Abstract: In a radio receiver in accordance with the heterodyne principle or with the homodyne principle, two additional transmission channels are provided for interference suppression. The two additional transmission channels have a different degree of distortion. Either mixing with a heterodyne oscillator signal takes place in each of the two transmission channels and the resultant intermediate frequency signals or baseband signals are added in phase opposition to give a sum signal, or the output signals of the two additional transmission channels are added in phase opposition to give a sum signal and the resultant sum signal is mixed with a heterodyne oscillator signal to give an intermediate frequency signal or baseband signal. The signals obtained after addition and mixing and derived from the output signals of the two additional transmission channels are frequency-selected and demodulated, and the demodulated signal is used for gain control.

Abstract: Crystal oscillator and method which in one embodiment have a crystal element connected in a positive feedback loop with a charge amplifier and an integrator, with the gain of the loop being maintained at a level of unity. Compensation is provided to offset the effects of shunt capacitance in the crystal element, and precise phase control is maintained around the loop. In other embodiments, a crystal element is connected in a series feedback loop with a buffer amplifier, and operation is provided by maintaining the oscillation signal at level at which distortion, clipping, and saturation do not occur. Compensation for shunt capacitance across the crystal element is provided by applying a compensation signal which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance.

Abstract: A receiver 200 automatically compensates for intermodulation of an input signal. The receiver 200 is preceded by a receiver front-end 105 which is coupled to antennas 100-102 receiving the signal. The gain of the antenna path/frequency is calibrated and stored for all combinations of antenna path/frequency. When a signal is received, the receiver 200 determines the correct stored gain factor representing the antenna receiving the signal and the frequency of the signal. The gain factor is compared against a predetermined threshold, and if the gain factor is greater than the threshold, an attenuator 400 placed at the front of the receiver 200 is inserted to optimize signal intermodulation. If the gain factor less than the threshold, the attenuator 400 is bypassed to optimize the sensitivity of the receiver 200.

Abstract: Apparatus for synthesising a composite signal (53) which has spaced first and second frequency channels of which each has an independently predetermined power, the power of the first channel being substantially below that of the second, and each channel being frequency modulated by an independent signal, the apparatus including a generator (51) responsive to the independent signals and to representations of the said powers and to the channel spacing to generate a composite modulation signal, and a single, high purity radio frequency source (52) connected for modulation by the output of the composite modulation signal-generating generator to produce the composite signal (53).

Abstract: A noise blanker is disclosed which blanks out impulse noise emanating from the alternator, ignition systems of motor vehicles, and other sources. This is accomplished by delaying an input IF signal while generating a blanking gate pulse occurring at the same time as the noise pulses. These blanking pulses are then used to turn off the delayed IF signal precisely where the noise occurs, resulting in noise-free audio reception. The noise blanker operates to detect noise pulses by detecting the leading edge of any narrow pulse which is received at the front end of the receiver and is reflected in the IF input signal. At the same time, by virtue of the operation of an AGC amplifier the noise blanker's vulnerability to interference or capture by continuous-wave signals is reduced.

Abstract: A sampling signal analyzer in which the frequency of an input signal to be measured is initially ascertained, an appropriate sampling frequency is then determined, data needed to reconstruct the wave form of the input signal is acquired, and the input signal wave shape is reconstructed with a calibrated time axis and preferably displayed. The sampling signal analyzer synthesizes a sampler drive signal to enable continuous sampling of the input signal and therefore has the advantage over known data sampling signal measurement instruments that it is not triggered directly in response to the level of the input signal to be measured. Instead, sample timing is based on numerical analysis of the intermediate frequency (IF) signal produced by the sampler. The IF frequency can be an arbitrarily low frequency, which allows digitizing and digital signal processing for aligning measurement data from sweep to sweep with precision.

