Telecommunications – Transmitter – Angle modulation
Patent
1984-05-22
1985-01-01
Ng, Jin F.
Telecommunications
Transmitter
Angle modulation
455108, 455116, 330294, 330303, H04B 104, H03F 134
Patent
active
044919727
ABSTRACT:
Improved radio transmitter modulation control circuitry is described which significantly increases the average power of the modulating signal, resulting in enhanced audio signal quality since the signal-to-noise ratio is likewise increased. The inventive modulation control circuitry includes a microphone 110, audio amplifier 120, splatter filter 130, modulator 150, potentiometer 140, oscillator and transmitter 180, and antenna 190. The audio amplifier 120 further includes an operational amplifier 160 having an input resistor 162 coupled via capacitor 168 to microphone 110, a phase-lag filter 170 coupled to the output of the operational amplifier 160, and a feedback resistor 161 coupled between the filter 170 and the input resistor 162. When driven into amplitude limiting, the phase and amplitude of harmonic signals from the operational amplifier 160 are altered by phase-lag filter 170 to produce a waveform similar to that shown in FIG. 2. When operated linearly, the audio amplifier 120 has a flat frequency response, the filter 170 having no effect since it is in the feedback loop. The improved modulation control circuitry of the present invention can be advantageously utilized in both amplitude and frequency modulated radios 100 for enhancing the audio signal quality thereof.
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Gillman James W.
Hackbart Rolland R.
Motorola Inc.
Ng Jin F.
Roney Edward M.
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