Modulators – Amplitude modulator – Nonlinear device controlled by modulating signal
Patent
1977-02-18
1978-12-26
Griffin, Robert L.
Modulators
Amplitude modulator
Nonlinear device controlled by modulating signal
325145, 332 16R, 332 45, H04B 166
Patent
active
041318501
ABSTRACT:
A radio transmitter, or transceiver, provides for single side band transmission. A first carrier frequency source provides a first carrier frequency (term the deleted carrier) for balanced modulation by at least one balanced modulator. The resulting side band signal is ultimately applied to an add mixer along with a second carrier. The add mixer ultimately feeds a subtract mixer which also receives the deleted carrier frequency and subtracts same from the side band sum signal from the add mixer to provide the side band signal at the second carrier frequency, i.e., with the first carrier deleted. Alternative embodiments provide for single side band generation by use of a band pass filter following the balanced modulator or use of double balanced modulators with phase shift networks coupling the deleted carrier source and a source of modulating signals thereto. In a further embodiment, a phase lock loop synthesizer is employed for generating one of said carrier signals. In a preferred embodiment, the single side band transmission is built into an AM transmitter, or transceiver, to use the modulating signal source and basic AM carrier source (as the source of the second carrier of the side band system) and the transmitter output amplification portions thereof. Also in such a preferred embodiment, a substantial selection of output frequencies is provided by mixing of the carrier frequency outputs of a pair of crystal controlled oscillators each with several alternatively selectable crystals in the AM portion of the transmitter, wherein the deleted carrier source in the side band portion of the transmitter incorporates a pair of crystals tuned to upper and lower frequencies and permitting alternative selection of upper and lower side bands for each of the several synthesized AM transmit frequencies.
REFERENCES:
patent: 3588702 (1971-06-01), Tisi
patent: 3701852 (1972-10-01), Sluijter et al.
patent: 3714577 (1973-01-01), Hayes
patent: 3795865 (1974-03-01), Armstrong
patent: 3803490 (1974-04-01), Almering et al.
patent: 4025855 (1974-05-01), Atkinson
Chin Tommy P.
Griffin Robert L.
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