Digitally implemented fast frequency estimator/demodulator for low bit rate maritime and mobile data communications without the use of an acquisition preamble
US5272446A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 17, 1992 |
| Grant date | Dec 21, 1993 |
| Priority date | — |
| Expiry date | Aug 17, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L2027/0095
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A low-bit-rate, low-cost, all-digital preambleless demodulator for maritime and mobile data communications operates under severe high noise conditions, fast Doppler frequency shifts, large frequency offsets, and multipath fading. Sophisticated algorithms, including an FFT-based burst acquisition system, a cycle-slip resistant carrier phase tracker, an innovative Doppler tracker, and a fast acquisition symbol synchronizer, provide reliable burst reception. The compact DSP-based demodulator includes an input buffer receiving a complex sampled baseband input signal and providing a baseband output to a coarse frequency estimator fast Fourier transform (FFT) or discrete Fourier transform (DFT) module which produces a first estimation of the carrier frequency. A fine frequency estimator FFT or DFT module receives the first estimation and provides a second estimation of the carrier frequency. An extra coarse frequency estimator FFT or DFT module may be provided between the buffer and the coarse frequency estimator.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.