Four-channel stereophonic demodulating system

Claim 2

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonic composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; and means adding the signal at the input of each of said switching circuits to the output thereof to obtain level adjustments between the first, second and third subchannel signal components.

Claim 3

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonIc composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; means adding the signal at the input of at least one of said switching circuits to the output thereof to obtain a level adjustment between at least two of the first, second and third subchannel signal components; and means adding said four-channel stereophonic comosite signal at least including the main channel component to the outputs of the second and third switching circuits.

Claim 4

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonIc composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; means adding the signal at the input of at least one of said switching circuits to the output thereof to obtain a level adjustment between at least two of the first, second and third subchannel signal components; and means adding said four-channel stereophonic comosite signal at least including the main channel component to the outputs of the second and third switching circuits.

Claim 5

A four-channel stereophonic demodulating system according to claim 2, wherein the input signal to the first switching circuit is added to the outputs of the first switching circuit for obtaining a level adjustment between two of the first, second and third subchannel components, and the input signals to the second and third switching circuits are respectively added to the outputs of the second and third switching circuits for obtaining a level adjustment between another two of the first, second and third subchannel components.

Claim 6

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonic composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one Half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; and means adding the signal at the input of each of said switching circuits to the output thereof for level adjustment of the subchannel signal components relative to one another, said subchannel level adjusting adding means including first and second means, said first means adjusting the levels between said second and third subchannel signal components at the outputs of the first switching circuit when said first and second switching signals are at the frequencies of the first and third subcarrier signals, and said second means adjusting the levels between the first and second subchannel signal components at the outputs of the second and third switching circuits when said first and second switching signals are at the frequencies of the first and third subcarrier signals.

Claim 7

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonic composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one Half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; and means adding the signal at the input of each of said switching circuits to the output thereof for level adjustment of the subchannel signal components relative to one another, said subchannel level adjusting adding means including first and second means, said first means adjusting the levels between said second and third subchannel signal components at the outputs of the first switching circuit when said first and second switching signals are at the frequencies of the first and third subcarrier signals, and said second means adjusting the levels between the first and second subchannel signal components at the outputs of the second and third switching circuits when said first and second switching signals are at the frequencies of the first and third subcarrier signals.

Claim 8

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonic composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; and means adding the signal at the input of each of said switching circuits to the output thereof for level adjustment of the subchannel signal components relative to one another, said subchannel level adjusting adding means including a first and second means, said first means adJusting the levels between said second and third subchannel signal components at the outputs of the first switching circuit when said first and second switching signals are at the frequencies of the first and second subcarrier signals, and said second means adjusting the levels between the first and third subchannel signal components at the outputs of the second and third switching circuits when said first and second switching signals are at the frequencies of the first and second subcarrier signals.

Claim 9

A four-channel stereophonic demodulating system for demodulating a four-channel stereophonic composite signal containing a main channel signal component constituted by a first one of four different combinations of signals, said combinations of signals being obtained from four signals stereophonically related to one another, a first subchannel signal component obtained through suppressed-carrier amplitude modulation of a second one of said combinations of signals on a first subcarrier wave, a second subchannel signal component obtained through suppressed-carrier amplitude modulation of a third one of said combinations of signals on a second subcarrier wave 90* out of phase with respect to said first subcarrier wave, a third subchannel signal component obtained through suppressed-carrier amplitude modulation of a fourth one of said combinations of signals on a third subcarrier wave at double the frequency of said first and second subcarrier waves, at least one of said subchannel signal components having a level different from the levels of the other subchannel signal components, and a pilot signal having a frequency one half of said first subcarrier wave, said demodulating system comprising: means for producing a first switching signal at a harmonic frequency of said pilot signal; means for producing a second switching signal at another harmonic frequency of said pilot signal; a first switching circuit supplied with said four-channel stereophonic composite signal and operated by said first switching signal for producing a pair of output signals from the supplied composite signal; second and third switching circuits operated by said second switching signal for producing four audio signals at their output terminals from the supplied output signals of said first switching circuit; means for supplying the outputs of said first switching circuit to said second and third switching circuits; means for deriving said four audio signals from the outputs of said second and third switching circuits; and means adding the signal at the input of each of said switching circuits to the output thereof for level adjustment of the subchannel signal components relative to one another, said subchannel level adjusting adding means including a first and second means, said first means adJusting the levels between said second and third subchannel signal components at the outputs of the first switching circuit when said first and second switching signals are at the frequencies of the first and second subcarrier signals, and said second means adjusting the levels between the first and third subchannel signal components at the outputs of the second and third switching circuits when said first and second switching signals are at the frequencies of the first and second subcarrier signals.