Indirect FM modulation scheme using phase locked loop

Details Indirect FM modulation scheme using phase locked loop Indirect FM modulation scheme using phase locked loop

1976-12-13

1978-08-29

Grimm, Siegfried H.

Modulators

Amplitude modulator

Nonlinear device controlled by modulating signal

325 45, 325148, 325178, 325184, 331 23, H03C 310

Patent

active

041107071

ABSTRACT:
A phase space locked loop system used for performing indirect frequency modulation. A phase locked loop is comprised of a phase detector coupled to a low pass filter coupled to a voltage controlled oscillator with a feedback loop to the phase detector. Input signals provided by a crystal controlled oscillator are fed to the phase detector. A phase difference other than 90.degree. between the voltage controlled oscillator output and the input signal will result in the phase detector generating an error voltage which is filtered by the low pass filter to alter the voltage controlled oscillator until its phase is 90.degree. from the input signal. A modulating signal is injected into the phase locked loop which causes the voltage controlled oscillator to momentarily change frequency until the output of the phase detector changes enough to balance the modulating signal.

REFERENCES:
patent: 2989622 (1961-06-01), Doherty
patent: 3579281 (1971-05-01), Kam et al.
patent: 4009455 (1977-02-01), Ishigaki et al.
Ostlund et al, "Center-Frequency-Stabilized Frequency Modulation System", IRE Proceedings, vol. 35, Oct. 1947, pp. 1144-1147.
Morgan, "Micro-Power Phase-Locked Loop Widens Designer's Choice", Electronics, Sep. 25, 1972, pp. 121-122.

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