Digital modulators for use with sub-nyquist sampling of raster-s

Details Digital modulators for use with sub-nyquist sampling of raster-s Digital modulators for use with sub-nyquist sampling of raster-s

1994-08-26

1996-11-19

Tran, Thai Q.

Motion video signal processing for recording or reproducing

Local trick play processing

With randomly accessible medium

348427, 386109, 386112, H04N 979, H04N 712, H04N 1104, H04N 1102

Patent

active

055768377

ABSTRACT:
Apparatus useful in electronics for the tape recording of a video signal, which is a baseband signal of a prescribed bandwidth extending up to a prescribed maximum frequency, processes the video signal to generate a folded-spectrum video signal. The video signal is digitized and supplied to a digital band-splitting filter with a cross-over frequency at one-half said prescribed maximum frequency, for separating the digitized video signal into samples of a lower-frequency-band component and into samples of a higher-frequency-band component. A balanced modulator is connected for modulating a folding carrier wave of the prescribed maximum frequency, which modulation is done in accordance with the higher-frequency-band component to generate a balanced modulation signal; and the balanced modulation signal is linearly combined with the lower-frequency-band component to generate the folded-spectrum video signal. Preferably, the sampling rate of the digitized video signal is exactly the Nyquist rate of the prescribed maximum frequency, reduces the balanced modulation of a suitably phased folding carrier wave to multiplication of successive samples of the modulating signal alternately by plus one and by minus one. Such multiplications are done without having to use a digital multiplier.

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