US3786193A - Four channel decoder with variable mixing of the output channels - Google Patents

Four channel decoder with variable mixing of the output channels Download PDF

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US3786193A
US3786193A US00272439A US3786193DA US3786193A US 3786193 A US3786193 A US 3786193A US 00272439 A US00272439 A US 00272439A US 3786193D A US3786193D A US 3786193DA US 3786193 A US3786193 A US 3786193A
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signals
signal
subdominant
phase
composite
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K Tsurushima
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Sony Corp
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Sony Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/02—Systems employing more than two channels, e.g. quadraphonic of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

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  • ABSTRACT A crosstalk eliminating circuit for use in a four channel stereo decoder of the type which converts two composite signals L and R into four output signals containing dominant signal components L], R,, L,, and R respectively, with each of the output signals further including subdominant signal components as crosstalk.
  • the elimination circuit includes a crosstalk detecting circuit having a plurality of all wave rectifying circuits and subtraction circuits for producing tseparate signals for controlling a plurality of mixing circuits connected between separate pairs of output channels for transmitting the output signals, the mixing circuits being controlled so as to mix two output signals in accordance with the respective control signal in such a manner that the crosstalk signals contained therein are cancelled.
  • the corresponding original sound signals L L,,, R, and R be reproduced only from separate loudspeakers.
  • another sound signal which must be reproduced through another loudspeaker is atthe same time, reproduced as a crosstalk, which is an obviously undesirable result.
  • a multisignal decoding apparatus comprising, a first channel for transmitting a first composite signal containing a first dominant signal and at least one subdominant signal, a second channel for transmitting a second composite signal containing a second dominant signal and at least one subdominant signal which is of the same kind and in phase opposition to the subdominant signal in the first composite signal, a third channel for transmitting a third composite signal containing a third dominant signal and at least one subdominant signal, and a fourth channel for transmitting a fourth composite signal containing a fourth dominant signal and at least one subdominant signal which is of the same kind and in phase opposition to the subdominant signal in the third composite signal.
  • Circuit means are provided for producing a first and a second control signal by comparison with at least two of the first through four composite signals.
  • the first control signal is supplied to a first variable mixing means connected between the first and second channels for mixing the first and second composite signals with each other so as to cancel the out of phase subdominant signals contained thereinQ
  • the second control signal is supplied to a second variable mixing means connected between the third and fourth channels for mixing the third and fourth composite signals with each other so as to cancel the out of phase subdominant signals contained therein.
  • an object of the invention is to provide a multisignal transmission apparatus in which separation between channels is improved.
  • Another object of the invention is to provide a multisignal transmission apparatus in which a crosstalk signal can be cancelled without losing a main signal.
  • Another object of the invention is to provide a multisignal transmission apparatus which can eliminate a crosstalk signal between a pair of channels with a variable mixing circuit of simple construction.
  • a further object of the invention is to provide a multisignal transmission apparatus having a novel crosstalk canceller which applies encoded composite signals of different types to a matrix circuit for decoding the respective composite signals to thereby improve separation between channels.
  • Yet another object of the invention is to provide a multisignal transmission apparatus which cancels a crosstalk between channels without varying the gain of a channel transmitting a signal and consequently keeps a noise signal peculiar to sound elements substantially constant.
  • FIG. I is a schematic diagram illustrating an encoder for a better understanding of the invention.
  • FIG. 2 is a schematic diagram of one embodimentof a decoder in accordance with the invention.
  • FIG. 3 is a schematic diagram showing a crosstalk signal detecting circuit to be employed in the apparatus illustrated in FIG. 2;
  • FIG. 4 is a circuit diagram showing a mixing circuit to be employed in the apparatus illustrated in FIG. 2;
  • FIG. 5 is a schematic diagram of another encoder for explaining the invention.
  • FIGS. 6 and 7 are phasor diagrams for use in explaining the operation and advantages of the encoder shown in FIG. 5;
  • FIG. 8 is a schematic diagram of a second embodiment of a decoder used in connection with the invention.
  • FIG. 9 is a schematic diagram of another crosstalk detecting circuit to be employed in the decodershown in FIG. 8; I
  • FIG. 10 is a schematic diagram of a third embodiment of a decoder used in connection with the invention.
  • FIG. 11 is a schematic diagram of another crosstalk detecting circuit to be employed in the decoder shown in FIG. 10.
  • An encoder which encodes four original sound signals into two composite signals.
  • An encoder as illustrated in FIG. 1, has four input terminals 10, 12, 14 and 16 to which four original sound signals L,, L,, R, and R,, depicted as in-phase signals of equal amplitude in the figure, are respectively applied.
  • the total L, signal applied to the input terminal is added in a summing junction 18 to 0.707 of the R signal applied to the input terminal 14.
  • the output of the summing junction 18 is applied to a I -network (all-pass phaseshifting network) 20 which provides a phase-shift of I 90 (where I is a function of frequency).
  • the full R, signal applied to the input terminal 16 is added in a summing network 22 to 0.707 of the L, signal appearing at the input terminal 12 after it is passed through a phase inverter 12a.
  • the output of the summing network 22 is passed through a I -network 24, which also provides a phase-shift of I 90.
  • the phase-reversed L,, signal from the inverter 12a and the R signal are also applied to respective I -networks 26 and 28 which each provide a phase-shift of I.
