Scrambled video signal transmission system with pulse-code modulated subcarrier

A scrambled FM video signal transmission system comprising:

• an amplitude modulator;
• a scrambler coupled to the output of said amplitude modulator;
• an amplitude demodulator coupled to the output of said scrambler;
• a frequency splitter coupled to the output of said amplitude demodulator, said splitter having a first and a second output for providing a first signal having a first frequency range and a second signal having a second frequency range, respectively;
• a sucarrier modulator for providing a pulse-code modulated subcarrier signal coupled to said first output of said splitter;
• a first signal combiner having a first input coupled to said subcarrier modulator and a second input coupled to said second output of said splitter;
• a frequency modulator coupled to the output of said signal combiner;
• a frequency demodulator;
• means for transmitting video signals from said frequency modulator to said frequency demodulator;
• a subcarrier demodulator for demodulating said pulse-code modulated subcarrier signal coupled to said frequency demodulator;
• a second signal combiner having a first input coupled to said subcarrier demodulator and a second input coupled to said frequency demodulator;
• an amplitude modulator coupled to said second signal combiner;
• a descrambler coupled to said amplitude demodulator;
• and
• an amplitude demodulator.

A scrambled FM video signal transmission system comprising:

• means responsive to a baseband video signal for modulating the amplitude of a first carrier signal, said first carrier signal modulating means having an output for providing a first amplitude modulated signal;
• means responsive to said first amplitude modulated signal for scrambling said first amplitude modulated signal, said scrambling means having an output for providing a scrambled first amplitude modulated signal;
• means responsive to said scrambled first amplitude modulated signal for removing said first carrier signal from said scrambled first amplitude modulated signal, said first carrier signal removing means having an output for providing a scrambled baseband video signal;
• means responsive to said scrambled baseband video signal for splitting the frequencies in said scrambled baseband video signal, said frequency splitting means having a first output for providing a first signal having a first range of frequencies and a second output for providing a second signal having a second range of frequencies;
• means responsive to said first signal for pulse-code modulating a second carrier signal, said second carrier modulating means having an output for providing a pulse-code modulated subcarrier signal;
• means responsive to said pulse-code modulated subcarrier signal and said second output of said frequency splitting means for combining said pulse-code modulated subcarrier signal and said second signal from said second output of said frequency splitting means, said combining means having an output for providing a first combined output signal;
• means responsive to said first combined output signal for modulating the frequency of a third carrier signal, said frequency modulating means having an output for providing a scrambled frequency modulated video signal;
• means responsive to said scrambled frequency modulated video signal for removing said third carrier signal from said scrambled frequency modulated video signal, said third carrier signal removing means having an output for providing a frequency demodulated output signal;
• means responsive to said frequency demodulated output signal for removing said second carrier signal from said frequency demodulated output signal, said second carrier removing means including pulse-code demodulating means for restoring said first signal having said first frequency range;
• means responsive to said restored first signal from said output of said second carrier removing means and said frequency demodulated output signal for combining said restored first signal from said second carrier removing means and said frequency demodulated output signal from said second carrier removing means for providing a second combined output signal;
• means responsive to said second combined output signal for modulating the amplitude of a fourth carrier signal, said fourth carrier signal modulating means having an output for restoring said scrambled amplitude modulated video signal;
• means responsive to said restored scrambled amplitude modulated video signal from said fourth carrier signal amplitude modulating means for descrambling said restored scrambled amplitude modulated video signal, said descrambling means having an output for restoring said amplitude modulated video signal;
• and
• means responsive to said restored amplitude modulated video signal for removing said fourth carrier signal, said fourth carrier signal removing means having an output for restoring said baseband video signal.

A method of transmitting a scrambled FM video signal comprising the steps of:

• removing the amplitude modulation from a scrambled amplitude modulated video signal for providing a scrambled video signal, said scrambled video signal having low and high frequency components therein;
• separating said low frequency components from said high frequency components in said scrambled video signal;
• pulse-code modulating a subcarrier in response to said low frequency components for providing a pulse-code modulated subcarrier signal;
• providing in response to said pulse-code modulated subcarrier signal and said high frequency components in said scrambled video signal a scrambled frequency modulated video signal;
• and
• restoring in response to said scrambled frequency modulated video signal said scrambled amplitude modulated video signal.