Abstract: A receiver suitable for use in a radio-telephone system for recovering data from encoded, quadrature-modulated communication signals employs a feedback arrangement for suppressing cross-talk between the receiver's in-phase and quadrature channels to improve data recovery rates during decoding. The receiver converts in-coming analog communication signals into in-phase and quadrature digital signals, which may have cross-talk components. The receiver has an attenuator for subtracting feedback signals from the in-phase and quadrature digital signals to produce cross-talk-attenuated in-phase and quadrature digital signals, a decoder for decoding the cross-talk-attenuated in-phase and quadrature digital signals to generate first and second data output signals, and the above-mentioned feedback arrangement, which preferably employs a recoder and cross-correlation techniques, for generating the feedback signals.

Abstract: The present invention relates to an economical yet effective technique for locating and defeating intentional or unintentional interfering signals transmitted to a commercial communications satellite on a channel-by-channel basis. The satellite arrangement includes a first and a second configuration of hybrids and Variable Power Combiners (VPCs), respectively, that concurrently combine the channels received from a plurality of ground regions for delivery to at least one input multiplexer. In one arrangement, the corresponding channel outputs from the at least one input multiplexer, are each connected to a different input of a separate Single Pole Double Throw (SPDT) switch. Channel switching is accomplished by transmitting commands to the VPCs and SPDT switches from a command earth station. Noting the presence or absence of the interfering signal for a given channel switch and VPC setting will provide the location of the interferer and the elimination of the interfering signal.

Abstract: There is disclosed a method and apparatus for demodulating an R.F. modulated signal having a known carrier frequency Fo. A first reference signal of a frequency matching approximately the carrier frequency Fo, is mixed with the input R.F. modulated signal to produce the demodulated signal. The first reference signal is generated by a reference oscillator which provides a second reference signal of a second distinct reference frequency, a voltage control oscillator for generating the first reference signal dependent upon the amplitude of an error signal applied thereto, a selectively variable divider circuit for receiving and dividing the first frequency by a selected number to provide a third divided signal, and a comparator for comparing the phase of the second reference signal with that of the third divided signal to generate and apply the error signal to the voltage control oscillator.

Abstract: A television signal transmission signal comprises a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of a 6 MHz television channel, the center frequency of the Nyquist slope at the lower edge of the channel being substantially coincident with the frequency of the suppressed carrier, and a pilot signal in quadrature relation with the suppressed carrier. The suppressed carrier is modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency, with the frequency of the color subcarrier being less than the co-channel NTSC picture carrier by an amount equal to about fs/12. The received signal is demodulated by a synchronous detector in response to the received pilot signal and interfering NTSC beat components are attenuated by a linear filter having notches at fs/12, 5fs/12 and fs/2.

Abstract: A dual polarization transmission system for transmitting digital modulated signal each having a particular bandwidth by use of two polarized waves which have the same center frequency and are orthogonal to each other. The receiver side of the system demodulates radio frequency signals sent by a horizontally and a vertically polarized wave and coming in through a receiving antenna into IF signals. From the received signal of one polarization, an interference component of the other polarization generated on the basis of the cross-polar IF signal or demodulated signal is removed.

Abstract: In a cross-polarization interference conceller for use in a digital radio communication system which transmits digital modulated signals over radio frequencies having planes of polarization orthogonal to each other, signals from the interfering polarized wave are sampled with a frequency equal to double the frequency of the affected polarized wave and, after latching the sampled signals with the frequency of the symbol rate, interference cancelling signals are generated by adding the products of their multiplication with control signals. Therefore, the digital multipliers and the digital adders for generating the interference cancelling signals can be operated at low speed.

Abstract: In this radio receiver, the charge on a capacitor (14) controls the bandwidth of filters in the receiver's audio circuits. When tuning the radio, a bandwidth control circuit (13) forces this capacitor (14) to discharge, thereby forcing the audio path to be bandwidth restricted, thereby minimizing interstation noise reproduction.

