Matrix decoders for quadraphonic sound system

Claim 2

Apparatus for decoding four individual audio information signals to the extent they are contained in first and second encoded composite signals, each of which contains up to three of said audio information signals, two of which are common in said two composite signals and corresponding ones of said common signals being at a predetermined phase angle relative to each other, said apparatus comprising: first and second input terminals to which said first and second composite signals are respectively applied, first, second, third and fourth output channels, means for coupling said first and second composite signals to said first and second output channels, respectively, with the same relative phase as they exhibit at said input terminals, all-pass phase-shifting means connected to said input terminals for shifting the phase of one of said composite signals relative to the other by said predetermined phase angle over the frequency range of interest for positioning said common signals in one of said relatively phase-shifted composite signals either substantially in phase coincidence or substantially in phase opposition with corresponding ones of said common signals in the other of said relatively phaseshifted composite signals, means for selectively combining predetermined proportions of said relatively phase-shifted first and second composite signals and operative to produce third and fourth composite signals each containing a different one of said common signals as its predominant component, and means for coupling said third and fourth composite signals to said third and fourth output channels, respectively.

Claim 3

Apparatus in accordance with claim 1, wherein said phase-shifting means comprises first and second all-pass phase-shifting networks operative to shift the phase of said first composite signal relative to said second composite signal by said predetermined phase angle, wherein said means for coupling said first and second composite signals to said first and second output channels comprises said first and second phase-shifting networks and third and fourth all-pass phase-shifting networks respectively connected between said first phase-shifting network and said first output channel and between said second phase-shifting network and said second output channel, said third and fourth phase-shifting networks being operative to shift the phase of the phase-shifted first composite signal from said first phase-shifting network relative to the phase-shifted second composite from said second phase-shifting network signal by said predetermined phase angle, and wherein said means for coupling said third and fourth composite signals to their respective output channels comprises fifth and sixth all-pass phase-shifting networks operative to shift the phase of said third composite signal relative to said fourth composite signal by said predetermined phase angle.

Claim 4

Apparatus in accordance with claim 1 wherein said predetermined phase angle is substantially 90* and said predetermined proportion is substantially the decimal fraction 0.707.

Claim 5

Apparatus in accordance with claim 2, wherein said predetermined phase angle is substantially 90* and said predetermined proportion is substantially the decimal fraction 0.707.

Claim 6

Apparatus in accordance with claim 1, wherein said phase-shifting means comprises first and second pairs of all-pass phase-shifting networks and wherein said first and second composite signals are applied to both phase-shifting networks of its respectIve pair, the first network of each pair being operative to shift the phase of signals applied thereto relative to the signals applied to the second network of the pair by said predetermined phase angle, wherein said means for coupling said first and second composite signals to their respective output channels comprises connections between the first network of the first pair and said first output channel and between the first network of the second pair and said second output channel, and wherein said combining means comprises a first network for combining said predetermined proportion of the output signal from the second network of the first pair with said predetermined proportion of the output signal from the first network of the second pair for producing said third composite signal, and a second network for combining said predetermined proportion of the output signal from the first network of the first pair with said predetermined proportion of the output signal from the second network of the second pair for producing said fourth composite signal.

Claim 7

Apparatus in accordance with claim 5 wherein said predetermined phase angle is substantially 90* and wherein said predetermined proportion is substantially the decimal fraction 0.707.

Claim 8

Apparatus in accordance with claim 1, wherein said phase-shifting means comprises first and second pairs of all-pass phase-shifting networks each having input and output terminals, the first network of each pair being operative to shift the phase of signals applied thereto by a predetermined reference angle and the second network of each pair being operative to shift the phase of signals applied thereto by an angle which differs from said predetermined angle by 90*, means for coupling said first composite signal to the input terminals of both phase-shifting networks of said first pair, and means for coupling said second composite signal to the input terminals of both phase-shifting networks of said second pair, and wherein said combining means comprises first summing means connected to the output terminal of the second phase-shifting network of said first pair and to the output terminal of the first phase-shifting network of said second pair operative to add equal proportions of the signals appearing thereat to produce said third composite signal, and second summing means connected to the output terminal of the first phase-shifting network of said first pair and to the output terminal of the second phase-shifting network of said second pair operative to add equal proportions of the signals appearing thereat to produce said fourth composite signal.

Claim 9

Apparatus in accordance with claim 7 wherein said proportion is substantially the decimal fraction 0.707.

