BPSK demodulator and FM receiver for digital data pagers
US4816769A · kind A · utility
Inventors
Key dates
| Filing date | Jan 16, 1987 |
| Grant date | Mar 28, 1989 |
| Priority date | — |
| Expiry date | Jan 16, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D2200/0031
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An FM receiver for the reception of digital data modulated on a Subsidiary Communication Authorization (SCA) subcarrier is provided with automatic tuning capability and a coherent demodulator for minimizing noise, distortion and interference. The FM receiver is tuned automatically to minimize the measured amplitude of noise and distortion at the high frequency end of the spectrum of the FM demodulator output, above the frequencies of the SCA signal. The SCA signal is tuned by a heterodyne circuit including a balanced modulator, a voltage-controlled oscillator (VCO), and a bandpass filter. The VCO is automatically tuned to maximize the measured amplitude of the SCA signal selected by the bandpass filter. For coherent detection of BPSK (Binary-Phase-Shift-Keying), the coherent demodulator is preferably and kind of data-aided Costas loop in which digital logic circuits perform phase shifting, phase detecting, a multiplying functions. The feedback of the phase error signal is preferably inhibited whenever the signal-to-noise ratio falls below the level which ensures phase-lock, for example, by inhibiting feedback whenever the amplitude of the filtered in-phase signal in the Costas loop…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.