Abstract: A series-feedback crystal oscillator has a crystal element in series with a buffer amplifier. The oscillator maintains a linear oscillation signal by using an amplitude control circuit to hold the oscillation signal to a certain level at which distortion, clipping, or saturation does not occur. A control signal indicative of the amplitude of the oscillation signal linearly multiplies the oscillation signal to control the amplitude of the oscillation signal. Shunt capacitance across the crystal is compensated for by connecting a compensating capacitor to the same input terminal of the buffer amplifier as is connected the crystal. A compensating signal, which is equal in amplitude but opposite in phase to the signal passing through the shunt capacitance of the crystal is fed to the input terminal of the buffer amplifier to cancel the effect of the shunt capacitance. A noninverted tracer signal is injected in the feedback loop and passes through the shunt capacitance.

Abstract: A receiver includes an interference canceller circuit which receives a corrupted signal and makes an estimate of the desired signal. Subsequently, an estimate of the interference signal is determined by subtracting the estimated desired signal from a delayed version of the received signal. The receiver forms a final estimate of the desired signal by subtracting the estimated interference from a second delayed version of the received signal.

Abstract: In a digital radio transmission system for transmitting independent dual data by using cross polarization, an interference canceller detects cross polarization interference either directly or indirectly. An interference compensating signal is generated and applied to the main signal to cancel the interference element. In a case where no interference element is present, deterioration of cross polarization discrimination from an interference cancelling circuit is prevented by first determining whether an interference element actually exists and applying the interference compensating signal only when it does exist. The interference compensating signal can be attenuated based on the value of interference element so as to prevent undo deterioration of the cross polarization discrimination when the interference element is minimal.

Abstract: For the reduction of noise signals, and particularly crosstalk signals, in measurement systems for analyzing emission or transmission processes and composed of a serial arrangement of a signal source (1), a measurement path (2) with or without a transmission test object (8), a detector (3), and a measurement and display circuit (5), an identification modulation is imparted to the signal component carried in the measurement path by means of repeated modulation (6, 9). The evaluation of the detector output signal may be performed with respect to a frequency which is free of the effects of the single modulation signals occurring in the detector output signal because of noise pick-up. Use of this method in homodyne systems for quadrupole parameter measurements further eliminates the effects of crosstalk reflections which typically occur in these systems.

Abstract: A cordless telephone of multi-channel access (MCA) type has a master station which includes a plurality of sets of transmitting and receiving circuits and communication channels are simultaneously opened between the master station and a plurality of remote stations or handset units.

Abstract: A noise blanker is disclosed which blanks out impulse noise emanating from the alternator, ignition systems of rotor vehicles, and other sources. This is accomplished by delaying an input IF signal while generating a blanking gate pulse occurring at the same time as the noise pulses. These blanking pulses are then used in turn off the delayed IF signal precisely where the noise occurs, resulting in noise-free audio reception. The noise blanker operates to detect noise pulses by detecting the leading edge of any narrow pulse which is received at the front end of the receiver and is reflected in the IF input signal. At the same time, by virtue of the operation of an AGC amplifier the noise blanker's vulnerability to interference or capture by continuous-wave signals is reduced.

Abstract: An interference cancelling system for cancelling or minimizing multiple signal components of a received signal in a radio receiver caused by an interfering signal from a radio transmitter which interfering signal follows multiple paths to the radio receiver includes a directional coupler which samples the interfering signal transmitted from the radio transmitter and provides a primary sample signal, a transmission link which defines a primary sample signal path from the radio transmitter to the radio receiver, a power splitter for dividing a portion of the primary sample signal path into a plurality of secondary sample signal paths, a power combiner for combining the plurality of secondary sample signal paths back into the primary signal path, and a 180.degree. hybrid coupled to the primary sample signal path and to the radio receiver. The secondary sample signal paths include delay lines and attenuator pads.

Abstract: An output processing circuit comprises a level detector for detecting a level of a signal corresponding to an intensity of a reception electric field, a gradient controller for controlling a gradient of a signal level detected by the level detector so as to correspond to the intensity of the electric field, a potential slider including a level shifter having a variable shift amount for shifting the level detected by the level detector by a predetermined amount, and an output control circuit for processing a reception signal in accordance with an output level from the potential slider. The output processing circuit includes a level shifter having a variable level shift amount for shifting the level of the signal detected by the level detector by a predetermined amount. The operation range of the output control circuit is continuously changed.

