Pulse or digital communications – Repeaters – Testing
Patent
1992-05-21
1994-07-26
Chin, Stephen
Pulse or digital communications
Repeaters
Testing
375 82, 329302, 329321, H04L 2722
Patent
active
053331508
ABSTRACT:
A digitally modulated signal of the FSK type is subjected to limiting and linear FM demodulation to produce a baseband signal which often fails to show clearly the serial binary digital signal because of distortion and disturbances prior to its reception. The amplitude of the base-band signal is digitally sampled (quantized) at a uniform sampling rate which is an integral multiple of the symbol rate of the base-band signal. A sequence of successive amplitude samples spanning at least a symbol period addresses, at twice the symbol rate a look-up table containing a set of stored signal patterns and correspondence of patterns within a predetermined degree of similarity is elicited at twice the symbol rate along with information on the degree of similarity, and also a synchronizing pulse when the amplitude pattern shows that a binary signal transition is detected at a particular part of the pattern of the amplitude sample sequence. The synchronizing signal goes to a phase locked loop for clocking the system, so that the clock phase will shift until it is locked so that the comparison results at twice the symbol rate will show transitions and logic levels in the comparison results. A second stage for a look-up table similarly addressed but clocked at the symbol rate and encompassing at least two consecutive symbol periods further assures a high degree of accuracy in reproducing the digital signal content of the base-band signal.
REFERENCES:
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patent: 4378526 (1983-03-01), Champagne et al.
patent: 4486716 (1984-12-01), Le Floch
patent: 5073905 (1991-12-01), Dapper et al.
B. W. Maples, et al, "Rapid Clock Recovery Technique with Monotonic Phase Error Metric", 1990, pp. 0141-0145, IEEE Military Communications Conference.
Chin Stephen
Robert & Bosch GmbH
Tse: Young
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