Walsh function signal scrambler

Details Walsh function signal scrambler Walsh function signal scrambler

1975-05-28

1977-10-04

Birmiel, Howard A.

Telegraphy

Systems

Printing

179 15R, 325 32, 179 15BC, 178 22, H04K 100

Patent

active

040525651

ABSTRACT:
A digital speech scrambler system allowing for the transmission of scrambled speech over a narrow bandwidth by sequency limiting the analog speech in a low-pass sequency filter and thereafter multiplying the sequency limited speech with periodically cycling sets of Walsh functions at the transmitter. At the receiver, the Walsh scrambled speech is unscrambled by multiplying it with the same Walsh functions previously used to scramble the speech. The unscrambling Walsh functions are synchronized to the received scrambled signal so that, at the receiver multiplier, the unscrambling Walsh signal is the same as and in phase with the Walsh function which multiplied the speech signal at the transmitter multiplier. Synchronization may be accomplished by time division multiplexing sync signals with the Walsh scrambled speech. The addition of the sync signals in this manner further masks the transmitted speech and thus helps to prevent unauthorized deciphering of the transmitted speech.

REFERENCES:
patent: 3204035 (1965-08-01), Ballard et al.
patent: 3678204 (1972-07-01), Harmuth
patent: 3742201 (1973-06-01), Groginsky
patent: 3859515 (1975-01-01), Radcliffe, Jr.

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