Abstract: This circuit compensates for phase variation introduced by the delay element in a PSK (phase shift keyed) demodulator. The signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a phase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are fed to a phase tracking circuit. This phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element. The fixed component of difference in phase between the delayed signal and the shifted signal is either a multiple of 180.degree. or an odd multiple of 90.degree. , depending upon the coding system employed.

Abstract: A differentially coherent signal detector capable of detecting arbitrary-even-ordered phase shift keyed signals, such as quadraphase (QSK), hex (HSK), octo (OSK), etc. In the case of QSK, the signal to be demodulated is split. One portion is delayed while the other portion is fed to a variable phase shifter and then to a hybrid splitter. The delayed signal and quadrature output of the hybrid splitter are fed to a quadraphase detector which recovers the information. The delayed signal and inphase output of the hybrid splitter are each fed to a phase tracking circuit via frequency doublers. The phase tracker controls the variable phase shifter in a manner which maximizes the detected signal by compensating for phase variations introduced by the delay element.

Abstract: The tracking signals of a monopulse satellite tracking system are optimized by aligning the phases of the azimuth and elevation channels (the "difference" channels) with the reference (or "sum") channel using an autophase controller and a simulated far field source in the near field. The autophase controller monitors the output of the tracking receiver and adjusts phase shifters along the transmission paths of the azimuth and elevation channels, in a manner to maximize the outputs of the receiver. The simulated far field source provides an alignment signal for the autophase controller. The simulated far field source consists of a signal generator, a near field probe, and near field phase compensators. The probe is positioned to avoid any nulls in the simulated tracking signal for the frequencies of interest. The probe is also positioned to limit the range of the phase shifts introduced by near field placement, for the frequencies of interest.

Abstract: A field effect transistor bias circuit is presented which exhibits a low impedance for small signals and a high impedance for large signals. This circuit uses an operational amplifier to provide a temperature compensated low impedance voltage source for the gate bias which is optimal for small signal operation. In the presence of a large signal, the gate begins to draw current. This causes the operational amplifier to saturate and transforms the bias circuit into a high impedance source, which is optimal for large signal operation.

Abstract: A high bandwidth transversal filter is described having an input impedance matching network, a tapped delay line, a plurality of weighting amplifiers, a distributed summing circuit, and an output impedance matching network. The delay line is implemented with a transmission line. The input impedance of this transversal filter depends on the inductance and capacitance of the transmission line and the capacitance of the inputs of each of the FET's used as weighting amplifiers. The gates of the FET's provide high impedance low loss taps of the delay line. The weighting is accomplished by either varying the drain current of the FET's or by using capacitive voltage dividers to apportion the tapped signals. The resulting weighted signals are applied to a distributed summing circuit which provides both high bandwidth summing and additional delays. This summer is also implemented with a tapped transmission line.