Trw Limited

Peter L McAdam

Arnold H Silver

Gregory A Shreve

Dale J Durand

Thomas G Schnerk

A control scheme for operating an oscillator/counter A/D converter so that it simultaneously provides frequency downconversion, band pass filtering and analog-to-digital conversion of an analog signal, where the analog signal includes a carrier wave modulated with information by any known modulation technique. The converter uses a superconducting, Josephson single flux quantum circuit operating as a voltage controlled oscillator. The voltage controlled oscillator receives the analog signal to be converted, and generates a series of sharp, high frequency pulses based on the characteristics of the carrier signal. The series of pulses are applied to a gate circuit that, depending on a gate control signal, either blocks the pulses or passes the pulses to either an increment or a decrement port of a digital counter. When the pulses are passed by the gate circuit, the counter circuit accumulates the pulses during a sampling period. The sampling period covers a range of gate control pulses so that the accumulation of pulses defines consecutive on/off periods of the gate control signal. The scheme provides for frequency conversion and eliminating or minimizing the amount of DC response present in the digital output signal.

Direct digital downconverter and method for converting an analog signal to a digital signal

A television signal encoding and decoding system providing a line-spin scrambled video signal with substantially reduced amplitude gaps and line tilt and a digitally-encrypted audio signal that can be transmitted within the bandwidth limitations of a conventional NTSC television signal. The television signal encoding system, located at a television transmitter, includes a video and an audio encoder. The video encoder selectively line spin scrambles, reverses and inverts certain video lines or video line segments to generate a line-spin scrambled video signal having amplitude gaps less than some desired value. The audio encoder digitally encrypts the audio signal and modulates the encrypted audio signal with a three-level partial response waveform to generate and encrypted audio signal that can be transmitted within the bandwidth limitations of a conventional NTSC television signal. The television signal decoding system, located at a television receiver, includes a video and an audio decoder. The video decoder applies line tilt compensation to the received line-spin scrambled video signal and then unscrambles the compensated scrambled video signal. The audio decoder demodulates and decrypts the received audio signal.

Secure television signal encoding and decoding system

Apparatus for acquiring and demodulating a communication signal employing a feedforward approach to minimize acquisition time. The apparatus includes a phase detection circuit for generating a phase difference signal indicative of the phase difference between an incoming signal and a local reference oscillator, and a phase rotation circuit for adjusting the phase of the local reference by the amount of the phase difference signal, so that the rotated local reference matches the phase of the incoming signal. Basically the same approach is used for carrier acquisition and for data clock acquisition or bit synchronization. A data resolution circuit removes the phase-angle effect of data modulation from the phase error signal, so that an accurate carrier phase error signal is obtained even when the carrier is modulated by data. A special embodiment of the data resolution circuit is provided for the case of non-random data signals.

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Los Angeles, CA, United States of America

Peter L McAdam