  • the full signal appearing at the output side of the I -network 20 is added in a summing circuit 30 to 0.707 of the signal appearing at the output side of the network 26 to produce at its output terminal 32 a composite signal designated as L
  • the full signal from network 24 is added in a summing circuit 34 to 0.707 of the signal from the network 28 to produce at its output terminal 36 a composite signal designated at R,.
  • a phasor group 38 of the composite signal L consists of the L, signal, a 0.707R signal in phase with respect to the L, signal and a 0.707L,, signal lagging the L, signal by 90.
  • the phasor group of the composite signal R consists of the R, signal, a 0.707R signal leading the R, signal by 90 and a 0.707L,, signal leading the 0.707R, signal by 90.
  • composite signals L and R may be transmitted by an FM multiplex radio, or they may be recorded on any two-channel medium such as a two-track tape or stereophonic record for later reproduction.
  • the two composite signals L, and R, which are encoded by the encoder illustrated in FIG. 1 can be decoded by a decoder illustrated in FIG. 2 to four output signals containing dominant signals corresponding to the respective original signals.
  • the composite signals L, and R represented by the phasor groups 38 and 40 are applied to input terminals 50 and 52, respectively, of the decoder shown in FIG. 2. From the terminals 50 and 52 the signals are applied to respective I -networks 54 and 56. In this manner, the composite signal L passes without relative phase-shift through the network 54 and is thereafter applied to an amplifier 58.
  • the other composite signal R passes with a relative phaseshift of 90 through the network 56 and is next applied to an amplifier 60.
  • a 0.707 portion of the signal appearing at the output side of the network 54 is added in a summing junction 60 to -0.707 of the signal appearing at the output side of the network 56, the summed signal thus formed being applied to an amplitier 62.
  • a 0.707 portion of the signal appearing at the output side of the network 54 is also added in a summing junction 64 to 0.707 of the output signal of the network 56, and the summed signal thus formed is applied to an amplifier 66.
  • Phasor groups 68, 70, 72 and 74 indicate the output of the amplifiers 58, 62, 66 and 60, respectively.
  • the phasor group 68 consists of the L, signal, a 0.707 R, signal in phase with the L, signal and a 0.707 L,, signal lagging with respect to the R, and 0.707 R, signals by 90.
  • the phasor group 70 consists of the L,, signal, a 0.707 L, signal leading with respect to the L,, signal by 90 and a 0.707 R, signal leading with respect to the 0.707 L, signal by 90.
  • the phasor group 72 consists of the R signal, a 0.707 L, signal in phase with the R signal and a 0.707 R, signal lagging with respect to the R and 0.707 L, signals by 90.
  • the phasor group 74 consists of the R, signal, a 0.707 R, signal leading with respect to the R, signal by 90 and a 0.707 L,, signal leading with respect to the 0.707 R, signal by 90.
  • the 0.707 L, signal of the phasor group 68 and the 0.707 L,, signal of the phasor group 74 are out of phase with each other, and also that the 0.707 R, signal of the phasor group 70 and the 0.707 R, signal of the phasor group 72 are out of phase with each other.
  • the output signals of the amplifiers 60 and 66 are supplied to phase-inverters and 82, respectively, so that the polarities of the output signals of the phaseinverters 80 and 82 are reversed as shown by phasor groups 84 and 86.
  • phasor groups 84 and 86 It will be noted that the 0.707 R, signal of the phasor group 68 and the 0.707 R, signal of the phasor group 84 are out of phase with each other,-and also that the 0.707 L, signal of the phasor group 70 and the 0.707 L, signal of the phasor group 86 are out of phase with each other.
  • the output signals of the amplifiers 58 and 62 and the output signals of the phase-inverters 82 and 80 are respectively applied to I -networks 88, 90, 92 and 94.
  • the P-networks 88 and 92 provide a phase-shift of I while the P-networks 90 and 94 provide a phase-shift of I 0.
  • Output signals appearing at the output sides of I -networks 88 and 90 are transmitted to output terminals 112 and 114 through phase-inverters 96 and 98, respectively, and output signals appearing at the output sides of I -networks 92 and 94 are directly transmitted to output terminals 116 and 118, respectively.
  • Phasor groups of the output signals derived at the respective output terminals 112-118 are designated as 104, 106, 108 and 110, respectively. It will be noted that respective dominant signals, namely the L,, L,,, R, and R, signals in the respective phasor groups are in phase with one another.
  • the original sound signals L,, L,,, R, and R contained in the composite signals L, and R appear in the signals derived at the output terminals 112 118 as the dominant signals, respectively.
  • the output signal appearing at the output terminal 112 contains undesired subdominant signals L,, and R, which will cause crosstalk.
  • the output signal appearing at the output terminal 114 contains undesired subdominant signals L, and R, which will also cause crosstalk.
  • the mixing circuits are controlled in operation with the crosstalk components applied thereto in order to cancel or reduce the crosstalk components.
  • a first crosstalk canceller or a first variable mixing circuit means 120 is connected between the output sides of amplifiers 58 and 60.
  • a second variable mixing circuit means 122 is connected between the output sides of amplifiers 62 and 66,. the outputs of which contain the out of phase subdominant signals R,.
  • a third variable mixing circuit means 124 is connected between the output side of the amplifier 58' and the phase-inverter 80, in which the subdominant signals R, are out of phase.
