FM Modulator phase-locked loop with FM calibration

Details FM Modulator phase-locked loop with FM calibration FM Modulator phase-locked loop with FM calibration

1984-02-29

1986-02-25

LaRoche, Eugene R.

Modulators

Amplitude modulator

Nonlinear device controlled by modulating signal

332 19, 332 30V, 331 17, 331 23, 455 42, 455 75, 455113, 455119, H03C 308, H03C 320, H03L 706, H04B 100

Patent

active

045730261

ABSTRACT:
Apparatus to provide calibrated frequency modulation (FM) of frequencies generated in a phase-locked loop is disclosed. A phase-locked loop (PLL) includes a voltage-controlled oscillator (VCO) which is locked to a loop frequence signal frequency. A modulo-10 divider is included which adds integral multiples of two pi radians of phase to the output signal of the VCO whenever the modulus of the divider is reduced by an integer. This forces the PLL to step change the loop frequency by an integral multiple of the reference frequency. A sampling circuit senses and measures the change in the VCO control voltage resulting from the step change in the loop frequency. The change in the control voltage is a measure of the VCO gain at that frequency. The change in the control voltage is converted to a digital number which is loaded into a multiplying digital-to-analog converter (DAC) to adjust the gain of the DAC. The effective combined gain of the DAC and the VCO is constant and independent of the VCO gain over the entire range of the VCO thereby providing an equal amount of modulation from an FM signal at any frequency of the VCO.

REFERENCES:
patent: 4052672 (1977-10-01), Enderby et al.
patent: 4282497 (1981-08-01), Hulbert
patent: 4309674 (1982-01-01), Owen

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