FSK demodulator
US4987374A · kind A · utility
Inventor
Key dates
| Filing date | Oct 5, 1989 |
| Grant date | Jan 22, 1991 |
| Priority date | — |
| Expiry date | Oct 5, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D2200/005
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An improved multilevel FSK demodulator, according to the invention, is provided that down-converts the IF frequency back to baseband quadrature via dual mixers. The improved multilevel FSK demodulator uses time-delay demodulation. This method requires a .+-.90.degree. phase difference between 2 modulated signals to produce a maximum demodulated output amplitude at the maximum frequency deviation. Since the IF frequencies have been down-converted back to baseband quadrature, these 2 signals are only "out of phase" by an amount .DELTA.t that is equal to 90.degree./d.omega.. For a .DELTA..omega.of 4 MHz, this gives a .DELTA.t=62.5 nonoseconds. As a result, it is easy to achieve a delay line using multiple tap positions for 62.5 nonoseconds total delay.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.