  • a fourth variable mixing circuit 126 is connected between the output sides of the amplifier 62 and the phase-inverter 82 in which the subdominant signals L, are out of phase.
  • the amount of signal mixing produced by the circuits 120 126 is controlled with signals obtained from a crosstalk signal detecting circuit described hereinafter.
  • FIG. 3 shows an example of the crosstalk, signal detecting circuit employed in the apparatus shown in FIG. 2.
  • reference numeral 130 generally des'ig nates the crosstalk signal detecting circuit.
  • Input terminals 132, 134, 136 and 137 of the circuit 130 are respectively connected between the output terminals 132a, 134a, 136a and 137a of the amplifiers 58, 62, 66 and 60 (referring to FIG. 2) and the all-wave rectifier circuits I38, 140, 142 and 144.
  • the signals represented by the phasor groups 68, 70, 72 and .74 are then allwave-re'ctified.
  • the output of the rectifier circuit 138 which is shown in the figure as a phasor group 146, includes the 0.707 L signal reversed in phase withrespect to the input signal component.
  • the output of the rectifier circuit 144 which is shown in the figure as a phasor group l48,includes the R, signal reversed in phase with; respect to that applied thereto previously.
  • the outputs of the rectifier circuitsl40 and 142 are shown'in the figure as phasor groups 150 and 152, respectively and: the phasor group 150 includes the L, signal in phase with the 0.707 R,signal thereof while the phasor group 152includesthe'0.707 R, signal leading the R signal by 90".
  • the outputs of the rectifier circuits 138 and 144 are supplied to a subtracting circuit 154 to produce a subtraction signal of L, and R, signals, namely
  • the output of the rectifier circuits 140 and 142 are supplied to a subtracting circuit 156 to produce a subtraction signal of L and R, signals, namely
  • the outputs of the subtracting circuits I54 and 156 can be referred to as absolute comparison outputs between the dominant signals in the front and back channels.
  • the output signal a is supplied to an output terminal 160a through a rectifier 160 and also to an output terminal 164a through a phase-inverter 162 and a rectifier 164.
  • ' output signal B is delivered to an output terminal 166a through a rectifier 166 and also to an output terminal 170a through a phase-inverter 168 and a rectifier 170.
  • the output terminals 160a, 164a, 166a and 170a of the crosstalk signal detecting circuit 130 are connected to the input tenninals 126a, 122a, 120a and 124a of the mixing circuits 126, 122, 120 and 124 respectively (referring to FIG. 2).
  • the mixing circuit 120 comprises a transistor Tr, the collector of which is connected to the output side of the amplifier 58 through a resistor R and the emitter of which is connected to the output side of the amplifier through a resistor R
  • the base of the transistor Tr serves as the input terminal a of the mixing circuit 120 to which the control signal is supplied.
  • the other mixing circuits may be constructed similarly. It will be, however, apparent that circuits of other types can be employed as the mixing circuits of this invention.
  • the transistor Tr of the mixing circuitl26 becomes conductive between its collector and emitter and the respective signals of the phasor groups 70 and 86 are mixed with each other in thernixing circuit 126 to can: tie] the 0.707 L, signals thereof which are out of phase. Accordingly, no L, signals are derived from the output terminals 114, and 1.16.
  • the inverted a signal, -a which is supplied at the same time by the inverter 162 to the anode of diodel64 is not passed by the diode be! cause it is of the wrongpolarity.
  • the R signal appears at the output terminal 116 as the dominant signal. R and also appears at the outputterrninals 112 and 118 as the subdominant signals or crosstalk signals.
  • the D.C. component of the IR, signal, or the B signal is obtained as the control signal. That the ,8 signal is negative is apparent when the phasor group 152 is subtracted from the phasor group 150, taking into consideration that no L, or R, signal components are present.
  • the control signal B is delivered to the output terminal a through the phase-inverter 168 which converts it to +13 so that is passed through the anode to cathode terminals of the rectifier 170 and is then supplied to the input terminal 124a of the mixing circuit v 124.
  • the respective signals of the phasor groups 68 and 84 are mixed with one another in the mixing circuit 124 with the result that the 0.707 R, signals contained therein which are out of phase are cancelled.
  • the 0.707 R, signals which will cause the crosstalk are prevented from being delivered to the output terminals 112 and l18.
  • the -/3 control obtained from the subtracting circuit 156 is also supplied to the anode of the rectifier 166 at the same time but it is not transmitted to the output terminal 166a of the circuit 130 due to the fact that it is a negative signal component and is therefore prevented from being passed through the anode to cathode terminals of the rectifier 166.
  • FIG. shows an encoder of modified form which has four input terminals 210, 212, 214 and 216 to which four original sound signals I..,, L,,, R,, and R, depicted as in phase signals of equal amplitude are respectively applied.
  • the total L signal is added in a summing junction 218 to 0.707 of the R signal, with the output of the summing junction 218 being applied to a phase-shifting network 220 which introduces a reference phase-shift I, which is a function of frequency.
  • the full R, signal at the terminal 216 is added in a summing network 222 to 0.707 of the L signal appearing at the input terminal 212, and the output is passed through a I -network 224, which also provides the reference phase-shift I.
  • the L, and R signals are also applied to respective P-networks 226 and 228, each of which provides a phase-shift of I 90.
