Electrical transmission or interconnection systems – Nonlinear reactor systems – Parametrons
Patent
1979-09-25
1982-02-16
Heyman, John S.
Electrical transmission or interconnection systems
Nonlinear reactor systems
Parametrons
307512, 307320, 328166, 455339, 455340, H03L 704
Patent
active
043161081
ABSTRACT:
A tracking filter suitable for use in the IF stage of FM receiver circuitry incorporates a bandpass filter the components of which yield a characteristic that permits the filter to provide substantially the entirety of a required 90.degree. phase shift for phase detection control circuitry that rapidly actively tunes capacitive components of the filter without imparting unacceptable group delay behavior to the configuration. The filter is a two-pole pair, single zero at the orgin, bandpass filter inserted in the signal path between a pair of signal power splitters. Part of the input signal is applied from the first splitter to one input of a phase comparator the other input of which is derived from the output signal via the second power splitter. The output of the phase comparator is applied through a broadband control amplifier to actively adjust the center frequency of the bandpass filter. Advantageously, this configuration enables the filter to have its center frequency effectively coincide with the instantaneous frequency of the deviating input signal, whereby an increase in performance over conventional filter approaches is obtained.
REFERENCES:
patent: 2915631 (1959-12-01), Nilssen
patent: 2976408 (1961-03-01), Colaguori
patent: 3079571 (1963-02-01), Elliott et al.
patent: 3436647 (1969-04-01), Gobeli et al.
patent: 3748499 (1973-07-01), Schaffner
patent: 3805173 (1974-04-01), Nakamura et al.
patent: 3821652 (1974-06-01), Wiebe et al.
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