Claim 10

Apparatus for decoding first and second composite input signals respectively containing dominant signals a and b and each including a sub-dominant signal component c of substantially equal magnitude and in substantially quadrature phase relationship in said first and second composite signals and a sub-dominant signal component d of substantially equal magnitude and in substantially quadrature phase relationship in said first and second composite signals, the signal components c and d in one of the composite signals being in leading and lagging relationship, respectively, with the signal components c and d in the other of the composite signals, said apparatus comprising: first and second input circuits having respective first and second input terminals and each including all-pass phase-shifting means for deriving from the first and second composite signals first and second composite output signals which are in phase quadrature relationship with one another, first, second, third and fourth output channels, means for coupling the first and second composite signals from the first and second input terminals without relative phase-shift to said first and second ouptut channels, respectively, first summing means for combining equal proportions of the first composite output signal from the first input circuit and of the second composite output signal from the second input circuit to produce a third composite signal predominantly containing the signal component c, second summing means for combining equal proportions of the second composite signal from the first input circuit and of the first composite output signal from the second input circuit to produce a fourth composite signal predominantly containing the signal component d, and means for coupling said third and fourth composite signals to said third and fourth output channels, respectively.

Claim 11

Apparatus for decoding first and second composite input signals respectively containing dominant signals a and b and each including a sub-dominant signal component c of substantially equal magnitude and in substantially quadrature phase relationship in said first and second composite signals and a sub-dominant signal component d of substantially equal magnitude and in substantially quadrature phase relationship in said first and second composite signals, the signal components c and d in one of the composite signals being in leading and lagging relationship, respectively, with the signal components c and d in the other of the composite signals, said apparatus comprising: first and second input circuits having respective first and second input terminals and each including all-pass phase-shifting means for deriving from the first and second composite signals first and second composite output signals which are in phase quadrature relationship with one another, first, second, third and fourth output channels, means for coupling the first and second composite signals from the first and second input terminals without relative phase-shift to said first and second ouptut channels, respectively, first summing means for combining equal proportions of the first composite output signal from the first input circuit and of the second composite output signal from the second input circuit to produce a third composite signal predominantly containing the signal component c, second summing means for combining equal proportions of the second composite signal from the first input circuit and of the first composite output signal from the second input circuit to produce a fourth composite signal predominantly containing the signal component d, and means for coupling said third and fourth composite signals to said third and fourth output channels, respectively.

Claim 12

Apparatus in accordance with claim 9, wherein said input circuits each include a pair of all-pass phase-shifting networks to both of which the corresponding composite input signal is applied, one of the phase-shifting networks of the pair being operative to shift the phase of the applied signal by a predetermined reference angle and the other phase-shifting network of the pair being operative to shift the phase of signals applied thereto by an angle which differs by 90* from the said reference angle.

Claim 13

Apparatus in accordance with claim 10, wherein for each of the composite output signals, the proportion of the signal applied to the first and second summing means is 0.707.

Claim 14

Apparatus for decoding first and second input composite signals respectively designated LT and RT and each including to the extent they are present sub-dominant left back (Lb) and right back (Rb) component signals with the same predetermined phase-shift angle between said Lb component signals and between said Rb component signals and with the Lb component signal in one of said composite signals leading the Lb component signal in the other and with the Rb component signal in said one composite signal lagging the Rb component signal in the other, and respectively including to the extent they are present dominant left front (Lf) and right front (Rf) component signals, into four composite output signals respectively containing said Lf, Rf, Lb and Rb component signals as its predominant signal, said apparatus comprising: first and second input terminals to which said LT and RT signals are respectively applied, first, second, third and fourth output channels respectively identified as Lf, Rf, Lb and Rb output channels, means connected between said first and second input terminals and said first and second output channels for coupling said first and second input composite signals respectively containing said Lf and Rf component signals as predominant signals to said first and second output channels, means connected to said first and second input terminals including all-pass phase-shifting networks for shifting the phase of one of said input composite signals relative to the other by said predetermined phase-shift angle for positioning the Lb and Rb components in one of said relatively phase-shifted composite signals either in phase coincidence or in phase opposition with the Lb and Rb components, respectively, in the other relatively phase-shifted composite signal, and means connected in circuit between said phase-shifting means and said third and fourth output channels for selectively combining predetermined proportions of said relatively phase-shifted first and second composite signals and operative to couple to said third and fourth output channels composite signals which respectively contain said Lb and Rb component signals as predominant components.

