Abstract: An interference cancellation circuit which can remove the interference signal caused by other systems and contained in received signals. The interference signal can be cancelled even if the interference signal is not directly obtained or plural interference signals exist, or the interference signal is a wide band signal or raster interference simply by receiving two signals which have passed through different transmission paths, combining the main signals contained in each of the received signals in a manner to offset each other to the extract interference signal, and removing the interference signal component from the received signal based on the expected interference signal.

Abstract: Undesired signals detected by a main antenna are cancelled by corresponding interference cancelling signals. The output of the main antenna is frequency converted to IF region and decomposed into first and second main baseband components. Decision circuits are provided for making a decision on whether each of the first and second main baseband components exceeds each of multiple thresholds and produces multibit codes as well as error signals. Auxiliary antennas respectively detect the undesired signals and feed auxiliary frequency converters for translating the frequency of the respective outputs of the auxiliary antennas to the intermediate frequency. Auxiliary quadrature demodulators are provided for respectively decomposing the output of each auxiliary frequency converter into first and second auxiliary baseband components. Correlations are detected between the first auxiliary baseband components and the first error signal and between the second auxiliary baseband component and the second error signal.

Abstract: A receiver for a space diversity radio transmission system, the receiver including a diversity combiner (CD) and a diversity control circuit (7) which is responsive, inter alia, to a distortion value (F). If the receiver includes a self-adaptive equalizer (6) in the transmission path of the composite output, the control circuit may calculate the distortion value from the coefficients (ai, bi) used to control the filter portion (EG) of the equalizer. If the combiner is also responsive to an insufficient power value (G), the distortion value may be added to the insufficient power value in order to obtain a single control magnitude (8) which is used for controlling the diversity combiner in a manner that avoids any abrupt transition between the low power mode and the low distortion mode.

Abstract: A method of servo-controlling the instant of regeneration in a digital transmission in which a carrier is modulated along two axes in quadrature, in which the optimum instant of regeneration is sought on one of the paths (path X) by manual adjustment, the method being characterized in that two corresponding samples of the phase impulse response on the two paths are compared and the offset of the instant or regeneration on the second path (path Y) is adjusted so that the two samples of heeimoule essonpe enn tt bb enual.

Abstract: To increase the fidelity of radio reception in a moving receiver, for example a car radio, the signals received from various antennas on the radio are mixed with a carrier in the receiver, and the resulting mixed signals, directly and 90.degree. phase-shifted, are added to a summing signal, in which, additionally, the phase positions of the direct and 90.degree. phase-shifted signals are changed in dependence on the phase difference between the respective intermediate frequency mixed signal and the overall summed signal in a direction to maximize the summed signal (u.sub.s).

Abstract: A diversity combiner is provided for combining two received radio signals having the same frequency and modulation. For each of the radio signals (s, s') there is included a mixer (1, 1') with an associated voltage controlled local oscillator (2, 2') and a following intermediate frequency filter (3, 3') for generating an intermediate frequency signal (m,m') and a phase comparator (5, 5') for comparing the intermediate frequency signal with a reference signal (a) originating from a weighted aggregate (e) of the intermediate frequency signals (m, m). Each phase comparator (5, 5') sends a signal responsive to the phase difference and which controls the frequency of the local oscillator (2, 2'). The weights of the sub signals can be varied such that the quotient of the contribution of the sub-signals to the aggregate can be caused to correspond to an arbitrary power, which is greater than or equal to one, of a corresponding quotient before the addition.

Abstract: A circuitry in a diversity unit of an FM receiver for a telephone system having at least two channels for receiving signals, and at least one phase-lock loop. The signals received by the channels which possibly differ from each in amplitude and frequency. Each channel comprises a mixer and a band-pass filter for forming an intermediate-frequency signal. The phase-lock loop has phase-lock branches operably connected between each mixer of the channels which comprises a frequency-phase comparator. The phase-lock loop equalizes the channel signals in phase and amplitude. The phase-lock loop further has a summation circuit for adding the channel signals which have been equalized. The frequency-phase comparator has a single phase-lock branch exiting therefrom along with a voltage-controlled oscillator connected to one of the mixers of one of the channels. The voltage-controlled oscillator has a switch on an input side thereof.

