Scientific-atlanta, Inc.

Neil C Robertson

Samuel H Russ

Mark E Schutte

David B Lett

Ajith N Nair

Michael A Gaul

Jose M Fernandez

Bohdan S Prus

Ronald C Stirling

An off-premises method and apparatus for the interdiction of unauthorized channels of a broadband cable television signal includes common circuitry for adjusting the amplitude and equalization levels of the broadband CATV signals and one or more subscriber modules for generating jamming signals of different frequencies which are used to interdict one or more unauthorized channels. Each subscriber module is associated with a subscriber and is programmable and addressable to adjust the jamming parameters of that subscriber independently of other subscribers. Each subscriber module circuit comprises a plurality of latches, each of which is associated with one of a plurality of digital to analog converters. Each of the digital to analog converters drives one or more frequency agile oscillators with its analog output to generate the jamming signals. The subscriber module is based on a sequential state machine which loads frequency control words corresponding to the jammed channels from a frequency control memory into each latch on a cyclic basis. In this manner, the jamming signals generated by each latch, digital to analog converter, and oscillator combination can be varied easily and quickly by a memory to memory transfer and be sustained between frequency hops without any change in frequency. The circuitry lends itself easily to large scale integration and miniaturization while eliminating the need to refresh the circuit to prevent frequency change because of voltage droop.

Interdiction method and apparatus with direct memory control of variable

An off-premises method and apparatus for the interdiction of unauthorized channels of a broadband cable television signal includes common circuitry for adjusting the amplitude and equalization levels of the broadband CATV signals and one or more subscriber modules for generating jamming signals of different frequencies which are used to interdict one or more unauthorized channels. Each subscriber module is associated with a subscriber and is programmable and addressable to adjust the jamming parameters of that subscriber independently of other subscribers. Each subscriber module circuit comprises a plurality of latches, each of which is associated with one of a plurality of digital to analog converters. Each of the digital to analog converters drives one or more frequency agile oscillators with its analog output to generate the jamming signals. The subscriber module is based on a sequential state machine which loads frequency control words corresponding to the jammed channels from a frequency control memory into each latch on a cyclic basis. The state machine is adapted to vary the sequence in which frequency control words are read out of the memory to modify the jamming pattern of the subscriber. Corresponding to each frequency control word in the memory is stored one or more mode control bits which are read out contemporaneously with the frequency control words. The mode control bits are used to allow a single digital to analog converter to control one or more voltage control oscillators with different frequency ranges, or to allow control of a single voltage control oscillator with multiple frequency ranges.

Interdiction method and apparatus with mode control for variable

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Norcross, GA, United States of America

Neil C Robertson