Claim 15

Apparatus for decoding first and second input composite signals respectively designated LT and RT and each including to the extent they are present sub-dominant left back (Lb) and right back (Rb) component signals with the same predetermined phase-shift angle between said Lb component signals and between said Rb component signals and with the Lb component signal in one of said composite signals leading the Lb component signal in the other and with the Rb component signal in said one composite signal lagging the Rb component signal in the other, and respectively including to the extent they are present dominant left front (Lf) and right front (Rf) component signals, into four composite output signals respectively containing said Lf, Rf, Lb and Rb component signals as its predominant signal, said apparatus comprising: first and second input terminals to which said LT and RT signals are respectively applied, first, second, third and fourth output channels respectively identified as Lf, Rf, Lb and Rb output channels, means connected between said first and second input terminals and said first and second output channels for coupling said first and second input composite signals respectively containing said Lf and Rf component signals as predominant signals to said first and second output channels, means connected to said first and second input terminals including all-pass phase-shifting networks for shifting the phase of one of said input composite signals relative to the other by said predetermined phase-shift angle for positioning the Lb and Rb components in one of said relatively phase-shifted composite signals either in phase coincidence or in phase opposition with the Lb and Rb components, respectively, in the other relatively phase-shifted composite signal, and means connected in circuit between said phase-shifting means and said third and fourth output channels for selectively combining predetermined proportions of said relatively phase-shifted first and second composite signals and operative to couple to said third and fourth output channels composite signals which respectively contain said Lb and Rb component signals as predominant components.

Claim 16

Apparatus in accordance with claim 12, wherein said predetermined phase-shift angle is substantially 90*, and wherein said predetermined propoRtion is substantially the decimal fraction 0.707.

Claim 17

Apparatus in accordance with claim 12, wherein said input circuits each include a pair of all-pass phase-shifting networks to both of which the corresponding composite input signal is applied, one of the phase-shifting networks of the pair being operative to shift the phase of the applied signal by a predetermined reference angle and the other phase-shifting network of the pair being operative to shift the phase of signals applied thereto by an angle differing from said reference angle by said predetermined phase-shift angle, and wherein said signal-combining means comprises first summing means for combining equal proportions of the composite signal from the first network of the first pair and the composite signal from the second network of the second pair and coupling to said Lb output channel a composite signal which contains said Lb component signal as its predominant component, and second summing means for combining equal proportions of the composite signal from the second network of the first pair and the composite signal from the first network of the second pair and coupling to said Rb output channel a composite signal which contains said Rb component signal as its predominant component.

Claim 18

Apparatus in accordance with claim 14, wherein said predetermined phase-shift angle is substantially 90*, and wherein for each of the composite signals from said phase-shifting networks, the proportion of the signal applied to the first and second summing means is 0.707.

Claim 19

Apparatus in accordance with claim 14, wherein said predetermined phase-shift angle is substantially 90*, wherein for each of the composite signals from the first network of the first pair and from the second network of the second pair, the proportion of the signal applied to the first summing means is 0.707, and wherein for each of the composite signals from the second network of the first pair and from the first network of the second pair, the proportion of the signal applied to the second summing means is -0.707.

Claim 20

Apparatus in accordance with claim 12, wherein said input circuits each include first and second all-pass phase-shifting networks to both of which the corresponding composite input signal is applied, said first phase-shifting network being operative to shift the phase of the applied signal by a predetermined reference angle and said second phase-shifting network being operative to shift the phase of the applied signal by an angle differing from said reference angle by substantially 90*, wherein the composite signals from the second network of said first and second input circuits, respectively containing said Lf and Rf component signals as their predominant component, are respectively coupled to said first and second output channels, and wherein said signal-combining means comprises first summing means for combining substantially 0.707 of the composite signal from said second network of said first input circuit and substantially 0.707 of the composite signal from said first network of said second input circuit and coupling to said third output channel a composite signal which contains said Lb component signal as its predominant component, and second summing means for combining substantially 0.707 of the composite signal from said first network of said first input circuit and substantially 0.707 of the composite signal from said second network of said second input circuit and coupling to said fourth output channel a composite signal which contains said Rb component signal as its predominant component.

Claim 23

The method according to claim 18, wherein said predetermined phase-shift angle is substantially 90*, wherein the signals in the two channels are relatively shifted in phase by substantially 90*, and wherein said predetermined proportion is substantially the decimal fraction 0.707.

Claim 24

Apparatus for reproducing at least four individual audio information signals to the extent they are contained in two information channels, wherein the signal in each of said channels comprises a combination of at least three of said audio information signals with preselected phase and amplitude relationships, said apparatus comprising first and second input circuits to which the signals in said two information channels are respectively applied, said input circuits including all-pass phase-shifting means operative to shift the phase of one of said channel signals relative to the other channel signal by a preselected angle which remains substantially constant over the frequency range of said audio information signals thereby to produce relatively phase-shifted first and second channel signals, electrical circuit means for combining said relatively phase-shifted first and second channel signals with preselected amplitude and phase relationships for deriving a first pair of output signals in each of which a different desired one of two of said audio information signals is predominant, and circuit means for deriving from said first and second channel signals a second pair of output signals in each of which a different desired one of the other two of said audio information signals is predominant, whereby a different desired one of said audio information signals is predominant in each of said four output signals.

