Digital FM receiver back end

Details Digital FM receiver back end Digital FM receiver back end

1996-06-27

1999-05-11

To, Doris H.

Telecommunications

Receiver or analog modulated signal frequency converter

Frequency or phase modulation

455214, 455337, 455296, 375375, H04B1/16

Patent

active

059038250

ABSTRACT:
The digital FM receiver back end receives an analog intermediate frequency signal from a radio frequency front end (310) having a heterodyne circuit (312) and an intermediate frequency filter (314). In the receiver back end (307), a digital demodulator (330) having a hard limiter (333), a direct phase digitizer (336), and a phase differential circuit (339) produces a digital phase differential signal from the analog intermediate frequency signal. Next, a digital processor (360) filters and reduces noise in the digital phase differential signal using a bandpass filter (362), a de-emphasis filter (364), and an expandor (366). Finally, a pulse-width-modulation audio amplifier (380) prepares the signal for reproduction on an audio speaker (390). The digital FM receiver back end avoids inherent DC offset problems common to analog FM receivers, and it also offers a reduced complexity, size, and power consumption alternative to conventional digital FM receivers.

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