Cryptography – Cryptanalysis
Patent
1988-05-09
1991-11-26
Buczinski, Stephen C.
Cryptography
Cryptanalysis
333155, 333176, 333193, 455 1, 455286, 455339, H04N 7167, H04K 300, H03H 900
Patent
active
050688936
ABSTRACT:
Networks which remove the jamming signal from the television signal supplied to subscribers for a premium T.V. channel in a cable (CATV) or other subscription television system utilizes surface accoustic wave (SAW) devices arranged to provide a broadband all pass response across the entire band covered by all of the transmitted television channels except for a notch at the frequency of the jamming signal. The narrow band response of the filter in the premium channel is such that the notch presents insertion loss at the jamming signal frequency and over a frequency range to accommodate shifts in the frequency response of the SAW devices with respect to the frequency of jamming signal, which insertion loss is about 100 times the insertion loss at the picture carrier frequency of the television signal, even though the picture carrier and the jamming signal frequency may be within about 200 KHz apart from each other. The network includes circuit elements which utilize the characteristics of the SAW devices to create a filter network which has a transmission null (notch) at the frequency of the jamming signal.
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Cook, Jr. Alex M.
Ghanouni Majid
LaFay William P.
West Lamar E.
Buczinski Stephen C.
Lukacher Martin
Scientific - Atlanta, Inc.
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