  • the full signal appearing at the output of the network 220 is added in a summing circuit 230 to 0.707 of the signal appearing at the output of the network 226 to produce at its output terminal 232 a composite signal designated L
  • the full signal from the network 224 is added in a summing junction 234 to 0.707 of the signal from the network 228, the latter in this case being in the positive sense.
  • the signal appearing at an output terminal 236 of the network 234 is the composite signal designated R.
  • the phasor group 238 consists of the signal L, (which although shown in the same phase relationship as the input signal L, has a I'as-a-function-offrequency angle difference between them), a signal 0.707 R, in a negative sense with respect to its corresponding input phasor, and a 0.707 L signal which lags the phasor 0.707 R, by 90 because of the action of the netowrk 226.
  • the phasor group 240 consists of the original signal R, in the same relative phase position as its corresponding input signal, a signal 0.707 L in phase with the R, signal, and a 0.707 R, signal lagging the 0.707 L signal by 90 due to the action of the I -network 228.
  • the effect of the panning is to divide the signal (as by means of two coupled attenuators) between two channel inputs.
  • the signal becomes precisely divided between the front channels L, and R,, or between the back channels L,, or R,,; this condition will now be examined.
  • the phasor groups 238 and 240 from FIG. 5 are repeated here as phasor groups 250 and 252, respectively, and the panned center signals have been added.
  • the front center signal C is placed in the proportion 0.707 C, and in-phase in the phasor groups 250 and 252, appearing as phasors 254 and 256.
  • center-back channel C is divided in the proportion 0.707 in the left back channel and 0.707 in the right back channel, and since these two phasors appear as a 0.707 fraction, the corresponding fraction of the C,, signal which is in phase with the 0.707 L, phasor is 0.5 and the fraction which is in phase with the 0.707 R phasor is 0.5, in both the phasor groups.
  • phasor groups 256 and 258 Another significant feature of the encoder is illustrated by the phasor groups 256 and 258 in FIG. 7, the former depicting the situation which results when the phasor groups 250 and 252 of FIG. 6 are added and the latter depicting the situation when the composite signal R (phasor group 252) is subtracted from the signal L (phasor group 250).
  • the L and R signals are added the phasors L,, L R and R, all have an intensity equal to unity, whereas the front center signal C, is augmented by a factor 1.414, which is exactly what happens when a stereophonic record is played over a monophonic player.
  • the back center signal C is cancelled, however, because of the aforementioned out-of-phase relationship.
  • the phasor groups 256 and 258 are extremely important since they indicate that if only a center front signal is present (i.e., no center back signal) the phasor group 256 will be greater than the group 258 and, conversely, if there is only a center back signal but no center front signal, the phasor group 258 will be the larger. This interesting property is used to advantage to enhance the operation of a decoder which will now be described to be utilized with the encoder of FIG. 5.
  • the decoder illustrated in FIG. 8, is in many respects similar to the decoder of FIG. 2.
  • each of the signals L and R passes with only I -function of frequency phase-shift through the networks 304 and 308, respectively, and also passes with I -function of frequency a phase-shift through the networks 306 and 310.
  • the outputs of the networks 304 and 308 are applied directly to the input terminals of respective amplifiers 313 and 315, the outputs of which are applied to respective loudspeakers 316 and 318 which are positioned at the front left and front right comers in a listening room M.
  • the signals applied to the loudspeakers 316 and 318 contain the dominant original signals L, and R respectively, and the two subdominant contaminating" signals 0.707 L, and 0.707 R,,.
  • Equal proportions namely, 0.707 of the output of the networks 306 and 308 are summed at a summing junction 320 to produce a composite signal consisting of a dominant signal L,, which is applied to an amplifier 322 and thence to a loudspeaker 324 which is positioned at the left back corner of the room M.
  • Equal negative portions, namely, 0.707 of the outputs of the networks 304 and 310 are summed at a second summing network 326 to produce a composite signal composed of a dominant signal R together with 0.707 R, and 0.7071 signal after amplification, and this composite signal is applied to an amplifier 328 whose output is fed to a loudspeaker 330 which is positioned at the right back corner of the room M.
  • the composite signals L and R contain the center front signal C
  • the 0.707 portion of the center front signal C appears in phase in the L, and R, signals of the decoded phasor groups 332 and 338, respectively.
  • the total center front signal 1.4 C, of both the phasor groups 332 and 338 can be represented by a phasor 340 in FIG. 8.
  • the center front signal components C, of the phasor group 334 can be shown in total by a phasor 342 and the center front signal components of the phasor group 336 can be shown in total by a phasor 344.
  • the center front sound is reproduced from the loudspeakers 324 and 330 for the back channels in opposite phase relationship, respectively.
  • the center back signal C appears in both the phasor gorups 334 and 336 and also in the phasor groups 332 and 338.
  • center back signals in the phasor groups are respectively represented by phasors 346, 348 and 350 in the figure. Accordingly, if a center back sound exists in an original sound field, in a reproduced sound field a center back sound is respectively repro-- cuted, from the loudspeakers 316 and 318 for the front channels in opposite phase relationship, respectively. For this reason, a listener in the reproduced sound field can not spearate the center front and center back sounds and is subjected to an uncomfortable experience.
  • a mixing circuit 360 is connected between the input sides of the amplifiers 313 and 315 as a first crosstalk canceller and a second mixing circuit 362 is connected between the input sides of the amplifiers 322 and 328 as a second crosstalk canceller.
