Television signal enhancement and scrambling system

Abstract

A television signal is distorted by passing it through a distortion amplifier which applies a Gaussian distortion curve to the signal. The curve has a maximum increase in amplitude of about 38 dB, which is about 30 dB with respect to the amplitude increase of the video carrier. The signal is further modified by the addition of gated jamming signals between the video and audio carriers. The jamming signals are present only during the horizontal and vertical blanking intervals and so do not affect the quality of the picture reproduced by the receiver. The distorted television signal is restored by applying a filter function which is the inverse of the distortion function. The gated jamming signals are removed by the restoring filter to a degree which permits the television receiver to read the horizontal and vertical sync signals and the color burst signal during the blanking intervals.

I claim: 
     
       1. A television system comprising: means for generating a television signal having frequency spaced video and audio carriers;   means for distorting said television signal in the region of said signal between said video and audio carriers by increasing the peak amplitude of .[.the signals.]. .Iadd.said signal .Iaddend.in said region .[.by an amount such that said video carrier experiences carrier pinch off.]. .Iadd.in accordance with a distortion curve.Iaddend., wherein said means for distorting comprises means for increasing the amplitude of said signal in said region as a function of frequency.   
     
     
       2. A television system according to claim 1 wherein said means for distorting increases the amplitude of .[.the.]. .Iadd.said .Iaddend.signal in said region with respect to frequency such that group delay of .[.the signals.]. .Iadd.said signal .Iaddend.in said region is minimized. 
     
     
       3. A television system according to claim 2 wherein said means for distorting comprises means for increasing said amplitude in accordance with a Gaussian .Iadd.distortion .Iaddend.curve. 
     
     
       4. A television system according to claim 3 wherein said means for distorting increases said peak amplitude by approximately 40 dB. 
     
     
       5. A television system according to claim 1 further comprising means for restoring said television signal by decreasing the magnitude of said .[.signals.]. .Iadd.signal .Iaddend.in said region by .[.amounts.]. .Iadd.an amount .Iaddend.substantially equal in magnitude but opposite in sign to the amount of increase provided by said means for distorting. 
     
     
       6. A television system according to claim 1 further comprising means for supplying a gated jamming signal in said region during one of a vertical or horizontal blanking portions of said signal. 
     
     
       7. A method for scrambling a television signal having a video carrier and an audio carrier comprising distorting said signal by increasing the amplitude of said signal between said video and audio carriers as a function of frequency by a characteristic curve having a maximum of about 30 dB with respect to the amplitude of said video carrier to produce a distorted signal. 
     
     
       8. A television system according to claim .[.7.]. .Iadd.13 .Iaddend.wherein said means for reducing comprises means for restoring said television signal by decreasing the magnitude of said signals in said region by amounts substantially equal in magnitude but opposite in sign to the amount of increase provided by said means for distorting. 
     
     
       9. A method for scrambling a television signal having a video carrier and an audio carrier comprising distorting said signal by increasing the amplitude of said signal between said video and audio carriers .Iadd.as a function of frequency .Iaddend.by a characteristic curve having a maximum of about 30 dB with respect to the amplitude of said video carrier to produce a distorted signal. 
     
     
       10. A method according to claim 9 further comprising the step of increasing the amplitude of said video carrier by about 8 dB. 
     
     
       11. A method according to claim 10 further comprising the step of supplying jamming signals between said audio and video carriers during at least one of the horizontal or vertical blanking intervals. 
     
     
       12. A method according to claim 11 further comprising the step of restoring said television signal by decreasing the amplitude of said distorted signal by an amount equal to but opposite .[.is.]. .Iadd.in .Iaddend.sign to said characteristic curve. .Iadd.13. A television system according to claim 6 further comprising means for reducing the amplitude of said gated jamming signal to permit a receiver to detect synchronizing pulses and color burst signals..Iaddend. .Iadd.14. A television signal enhancement and scrambling system, comprising: an input, for receiving a video IF signal having a video carrier at an intermediate frequency and a video signal portion with horizontal and vertical blanking intervals; and   distortion means, coupled to said input, for distorting the video signal portion of said IF signal by increasing the amplitude of the video signal portion, as a function of frequency and in accordance with a distortion curve, to form a distorted IF signal..Iaddend. .Iadd.15. A system as recited in claim 14, wherein the distortion curve of said distortion means has a maximum of at least 30 dB with respect to its level at the   
     
     
        intermediate frequency of the video carrier..Iaddend. .Iadd.16.  A system as recited in claim 14, further comprising modulator means, coupled to said distortion means, for producing a television signal from said distorted IF signal, wherein said television signal includes video and audio carriers at respective radio frequencies, and the video signal portion of said distorted IF signal is relocated between the video and audio carriers of said television signal, whereby said television signal is distorted by the increase in amplitude of the video signal portion..Iaddend. .Iadd.17. A system as recited in claim 14, further comprising means for supplying a jamming signal to the video signal portion of said IF signal during the horizontal blanking intervals of the video signal portion..Iaddend. .Iadd.18. A system as recited in claim 14, further comprising means for supplying a jamming signal to the video signal portion of said IF signal during the vertical blanking intervals of the video signal portion..Iaddend. .Iadd.19. A system as recited in claim 14, further comprising means for supplying a jamming signal to the video signal portion of said IF signal during both the horizontal and vertical blanking intervals of the video signal portion..Iaddend. .Iadd.20. A system as recited in claim 15, wherein the distortion curve of said distortion means has a Gaussian shape..Iaddend. .Iadd.21. A system as recited in claim 16, further comprising means for restoring said television signal by decreasing the amplitude of the video signal portion of said television signal in accordance with a restoring curve that is 
     