Abstract: The effects of multipath and other interference signals in communication receivers are reduced by implementing an adaptive array. The invention addresses a signal environment in which the directions of arrival and the time of arrival of the signal of interest and the unwanted multipath or interference signals are unknown. The feedback equation of the LMS adaptive array is changed so that a reference signal is not needed. The system uses the strongest received signal as the signal of interest and rejects the other received signals.

Abstract: A receiver adapted for in-phase combining of plural received signals includes a phase shift circuit for adjusting the phase of at least one of the received signals. The phase shift circuit is controlled by a phase control circuit which operates in response to variances detected in the gain control voltage of an AGC amplifier which follows the signal combiner of the receiver.

Abstract: An interference cancellation system at a receiver side for digital radio system has a first quadrature phase detector for demodulating the main signal. A second quadrature phase detector (or a phase detector) is supplied with the same reference carrier and clock signal as that of the first quadrature phase detector, for phase detecting an interference signal. A decision circuit is coupled with the first quadrature phase detector to provide a baseband signal. An error signal detector provides a difference between a decision level of a digital signal and an input of the decision circuit due to the interference signal. A correlation device provides a correlation signal between an error signal and a phase detected interference signal. A control device provides a compensation signal which has the same amplitude and anti-phase as those of the interference component included in the main signal according to the correlation signal.

Abstract: An adaptive filter (11) for use in a diversity receiver system (10) which includes circuitry (23, 24, 25, 26, 34) for determining the strongest received diversity signal or group of signals at each of a plurality of time delays or group of time delays and circuitry (27, 28, 29, 30, 31, 34) for calculating a weighting signal and for weighting only the strongest received diversity signal or group of signals at each of the time delays or group of time delays, the other received diversity signals at each time delay thereby being in effect weighted by zero. The weighted signals are then combined in a delay line (32, 33) having a plurality of taps at such time delays to produce an output receiver signal. In a particular embodiment, for example, the received signals are complex signals and the weights used for the strongest received diversity signal at each time delay are quantized weights selected from the group .+-.1.+-.j.

Abstract: A space diversity reception system which minimizes the inband amplitude and/or phase dispersion by controlling the phase shifter is described. According to the present invention, the interference waves in the two antenna outputs are combined in anti-phase condition. The phase shifter control direction is decided by the sign of the two parameters. One of them is difference between two antenna levels at the center frequency of the pass-band, and the other is the difference of the combined signal levels at the extreme edges of the pass-band. The control means comprises four detectors for detecting said levels, two subtractors for providing said level differences between them, and the control circuit for deciding the phase shifter control direction.

Abstract: A method for the reception and the detection of digital signals wherein at least two signals (s.sub.1, s.sub.2, . . . s.sub.M) having at least approximately the same information content are received and at least all signals (s.sub.1, s.sub.2, . . . , s.sub.M) but one are subjected to a phase shift. The shifted signals (s'.sub.1, s'.sub.2, . . . , s'.sub.M) are combined in a summing point, the sum signal (s) is fed to a detector for detection, a reference carrier (ca) is generated in a reference carrier generator and a coherent demodulation and detection is carried out in the detector by means of said carrier (ca). According to the invention a projection voltage (z.sub.k) defined by the equation z.sub.k =y.sub.Qk s.sub.Ik -y.sub.Ik s.sub.Qk is generated, wherein y.sub.Ik is a signal sample in the in-phase branch before threshold decision in the detector, y.sub.Qk is the signal sample in the quadrature branch before decision, s.sub.Ik is the detected signal in the in-phase branch, and s.sub.

Abstract: A space-diversity receiving system for microwave band radio communication including two antennas and receivers, an endless phase shifter, a hybrid combiner, a hybrid distributor, a voltage controlled oscillator, a signal mixer, a low pass filter, a detector, and a control circuit.Microwaves received by the antennas are detected by the receivers. One received signal is directly applied to the hybrid combiner. The other received signal is applied to the hybrid combiner via the endless phase shifter. The hybrid combiner combines these signals and outputs to the hybrid distributor. The hybrid distributor distributes the amplified output to as an intermediate frequency output and a sub output. The voltage controlled oscillator generates a series of sequential frequencies based on the control of its input voltage. The signal mixer mixes the sub output with the each sequential frequency output. The detector detects the mixed signal and transmits the detected signal to the control circuit.

