Digital FM receiver back end
US5903825A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 27, 1996 |
| Grant date | May 11, 1999 |
| Priority date | — |
| Expiry date | Jun 27, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D3/006
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.