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(2000 A) 1 ° September 29, 1974 誹 σ day W 長官 Patent Office Secretary Hideo Saito, Tokyo
(03) 343-5821 (Representative) Akira m letter ■ Japan Patent Office ■ JP JP 51-361 -Patented
as Japanese Patent Application No. 4c / '-, 1093 0 internal office serial number 73'-62370 /
S53R, B, signal of vector 2 shown in FIG. Method The carrier wave is modulated by VSB
according to the forward signal or the sum signal of the forward and backward signals to obtain
the first modulated wave, and the backward signal with a narrow band compared to the upstream
signal or the sum signal of forward and backward signals Alternatively, the second carrier wave
is obtained by modulating the carrier wave different in phase from the above carrier wave by the
D8F3 system by the difference signal of the front and rear signals to obtain the second
modulated wave, and the first and second modulated waves are multiplexed. Two sets of
multiplexed signals corresponding to the left and right . A transmission method of a four-channel
stereo signal adapted to transmit two sets of multiplexed signals.
Detailed Description of the Invention As a method of transmitting a four-channel stereo signal, a
variety of methods have been conventionally proposed, and one of them is a matrix method. This
is the signal corresponding to the sound in front of MN left front, left rear, right front, right rear
respectively LF, L and RF. EndPage: It can be said that it is deteriorated compared to 1-d. In
addition, as another one of the four-channel stereo method, the CT) -4 method is suitable. This is
shown in FIG. 2 as its frequency spectrum, signal (Lp + LB) (! For example, frequency
multiplexing is performed on an Ii'M signal SF'M (carrier band) FM-adjusted with a signal (LF-LB)
(or T'Lp-RB) using 'RF, RB' as a baseband. The multiplexed signal is registered on one of the
groove walls of the record tone groove, and at the time of reproduction, the signal (Lp-LB) is
adjusted from the signal SFM, and this signal (LF-LB) and the signal (Lp + LB) are added. Thus,
the signal LFf is output and subtracted to increase the -C signal LB. According to this method, the
sound image localization is superior to that of the above-described matrix method, but there are
still some problems. Hithering, since two of the four transmission paths are separated from each
other by the same wave number band, a change in size, crosstalk occurs during demodulation,
and especially in the carrier band, the band restriction There is also a phenomenon that cross
talk and distortion occur. In order to prevent this, the level of the carrier band and the degree of
modulation are lowered, and distortion and crosstalk are within the allowable limits. However,
the dynamic range is significantly degraded. Here, since each azimuth signal is obtained by
finally mixing the information of the baseband and the carrier band, the dynamic range is
entirely limited at the worse one (carrier band). Further, a 45 kHz band is required as shown in
FIG. 2 to transmit information in the 30 kHz band, and the signal SFM of the carrier band is an
F'M signal, so this signal SFM 75-et al. Signal (LF-LB) In order to faithfully reproduce the
frequency characteristics and phase characteristics of the cartridge for reproduction, such as the
frequency characteristics and phase characteristics of the cartridge for reproduction must be
sufficiently flat to the high frequency side of this signal 8FM. Such characteristics can not be
obtained, and therefore, the reproduced signal Lp, LB distortion or S / Nit deterioration is
required, and a special cartridge or record needle is required for reproduction. Furthermore, even
on the side of making a record, the frequency is too high for the multiplexed signal having the
spectrum of FIG. 2 [because it can not be cut, the frequency of the multiplexed signal is set to, for
example, "/2.7" !
