Three-channel fm stereo transmission

Claim 2

A three-channel FM stereo transmission system comprising meAns for transmitting a carrier frequency-modulated in accordance with the modulation function where X, Y and Z are three independent audio signals, K1 and K2 are predetermined constants, M is the amplitude of a phase reference pilot signal sin( omega st/2), and omega s 2 pi fs where fs is the fundamental frequency of subcarrier signals cos omega st, cos ( omega st - 2/3 pi ) and cos ( omega st - 4/3 pi ), each subcarrier signal being suppressed-carrier doublesideband amplitude-modulated by a respective one of said audio signals; and receiver means operative in response to the reception of said frequency-modulated carrier for reproducing each of said three audio signals.

Claim 3

A stereo transmission system as defined in claim 1 wherein the constant K1 2/ Square Root 3.

Claim 4

A stereo transmission system as defined in claim 2 wherein the constant K2 1/3 .

Claim 5

A stereo system as defined in claim 3 wherein said receiver means includes means for alternatively reproducing conventional monophonic and two-channel stereophonic broadcasts.

Claim 6

In a three-channel FM stereo transmission system, a transmitter for generating and broadcasting a carrier frequency-modulated in accordance with the modulation function where X, Y and Z are three independent stereophonically related audio signals, M is the amplitude of a sin( omega st/2) pilot signal, and omega s 2 pi fs where fs is the fundamental frequency of the cos omega st, cos ( omega st - 2/3 pi ) and cos ( omega st - 4/3 pi ) subcarrier signals, each subcarrier signal being suppressed-carrier double-sideband amplitude-modulated by a respective audio signal.

Claim 7

In a three-channel FM stereo transmission system, a transmitter for generating and broadcasting a carrier frequency-modulated in accordance with the modulation function where X, Y and Z are three independent stereophonically related audio signals, M is the amplitude of a sin( omega st/2) pilot signal, and omega s 2 pi fs where fs is the fundamental frequency of the cos omega st, cos ( omega st - 2/3 pi ) and cos ( omega st - 4/3 pi ) subcarrier signals, each subcarrier signal being suppressed-carrier double-sideband amplitude-modulated by a respective audio signal.

Claim 8

A stereo system as defined in claim 5 including receiver means for reproducing monophonic, two-channel stereophonic and three-channel stereophonic broadcasts, said receiver means being switched to a three-channel stereophonic mode of operation in response to the reception of a frequency-modulated carrier comprising a sin (3/2) omega st signal.

Claim 9

In a three-channel FM stereophonic transmission system, a transmitter comprising three independent sources of stereophonically related audio frequency waves, means for adding the audio waves together to obtain a sum signal, means for generating three subcarriers of the same frequency and spaced 120* apart in phase, means for amplitude-modulating each subcarrier with a respective one of said audio waves to develop three double-sideband suppressed-carrier signals, the frequency of said subcarriers being sufficiently high as to assure a frequency gap between the lower sidebands of the modulated subcarrier signals and said sum signal, a phase reference pilot signal having a frequency which lies within said frequency gap, means for amplitude multiplying each double-sideband signal by a factor of 2 / Square Root 3, means for generating a three-channel mode switching signal which comprises an integral harmonic of said pilot signal, and means for frequency modulating the aforementioned signals onto a high frequency carrier for the purpose of transmitting the same to one or more remote receivers.

Claim 10

In a three-channel FM stereophonic transmission system, a transmitter comprising three independent sources of stereophonically related audio frequency waves, means for adding the audio waves together to obtain a sum signal, means for generating three subcarriers of the same frequency and spaced 120* apart in phase, means for amplitude-modulating each subcarrier with a respective one of said audio waves to develop three double-sideband suppressed-carrier signals, the frequency of said subcarriers being sufficiently high as to assure a frequency gap between the lower sidebands of the modulated subcarrier signals and said sum signal, a phase reference pilot signal having a frequency which lies within said frequency gap, means for amplitude multiplying each double-sideband signal by a factor of 2 / Square Root 3, means for generating a three-channel mode switching signal which comprises an integral harmonic of said pilot signal, and means for frequency modulating the aforementioned signals onto a high frequency carrier for the purpose of transmitting the same to one or more remote receivers.

Claim 11

A stereophonic system as defined in claim 7 including receiver means operative in response to the reception of said high frequency carrier to reproduce each of the audio frequency source signals.

Claim 12

A stereophonic system as defined in claim 8 wherein said receiver means includes means for reproducing conventional monophonic and two-channel stereophonic broadcasts.

Claim 13

A stereophonic system as defined in claim 9 wherein said receiver means is normally enabled to reproduce received monophonic or two-channel stereophonic broadcasts, with said receiVer means including a switching means operatively responsive to said mode switching signal to switch said receiver means to a three-channel stereophonic reception mode.

Claim 14

A stereophonic system as defined in claim 10 wherein said phase reference pilot signal is of a frequency one-half that of the subcarrier frequency, with said mode switching signal equal to one-third the amplitude of the third harmonic of said phase reference pilot signal.