Claim 25

Apparatus for reproducing at least four individual audio information signals to the extent they are contained in two information channels, wherein the signal in each of said channels comprises a combination of at least three of said audio information signals with preselected phase and amplitude relationships, said apparatus comprising first and second input circuits to which the signals in said two information channels are respectively applied, said input circuits including all-pass phase-shifting means operative to shift the phase of one of said channel signals relative to the other channel signal by a preselected angle which remains substantially constant over the frequency range of said audio information signals thereby to produce relatively phase-shifted first and second channel signals, electrical circuit means for combining said relatively phase-shifted first and second channel signals with preselected amplitude and phase relationships for deriving a first pair of output signals in each of which a different desired one of two of said audio information signals is predominant, and circuit means for deriving from said first and second channel signals a second pair of output signals in each of which a different desired one of the other two of said audio information signals is predominant, whereby a different desired one of said audio information signals is predominant in each of said four output signals.

Claim 26

Apparatus in accordance with claim 20 wherein said phase-shifting means is operative to shift the phase of one of said channel signals relative to the other by substantially 90*.

Claim 27

A decoder for reproducing at least first, second and third of first, second, third and fourth audio information signals to the extent said four audio information signals are contained in first and second composite input signals respectively containing said first and second audio information signals in equal predominant proportions and both containing said third and fourth audio information signals in equal sub-dominant proportions with said third and fourth audio information signals in one of said composite input signals in substantially quadrature relationship with the third and fourth audio information signals, respectively, in the other composite input signals, said decoder comprising: means for coupling said first and second composite signals without relative phase shift between them to first and second output terminals, respectively, as first and second output signals in which said first and second audio information signals are respectively predominant, means for shifting the phase of one of said composite input signals relative to the other by about 90* for positioning the third audio information signal in the phase-shifted one input signal in phase with the third audio information signal in the unshifted other input signal and for positioning the fourth audio information signal in the phase-shifted one input signal in phase opposition with the fourth audio information signal in the unshifted other input signal, and means for combining said phase-shifted one input signal and said unshifted other input signal to produce at a third output terminal a third output signal in which said third audio information signal is predominant.

Claim 28

A decoder for reproducing at least first, second and third of first, second, third and fourth audio information signals to the extent said four audio information signals are contained in first and second composite input signals respectively containing said first and second audio information signals in equal predominant proportions and both containing said third and fourth audio information signals in equal sub-dominant proportions with said third and fourth audio information signals in one of said composite input signals in substantially quadrature relationship with the third and fourth audio information signals, respectively, in the other composite input signals, said decoder comprising: means for coupling said first and second composite signals without relative phase shift between them to first and second output terminals, respectively, as first and second output signals in which said first and second audio information signals are respectively predominant, means for shifting the phase of one of said composite input signals relative to the other by about 90* for positioning the third audio information signal in the phase-shifted one input signal in phase with the third audio information signal in the unshifted other input signal and for positioning the fourth audio information signal in the phase-shifted one input signal in phase opposition with the fourth audio information signal in the unshifted other input signal, and means for combining said phase-shifted one input signal and said unshifted other input signal to produce at a third output terminal a third output signal in which said third audio information signal is predominant.

Claim 29

Apparatus in accordance with claim 22 wherein said predominant and sub-dominant proportions are in the ratio of about 1:.707, wherein said phase-shifting means comprises first and second all-pass phase-shifting networks to which said first and second composite input signals are respectively applied for shifting the phase of one of said composite input signals relative to the other by about 90*, and wherein said combining means comprises first means for adding substantially 0.707 of the output signal from one of said first and second phase-shifting networks to substantially 0.707 of the output signal from the other for producing said third output signal, and second means for subtracting substantially 0.707 of the output signal from one of said first and second phase-shifting networks from substantially 0.707 of the output signal from the other for producing at a fourth output terminal a fourth output signal in which said fourth audio information signal is predominant.

Claim 30

Apparatus in accordance with claim 22, wherein said predominant and sub-dominant proportions are in the ratio of about 1:.707, wherein said phase-shifting means comprises first and second pairs of all-pass phase-shifting networks, the first network of each pair being operative to shift the phase of signals applied thereto relative to the signals applied to the second network of the pair by about 90*, and wherein said first and second composite input signals are applied to both phase-shifting networks of a respective pair, and wherein said combining means comprises a first network for combining substantially 0.707 of the output signal from the second phase-shifting network of the first pair with substantially 0.707 of the output signal from the first phase-shifting network of the second pair for producing said third output signal in which said third audio information signal is predominant, and a second network for combining substantially 0.707 of the output signal from the first phase-shifting network of the first pair with substantially 0.707 of the output signal from the second phase-shifting network of the second pair for producing a fourth output signal at a fourth output terminal in which said fourth audio information signal is predominant.

Claim 31

Apparatus in accordance with claim 24, wherein the first network of each of said pairs is operative to shift the phase of signals applied thereto by a predetermined reference angle and the second network of each of said pairs is operative to shift the phase of signals applied thereto by an angle differing from said reference angle by about 90*.