Cincinnati Electronics Corporation

Frank A Wissel

Mark J Dapper

Charles A Bucher

Robert L Martinet

Douglas A Kiliman

Donald E Smith

Bit timing references are derived at a receiver for a carrier modulated by OQPSK. A carrier is transmitted with a constant reference phase modulation during a first interval. During a subsequent, second interval the carrier is transmitted with rotational phase modulation representing binary bit values so that orthogonal components phase modulate the carrier with a predetermined bit sequence. A receiver responds to the constant phase modulated carrier to lock the frequency and phase of a phase lock loop oscillator of a carrier recovery loop. Synchronization at the receiver is achieved in response to a reception of the rotational phase modulation, while maintaining the frequency and phase lock. A carrier recovery loop of the receiver is activated to a decision directed operation after bit synchronization has been achieved. Decision directed operation is achieved by sampling and comparing components derived in orthogonal channels of the carrier recovery loop while the receiver is responsive to the rotational phase modulation. The bandwidth of a filter used in achieving bit synchronization is reduced after there has been a decay of transients in the carrier tracking loop resulting from a transition between locking of the loop and initiation of the decision directed operation. Then the bandwidth of a filter in the carrier tracking loop is adjusted as a function of the quality of the received rotational modulated suppressed carrier.

Method of and apparatus for transmitting and recovering offset QPSK

A portable radio receiver powered by a battery includes an RF amplifier, an IF amplifier and an audio amplifier powered by a first regulated, switched, DC power converter that derives a first DC voltage. A frequency synthesizer, including varactor diodes, is powered by a second regulated, switched DC power converter that derives a second DC voltage. Digital circuitry included in the synthesizer is powered by opposite polarity, third and fourth power converters. A synchronizing source for switching all of the power converters simultaneously has a fundamental and harmonics outside of the bandpasses of the audio and IF amplifiers to minimize the injection of spurious signals by the power converters into the amplifiers. The synchronizing source is FM modulated by an audio source so that harmonics of the synchronizing source are spread over a predetermined spectrum and the harmonics have noise-like characteristics spread over relatively wide frequency ranges.

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Cincinnati, OH, United States of America

Frank A Wissel