     
        substantially the inverse of said distortion curve..Iaddend. .Iadd.22.  A system as recited in claim 17, further comprising means for supplying a second jamming signal to the video signal portion of said IF signal during the vertical blanking intervals of the video signal..Iaddend. .Iadd.23. A system as recited in claim 19, wherein said jamming signal is a single frequency carrier signal..Iaddend. .Iadd.24. A system as recited in claim 19, wherein said jamming signal is a noise signal..Iaddend. .Iadd.25. A system as recited in claim 21, wherein said restoring means is a passive filter..Iaddend. .Iadd.26. A system as recited in claim 21, wherein both the distortion curve and the restoring curve have Gaussian shapes..Iaddend. .Iadd.27. An apparatus for distorting a television signal such that a television receiving said distorted signal is unable to produce an acceptable picture unless said signal is properly restored, said television signal having frequency spaced video and audio carriers and horizontal and vertical blanking intervals, said apparatus comprising an encoder that effects an increase in the amplitude of said television signal, as a function of frequency, between said video carrier and said audio carrier, by such an amount that said television signal is distorted thereby..Iaddend. .Iadd.28. An apparatus as recited in claim 27, wherein said encoder effects the increase in amplitude in accordance with a   
     
     
        distortion curve..Iaddend. .Iadd.29.  An apparatus as recited in claim 27, wherein said television signal is produced from a video IF signal having a video carrier and a video signal portion, and wherein said encoder effects the increase in amplitude of said television signal by increasing the amplitude of the video signal portion of said IF signal, in accordance with a distortion curve. .Iaddend. .Iadd.30. An apparatus as recited in claim 27, further comprising means for supplying a jamming signal to said television signal, between said video and said audio carriers, during the horizontal blanking intervals of said signal..Iaddend. .Iadd.31. An apparatus as recited in claim 27, further comprising means for supplying a jamming signal to said television signal, between said video and said audio carriers, during the vertical blanking intervals of said signal..Iaddend. .Iadd.32. An apparatus as recited in claim 28, further comprising means for restoring said television signal by decreasing its amplitude, between the video and audio carriers, in accordance with a restoring curve that is substantially the inverse of said distortion curve..Iaddend. .Iadd.33. An apparatus as recited in claim 32, wherein said distortion curve and said restoring curve have Gaussian shapes..Iaddend. .Iadd.34. A method of distorting a television signal such that a television receiving said distorted signal is unable to produce an acceptable picture unless said signal is properly restored, said television signal having frequency spaced video and audio carriers and horizontal and vertical blanking intervals, the method comprising the step of increasing the amplitude of said television signal, as a function of frequency, between said video carrier and said audio carrier, by such an amount that said television signal is distorted thereby..Iaddend. .Iadd.35. A method as recited in claim 34, wherein said television signal is produced from a video IF signal having a video carrier and a video signal portion, and wherein said step of increasing the amplitude of said television signal is effected by increasing the amplitude of the video signal portion, in accordance with a distortion curve..Iaddend. .Iadd.36. A method as recited in claim 34, wherein the amplitude of said television signal is increased in accordance with a distortion curve..Iaddend. .Iadd.37. A method as recited in claim 34, wherein comprising the step of supplying a jamming signal to said television signal, between said video and said audio carrier frequencies, during the horizonal blanking intervals of said signal..Iaddend. .Iadd.38. A method as recited in claim 34, further comprising the step of supplying a jamming signal to said television signal, between said video and said audio carrier frequencies, during the vertical blanking intervals of said signal..Iaddend. .Iadd.39. A method as recited in claim 36, further comprising the step of restoring said television signal by decreasing the amplitude of the scrambled signal between the video and audio carriers in accordance with a restoring curve that is substantially the inverse of said distortion curve..Iaddend. .Iadd.40. A method as recited in claim 37, further comprising the step of supplying a second jamming signal to said television signal, between said video and said audio carrier frequencies, during the vertical blanking   
     
     
        intervals of said signal..Iaddend. .Iadd.41.  A method as recited in claim 39, wherein the distortion curve and the restoring curve have Gaussian shapes..Iaddend. .Iadd.42. An apparatus for restoring a television signal that has been distorted by an increase in its amplitude, between its video and audio carriers, in accordance with a distortion curve, said restoring apparatus comprising: an input for accepting the distorted television signal; and   means, coupled to said input, for decreasing the amplitude of the distorted television signal, between the video and audio carriers, in accordance with a restoring curve that is substantially the inverse of said distortion curve..Iaddend. .Iadd.43. An apparatus for restoring a television signal that has been distorted by an increase in its amplitude as a function of frequency and in accordance with a distortion curve, said restoring apparatus comprising:   a filter having a restoring curve that is substantially the inverse of said distortion curve, so that when the distorted television signal is passed through said filter, its amplitude is decreased in accordance with said restoring curve, to produce a restored television signal..Iaddend. .Iadd.44. An apparatus as recited in claim 43, wherein said filter is a passive filter..Iaddend. .Iadd.45. An apparatus as recited in claim 43, wherein the restoring curve of said filter has a Gaussian shape..Iaddend. .Iadd.46. A method of restoring a television signal that has been distorted by an increase in its amplitude as a function of frequency and in accordance with a distortion curve, said method comprising the steps of:   receiving the distorted television signal; and   decreasing the amplitude of the distorted signal in accordance with a restoring curve that is substantially the inverse of said distortion curve..Iaddend.