Demodulators – Frequency modulation demodulator – Input signal converted to and processed in pulse form
Patent
1996-06-27
1997-08-26
Mis, David
Demodulators
Frequency modulation demodulator
Input signal converted to and processed in pulse form
455214, 455337, H03D 300
Patent
active
056614330
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.
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Carney Michael John
LaRosa Christopher Peter
Chen Sylvia
Mis David
Motorola Inc.
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