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:
Aug. 26, 1997
Filed:
Jun. 27, 1996
Christopher Peter LaRosa, Lake Zurich, IL (US);
Michael John Carney, Mundelein, IL (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
In the digital FM demodulator (330), a hard limiter (333) receives a modulated analog IF signal and limits the voltage of the IF signal to two levels. Next, a direct phase digitizer (336) uses zero-crossings of the limited IF signal to generate N-bit digital words. A phase differential circuit (340) computes the phase shift of the signal from the direct phase digitizer over a predetermined time interval. The dynamic range of the phase differential signal can be increased by replacing the phase differential circuit (340) with a high-resolution phase differential circuit (700). After digital demodulation and filtering and gain control by audio processor (360), the recovered signal is forwarded to a speaker (390) to produce an audio output. Thus, the digital FM demodulator both avoids problems common to analog discriminator circuitry and offers a reduced complexity, size, and power consumption alternative to conventional digital FM demodulators.