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JPS5213082

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DESCRIPTION JPS5213082
■ Demodulation circuit ■ Japanese Patent Application No. 46-53771 [Phase] Application No.
46 (1971) published on July 19 closed 48-20402 @ Akira 48 (1973) March 14 0 Inventor
Tsurushima Katsuaki Yokohama city Kashihara Nishicho 36 DETAILED DESCRIPTION OF THE
INVENTION The present invention relates to a demodulation circuit for 4-channel stereo
reproduction. For example, as shown in FIG. 1, speakers 0, 20 ° 30. 40 are arranged on the left
front, left back, right back and right front of the listener 1, respectively, and the second speaker 0
to 40 corresponds to the speaker position That is, there is a method of performing 4-channel
methyleo regeneration by supplying stereo signals Lf, Lb, Rb and Rf corresponding to left front,
left rear, right rear and right front positions of the listener 1, respectively. In this case, such a 4channel stereo signal is once converted into a 2-channel signal, which is then transmitted
through broadcast or record 14, and is considered to be a method of performing 4-channel
stereo reproduction by demodulating it back to the original 4-channel stereo signal. It is done. 2
to 9 show an example of the method, and FIG. 2 is a circuit system for converting a 4-channel
stereo signal to a 2-channel signal. The signal obtained by supplying the obtained sum to the
phase shift circuit 11 having a larger phase shift amount and obtained by the arithmetic circuit 4
is supplied to the phase shift circuit 41 having a larger phase shift amount and for the signal
obtained. In the case of this phase shift load, the scale of 10--barrel phase delay 2 [111 111]
EndPage: 1 is indicated. Accordingly, as shown in FIG. 3, the first synthesized signal Lt is doubled
with respect to the signal Lf of the reference phase by a level 3 dB more than this, and the phase
LB is advanced in phase and the signal Rb is in antiphase. As shown in FIG. 4, the second
synthesized signal Rt is in phase with the signal Lb at a level 3 dB lower than that of the signal Rf
of the reference phase and the signal Rb is − The phase is delayed and then combined. FIG. 5
shows a demodulation circuit, which supplies the first combined signal Lt to the phase shift
circuit 12 having a phase shift amount exceeding the phase shift amount and a phase shift circuit
22 having a phase shift amount having a magnitude of 10; The signal is supplied to the phase
shift circuit 42 having a large phase shift amount, and the first demodulated signal Lf 'is obtained
from the phase shift circuit 12, and is added to obtain the second demodulated signal Lb'. The
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ones of the outputs of are multiplied by one and the ones of σ are added in the arithmetic circuit
9 to obtain the third demodulated signal Rb ′ from this, and the fourth demodulated signal Rf ′
is obtained from the demodulator circuit.
Therefore, as shown in FIG. 6, the first demodulation signal Lf 'is advanced by 9 dB at a level 3
dB lower than that of the signal Lf "of the reference phase, and the phase is advanced and the
signal Rb # is reversed. The second demodulated signal Lb 'is 3 dB lower than the signal Lt /' of
the reference phase as shown in FIG. 7, and the signal Rf 'is in phase with that of the signal Lt /'.
As shown in FIG. 8, the third demodulated signal Rb 'is at a level 3 dB lower than that of the
reference phase signal R.sub .--, and the signal Rf "is generated at the level of [111111]. And the
fourth demodulated signal Rf 'is L3 dB lower than that of the reference phase signal Rf "as shown
in FIG. 9, respectively. Signal Lb ′ ′ is in phase and signal Rb ′ ′ is M, the one which is
synthesized by a state in which the phase is delayed. That is, each demodulation signal Lf ', Lb'.
