Digital FM demodulator using digital quadrature filter
US4799025A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 21, 1987 |
| Grant date | Jan 17, 1989 |
| Priority date | — |
| Expiry date | Sep 21, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D2200/0062
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A frequency-modulated digital signal demodulator includes a digital quadrature filter having n elements arranged in cascade, each delaying the input signal by a value T.sub.E =1/F.sub.E, where F.sub.E is the sampling frequency, a number of channels arranged in parallel with the cascade arrangement of delay elements, each channel having a multiplier for multiplying by a given coefficient, a first and a second summing circuit for summing the respective output signals of said multipliers, the output signals of the two summing circuits constituting the quadrature output signals of the filter and being referred to as reference and phase-shifted signals. At the output of the filter a circuit for calculating the instantaneous phase .phi..sub.n of successive signal samples is provided. In order to provide a demodulator with an improved threshold and with a digital quadrature filter having an identical amplitude-frequency response for the quadrature channels and, with a view to reducing the cost, a smaller number of electronic components than that in prior art arrangements is used. The demodulator according to the invention includes, in parallel with the circuit for calculating the instanta…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.