  • the degree of mixing in the circuits 360 and 362 is changed or controlled as a function of the crosstalk signals.
  • Mixing circuits similar to the circuit 120 described in reference to FIG. 4 may also be used as the variable mixing means of this embodiment.
  • FIG. 9 shows a circuit generally designated 370, which detects the center front or center back signal (crosstalk signals).
  • Input terminals 372 and 374 of the circuit 370 are respectively connected to terminals 300a and 302a shown in FIG. 8, so that the input signals L and R applied to the input terminals 300 and 302 are also applied to the input terminals 372 and 374 and then are applied to a summing; junction 376 and to a subtracting junction 378 respectively.
  • the sum signal appearing at the output of the summing junction 376 is the sum of L and R and is depicted by the phasor group 256 in FIG. 7.
  • the output of the subtracting junction 378 is a composite signal having the properties portrayed by the phasor gorup 258 in FIG. 7.
  • the outputs of the junctions 376 and 378 are amplified in respective quasi-logarithmic amplifiers 380 and 382, respectively, and are then rectified by respective rectifiers 384 and 386, which are preferably full-wave rectifiers.
  • the rectified signals from rectifiers 384 and 386 are integrated by leaky integrators 388 and 390, respectively.
  • the output signals of the integrators 388 and'390 are applied to a subtracting circuit 392 the output of which is applied to an output terminal 394a through a rectifier 394 and also to an output terminal 398a through a phase-inverter 396 and arectifier 398.
  • the output terminals 394a and 398a of the circuit 370 are connected to control terminals 362a and 360a of the mixing circuits 362 and 360, respectively.
  • the center front signal is detected by the summing junction 376 and is then applied to the subtracting circuit 392 through the logarithmic amplifier 380 and the rectifier 384. Meanwhile, since the output of the subtracting junction 378 contains no cen ter front signal, a positive output appears at theoutput terminal of the subtracting circuit 392 as a control signal, which is then applied to the mixing circuit 362 through the rectifier 394. As a result, the outputs of the summing junctions 320 and 326 are mixed in the mixing circuit 362 to cancel the out of phase center front signal components C,.
  • the output of the subtracting circuit 392 is also applied to the phase-inverter 396 and is thereby made into a negative control signal which is blocked at the anode terminal of rectifier 398 so that no control signal is delivered to the output terminal 398a. Accordingly, the mixing circuit 360 does not operate and hence thecenter front signal is reproduced from the front loudspeakers 316 and 318.
  • a negative control signal is derived from the output terminal of the subtracting circuit 392, since the output of the subtracting junction 378 becomes greater than that of the subtracting junction 376.
  • the negative control signal is inverted to a positive control signal by I the phaseinverter 396 and is then applied to the control terminal 360a of the mixing circuit 360 through the rectifier 398. Accordingly, the outputs of the networks 304 and 308 are mixed in the mixing circuit 360 and the out of phase center back signal components C,, are cancelled.
  • the negative control signal from the subtracting circuit 392 is blocked from delivery to the output terminal 394a due to the function of the rectifier 394.
  • FIG. shows another decoder according to the invention.
  • the decoder of FIG. 10 has a pair of input terminals 402 and 404 which are supplied with the composite signals L, and R
  • the composite signals L and R are produced by an encoder (not shown) which is known as a Regular Matrix Encoder" in Japan.
  • the composite signal L consists of an L, signal, a 0.4 R, signal in phase with the L, signal, an L, signal leading by 90 with respect to the L, signal and a 0.4 R,, signal in phase with the L, signal
  • the composite signal R consists of an R, signal, a 0.4 L, signal in phase with the R, signal, an R, signal lagging with respect to the R, signal by 90 and a 0.4 L, signal in phase with the R signal.
  • a basic matrix circuit 406 is connected to the input terminals 402 and 404 and provides four output terminals 408, 410, 412 and 414 for delivering four output signals therefrom, shown in the figure as phasor groups 420, 422, 424 and 426, respectively.
  • the output from terminal 408 is transmitted through a I 90 -network 440 to an output terminal 460.
  • the output from terminal 410 is transmitted through a phase-inverter 442 and a I +0 -network 444 to an output terminal 462.
  • the output from terminal 412 is transmitted through a phase-inverter 446 and a IN-0 -network 448 to an output terminal 464 and the output from terminal 414 is transmitted through a I 90 -network 450 to an output terminal 466.
  • the phasor group 420 consists of the L, signal, a 0.707 R, signal in phase with the L, signal and a 0.707 L signal leading with respect to the L, signal by 90.
  • the phasor group 422 consists of an L, signal, a 0.707 R, signal in phase with the L, signal and a 0.707 L, signal lagging with respect to the L, signal by 90.
  • the phasor group 424 consists of an R, signal, a 0.707 L signal in phase with the R signal and a 0.707 R, signal leading with respect to the R signal by 90.
  • the phasor group 426 consists of an R, signal, a 0.707 L, signal in phase with the R, signal and a 0.707 R, signal lagging with respect to the R, signal by 90.
  • the L,, L,,, R and R, signals in the respective phasor groups 420 426 are dominant signals, and the other signals are subdominant signals which produce crosstalk.
  • the signal components of R, in the phasor groups 420 and 424 are of the same amplitude but are out of phase with each other.
  • the signal components of R in the phasor groups 422 and 426 are of the same amplitude but are out of phase with each other.
