Abstract: An adaptive multipath fade equalizer is disclosed comprising differencing means (24) for forming a difference between an input equal to said equalizer and a component of the equalizer output signal and a feedback loop (21) for coupling said component of output signal to the differencing means. The feedback loop includes a fixed delay T (22), a variable attenuator (23) and a variable phase shifter (25). A phase control network (30) and an attenuation control network (31) compare selected portions of the frequency spectrum of the signal and adjust the variable controls to minimize the effects of multipath fades upon the signal. It is an advantage of the equalizer that it automatically adjusts for changes in the frequency and depth of the fade notch.

Abstract: A Loran-C receiver signal processor is disclosed which processes radio frequency Loran-C signal pulses on a point-by-point, cycle-by-cycle basis to provide the ability to locate on each pulse a tracking point which is used for accurate time difference of arrival measurements between successively received signal pulses or to improve the signal-to-noise ratio of the received signal.

Abstract: A noise removing apparatus is interposed between an FM detecting circuit and a stereo demodulating circuit. The noise removing apparatus is responsive to a pulsive noise included in the output from the detecting circuit to enable a first gate to interrupt transmission of the output. Although the stereo pilot signal is disturbed during the interruption period, the disturbed stereo pilot signal is canceled by a pseudo-stereo pilot signal (a signal similar to the pilot signal) separately generated, whereby the disturbed stereo pilot signal is prevented from being applied to the stereo demodulating circuit.

Abstract: A circuit for reducing the effects of polarization crosstalk occurring on a first RF signal due to a second RF signal, wherein the first and the second RF signals are two approximately orthogonally polarized RF signals having essentially the same frequency. The circuit comprises a first antenna and a first signal path (including RF and IF sections) for the first RF signal and a second antenna and a second signal path (including RF and IF sections) for the second RF signals. A first coupler diverts a portion of the signal on the second signal path into a first network comprising the series combination of a variable attenuator and a variable phase shifter. A summing circuit sums both the signal on the first signal path and the signal output from the first network with the result that the undesired signal on the first signal path is reduced. A logic circuit, responsive to the magnitude of one of the RF signals, controls the first network according to a predetermined relationship.

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 noise pulse suppression system for a receiver comprising holding means for holding an input signal level which precedes immediately the appearance of a noise pulse for a predetermined time duration upon appearance of the noise pulse in an input signal, subtracting means for determining the difference between the input and output of a delay circuit for delaying the input signal or a difference between the delayed output and an output obtained by holding the delayed output for a predetermined time duration, and adding means for adding a correcting signal obtained from the subtracting means to the output of the holding means. The circuit suppresses noise pulses in the input signal and does not generate additional noise.

Abstract: In order to reduce a discontinuity resulting from noise cancellation in an output signal of a noise canceller, particularly in lower-frequency components, a compensator (10) for use in, for example, a radio receiver, comprises two amplifiers (21, 22) for amplifying an input signal in which one or more noise pulses may be superposed. One of the amplifier output signals is given a delay relative to the other. Supplied with a noise detection signal, gates (26, 27) interrupts the amplifier output signals to cancel the noise pulse that substantially simultaneously appears in the both signals. A combination of capacitors (31-33) superposes one of the noise-cancelled signal on the other during presence of the noise pulse to provide an output signal in which the discontinuity is compensated for.

Abstract: Apparatus and method for controlling the crosspolarization of signals in a satellite communications, frequency reuse system. Each earth station in the system includes one crosscoupling network that compensates for the crosspolarization of signals transmitted by such earth station uplink to the satellite due to the propagative medium around such earth station, and an adaptive feedback control system having another crosscoupling network that compensates for the crosspolarization of signals received from the other earth stations due to such propagative medium around such earth station.

Abstract: A code tracking loop for a spread spectrum receiver includes a pair of mixer circuits to which phase offset or relatively delayed pseudo noise code signals are applied and combined with an incoming IF spread spectrum signal. The output of the mixers are coupled to a sum and difference hybrid. The hybrid produces a sum signal corresponding to the sum of the mixer outputs and a difference signal corresponding to the difference between the mixer outputs. These sum and difference signals are separately filtered, amplified and then coupled to a further mixer or phase detector. Appropriate AGC circuitry is controlled by the envelope of the sum signal to adjust the gains of the respective amplifiers. The output of the phase detector is proportional to the difference between the squares of the outputs of the hybrid and represents the phase of the sum signal relative to the difference signal.

Abstract: A channel level adjusting apparatus for equalizing the amplitude level of the received television signals of a plurality of channels. The channel level adjusting apparatus is designed so that when the input amplitude level of the television signals of a relatively small number or at least one channel is different from the more nearly equal or uniform input amplitude level of the television signals of the remaining relatively large number of channels, only the television signal or signals of the higher amplitude level are taken out, attenuated to a desired level and then combined, with a 180-degree phase difference, with the television signals of all the channels, thus making the television signal or signals of the higher input amplitude level more nearly equal in amplitude level to the television signal or signals of the lower input amplitude level and thereby generating the television signals of all the channels having relatively uniform amplitude levels.

Abstract: A television receiver in which video IF signal is detected to produce a sound IF signal which is then detected to produce a sound signal, while at the same time video signal is produced by detecting the video IF signal. A buzz cancelling system is provided in which phase-modulated component of the video IF signal is detected or, alternatively, the detected video signal is differentiated thereby to produce a buzz cancelling signal which is then synthesized with the sound signal to cancel out the buzz component contained therein.

Abstract: Continuously variable phase shift is obtained by means of two variable phase shifters (20,21) located in two separate, switchable parallel wavepaths (18, 19). The first phase shifter (20) is variable over, at least, the range between zero and 180 degrees. The second phase shifter (21) is variable over, at least, the range between 180 degrees and 360 degrees. Switching means (22, 23) are provided for switching the signal to one or the other phase shifter. A control circuit (16) simultaneously causing the phase shift through the two phase shifters to vary in the opposite sense. When maximum phase shift is reached, the control circuit switches the signal from one phase shifter to the other, thereby providing continuously variable phase shift through the network.

Abstract: A cross-talk component cancellation circuit is used in an angle-modulated wave signal transmission system for transmitting first and second angle-modulated wave signals of at least two channels, wherein a cross-talk component of the second angle-modulated wave signal is admixed in the first angle-modulated wave signal.