Polar loop transmitter

Details Polar loop transmitter Polar loop transmitter

1985-09-09

1986-10-21

Ng, Jin F.

Telecommunications

Transmitter

Amplitude modulation

455126, 332 37D, H04B 104

Patent

active

046189998

ABSTRACT:
A polar loop transmitter having particular, but not exclusive, application in VHF single-sideband radio systems.
In order to avoid having to match the amplitude detectors used in known polar loop transmitters, it is proposed as an alternative to provide a subtracting circuit which produces a difference signal from between the low level input signal and the attenuated output signal. The difference signal is amplitude demodulated in a mixer and the demodulated signal is used as a control signal for the amplitude modulator.
First and second limiting amplifiers are used to derive the carrier signals from the input and output signals. The outputs of the limiting amplifiers are applied to a phase sensitive detector formed by another mixer whose output is used as a correction signal for a voltage controlled oscillator coupled to the amplitude modulator. The output of the first limiting amplifier is also used as the local oscillator signal for the amplitude demodulator.
Means are proposed for compensating for the phase shifts introduced by the limiting amplifiers.

REFERENCES:
patent: 3662290 (1972-05-01), Elliott
patent: 3900823 (1975-08-01), Sokal et al.
patent: 4237555 (1980-12-01), Dishal
patent: 4481672 (1984-11-01), Watkinson
"The Design of VHF SSB Polar-Loop Transmitters" by Petrovic et al., 4/1982.

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