Patent
1975-06-23
1976-06-29
Stewart, David L.
179 1G, 325477, H04B 110
Patent
active
039672042
ABSTRACT:
RC low-pass and high-pass filters are fed in common with a demodulated broadcast signal through a noise blanking switch device and the outputs of the respective filters are added in a summing amplifier, of which the output is supplied to the low-frequency stages of the receiver. For stereo reception, the crossover between the filters is made lower than the lowest pilot frequency of the composite demodulated signal, so that the circuit functions as an all-pass filter in the absence of disturbances and stores only the audible frequency program signal for transmission to the low-frequency stages during blanking intervals. For purely monophonic receivers, the passbands of the two filters may be spaced apart in frequency so as to provide a dip in the sum characteristic in the transition region contributing high-frequency de-emphasis to the audible signal, while still allowing transmission of an inaudible pilot signal or other superposed demodulated signal above the audible range when there is no interference blanking taking place.
REFERENCES:
patent: 2802932 (1957-08-01), Klehfoth
patent: 3231823 (1966-01-01), Garfield
patent: 3241073 (1966-03-01), Hummel
Blaupunkt-Werke GmbH
Stewart David L.
Woodward William R.
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