Abstract: An improvement to a baseband system having a plurality of down converters feeding a single baseband receiver for assuring the same mean time to intercept while maximizing the probability of intercept as a multi-band, autonomous receiver. All channels of the converter unit are operated simultaneously and a unique tag is added to the output signal from each of the down converters whereby the signal can be identified by the balance of the system as to its associated converter. In one embodiment, the tag comprises an amplitude notch appearing on the output signal at a different time following the receiver threshold being exceeded. In a second embodiment, the tag comprises a frequency step added to and/or subtracted from each output signal at the same time following the exceeding of the receiver threshold. In a third embodiment, the tag comprises a phase shift applied to the output signal.

Abstract: Circuitry for use in an IF combiner, where main and diversity receiver path signals are combined. The circuitry generates an error signal for the purpose of controlling the phase of one of these signals by deriving a broad-band phase-modulated feedback path version of the signal. No modulation is introduced into the message channel. The feedback path version of the signal is quadrature modulated and combined with signals from the main and diversity receiver paths to generate an error signal providing maximum control loop sensitivity.

Abstract: The present invention relates to a space diversity combiner which includes two branches wherein separate multipath signals received from a remote source are propagated. The branch signals are combined and the combiner output signal is used for obtaining noncoherent spectrum measurements which are in turn used to account for both dispersion and noise in controlling the relative amplitudes and phases of the two branch signals to provide a maximum performance measure for the combiner.

Abstract: A space diversity system for transmitting digital microwaves is disclosed. Each of two antennas receives a direct wave and an interference wave. The output phase of one of the two antennas is controlled to combine an output thereof with that of the other antenna, so that the interference waves cancel each other and a vector sum of the direct waves is produced as a combined output. Even if the two antenna inputs are so much alike, the combined output level and thereby the signal-to-noise ratio is prevented from being lowered whereby error in identification is eliminated.

Abstract: An interference cancellation type space diversity system transmits digital microwaves in a sure and stable manner. Signals coming in through two spaced antennas are combined together into a single input signal and the composite signal is processed by a demodulator into a baseband signal which is identical with a transmitted signal. The demodulated baseband signal is processed by a frequency/amplitude characteristic detector network, which comprises a correlation circuit and an identification circuit, thereby controlling output phases of the antennas.

Abstract: A subscriber distribution terminal is connected to the transmission medium for serving a group of subscribers. Within the distribution control terminal is located a plurality of television converters. A local oscillator in each of the converters is controlled by a microprocessor, which establishes the channel selected from the multi-channel television signal received from the transmission medium. The output of each converter is connected to a subscriber drop which is connected to the subscribers television set.

Abstract: The stability of reception of information signals in a low-quality radio communication circuit is notably improved by a method and apparatus of diversity reception which, by means of the local oscillation frequencies of a plurality of receiving systems, permits one or more coherently interrelated received signals to be phase-locked in the phase-lock loops of the respective receiving systems and which, when any of the phase-lock loops has accidentally lost the phase-lock of the received signals, enables the lost phase-lock loop to resume normal phase-lock by borrowing and using, as its own local oscillation frequency, the local oscillation frequency of the phase-lock loop of one of the remaining receiving systems still locking the phases of the received signals.

Abstract: A space diversity receiver with a combiner in which the useful signals of two space diversity receiver branches are connected together with a summing amplifier in the IF frequency band, and wherein an electronically controlled phase corrector P is mounted in one of the receiver branches and in which a phase monitoring circuit provides an output signal to control the phase corrector and is connected at the output of the electronic phase corrector between the two receiving branches. The space diversity receiver is constructed in the simplest possible manner with the lowest possible electrical interference and provides that the phase monitoring circuit consists of a phase discriminator D1 to which the signal from one reception branch is supplied through an automatically gain control amplifier RV2 without phase shift and the signal from the other receiving branch is supplied with an identical automatically gain controlled amplifier RV1 and through a 90-degree phase shifter.

Abstract: An interference compensation system having a main antenna (1) which receives both the desired signal and the undesired interference signal I.sub.M, an auxiliary antenna (2) which receives only the interference signal I.sub.A, an amplitude-phase control circuit which modifies the amplitude and the phase of the interference signal I.sub.A from the auxiliary antenna (2) according to the control signals A+a.multidot.cos .omega.t, and B+a.multidot.sin .omega.t, to provide the output signal I.sub.VM, and a combiner (4) which combines said signals I.sub.M and I.sub.VM to provide the output signal I.sub.E which is considered to be free from the interference signal except for the very little residual component of said interference signal, where A and B change according to the difference between I.sub.M and I.sub.A, (a) and (.omega.) are amplitude and angular frequency of the output of the low frequency oscillator (7).

