FSK demodulator
US5053717A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 13, 1989 |
| Grant date | Oct 1, 1991 |
| Priority date | — |
| Expiry date | Nov 13, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/106
- WIPO fieldDigital communication
- 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 controllable time-delay in the demodulation process. 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.. A further aspect of this invention addresses minimizing the DC offset from the demodulator by providing a feedback signal which controls the amount of delay provided to one of the quadrature signals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.