Cryptography – Cryptanalysis
Patent
1989-11-27
1991-05-28
Tarcza, Thomas H.
Cryptography
Cryptanalysis
380 38, 375 22, 375122, 381 29, H04K 102
Patent
active
050201042
ABSTRACT:
The useful bandwidth of a bandwidth-limited input signal (s(t)) is reduced, to obtain a coded signal (q(t)) by forming a combined input and feedback signal, low-pass filtering the combined signal, and passing the low-pass filtered signal through a feedback loop which includes symmetrical frequency-voltage (f/V) conversion, substantial amplification, and voltage-frequency (V/f) reconversion, the reconverted signal being combined with the input signal in a multiplier, the coded output signal being derived from the output of the low-pass filter. Amplification of the amplifier is so high that the bandwidth of the resulting frequency-modulated feedback signal is greater than the bandwidth of the original input signal. The resulting coded signal can be decoded by derived scanning signals which are combined with bandwidth-enhanced coded signals and processed in an inversion matrix for subsequent reconstitution of the original signal.
REFERENCES:
patent: 4071707 (1978-01-01), Graf et al.
patent: 4700360 (1987-10-01), Visser
patent: 4817141 (1989-03-01), Taguchi
Cain David
Robert & Bosch GmbH
Tarcza Thomas H.
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