be broadcast from the first SFR, and one tag detection and canceling system is added to the first SFR for each SFR, in the system. Each tag detector senses the presence of tagged signal received by the first SFR and adjusts amplitude and phase of an appropriately delayed signal that is fed back to cancel the signal containing tag.

Abstract: A duplex transceiver comprises a receiver aerial and a transmitter aerial, a pair of balanced mixers each fed from the transmitter aerial and from the receiver aerial, a phase quadrature device interposed in a signal path between one of the aerials and a first one of the balanced mixers, a multiplier fed from the mixers, an oscillator/modulator arrangement feeding the transmitter aerial and phased locked to the frequency of a received carrier signal by means of a phase control signal fed from the multiplier, a first phase detector fed from that first one of the balanced mixers which is fed via the phase quadrature device, a delay device via which the said first phase detector is fed from a second one of the balanced mixers, thereby to provide a control signal which is fed back to control the balance of the first balanced mixer, and a second phase detector fed from the second balanced mixer with an undelayed signal and, via the delay device, with a delay signal from the first one of the balanced mixers, thereb

Abstract: Spillover of RF signal from the output of a same-frequency repeater to the input is reduced by attaching a tag to the output signal. The tag is double-sideband, suppressed carrier to place two spectral spikes, one above and one below the carrier. The tag is applied to the signal in the IF. A tagged signal of variable amplitude and phase is added to the received signal so as to cancel the tag and hence the spillover signal, leaving only the desired signal. A feedback system controls the amplitude and phase of the cancelling signal.

Abstract: Method and apparatus for improving the r.f. isolation between a transmitting and receiving antenna disposed at respectively corresponding spaced apart but relatively adjacent locations. A special compensation radiator is provided at the transmitting and/or receiving antenna site and fed from the same r.f. input/output which feeds the main antenna. The direction, magnitude and phase of r.f. energy radiated and/or received from the compensating radiator are chosen so as to substantially cancel the undesirable r.f. energy otherwise directly received by the receiving antenna from the transmitting antenna.