Abstract: A cross polarization interference canceller cancels interference polarization by providing a phase difference detecting circuit for detecting a phase difference between a main polarization and an interference polarization component of the main polarization, and a phase shifter for shifting a data discrimination clock signal of the interference polarization wave component.

Abstract: In a digital demodulation system (FIGS. 2, 3, 4, 7, 8) in a dual polarization radio system, having a first demodulator (4) and a first A/D converter (14) for a main signal, a second demodulator (5) and a second A/D converter (15c) for an interference signal (cross polarization signal), a transversal filter (18) for providing a compensation signal for cancelling an interference component in the main signal depending upon the demodulated interference component; the second A/D converter (15c) for providing the interference component in digital form is operated with a clock signal (102) regenerated in the main signal branch (4, 14) so that system operates correctly even when the main signal and cross polarization signal are in an asynchronous condition.

Abstract: A circuit for providing a mirrored version of a preselected transfer function includes a circuit having the preselected transfer function coupled to receive a signal modulated by a signal that is to experience the mirrored transfer function. The modulated signal at the output terminal of this circuit is mixed with a signal at a frequency that is greater than the carrier frequency of the modulated signal. The signal resulting from this mixing operation then is low pass filtered to provide the desired mirrored response.

Abstract: An adjacent channel interference suppressing system for an FM receiver which includes a first detecting device for amplifying and demodulating an intermediate frequency signal which has passed through a wide-band filter; a second detecting device for amplifying and demodulating an intermediate frequency signal which has passed through a narrow-band filter; a level adjusting device for receiving FM detection signals from the first and second detecting devices, and for complementarily and continuously adjusting the levels of the FM detection signals; and a control signal generating device for generating a control signal for controlling the level adjusting device according to the presence or absence of an adjacent channel interference.

Abstract: A system for preventing crosstalk in a stereo television receiver includes a signal selection switch for selecting between signals produced by a demodulator and signals received at an auxiliary input, a controller for generating a switching control signal and circuitry for muting the audio demodulator during channel change and when said auxiliary input is selected in response to said switching control signal.

Abstract: A tuner circuit for converting the frequency of an input signal with a local oscillator to a predetermined channel frequency. The tuner circuit includes an attenuation circuit responsive to the input signal for controlling the attenuated level of the input signal for reducing cross modulation and intermodulation distortions of the circuit, and for reducing distortion from the interference of the local oscillation, an amplifier circuit coupled to the attenuation circuit for amplifying the attenuated input signal, and a frequency conversion circuit coupled to the amplifier circuit for converting the frequency of the amplified input signal to a corresponding predetermined channel frequency.

Abstract: A privacy signal transmission system having a transmitter portion and a receiver portion. The transmitter portion digitizes an analog message signal and enciphers the digitized signal into a privacy signal before modulation and transmission to the receiver portion. The transmitter portion also extracts and modulates an analog error signal representative of the digitization error for transmission to the receiver portion. The receiver portion demodulates the digitized privacy signal and analog error signal, and after the privacy signal is deciphered and reconverted to an analog signal it is added to the received analog error to reconstitute the original analog message signal.

Abstract: In a radio receiver in which the received signal is converted by mixing into an intermediate frequency signal and/or a baseband signal, and in which an apparatus which generates an intermediate frequency signal and/or baseband signal and derives therefrom a control signal for suppression or reduction of interfering disturbances is provided, disturbance signals in the receiver are temporarily distorted in such a way that interfering disturbances in the receiver are suppressed or reduced.

Abstract: A television receiver which includes an automatic deghosting system synchronously demodulates IF television signals to generate baseband signals representing the in-phase and quadrature phase modulation components of the IF signals. A signal representing the phase difference between the carrier of the signal as broadcast and the carrier of the received signal, which may include ghosts, is generated from the in-phase and quadrature signals. This signal is applied to circuitry which develops signals proportional to the sine and cosine of the phase angle separating the broadcast carrier phase and the received carrier phase. The demodulated in-phase and quadrature phase baseband signals are multiplied by the sine and cosine signals in a complex multiplier to correct distortion resulting from the synchronous demodulation using the carrier of the received signal.