  • the output signals from the output terminals 410 and 412 are inverted in phase by the phase-inverters 442 and 446, respectively, and are shown in the figure as phasor groups 454 and 456, respectively.
  • the signal components of L, in the phasor groups 420 and 456 are the same in amplitude but are out of phase, and similarly, the signal components of L,in the phasor groups 426 and 454 are the same in amplitude but are out of phase.
  • the P-networks 440, 444, 448 and 450 act to make the dominant signals, contained in the output signals delivered to the output terminals 460, 462, 464 and 466, the same in phase.
  • the outputs obtained at the output terminals 460 466 are shown in the figure as phasor groups 470 476, respectively.
  • variable mixing circuits 480 486 are employed as crosstalk cancellers.
  • the mixing circuit 480 is inserted between the output terminals 408 and 412 of the basic matrix circuit 406, the mixing circuit 482 is inserted between the output terminals 410 and 414, the mixing circuit 484 is inserted between the output terminal 408 and the output side of the phase-inverter 446, and the mixing circuit 486 is inserted between the output side of the phase-inverter 442 and the output terminal 414.
  • Circuits similar to that described in reference to FIG. 4 may be used as the mixing circuits of this example.
  • FIG. 11 shows a circuit diagram of a crosstalk signal detecting circuit 488.
  • the circuit 488 provides four input terminals 490, 492, 494 and 496 which are connected to the output terminals 408, 412, 410 and 414, respectively, of the basic matrix circuit 406.
  • the input terminals 490 and 492 are connected to full-wave rectifiers 498 and 500, respectively.
  • the outputs from the rectifiers 498 and 500 are connected to a first subtracting junction 502.
  • the input terminals 494 and 496 are connected to full-wave rectifiers 504 and 506, respectively, and the rectifier outputs are connected to a second subtracting junction 508.
  • a first signal representative of the subtraction of the L, and R, signals is produced in the junction 502 and a second signal representative of the subtraction of the L, and R, signals is produced in the junction 508 as first and second control signals, respectively.
  • the first control signal is then applied through the anode to cathode terminals of a rectifier 512 to a first output terminal 510 which is connected to a control terminal 486a of the mixing circuit 486.
  • the first control signal is also applied through a phase-inverter 516 to the anode of a rectifier 518 whose cathode is connected to a second output terminal 514.
  • the terminal 514 is connected to a control terminal 482a of the mixing circuit 482.
  • the second control signal is applied through a rectifier 522 to a third output terminal 520 which is connected to a control terminal 480a of the mixing circuit 480 and is also applied through a phaseinverter 526 and through the anode to cathode terminals of a rectifier 528 to a fourth output terminal 524 which is connected to a control terminal 484a of the mixing circuit 484.
  • FIGS. 10 and 11 operate to cancel the crosstalk signals in a manner similar to the first and second examples already described.
  • the operation of the circuits of FIGS. 10 and 11, however, will now be described by way of example.
  • the mixing circuit 480 is controlled in its mixing condition by the control signal derived from the output terminal 520 of the detecting circuit 488.
  • the detecting circuits 130 and 488 are supplied with input signals from the output terminals of the decoders, but in other embodiments they may be supplied with input signals obtained from the composite signals which are passed through a matrix circuit which is separate from the decoder.
  • a multisignal transmission apparatus comprising;
  • c. means for arranging the phase of at least one subdominant signal in each of said output signals to be one hundred and eighty degrees out-of-phase with respect to the same subdominant signal contained in another of said output signals,
  • variable mixing means connected between the other two of said transmitting channels which con tain said out of phase subdominant signals, said variable mixing means being controlled with said control signal so as to mix said out of phase subdominant signals and thereby substantially cancel them.
  • a multisignal transmission apparatus as recited in claim 1, wherein said converting means comprises allpass phase-shifting networks for giving said two composite signals a relative phase difference of 90, a summing circuit for summing said phase-shifted two com posite signals derived from said all-pass phase-shifting networks, and a subtracting circuit for differencing said phase-shifted two composite signals derived from said all-pass phase-shifting networks.
  • variable mixing means comprises a variable impedance device to which said control signal is applied and the impedance of which is varied with the control signal.
  • control signal producing means comprises detector circuit means for receiving a first pair of said output signals which contain the same subdominant signals and a seocnd pair of signals corresponding to the other pair of said output signals which contain the same subdominant signals and comparing circuit means for separately comparing said first pair of signals and for comparing said second pair of signals, respectively, and to produce separate control signals representative of whether said pairs of signals contain subdominant signals which are in phase coincidence or in phase opposition.
  • a multisignal transmission apparatus as recited in claim 4, wherein said detector circuit means includes four input terminals for separately receiving said four output signals, each of said input terminals being connected to a separate full-wave rectifier circuit, and said comparing circuit includes a pair of subtracting circuits for subtracting the outputs from selected pairs of said full-wave rectifier circuits.
