CPFSK communication system employing nyquist-filtered modulator/demodulator
US4843615A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 8, 1987 |
| Grant date | Jun 27, 1989 |
| Priority date | — |
| Expiry date | May 8, 2007 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/2334
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
An improved narrowband continuous phase modulation system incorporates a filtering mechanism in the transmitter and receiver sites that enables the radiated spectrum characteristic to have a substantially reduced response at frequencies other than the channel of interest and thereby achieve a significant reduction in unwanted adjacent channel interference. Each of the transmitter and receiver sites contains a square root Nyquist filter upstream and downstream of the modulator and demodulator, respectively. The output of the Nyquist filter in the receiver is coupled to an accumulator which sums successive samples of the demodulated data signals (including noise). The noise is reduced as a consequence of its inherent negative correlation properties (utilized in the accumulation of successive samples of the recovered signal).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.