In-phase quadrature demodulator for CPSK signals
US4246653A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 8, 1979 |
| Grant date | Jan 20, 1981 |
| Priority date | — |
| Expiry date | Jan 8, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2278
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A system for demodulating a coherent, phase-shift-keyed signal that is modulated by a set of orthogonal or biorthogonal code words. The system does not require a local phase reference that is phase locked with the received signal. The system is made up of two demodulators and a microprocessor. One demodulator utilizes a local sinusoidal signal in the demodulation process, and the second uses a local cosinusoidal signal in the demodulation process. Because the phases of the local signals do not change significantly with respect to the unmodulated phase of the received signal during the period of time occupied by a single code word, the output of one or the other of the two demodulators resembles the code word which was transmitted. The set or orthogonal code words is compared with the outputs of the two demodulators to determine which code word was transmitted, and the data which corresponds to that code word is output by the system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.