Abstract: A multiple frequency adaptive filter system for filtering undesired periodic and/or correlated interference signals contained in the same frequency band as a desired input signal. The filter system is capable of filtering at least two sinusoidal interference signals and incorporates a negative feedback loop having a transfer function of that of narrow band-pass multiple filter. The feedback loop using interference frequencies generates a corresponding interference enhanced output signal. This enhanced output signal is combined with the input signal whereby to produce an error signal which corresponds to the desired signal contained in the input frequency band. A double or quadruple filter system is also described as examples of the present invention. The filter system is suitable for removing modulated sinusoidal interference and particularly for reducing TV co-channel interference.

Abstract: A device for the automatic precorrection of non-linearities of a power amplification chain in a common channel television transmitter. The device has a first circuit for detecting the component to be corrected prior to amplification and addition of the components to be simultaneously amplified, a circuit for selecting the same components after amplification in a common channel, an attenuator of the latter component having an attenuation coefficient equal to the linear part of the amplification chain gain, a second detection circuit, an analog divider receiving the two detected components, whereof the output is coupled to the precorrection control input of a precorrection circuit upstream of the first precorrection circuit.

Abstract: A method and system is described for use with or in a satellite for compensating for cross coupling of satellite feeder link signals from a first channel of a first linear polarization as received by a first linearly polarized satellite antenna element with adjacent signals from a second channel. The second channel signals are at a generally orthogonal linear polarization. The system includes a second linearly polarized antenna element oriented orthogonal to the first antenna element for sensing the second channel signal, a gain controlled amplifier for reducing the gain of the second channel signal received at the second antenna element in inverse proportion to the sensed amount of cross coupling (depolarization) and adding the reduced gain signals that have been inverted to the first channel signals from said first antenna element.

Abstract: A radio receiver includes a first tuner, a first intermediate-frequency amplifier, at least two intermediate-frequency filters connected between the first tuner and the first intermediate-frequency amplifier and having difference frequency bands, a switching circuit for applying an output signal from the first tuner through a selected one of the intermediate-frequency filters to the first intermediate-frequency amplifier, an automatic gain control circuit for controlling the gain of the first tuner, a first phase-locked loop for enabling a local oscillator in the first tuner to oscillate at a frequency dependent on the frequency of a desired channel, a second tuner, a level detector circuit for detecting the level of an output signal from the second tuner, a second phase-locked loop for enabling a local oscillator in the second tuner to oscillate at a prescribed frequency, and a controller for controlling the first phase-locked loop to enable the first tuner to receive and issue a desired signal from a desire

Abstract: An apparatus for locating passive interference sources by using a pair of different RF signals in conjunction with an acoustic signal to generate intermodulation products in metal-to-metal junctions. The acoustic tagging technique utilizes a focused, high power beam of acoustic energy to mechanically vibrate the suspected offending junction. This mechanical vibration causes the level of intermodulation products that are generated in the junction to become amplitude modulated at the frequency of the acoustic illumination. The detection of the AM sidebands with a low noise RF receiver that is tuned to a particular intermodulated component, permits the offending junction to be located.

Abstract: Data-aided equalization and cancellation in digital data transmission over dually polarized fading radio channels is disclosed. The present invention uses decision feedback structures with finite-tap transversal filters. Subject to the assumption that some past and/or future data symbols are correctly detected, formulas and algorithms for evaluating the least mean-square error for different structures are disclosed. In a sequence of curves, the performance of various structures for a particular propagation model and several fading events are evaluated and compared.