  • a multisignal transmission apparatus adapted to receive first and second composite signals L and R respectively containing dominant signals L, and R; in phase with each other and each including at least two subdominant signal components L and R,, the apparatus comprising;
  • circuit means including all-pass phase-shifting networks and combining networks for deriving first, second, third and fourth output signals containing in phase dominant signal components L,, R,, L,, and R respectively, said first and fourth output signals also containing subdominant L, and R, signals with said L' subdominant signal in each one of said first and fourth output signals being; in phase opposition to said R subdominant signal in the other of said first and fourth output signals, said second and third output signals also containing subdominant L, andR, signals with said L, subdominant signal in each one of said second and third output signals being in phase opposition to said R, subdominant signal in the other of said second and third output signals,
  • first and second variable mixing means connected between said first and fourth channels and between said second and third channels, respectively, for mixing said first and fourth and second and third output signals, respectively,
  • control circuit means for comparing the sum and difference of said L and R composite signals to produce a first control signal when the sum of said L and R composite signals exceeds the difference of said L and R composite signals and a second control signal if the difference of said L and R composite signals exceeds the sum of said L and R composite signals, and
  • a multisignal transmission apparatus comprising;
  • first, second, third and fourth. channels for transmitting, respectively, first, second, third and fourth composite signals each of which contains separate dominant signals a, b, c and d, respectively, said first composite signal also containing two subdominant signal components corresponding to portions of said c and d signals, said second composite signal also containing two subdominant signal components corresponding to portions of said c and d signals, said third composite signal also containing two subdominant signal components corresponding to portions of said a and b signals, and said fourth composite signal also containing two subdominant signal components corresponding to portions of said a and b signals,
  • comparing control means including means for comparing the magnitudes of said dominant a and b signals and for producing a first control signal when IaI-lbl 0 and a second control signal when lal Ibl 0; means for comparing the magnitudes of said dominant c and d signals and for producing a third control signal when Icl
  • control circuit means further comprises means for summing said L and R composite signals, means for subtracting said L and R composite signals, means for rectifying the outputs of said summing and subtracting means, and means for subtracting the rectified outputs to produce said first and second control signals.
  • a multisignal decoding apparatus comprising, first, second, third and fourth channels for transmitting first, second, third and fourth signals, respectively, as dominant signals, said first and fourth channels also containing oppositely phased subdominant signals corresponding to said second signal, said second and third channels also containing oppositely phased subdominant signals corresponding to said fourth signal, first comparing circuit means for producing at least a first control signal by comparisoon of the absolute magnitudes of at least said first and fourth dominant signals, first variable mixing means connected between said second and third channels for mixing said signals contained therein with each other so as to cancel said oppositely phased subdominant signals corresponding to at least one of said first and fourth dominant signals in response to said first control signal, second comparing circuit means for producing at least a second control signal by comparison of the absolute magnitudes of said second and third signals, and second variable mixing means connected between said first and fourth channels for mixing said signals contained therein with each other so as to cancel said oppositely phased subdominant signals corresponding to at least one of said second and third dominant signals in response to

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US00272439A 1971-07-19 1972-07-17 Four channel decoder with variable mixing of the output channels Expired - Lifetime US3786193A (en)

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DE (1) DE2235238A1 (enrdf_load_stackoverflow)
FR (1) FR2146394B1 (enrdf_load_stackoverflow)
GB (1) GB1400061A (enrdf_load_stackoverflow)
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Cited By (24)

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US3825684A (en) * 1971-10-25 1974-07-23 Sansui Electric Co Variable matrix decoder for use in 4-2-4 matrix playback system
US3836715A (en) * 1972-09-09 1974-09-17 Sansui Electric Co Decoder for use in 4-2-4 matrix playback system
US3875338A (en) * 1974-04-18 1975-04-01 Columbia Broadcasting Syst Inc Decoder matrix for quadraphonic sound systems
US3883692A (en) * 1972-06-16 1975-05-13 Sony Corp Decoder apparatus with logic circuit for use with a four channel stereo
US3890466A (en) * 1973-02-01 1975-06-17 Cbs Inc Encoders for quadraphonic sound system
US3892918A (en) * 1972-05-02 1975-07-01 Sansui Electric Co Sound signal converting apparatus for use in a four channel stereophonic reproduction system
US3919477A (en) * 1972-06-07 1975-11-11 Polygram Gmbh Method and apparatus for the production of multichannel sound signals
US3919478A (en) * 1974-01-17 1975-11-11 Zenith Radio Corp Passive four-channel decoder
