The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 05, 1983
Filed:
Nov. 13, 1980
Tim D Isbell, San Jose, CA (US);
Don R Sauer, San Jose, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
Abstract
In an AM stereo radio receiver, a pilot signal is recovered from the phase modulated channel. The pilot signal is sensed by means of a bandpass filter tuned to the subaudible signal frequency and is used to operate a detector-switching amplifier combination. The switching amplifier actuates a visual indicator which shows the presence of a stereo broadcast. The receiver is provided with an electronic blend function that operates in response to the pilot signal and an excess phase signal that is present when the receiver is mistuned. OR Logic, which responds to either mistuning or a lack of stereo pilot signal, switches the receiver to monaural response. If desired, further OR Logic can include response to weak signals, in which case an improvement in signal to noise ratio is achieved.