Abstract: The present invention relates to a bootstrapping cross-polarization canceler which includes a noise-blanking limiter in the path before a correlation detector, and a processor which uses the output from the correlation detector to provide cross-polarization cancellation continuously or just during an outage condition where orthogonally received signals from a communication path include error rates which exceed a predetermined threshold. Alternatively, the processor can use the output of a pseudo error detection, which detects the error rate of the orthogonally received signals, when the error rates in the received signals are below the predetermined threshold in order to achieve convergence and cross-polarization cancellation in the canceler during a non-outage period.

Abstract: An interference wave detection circuit is designed so as to detect whether a beat due to the difference between two carrier wave frequencies is included or not in a received signal for a radio receiver. The detection circuit comprises circuitry for deriving a first binary signal corresponding to a level of a signal of voice frequency band obtained by demodulating the received signal and for deriving a second binary signal corresponding to a level of an envelope signal of an intermediate frequency signal from the received signal to provide a predetermined time difference between the first and second binary signals.

Abstract: The present invention relates to a cross-polarization equalizer/canceler which simultaneously performs cross-polarization equalization/cancellation in a tapped delay line (TDL) matrix. More particularly, the present equalizer/canceler receives the first and second orthogonally polarized digital signals on separate paths which are each split into a straight through and cross-over paths that include a TDL matrix comprising a separate TDL, with a predetermined number of complex taps, in each of the paths. The individual complex taps are appropriately adjusted in response to control signals from a tap adjusting means which derives the appropriate control signals from current tap signals and computed gradients derived from a predetermined algorithm. Accurate data decisions, however, are not needed.

Abstract: A canceller for eliminating the cross-polarization interference in incoming signals having polarizations which are orthogonal to one another is proposed. Each incoming signal is coupled to an associated adaptive filter. Each filter output is then summed with an associated one of the incoming signals which has a polarization orthogonal to that of the filter input signal. The signal sums formed are the canceller output signals. Adjustment of the adaptive filters so as to cancel the cross-polarization interference in each received signal is made in response to the incoming signals and the canceller output signals at selected times. During these times, circuitry for adjusting the adaptive filters examines spectral tones formed by the incoming signals and the canceller output signals.

Abstract: A multipath distortion reducing circuit particularly adapted for use with stereophonic receiving circuits in which the amount of mixing between right and left channels is reduced. In accordance with the invention, the envelope of the received FM signal is AM detected, and the envelope detected circuit is multiplied by the FM detected signal differentiated to provide a distortion cancelling signal. The distortion cancelling signal is summed with the detected FM signal to provide an output having a reduced multipath distortion component.

Abstract: A method and apparatus for demodulating quadrature phase shift keyed (QPSK) signals in a manner which reduces crosstalk between channels. The in phase (I) data is recovered first by recovering the carrier frequency and then multiplying the carrier frequency by the QPSK signal. The I channel is contemplated to require higher power and thus the crosstalk error in the recovered I channel data is relatively small. The QPSK signal is then modulated with the recovered I channel data. The resulting signal is multiplied by a carrier in quadrature to the recovered carrier to produce a second signal in which the crosstalk component has been eliminated and which contains the quadrature (Q) channel data with the I channel modulation. The I channel modulation is removed by modulating the signal again by the I channel data to produce a signal containing only the Q channel data.

Abstract: The present invention relates to a cross-polarization cancellation arrangement for digital radio channels wherein the cancellation arrangement comprises a canceller section and an equalizer section in cascade which operate at baseband. The canceller section includes both a main lobe estimator and detection circuits. The estimator provides a preliminary estimate of the main lobe of the pulse response in each of the two received orthogonally polarized signals. The detection circuits take each of the estimator means output signals, relating to each received polarized signal, and generates therefrom error control signals for adaptively updating the main lobe estimate signals from the estimator and also to provide an output signal which is used to cancel the interferer main lobe in the received oppositely polarized signal. The equalizer section then mitigates intersymbol and cross-rail interference in each of the orthogonally received signals.

