General Electric Company

Rodney A Dolman

Stephen Robert Wynn

Frederick J Highton

Arvid E Englund, Jr

Gregory N Mears

Rickey D Harris

A novel circuit architecture is disclosed for achieving audio, tone, and digital data signal modulation in a full duplex radio transceiver. A single signal source is utilized to generate both transmitted carrier and receiver local oscillator injection signals. Yet the architecture is such that the transmitted data does not appear at the receiver's discriminator output--while a 'side tone' of transmitted audio does so appear. The audio to be transmitted is used to frequency modulate a VCO and provide the receiver first mixer injection signal as well as a 'carrier' input to a phase modulator. The data/tone signals are on the other hand, combined and integrated in a complex waveform and input to control the phase modulator. The resulting FM (data/tone and voice) output from the phase modulator is then input to a conventional duplexed r.f. transmitter.

Duplex radio transceiver having improved data/tone and audio modulation

An oscillator is controlled so that it produces the correct frequency in the transmitting condition, and so that it produces a slightly different frequency in the receiving condition. This is achieved by a circuit which supplies a first control voltage to the oscillator for transmitting and which supplies a second and different control voltage to the oscillator for receiving. This second and different control voltage causes the oscillator frequency in the receiving condition to be different so that there is no interference to or improper operation of a repeater system. The circuit also prevents any modulation signals from reaching the oscillator in the receiving condition, thus preventing false signals or other problems.

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Lynchburg, VA, United States of America

Rodney A Dolman