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:
Sep. 24, 2013
Filed:
Jan. 06, 2011
Chien-shan Chiang, Hsinchu Hsien, TW;
Chien-Shan Chiang, Hsinchu Hsien, TW;
MStar Semiconductor, Inc., Hsinchu Hsien, TW;
Abstract
An amplitude modulation (AM) demodulating circuit applied to a radio frequency identification (RFID) system attenuates carrier signals by a notch filter to increase a signal-to-carrier ratio and to reduce complexity and cost of circuit design. The AM demodulating circuit includes an envelope detector, a notch filter, a low-pass filter, and a comparing circuit. The envelope detector performs envelope detection on an AM signal modulated by a carrier frequency to generate an envelope signal. The notch filter filters the envelope signal to generate a first filtered signal, and a zero point of the notch filter corresponds to the carrier frequency of the AM signal. The low-pass filter filters the first filtered signal to generate a second filtered signal, and the carrier frequency of the AM signal corresponds to a stop band of the low-pass filter. The comparing circuit converts the second filtered signal to a digital signal according to a level value.