US3934086A (en) * 1973-08-20 1976-01-20 Sansui Electric Co., Ltd. Matrix four-channel decoding system
US3943293A (en) * 1972-11-08 1976-03-09 Ferrograph Company Limited Stereo sound reproducing apparatus with noise reduction
US3943287A (en) * 1974-06-03 1976-03-09 Cbs Inc. Apparatus and method for decoding four channel sound
US3944735A (en) * 1974-03-25 1976-03-16 John C. Bogue Directional enhancement system for quadraphonic decoders
US3944748A (en) * 1972-11-02 1976-03-16 Electroacustic Gmbh Means and method of reducing interference in multi-channel reproduction of sounds
US3952157A (en) * 1973-03-07 1976-04-20 Sansui Electric Co., Ltd. Matrix four-channel decoding system
US3985978A (en) * 1971-10-06 1976-10-12 Cooper Duane H Method and apparatus for control of FM beat distortion
US3987256A (en) * 1972-08-17 1976-10-19 Fumitaka Nagamura Grooved record playback system with multiple transducers
DE3607610A1 (de) * 1985-03-07 1986-09-18 Dolby Laboratories Licensing Corp., San Francisco, Calif. Decoder
US4862502A (en) * 1988-01-06 1989-08-29 Lexicon, Inc. Sound reproduction
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
US5136650A (en) * 1991-01-09 1992-08-04 Lexicon, Inc. Sound reproduction
US5157697A (en) * 1991-03-21 1992-10-20 Novatel Communications, Ltd. Receiver employing correlation technique for canceling cross-talk between in-phase and quadrature channels prior to decoding
US5796844A (en) * 1996-07-19 1998-08-18 Lexicon Multichannel active matrix sound reproduction with maximum lateral separation
US5870480A (en) * 1996-07-19 1999-02-09 Lexicon Multichannel active matrix encoder and decoder with maximum lateral separation
US20100128880A1 (en) * 2008-11-20 2010-05-27 Leander Scholz Audio system

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Publication number Priority date Publication date Assignee Title
US3632886A (en) * 1969-12-29 1972-01-04 Peter Scheiber Quadrasonic sound system
US3708631A (en) * 1970-06-08 1973-01-02 Columbia Broadcasting Syst Inc Quadraphonic reproducing system with gain control

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Publication number Priority date Publication date Assignee Title
US3632886A (en) * 1969-12-29 1972-01-04 Peter Scheiber Quadrasonic sound system
US3708631A (en) * 1970-06-08 1973-01-02 Columbia Broadcasting Syst Inc Quadraphonic reproducing system with gain control

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The New Sansui 20db Matrix, Audio Magazine, July 1972. *

Cited By (26)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3985978A (en) * 1971-10-06 1976-10-12 Cooper Duane H Method and apparatus for control of FM beat distortion
US3825684A (en) * 1971-10-25 1974-07-23 Sansui Electric Co Variable matrix decoder for use in 4-2-4 matrix playback system
US3892918A (en) * 1972-05-02 1975-07-01 Sansui Electric Co Sound signal converting apparatus for use in a four channel stereophonic reproduction system
US3919477A (en) * 1972-06-07 1975-11-11 Polygram Gmbh Method and apparatus for the production of multichannel sound signals
US3883692A (en) * 1972-06-16 1975-05-13 Sony Corp Decoder apparatus with logic circuit for use with a four channel stereo
US3987256A (en) * 1972-08-17 1976-10-19 Fumitaka Nagamura Grooved record playback system with multiple transducers
US3836715A (en) * 1972-09-09 1974-09-17 Sansui Electric Co Decoder for use in 4-2-4 matrix playback system
US3944748A (en) * 1972-11-02 1976-03-16 Electroacustic Gmbh Means and method of reducing interference in multi-channel reproduction of sounds
US3943293A (en) * 1972-11-08 1976-03-09 Ferrograph Company Limited Stereo sound reproducing apparatus with noise reduction
US3890466A (en) * 1973-02-01 1975-06-17 Cbs Inc Encoders for quadraphonic sound system
US3952157A (en) * 1973-03-07 1976-04-20 Sansui Electric Co., Ltd. Matrix four-channel decoding system
US3934086A (en) * 1973-08-20 1976-01-20 Sansui Electric Co., Ltd. Matrix four-channel decoding system
US3919478A (en) * 1974-01-17 1975-11-11 Zenith Radio Corp Passive four-channel decoder
US3944735A (en) * 1974-03-25 1976-03-16 John C. Bogue Directional enhancement system for quadraphonic decoders
US3875338A (en) * 1974-04-18 1975-04-01 Columbia Broadcasting Syst Inc Decoder matrix for quadraphonic sound systems
US3943287A (en) * 1974-06-03 1976-03-09 Cbs Inc. Apparatus and method for decoding four channel sound
DE3607610A1 (de) * 1985-03-07 1986-09-18 Dolby Laboratories Licensing Corp., San Francisco, Calif. Decoder
US4799260A (en) * 1985-03-07 1989-01-17 Dolby Laboratories Licensing Corporation Variable matrix decoder
US5046098A (en) * 1985-03-07 1991-09-03 Dolby Laboratories Licensing Corporation Variable matrix decoder with three output channels
US4862502A (en) * 1988-01-06 1989-08-29 Lexicon, Inc. Sound reproduction
US5136650A (en) * 1991-01-09 1992-08-04 Lexicon, Inc. Sound reproduction
US5157697A (en) * 1991-03-21 1992-10-20 Novatel Communications, Ltd. Receiver employing correlation technique for canceling cross-talk between in-phase and quadrature channels prior to decoding
US5796844A (en) * 1996-07-19 1998-08-18 Lexicon Multichannel active matrix sound reproduction with maximum lateral separation
US5870480A (en) * 1996-07-19 1999-02-09 Lexicon Multichannel active matrix encoder and decoder with maximum lateral separation
US20100128880A1 (en) * 2008-11-20 2010-05-27 Leander Scholz Audio system
US8520862B2 (en) * 2008-11-20 2013-08-27 Harman Becker Automotive Systems Gmbh Audio system

Also Published As

Publication number Publication date
IT963000B (it) 1973-12-31
GB1400061A (en) 1975-07-16
NL7209930A (enrdf_load_stackoverflow) 1973-01-23
JPS5213082B1 (enrdf_load_stackoverflow) 1977-04-12
DE2235238A1 (de) 1973-02-01
CA1001957A (en) 1976-12-21
FR2146394A1 (enrdf_load_stackoverflow) 1973-03-02
FR2146394B1 (enrdf_load_stackoverflow) 1977-04-01
CA991086A (en) 1976-06-15

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