Even LA, you have to do so-called low speed cutting to cut into seven. As described above, the
conventional four-channel stereo signal transmission method can independently improve b5
independently of each other with respect to one independence, distortion, and dynamic range,
which is an index in its qualitative aspect. It can not be said that it can be said that
commercialization is achieved at a mutual compromise point. The present invention is intended
to propose a method of transmitting a four-channel stereo signal with excellent independence
without sacrificing the dynamic range and without newly generating distortion in view of the
point of prayer. According to the present invention, the first modulated wave 5LF (S 几 F) is
obtained by modulating the carrier wave according to the VSB method according to the forward
and head Lp (Rp) and compared with the forward signal LP (R, F). A second transmitted wave 5La
(Sun) 't-obtained by modulating the finger transmission wave whose phase is different from that
of the carrier wave by the narrow backward signal LB (RB) to the DSB system, f41 and f With two
multiplexed signals (SLF + 5LB3 and (SBp ′ + SBB) 02 pairs corresponding to the left and right,
the two multiplexed signals are transmitted, and the multiplexed signal formed by multiplexing 2
撫 modulation waves is used. is there. Here, the carrier frequency t "f. Assuming that the band of
the signal LP (RP) is (0 to to) and the band of the signal LB (RB) is (0 to etc), the multiplexed
signal (SLF + 81. The frequency spectrum of B) or (SRF + 5 RB) is as shown in FIG. 3. Note that in
FIG. 3, So is a ゐ pilot signal which is required when demodulating the multiplexed signal. One
embodiment of the present invention will be described with reference to the drawings. FIG. 4
shows its modulation system. In FIG. 4, (l) indicates the terminal of the signal LP in the (0 to fo)
band, and this signal LF is a double balanced modulator (3) via the pre-emphasis circuit (2). The
signal LB is supplied to the low pass filter (6) from the terminal (4) through the pre-emphasis
circuit (5) from the terminal (4), and the low pass filter (6) After being banded, doubly balanced
modulators (supplied to the force as modulated waves. Also, (8) shows an oscillator. The f, o
oscillation output of the oscillator (8) is modulated as a carrier wave and supplied to the device
(3), and is also transmitted to the EndPage: 2 modulator (7) through the phase shifter (9).
Supplied. Therefore, from the modulator (3), the lower side band wave of (0 to f 0) and the upper
side band wave of (f, ˜2 f 0) are obtained: A modulated wave SLB is obtained which comprises a
lower sideband wave of [(fo-ft) to to] and an upper sideband wave of [f0 to (fo + f1)].
These modulated waves and the output of the oscillator (8) are attenuators (ill '! The low-pass
filter aυ in the pass band of [0 to (fo + f *)] is added to each other and the low-pass filter S0 of
(0+ (fo + f *)). A portion of the upper side band wave of the signal SLF 'is removed by the lowpass filter a', and the signal SLF 'is made a modulated wave SLF according to the VSB method.
Signal 81. B is a modulated wave according to the DSB method because one upper and lower side
wave is transmitted as it is. Therefore, the multiplexed signal SLF + SLB of the frequency
spectrum shown in FIG. 3 is formed at the output terminal α4 of the low-pass ventilation film
aυ. In the above description, although the modulation system of the signal LF-LB corresponding
to the left is used, the multiplex f-hi signal (SRF + SRB) corresponding to the right is also formed
by the sum of the same i! できる。 And one of these two sets of multiplexed signals 1-. For
example, one groove wall of the sound groove of the record is recorded, and the other one is
recorded on the other groove wall. Next, the reproduction system from the record will be
described with reference to FIG. 5. With reference to FIG. 5, the terminal (2B is supplied with the
reproduced multiplexed signal (SLF + 5LB), and further through the amplifier. It is fed to the
demodulator and to the trap. At the same time, the pilot signal S0 is taken out by the band pass
filter 3, and is supplied to the discrimination circuit Ω which discriminates the 2 channel 04
channel of the PLL circuit by the pilot signal. PLL circuit (2a. As is well known, it comprises a
phase comparison circuit, a low pass filter and a variable frequency oscillator, and generates a
carrier wave of frequency f0 whose phase is equal to that of the pilot signal S, at its output. This
carrier is fed to the demodulator and the signal SLF is synchronously demodulated. The 'a 祠
output of the demodulator Q3 is supplied to the high band compensation filter after the
unnecessary signal component is removed by passing the low pass filter (4t-through) of the (O to
to) pass band. The high-pass compensation filter has a signal SLF based on the VSB method, so
the demodulation output on the low band side (0 to rt) is twice as large as that on the south band
side (fs to fo). The entire switching circuit to be compensated is led 75A to the output terminal 洛
through 洛 C311. On the other hand, in the demodulator r21; If, the carrier wave from the PLL
circuit C port is supplied to the r #: 1st rS (via 3I, and the 1-i SLB is desynchronized. この″? y,
the demodulation output of the modulator ρa is a 1-pass filter of the pass band of (0 to fi) (3
blurs are passed to remove unnecessary signal components to obtain a signal LB, and further a
de-emphasis circuit C5 and The switch circuit 31) is led to the output terminal ().
