Telecommunications – Receiver or analog modulated signal frequency converter – Squelch
Patent
1988-02-16
1989-08-08
Griffin, Robert L.
Telecommunications
Receiver or analog modulated signal frequency converter
Squelch
455311, H04B 700
Patent
active
048560847
ABSTRACT:
To a standard AM radio receiver there is connected an impulse-noise suppression system comprising a preliminary blanking gate adapted for connecting to and for interrupting the AM-modulated signal path at the input of the IF section, and an audio blanking gate adapted for interrupting the audio circuit. Both blanking circuits detect impulse noise at the RF amplifier and with appropriate delays blank both points. Audio blanking masks the audio disturbance caused by the blanking in the AM-modulated-signal path. Audio blanking time is preferably from 2 to 3 times the duration of the blanking of the AM-modulated-signal path and is thus kept very short causing a minimum interruption of the wanted audio signal. Associated with the audio-signal-path blanking circuit is a sample and hold circuit for smoothing the blanked audio signal and virtually eliminating an audio disturbance or noise that is otherwise generated by the audio blanking circuit itself.
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James J. Lamb, "A Noise-Silencing I.F. Circuit for Superhet Receivers", OST--Feb. 1936, pp. 11-15, 38-39, 90-93, 106-112.
James J. Lamb, "More Developments in the Noise-Silencing I.F. Circuit", QST--Apr. 1936, pp. 16-19, 78-86.
J. D. Martin, "Audio Clipping and Blanking in an AM Receiver", IEEE Transactions on Vehicular Technology, vol. VT-29, No. 2, May 1980, pp. 298-304.
Griffin Robert L.
Kuntz Curtis
Sprague Electric Company
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