Rb 'and Rf' each consist of the main component corresponding to that channel and the leaked
components from the other two channels. Therefore, 4-channel stereo reproduction can be
performed by supplying the binary demodulation signals Lf ', Lb', Rb 'and Rf' to the speakers 0,
20 and 30. 40 respectively. By the way, when a 4-channel stereo signal is converted to a 2channel signal by the above method, there is a monaural signal Cf corresponding to the front
center position of the listener 1 and a signal Lf corresponding to the left front position of the
listener 1 and the right When the signal Rf corresponding to the forward position becomes
identical, this monaural signal component Cf is obtained in an in-phase relationship in the first
and second combined signals Lt and Rt as shown in FIGS. 10 and 11, On the other hand, when
there is a monaural signal cb corresponding to the rear center position of the listener 1, and the
signal · Lb corresponding to the left rear position of the listener 1 and the signal Rb
corresponding to the right rear position become identical, this monaural signal component cb As
shown in FIG. 10 and FIG. 11, the first and second combined signals Lt and Rt are obtained in the
reverse phase relationship. And four demodulated signals Lf 'obtained by phase-shifting and
operating the two combined signals Lt and Rt as described above. As apparent from FIG. 12,
regarding the reproduced sound field according to Lb ', Rb' and Rf ', if there is a monaural signal
component Cf corresponding to the front center position as described above, this is indicated by
the broken line in the left rear. Also in the demodulated signals Lb ′ and Rb ′ corresponding to
the position and the right rear position, a leaked component Cf ′ ′ appears, and if there is a
monaural signal component cb corresponding to the rear center position, this indicates the left
front position and The leaked component CbI also appears in the demodulated signals Lf ′ and
Rf ′ corresponding to the front-right position, and the second and third leakage components Cf
′ and cb ′ have the same size as the main component.
Therefore, there is a disadvantage that when there is a monaural signal component, separation
between the front and back can not be obtained. Furthermore, as is clear from the figure, each of
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the leaked components Cf 'and C' is in opposite phase to each other in the reverse [111111]
EndPage: bi-tonal signal corresponding to the respective left and right positions, resulting in a
sense of hearing discomfort. The present invention eliminates the above-mentioned drawbacks
by canceling the above-mentioned leakage component with a simple configuration by utilizing
the properties of two combined signals Lt and Rt. Let's explain the following. In FIG. 13, reference
numeral 50 denotes an adder which adds the first and second combined signals Lt and Rt and
supplies the addition output Lt + Rt to the detection rectification circuit 52 through the multiplier
51] to form lLt + Rtl. An output is obtained which is fed to one input of a differential amplifier 53.
Reference numeral 54 denotes a subtractor, which subtracts the first and second combined
signals Lt and Rt, supplies the subtraction output Lt-Rt to the detection / rectification circuit 56
through the amplifier 55, and outputs 1 Lt-Rtl. , And supplies this to the other input of the
differential amplifier 11-1. Therefore, the differential amplifier 53 obtains an output of ILt + RtlILt-Rtl. A mixing circuit for providing a mixing circuit 51 for mixing the pair of demodulation
signals Lb 'and Rb' corresponding to the power extraction position and for mixing the pair of
demodulation signals Lf 'and Rf' corresponding to the front position A circuit 58 is provided, and
the mixing signal in the mixing circuit 57 is controlled by the output signal from the differential
amplifier 53, and the output signal from the differential amplifier 53 is supplied to the polarity
inverting circuit 59 to obtain the signal. The mixing state in the mixing circuit 58 is controlled. In
this case, the mixing circuits 57 and 58 can be configured in the same manner. The mixing
circuit 57 will be described, for example, by providing an npn transistor 60 as shown in FIG. R1
and R2 are connected in series, resistors R3 and R4 are connected in series between the emitter
and the arithmetic circuit 9, a demodulation signal Lb 'is taken out from the connection point of
the resistors R1 and R2, and the resistors R3 and R2 The demodulation signal Rb 'is taken out
from the connection point with R4, and the signal from the differential amplifier 53 is supplied to
the base of the transistor 600. As described above, the monaural signal component Cf
corresponding to the front center position of the listener 1 is obtained in an in-phase relationship
with the first and second combined signals Lt and Rt, and the monaural signal corresponding to
the center rear position of the listener 1 Since the component cb is obtained in an antiphase
relationship in the first and second combined signals Lt and Rt, a monaural signal component Cf
corresponding mainly to the front center position appears in the output ILt [111111] ILt + from
the circuit 52. The monaural signal component cb corresponding to the rear center position is
canceled, while the output ILt-Rtl from the circuit 56 mainly cancels the monaural signal
component Cf corresponding to the rear center position.