The reproduction circuit is supplied to the other input terminal of the switch circuit 311 (the
other terminal of the switch circuit 311 is supplied with the reproduction signal, and the
switching is controlled by the discrimination circuit (27). That is, when playing back a 4-channel
stereo record, the pilot signal is included in the playback signal, so that the switch circuit 311 is
connected as shown, and the signals Lp and LB can be led to the output 1 and 0 and 0. . On the
other hand, when playing back a 2-channel stereo record, the switch circuit 3 ° C. is cut off, and
the signal on the left can be led to the output terminal U (Z and already). Although the abovementioned recovery n system is for one O multiplexed fL1 signal (SLI ′ ′ + SLB), the other
multiplexed signal (Si ()? The same can be applied to +81 (B). According to the present invention
described above, since it is possible to send V by the 18th Lp, -LB, 、 p%) 1'Bt homogeneous
transmission path, sound image localization is good. Moreover, in this case, the independence of
the transmission path with respect to the signals LF (R, F-) and LB (RB) is determined only by the
errors of the 1/2 phase shifter and the PLL circuit. In addition, the transmission band can be
narrowed as compared with the CD-4 system by adopting the VSB system while narrowing the
rear component according to the principle of front tendency. As an example, if (fo "20 kHz, fs =
12 to 15 kHz), the bandwidth required for the multiplexed signal is less than (32 to 35). This
makes it possible to use a conventional regenerator that requires low speed cutting, and offers
advantages that the device can be inexpensive and simple, and is advantageous in terms of
crosstalk and 8 / N for both EndPage: 3 There is no need to suppress the level and modulation of
the carrier band for this improvement, as in the CD-4 system. That is, according to the present
invention, unlike the conventional method, the parameters relating to the independence,
distortion and dynamic range of the transmission paths are independent of each other, and these
can be improved to individual best points. Furthermore, in the present invention, in one set of
multiplexed signals. Because the bands of the two signals are different (fo> fs). In the
demodulation system, crosstalk does not occur in the (0 to 0) band, and crosstalk occurring in
the (h to to) band can be advantageously removed by a filter. If the signals Lp and LB are
multiplexed and the signals Hp and RBk are multiplexed as in the above embodiment, the matrix
circuit is unnecessary and the quality of the signal by using the matrix circuit (S, distortion, cross
You can avoid the inferiority of the talk).
However, it is also possible to multiplex the signals (Lp + Ls) and (Lp-LB) and use the signal (几 F
+ RB) and ("F-RB) t-multiplexing by using all the matrix circuits. Has the advantage of narrowing
the bandwidth. That is, (fo = 20 kHz. f@=8kHz)とすることができるのである。
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vector diagram used to explain an example
of a conventional matrix system, FIG. 2 is a frequency spectrum used to explain a conventional
CD-4 system, and FIG. 3 is a frequency used to explain the present invention FIG. 4 is a system
diagram of a modulation system according to an embodiment of the present invention, and FIG. 4
is a system diagram of its demodulation system. Lp, LB, BP, R, a are signals corresponding to the
left front, left rear, right front, right rear, respectively (3), (7) are double balanced units 1, (8) is
an oscillator, (9) is an "l phase shifter, C3, e41 is a recovery, [1 unit, 園 is a PLL circuit. Speciallydesignated applicant Ninnichi Co., Ltd. · i · Fig. 1 Fig. 2 4
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