Jam-resistant TV system

• US 4,333,107 A
• Filed: 05/03/1979
• Issued: 06/01/1982
• Est. Priority Date: 05/03/1979
• Status: Expired due to Term

• Current Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Original Assignee: RCA Corporation
• Inventors: Brokl, Stanley S., McGuire, Kenyon E.
• Primary Examiner(s): Buczinski, S. C.
• Application Number:
  US06/035,771
• Time in Patent Office: 1,125 Days
• Field of Search: 358/120, 358/122, 358/123, 358/148, 358/153, 358/259, 358/264
• US Class Current: 380/221
• CPC Class Codes: H04N 7/1713 by modifying synchronisation signals

Abstract

A jam-resistant TV transmission system including means to transmit a composite video signal in which each vertical sync pulse is replaced by several increasingly-delayed symbols from a pseudo-random number generator. Receiver means includes a correlator which produces a correlation pulse on receipt of a predetermined one of the symbols. The timing of the correlation pulse and the known delay of the predetermined symbol are used to generate reconstituted vertical sync pulses.

Claims

1. A jam-resistant TV transmission system, comprising

transmitter means to transmit a composite video signal in which each vertical synchronizing pulse is replaced by a synchronizing signal of several symbols from a pseudo-random number (PN) generator, several symbols occurring with increasing phase delays relative to the vertical synchronizing pulse, and

receiver means for said transmitted signal, including

a correlator receptive to said sequential symbols and containing a predetermined one of said symbols as a reference, and producing a correlation pulse when the correlator receives a symbol which is the same as the reference, and

synchronization reconstituting means responsive to the correlation pulse and the known phase delay of the predetermined symbol in the sequence of symbols to produce a reconstituted vertical synchronizing pulse for synchronizing the received video.

2. A system according to claim 1 wherein said receiver includes a PN generator identical to the one in the transmitter.

3. A system according to claim 2 wherein said receiver includes a symbol number register for the number of the one of the several symbols to be used for vertical synchronization.

4. A system according to claim 3 wherein said receiver includes means responsive to the contents of said symbol number register to load the identified one of the several symbols from said PN generator into said symbols correlator as a reference symbol.

5. A system according to claim 4 wherein said receiver includes means to pass all sequential symbols of a received synchronizing signal through said correlator to produce a correlation pulse when the correlator receives a symbol which is the same as the predetermined reference symbol therein.

6. A system according to claim 5 wherein said synchronization reconstituting means includes means producing a pulse wave having a phase determined by the correlation pulse, and a frequency equal to the vertical synchronizing rate of the TV system.

7. A system according to claim 6 wherein said synchronization reconstituting means includes means responsive to said pulse wave, and to the number in the symbol number register, to produce a reconstituted vertical synchronizing pulse wave having a leading edge corresponding with the leading edge of the first of said received symbols.

8. A system according to claim 7 wherein said synchronization reconstituting means includes a sync generator responsive to said reconstituted vertical synchronizing pulse to produce vertical and horizontal synchronizing signals.

9. A system according to claim 8 wherein said synchronization reconstituting means includes means to combine the received video signal with the output of said sync generator to produce a reconstituted composite video signal.

10. A jam-resistant TV transmission system, comprising

transmitter means to transmit a composite video signal in which each vertical synchronizing pulse is replaced by a synchronizing signal of several symbols, of n serial bits each, from a pseudo-random number generator, said synchronizing signal starting at the beginning of the replaced vertical synchronizing pulse with a first one of the several successive symbols, and

receiver means for said transmitted signal, including

a second identical pseudo-random number generator,

an n-bit symbol correlator,

a symbol number register for the number of the one of the symbols to be used for vertical synchronization,

means responsive to the contents of said symbol number register to load the identified one of the several symbols from said pseudo-random number generator into said n-bit symbol correlator as a reference symbol,

means to pass all sequential symbols of a received synchronizing signal through said correlator to produce a correlation pulse when the correlator receives a symbol which is the same as the predetermined reference symbol therein,

means producing a pulse wave having a phase determined by the correlation pulse, and a frequency equal to the vertical synchronizing rate of the TV system,

means responsive to said pulse wave, and to the number in the symbol number register, to produce a reconstituted vertical synchronizing pulse wave having a leading edge corresponding with the leading edge of the first of said received symbols,

a sync generator responsive to said reconstituted vertical synchronizing pulse to produce vertical and horizontal synchronizing signals, and

means to combine the received video signal with the output of said sync generator to produce a reconstituted composite video signal.