Digital voice-band spectrum inversion apparatus

Details Digital voice-band spectrum inversion apparatus Digital voice-band spectrum inversion apparatus

1993-07-30

1994-08-02

Gregory, Bernarr E.

Cryptography

Communication system using cryptography

Frequency shift or inversion

380 9, 380 28, 380 49, H04L 900

Patent

active

053352793

ABSTRACT:
A digital speech-band spectrum inversion apparatus for use in a cordless telephone system provides transmission security of the voice signal between the handset (10) and the base station (18). The apparatus includes an A/D converter (24) for converting an input analog voice-band signal to a digital signal, a digital signal processor (30) for modifying the digital signal in accordance with a prescribed algorithm, and a D/A converter (32) for converting the modified digital signal to an output analog signal, the output analog signal being inverted in frequency spectrum from the input analog signal. A/D converter (24) samples the input analog signal at a periodic rate, and converts the sampled voltage levels to digital representations thereof. The algorithm performed by the digital signal processor (30) computes the two's complement inversion of the digital representations of alternate samples of the input analog signal.

REFERENCES:
patent: 4551580 (1985-11-01), Cox et al.
patent: 4560832 (1985-12-01), Bond et al.
patent: 4747137 (1988-05-01), Matsunaga
patent: 4937867 (1990-06-01), Kasparian et al.
patent: 5140635 (1992-08-01), Houghton et al.
patent: 5168522 (1992-12-01), Simanis et al.

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