Apparatus for the acquisition of a carrier frequency and symbol timing lock
US4215239A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 5, 1977 |
| Grant date | Jul 29, 1980 |
| Priority date | — |
| Expiry date | Dec 5, 1997 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/046
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
Acquisition of a carrier frequency lock and a symbol timing lock is efficiently achieved during the preamble of a data signal in a time division multiple access communication system by first operating the system in an acquisition mode and subsequently switching to a data recovery mode. In the acquisition mode, an input signal is passed through a transversal correlator and frequency multiplied by a factor of two. The multiplied signal is used to control a local oscillator for demodulating the carrier signal. Also in the acquisition mode, the output of the transversal correlator is envelope detected and applied to a symbol timing loop that produces a symbol timing signal. Upon the detection of a symbol timing lock, a lock detector switches the system to the data recovery mode. In the data recovery mode, the input signal is frequency multiplied by 4 and used to control the local oscillator for demodulating the input signal. The demodulated input signal is now applied to the symbol timing loop to maintain a symbol timing lock condition.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.