Abstract: Undesired, interfering narrow band received signals in a Loran-C receiver are automatically rejected and the resulting distortion of the received Loran beacon signals caused by this rejection is automatically compensated for. The received Loran-C beacon signals in the band 90 to 110 KHz are fed through a narrow band, variable reject filter that rejects the undesired signal and is controlled by a feedback circuit in response to an interference detector in the receiver, so that the reject filter is automatically set at the interfering signal, rejecting it. Meanwhile, distortion of the received Loran beacon signals caused by the rejection is compensated for by an automatic circuit that varies a delay and add circuit in the Loran receiver to compensate for the distortion.

Abstract: An interference detector for use in determining when two carriers are producing a beat signal, comprising a low frequency automatic gain control amplifier 1' amplifying the received signal, a demodulator 5 and voice detector 6 for determining if the received signal is modulated, an amplitude detector 2 for measuring the amplitude of the amplifier output, a level measuring circuit 3 for measuring the beat component of the amplitude detector output, a comparator 4 for outputting an interference signal when the beat component exceeds a predetermined level, and a gate 7, 8 controlled by the voice detector for inhibiting the interference signal when the received signal is modulated.

Abstract: A radio interference detection device for use in a multi-channel access angle-modulation radio system. A detecting system detects a received signal prior to angle demodulation and produces an AM component of the received signal which is then rectified. A determining section then determines the level of the rectified signal for use in detecting interference in accordance with a determination result. The determining section includes an angle demodulator for angle-demodulating the received signal, a first comparator for comparing the angle-demodulated signal and the rectified signal, a second comparator for producing the detection signal when the rectified signal exceeds a predetermined level and a gate for passing the output signal from the second comparator only when the angle-demodulated signal is smaller than the rectified signal.

Abstract: A cross-polarization crosstalk canceller is equipped to receive two polarized waves which are orthogonally crossing each other. The cross-polarization interference is eliminated by multiplying the signal received on one side by a compensating coefficient and adding the resulting product to the signal received on the other side. A discrimination error represents the difference between the reception signal after compensation and the identified value thereof. An adder and a subtractor supplies the sum and the difference between the real part and the imaginary part of the discrimination error. A discriminator detects equality between the absolute values of the real part and the imaginary part of the signal received on the interfering polarized wave side and supplies a control signal depending on the quadrant to which the signal belongs. A switch combines and varies a combination of the signs of the outputs of the adder and subtractor in response to the control signal supplied by the discriminator.

Abstract: A digital transmission system is provided based on a cross-polarization band-sharing technique using a conventional antenna system which does not have a sufficient cross-polarization discrimination.An interference elimination circuit receives two mutually orthogonal cross-polarized waves and restores to at least one of the received cross-polarized signals, a baseband signal which is free of cross-polarization interference attributable to orthogonal cross-polarization crosstalk components. This circuit includes an orthogonal cross-polarization, crosstalk component adder having a weighting circuit for multiplying an interference component of the received orthogonal cross-polarized signals by a compensation coefficient. A compensating adder adds the output of the weighting circuit to a desired one of the received cross-polarized signals.

Abstract: The present invention is a method and apparatus for separating a plurality of radio frequency signals, comprising N number of signal collectors, each signal collector receiving the plurality of signals from a location different than the other signal collectors, and N being an integer from 2 to infinity; N number of transmission means, each transmission means conducting the signals received from one signal collector; and, N (N-1) number of signal cancellation means, each signal cancellation means having reference, error input and output lines, the reference line coupled to one transmission means and the error and output lines coupled to another transmission means; the signal cancellation means and transmission means being interconnected so that each transmission means is coupled to the output and error lines of N-1 signal cancellation means and the reference line of N-1 other signal cancellation means, and no signal cancellation means having the same transmission means coupled to their output and reference lin

Abstract: Apparatus is provided for inhibiting the generation of intermodulation products in a radio frequency amplifier coupled to a circulator. A control circuit generates a control signal exhibiting indicia of the amount of isolation provided by the circulator. The control signal is provided to a variable impedance synthesis circuit coupled to the circulation isolation port such that the impedance synthesis circuit exhibits the appropriate impedance to maximize circulation isolation. Intermodulation is thus minimized.