Abstract: A receiver for processing signals transmitted through a dispersive medium which receiver provides received signals at a plurality of diversity channels and uses adaptive equalizer circuitry for providing an adaptive weighted equalizer output signal. An error signal is derived at an error circuit in response to the equalizer output signal and to a reference signal, the error signal being correlated at a correlator with the adaptive weighting signals at each weighting section of the adaptive equalizer circuitry to generate weighting factors for use in such weighting sections. Scale factor circuitry responds to a signal having an amplitude which is a reliable estimate of the amplitude of the adaptive equalizer output signal and to the reference signal to provide a scale factor by which the reference signal is multiplied at a multiplier prior to its use in deriving the error signal.

Abstract: Sidelobe jamming in dual diversity troposcatter link receivers is effectively suppressed by providing an auxilliary low power antenna, the output of which is differenced from the high power main antenna signals prior to processing in the receivers's dual diversity demodulator. The auxilliary antenna power is substantially equal to the sidelobe power of the main antennas. The auxilliary antenna receives jamming power that is comparable to the jamming power received by the main antennas. However, it receives much lower desired signal power. Differencing of the signals therefore, cancels jamming power with minimal effect on the desired signals.

Abstract: A signal processing system in a transmitter/receiver system for reducing undesired amplitude, frequency and/or phase distortions arising due to variations from transmitter pulse to transmitter pulse. A plurality of sequential samples of transmitted pulses are averaged and a plurality of filter coefficients are determined therefrom. The coefficients are used in a plurality of filters which respond to a plurality of sequential samples of received pulses, the filters providing output signals in which such distortions are reduced.

Abstract: A channel propagation simulator simulates a multi-diversity branch signal channel, which simulator uses in a preferred embodiment appropriate filter means, such as a plurality of tapped delay lines 11, 14, each capable of representing the impulse response of a diversity branch by means of correlated tap multipliers 12, 12A, 15, 15A . . . 15N, i.e., multipliers using correlated weighting signals 12', 12'A, 15', 15'A . . . 15'N as supplied from a matrix weighting correlator 19. The correlated weighted signals are combined for each diversity branch by suitable summation circuits 13, 16 to provide the diversity branch simulated outputs. By using correlated weighting signals, the simulator can more accurately reproduces the statistical behavior of a given communications link and verify that a given modem will satisfy the communication link specifications.

Abstract: An adaptive power equalizer circuit for use in a spread spectrum receiver system which includes an antenna system 12, 13 and a receiver 11, the circuit comprising adaptive power inversion circuitry 15 for producing a first signal having a minimized power level and a second signal having a substantially higher power level than that of the first signal. Such signals are supplied to a power equalizer circuitry 16 which equalizes the power levels thereof, such equalized power level signals then being combined in a suitable combiner circuit 30 for producing an output receiver output signal for the receiver 11.

Abstract: An apparatus for simulating the characteristics of a signal channel which uses two or more cascaded delay lines each of which in one embodiment has a single input and a plurality of tapped outputs. The tapped output signals from each delay line are each multiplied by randomly characterized signals and the multiplied signals are combined to supply an input signal to the next succeeding delay line. The input signal to the first of the cascaded delay lines is the channel input signal and the output of the last of the cascaded delay lines is the simulated channel output signal. The randomly characterized signals associated with all but one of the delay lines may be signals having random polarities or having random phases while the randomly characterized signals associated with the remaining one of the delay lines has Gaussian characteristics.

Abstract: A signal multiplier for multiplying first and second input signals each having time-varying amplitudes and relatively wide bandwidths in which a first input signal is added to at least one sinusoidal reference signal having an amplitude larger than that of the first input signal. The amplitude of the signal so produced is limited and the limited amplitude signal is multiplied by the second input signal to produce an unfiltered signal. The signal components thereof having undesired frequency spectra are then filtered to produce a signal proportional to the product of the first and second input signals.