Abstract: In a diversity signal combiner, the weaker of the two signals is attenuated an amount that varies as a function of the phase angle between the two signals. When the phase angle is small, the attenuation is small and the two signals add together. As the phase angle increases, the attenuation of the smaller of the two signals increases. For phase angles between 90 and 270 degrees, the contribution of the smaller signal is negligible. In digital systems, improvements in the bit error rate can be realized by introducing a 180 degree relative phase shift in the wavepath of the weaker signal whenever the phase angle exceeds a specified threshold.

Abstract: A signal having the form cos (.OMEGA.t+.phi.) where .OMEGA. is the frequency of the signal and .phi. is a phase angle which may be zero is phase shifted to improve the results of the summation of such a signal with other signals having the same form but different phase angles.

Abstract: In a space diversity receiver, the relative phase of the two received signals is varied in manner to minimize amplitude dispersion in the combined signal. A phase control signal is derived from the combined signal by phase modulating one of the received signals, and then detecting the fundamental amplitude component induced by said modulation within two selected portions of the combined signal spectrum. The fundamental component of the envelope modulation of the weaker of the two signal portions is used to control the relative phase of the two received signals so as to minimize the amplitude dispersion in the combined signal across the band. In the absence of inband phase dispersion needed in order for the compensating phase shift to effect the two signal portions differently, a relative delay is introduced in one of the two received signal paths.

Abstract: A processing circuit (50) in a communication system performs multi-channel adaptive array processing using a summed reference technique. A plurality of adaptive modules (56 and 58) modify the magnitude and phase of antenna element signals from a plurality of antenna elements. The outputs of the adaptive modules are combined by a combiner (60) to produce a summation signal. A modem (64) processes and divides the summation signal into a plurality of reference channel signals on channels 1 through K. A summer (70) adds the reference channel signals together to produce a composite reference signal that is subtracted by a subtractor (74) from the summation signal to produce an error signal. The error signal is applied to the adaptive modules (56 and 58) which respond to nullify interfering and noise signals and to enhance the signal-to-interference ratio for the summation signal.

Abstract: A pre-detection maximal ratio combining system for a plurality of received signals is provided in which a plurality of control devices are arranged for controlling the phase and amplitude of each of a number of pre-detection signals corresponding to the received signals. The control devices operate by correlating the mutually orthogonal components of the pre-detection signals with a reference comparison signal, which is derived by combining the outputs of the several control devices into a combined signal, and normalizing the amplitude thereof.

Abstract: A receiver system for processing diversity channel signals to substantially eliminate future and past intersymbol interference (ISI) in received signals which have been transmitted through a time-varying frequency selective transmission medium. The system includes lattice filter means which provide forward error residual signals which are used for generating uncorrelated adaptive weighting signals which eliminate future ISI and decision feedback circuitry which provide uncorrelated adaptive weighting signals which eliminate past ISI.

Abstract: A space diversity reception system which minimizes the inband amplitude and/or phase dispersion by controlling the phase shifter is described. According to the present invention, the interference waves in the two antenna outputs are combined in anti-phase condition. The phase shifter control direction is decided by the sign of the two parameters. One of them is difference between two antenna levels at the center frequency of the pass-band, and the other is the difference of the combined signal levels at the extreme edges of the pass-band. The control means comprises four detectors for detecting said levels, two subtractors for providing said level difference between them, and the control circuit for deciding the phase shifter control direction.

Abstract: Effects of multipath fading and Doppler frequency spread in a single sideband radio communication system are largely overcome by separating (17) from a received signal spectrum, a pilot frequency component including those effects and using that component to accomplish both phase (36) and gain (38) corrections on an information-containing frequency component. Signals essentially free of those effects are provided (10) for controlling necessary frequency translations in the receiver. One illustrative embodiment (FIG. 4) is conveniently arranged for facilitating diversity signal combining.

Abstract: A method and apparatus for measuring Faraday rotation of a received rf signal. The disclosure describes a specific implementation of a simultaneous orthogonal polarization receiver which compensates for a 3 db loss due to splitting of a received signal into left circular and right circular polarization channels. The compensation is achieved by rf and modulation arraying utilizing a specific receiver array which also detects and measures Faraday rotation in the presence or absence of spin stabilization effects on a linear polarization vector. Either up-link or down-link measurement of Faraday rotation is possible utilizing the method and apparatus disclosed herein.