Cryptography – Video cryptography – Video electric signal modification
Patent
1997-12-01
2000-06-27
Swann, Tod R.
Cryptography
Video cryptography
Video electric signal modification
H04N 7167
Patent
active
06081599&
ABSTRACT:
A television scrambling system in which a television signal is scrambled by means of placing a scrambling (or jamming) signal into the luminance signal spectrum on the transmit side. On the receive side, the jamming signal is removed by a Surface Acoustic Wave (SAW) notch filter. On the transmit side, pre-correction of the television signal is performed to compensate for amplitude and phase distortions introduced by the SAW notch filter. The pre-correction includes: inverting the television signal as a function of time; pre-distorting the phase of the time-inverted television signal in accordance with the phase response of the SAW notch filter; pre-emphasizing the time-inverted television signal using a first amplitude corrector having a phase response; restoring the television signal to a time uninverted state, such that the phase of the restored television signal is pre-distorted in accordance with the inverse of the SAW notch filter phase response; and pre-emphasizing the restored television signal using a second amplitude corrector having a phase response which is substantially equivalent to the phase response of the first amplitude corrector.
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"Saw Notch Filters", C.S. Hartmann, J.C. Andle and M. B. King, 1987 Ultrasonics Symposium.
Coddington Trevor Quick
Swann Tod R.
Telecom
Tresness Irrevocable Patent Trust
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