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

Facsimile and static presentation processing – Facsimile – Recording apparatus

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358330, 348424, 348427, 360 91, H04N 979, H04N 712

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active

055328202

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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"Reduction of Television Bandwidth by Frequency Interlace", E. A. Howson et al., Journal of Britishire, Feb. 1960, pp. 127-136.
"Development of HDTV Receiving Equipment Based on Band Compression Technique (MUSE)", Nakagawa et al, IEEE Transactions on Consumer electronics vol. CE-32, No. 4, Nov. 1986, pp.759-767.

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