Therefore, when there is a monaural signal component Cf corresponding to the front center
position, the output signal ILt + Rt1-ILt-Rtl from the differential amplifier rj counter 53 is larger
in a positive direction than a certain level, for example, a certain slice potential centered on zero
potential. On the other hand, when there is a monaural signal component cb corresponding to
the rear center position, it becomes larger in the negative direction than the predetermined level.
Therefore, when there is a monaural signal component Cf corresponding to the front center
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position, the transistor 60 is turned on in the mixing circuit 51 by an output signal larger in the
positive direction than a predetermined level from the differential amplifier 53, and
demodulation corresponding to the rear position is performed. Leakage component C'f of
monaural signal component Cf corresponding to the front center position indicated by a broken
line in FIG. 12 described above in which signals Lb 'and Rb' are mixed with each other and
included in second signal Lb 'and Rb'. 'Is partially canceled each other. At this time, since an
output signal larger in the negative direction than the predetermined level is obtained from the
polarity inverting circuit 59, the transistor 60 is turned off in the mixing circuit 58 and the
demodulation signals Lf 'and Rf' corresponding to the forward position are mixed with each
other. There is nothing to do. When the monaural signal component cb corresponding to the
center position of power extraction exists, an output signal larger in the negative direction than
the predetermined level is obtained from the differential amplifier 53, and the positive direction
from the predetermined level is obtained from the polarity inverting circuit 59. Since a large
output signal can be obtained, the demodulation signals Lf 'and Rf' corresponding to the front
bearing person are mixed with each other in the mixing circuit 58, and are included in the above
signals shown in FIG. The leaked components Cb 'of the monaural signal component cb
corresponding to are partially canceled each other. At this time, in the mixing circuit 57, the
demodulated signals LL / and Rb 'corresponding to the backward position are not mixed with
each other. Therefore, in either case, separation between the front and back is obtained, and
stable localization can be achieved at the front center side or the rear center side. For example, if
the mixing circuit 58 is composed of pnp transistors, the polarity inversion circuit 59 is not
necessary. According to the circuit of the present invention described above, separation between
the front center position and the rear center position can be obtained with certainty [111111]
EndPage: 3. Moreover, since it mutually cancels the leak component of an anti | reverse |
negative phase in part, it does not have a thing with a sense of hearing discomfort. In the present
invention, the output signal ILt + Rt1-ILt-RtI from the differential amplifier 53 is large in the
positive direction more than the predetermined level only when there is a monaural signal
component corresponding to the front center position or the rear center position. The mixing
operation is performed only when it becomes larger or in a negative direction than a
predetermined level, and there is no monaural signal component, and when the mixing operation
is not performed, the left front position and the right front position, and the left There is no loss
of separation between the rear and right rear positions.
Although it is also conceivable to provide a gain control amplifier in the transmission system of
each demodulated signal instead of providing a mixing circuit and to control the gain thereof, in
the above-mentioned present invention circuit, the leakage component of the monaural signal
component is mainly attenuated. Therefore, compared to the case where gain control is
performed as described above, the fluctuation of the demodulation output level is small and the
sound skipping is not noticeable, and the structure rl111111 is extremely simplified.
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BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of −ψ1 of a 4-channel stereo
reproduction sound field, FIG. 2 is a system diagram of a circuit for converting a 4-channel stereo
signal into a 2-channel signal, FIGS. 3 and 4 Is a vector diagram of the first and second combined
signals, FIG. 5 is a system diagram of the demodulation circuit, FIGS. 6 to 9 are vector diagrams
of the first to fourth demodulated signals, and FIGS. 10 and 11 Is a vector diagram of the
monaural signal component in the first and second combined signals, FIG. 12 is a vector diagram
showing the leakage component of the monaural signal component in the reproduction sound
field, and FIG. 13 is -f1 of the demodulation circuit according to the present invention FIG. 14 is a
connection diagram of an example of the main part. 12 to 42 are phase shift circuits, 8 and 9 are
arithmetic circuits, 50 is an adder, 54 is a subtractor, 52 and 56 are detection and rectification
circuits, 53 is a differential amplifier, 57 and 58 are mixing circuits, 59 Is a polarity inverting
circuit. [111111]EndPage: 4
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