Stereophonic television sound transmission system

The method of transmitting within a television broadcast channel having defined frequency limits left and right audio source signals and a video source signal each having a predetermined upper frequency limit, said video source signal being amplitude modulated on a video carrier to form an AM signal occupying a first portion of said channel, comprising the steps of:

• generating a composite signal including a first component representative of the sum of said left and right source signals, a second amplitude-modulated subcarrier component representative of the difference between said left and right signals, said subcarrier component having upper and lower sidebands centered about a suppressed subcarrier, and a pilot component having one-half the frequency of said suppressed subcarrier;
• generating an RF sound carrier in said broadcast channel having a predetermined frequency spacing from said video-modulated signal;
• modulating said sound carrier with said composite signal to form an FM signal occupying a second portion of said channel;
• conveying said video- and audio-modulated signals in said broadcast channel to a receiving location, and at said receiving location,
• developing said composite signal from said audiomodulated signal in said channel;
• and
• developing said left and right audio source signals from said composite signal.

A receiver for receiving stereophonic sound transmissions included on a television broadcast channel of defined frequency limits, wherein said sound transmissions comprise a sound carrier frequency-modulated by a composite signal including a first component representative of the sum of the left and right source signals, a second amplitude modulated subcarrier component representative of the difference between the left and right signals, said subcarrier component having upper and lower sidebands centered about a suppressed subcarrier, and a pilot component having a frequency one-half the frequency of said suppressed carrier;

• said receiver comprising, in combination:
• tuner means for converting said television broadcast channel to an intermediate frequency channel including an intermediate frequency sound signal;
• sound bandpass filter means for separating said sound signal from said intermediate frequency channel;
• sound detector means for deriving from said intermediate frequency sound signal a composite signal including said first, second and third components;
• and
• stereo demodulator means for deriving said left and right source signals from said composite signal.

A television sound converter for receiving on an FM stereo broadcast receiver adapted to receive signals having a predetermined maximum deviation within a predetermined frequency range stereophonic sound transmissions included on a television broadcast channel of defined frequency limits, wherein said sound transmissions comprise a sound carrier frequency-modulated by a composite signal including a first component representative of the sum of the left and right source signals, a second amplitude-modulated subcarrier component representative of the difference between the left and right signals, said subcarrier component having upper and lower sidebands centered about a suppressed carrier, and a pilot component representative of the phase and frequency of the suppressed carrier;

• said converter comprising, in combination:
• tuner means for converting said television broadcast channel to an intermediate frequency channel including an intermediate frequency sound signal, said signal having a frequency comprising a predetermined fraction of a predetermined reception frequency within said predetermined frequency range, and having a maximum frequency deviation equal to said predetermined fraction of said predetermined maximum deviation of said receiver, where said fraction has a numerator of unity and a denominator of integer n;
• frequency multiplier means for multiplying the frequency of an applied signal by a factor of n;
• and
• means for applying said sound signal to said frequency multiplier means to obtain an RF output signal for application to said FM broadcast receiver.

A system for simultaneously transmitting first and second audio program sources in conjunction with a video source signal modulated on an RF carrier on a television broadcast channel having defined frequency limits, said system comprising, in combination:

• generator means including a stereo multiplex generator for generating from left and right applied input signals a composite signal including a first component representative of the sum of said left and right signals, a second amplitude-modulated subcarrier component representative of the difference between said left and right signals, said subcarrier component having upper and lower sidebands centered about a suppressed subcarrier, and a pilot component representative of the phase and having one-half the frequency of said suppressed subcarrier;
• means for generating an RF sound carrier within said broadcast channel having a predetermined spacing from said video-modulated carrier,
• means for frequency-modulating said sound carrier with said composite signal;
• receiver means for receiving said television broadcast channel including means for deriving said composite signal;
• demodulator means for developing said first and second audio signals from said composite signal;
• first matrixing means associated with said generator means for combining said first and second audio program sources to form said left and right input signals whereby said first component of said composite signal conveys only said first program source and said second component of said composite signal conveys only said second program source;
• and
• second matrixing means associated with said demodulator means for combining said left and right audio signals to form said first and second program sources, respectively.