Pulse or digital communications – Receivers – Particular pulse demodulator or detector
Patent
1995-05-31
1996-12-17
Chin, Stephen
Pulse or digital communications
Receivers
Particular pulse demodulator or detector
375354, 342 99, H03D 100, H04L 2706
Patent
active
055861482
ABSTRACT:
A coherent detection system synchronously detects a received wave involving a Doppler shift. To realize a stable demodulation performance, the system has a memory for storing in advance Doppler shifts to be related to an input signal and corresponding pass bands to reduce the bit error rate of restored information to below an allowable maximum when the corresponding Doppler shifts are present; an estimating unit for finding levels of the input signal or instantaneous values R of the input signal that form an envelope, counting the number N per unit time of points where the envelope crosses a threshold, and estimating a Doppler shift fD according to an expression that indicates the ratio of the number N to the Doppler shift fD and involves the in-phase and orthogonal components of the input signal, a distribution of the temporal differentiation of these components, a distribution of power spectra, and the instantaneous values normalized by the threshold; and a band controller for retrieving a pass band corresponding to the estimated Doppler shift fD from the memory and setting the pass band to a filter of the system.
REFERENCES:
patent: 3903525 (1975-09-01), Mullins et al.
patent: 3939428 (1976-02-01), Shimizu et al.
patent: 5272446 (1993-12-01), Chalmers et al.
Furukawa Hideto
Kawabata Kazuo
Chin Stephen
Fujitsu Limited
Vo Don
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