Pulse or digital communications – Repeaters – Testing
Patent
1990-04-06
1992-07-28
Gregory, Bernarr E.
Pulse or digital communications
Repeaters
Testing
375 43, 375 61, 375 77, 455 46, H04B 1500, H04B 168, H04K 100
Patent
active
051346303
ABSTRACT:
In deriving a control signal for recombining the parts of the spectrum separated by a frequency notch in transparent tone-in-band signals, cross-correlation products give rise to undesirable frequency and phase jitter. In a receiver which overcomes this problem an input signal E containing the notch is passed to two first mixers and then portions corresponding to the lower and upper portions of the input spectrum are selected by two mirror filters before being translated in frequency by two second mixers to a final output band in which the notch is eliminated. Two selection filters select parts of the spectra at the outputs of the first mixers which correspond to an overlap region of the said lower and upper portions when derived in a transmitter and apply them to a control-signal mixer. A control signal for the second mixers is derived from the output of the control-signal mixer by noise filtering and frequency division by two. The above mentioned problem is overcome by giving the mirror filters transfer functions H.sub.1- (f) and H.sub.1+ (f) which are the same as the transfer functions of mirror filters in the transmitter which produced the notch and by giving the selection filters transfer functions H.sub.2- (f) and H.sub.2+ (f) which satisfy the relationships H.sub.2- (f)=.vertline.H.sub.1- (f).vertline..sup.2 and H.sub.2+ (f)=.vertline.H.sub.1+ (f).vertline..sup.2.
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"Digital Signal Processing Design", Andrew Bateman, PhD and Warren Yates, PhD, Pitman Publishing, 1988 pp. 52-55 and pp. 301-307, pp. 325-331.
Gregory Bernarr E.
National Research Development Corporation
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