Phase demodulator with offset frequency reference oscillator
US4042884A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Feb 20, 1975 |
| Grant date | Aug 16, 1977 |
| Priority date | — |
| Expiry date | Feb 20, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03D3/241
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A phase-locked demodulator for demodulating a phase-difference modulated carrier having a repeated phase offset increment introduced therein. The demodulator includes, in common with conventional phase locked demodulators, a mixer having a first input connected to receive the modulated carrier and a reference carrier generator such as a voltage controlled oscillator (VCO) connected in a phase-locked feedback loop forming the second input to the mixer. In order to reduce the number of output levels, the VCO is tuned to a frequency Fr=Fc.+-.Fb[(.alpha.)/360] where Fc is the carrier frequency, Fb is the baud rate and .alpha. is the repeated phase offset. In this way the phase offset increment introduced into the modulated carrier is substantially cancelled out thereby leaving only the phase changes containing data information.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.