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JPS5145902

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DESCRIPTION JPS5145902
4 channel stereo ? f, * ?: ? 412 Inventor address Osaka Prefecture Kadoma city Oda Kadama
name 1002 Name (582) Matsushita Electric Industrial Co., Ltd. Representative Matsushita Shoji 4
agent ? 517 Osaka Prefecture Kadoma city Ozad 1006 address 49 1196'z2 ? Japan Patent
Office 0 JP-A-51-459020 Published Japanese Patent Application 51. (1976) 4.19 Japanese
Patent Application No. 49-// '/ G' 12 ? 34-623 Specification 1, Title of the Invention
4 channel stereo demodulator
3. Detailed Description of the Invention The present invention relates to a four-channel stereo
demodulator for receiving four-channel stereo broadcasts, in particular, a so-called 4-channel 4channel stereo broadcast and a third sub-channel signal, so-called so-called. It is an object of the
present invention to provide a four-channel stereo recovery device provided with an automatic
switching circuit for automatically switching to and receiving stereo broadcasting of the 4-3-4
system. Currently, the 4-channel stereo broadcast system is undecided, but the stereo composite
signal is generally as shown in equation (1) with left front signal as LF, left rear signal as LB,
right front signal as RF and right rear signal as RB. Is representative. ???? (Ly + LB + Ry ten
RB) + (Ly ten LB-Ry-RB) 5 lntust + (Ly-LB + Ry-RB) oosa + st + (Ly-LB-Ry + RB) siz> 2? a ????
????????????????????????????? EndPage: 13 ии - bifurcated,
Section 2 sub-channel signals paragraph 3 first sub-channel signal second Section 1 wherein ----main channel signal ----- ----- 4 - .... is called a third sub-channel signals paragraph 6 ----- first pilot
signal Section 6 ----- second pilot signal. With such a configuration of No. 41, on the receiving
side 1 side, four audio signals Ly, Ry, LB, RB can be completely separated and demodulated, but
from the relationship of SCA broadcasting and the like, the third sub The channel signal may not
be transmitted. Further, it is conceivable to remove the third subchannel signal since the S / N
ratio is deteriorated when the 4-channel stereo broadcast is received around the service area or
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the like. In such a case, it is desirable to configure the 4-channel stereo demodulator so as to
automatically switch to the so-called 4-3-4 receiver (f operation). The present invention seeks to
provide a 4-JP-A 51 459 CI 2 (2) channel stereo demodulator with a circuit for switching as
described above. Hereinafter, one embodiment of the present invention will be described with
reference to the drawings. FIG. 1 is a system diagram of an embodiment of the present invention.
In FIG. 1, a part of the stereo composite signal detected by the FM tuner 1 is applied to a
subcarrier recovery circuit 2 to generate various signals necessary for demodulation of an audio
signal and detection of a pilot signal. On the other hand, the stereo composite signal is applied to
the first and second pilot signal circuits 1 and 3 and the second pilot signal detection circuit 4
and passes through the trigger circuits 6 and 7, respectively, for 2-channel stereo display lamp
7.4 channel stereo display The lamp 8 is turned on.
The trigger circuit 6 generates an automatic switching signal according to the presence or
absence of the first pilot signal, and the trigger circuit 8 generates the automatic switching signal
according to the presence t of the presence of the second pilot signal. No. 6 is controlled to turn
on the lamp 7 when the first and second pilot signals are simultaneously present (ie, at the time
of 4-channel stereo), and the trigger circuit 5 generates an automatic switching signal from the
generation wave reproduction circuit 2 to sin?at. A rectangular wave signal having a
fundamental wave and a rectangular wave signal having aos?st as a fundamental wave are
supplied to the first switching circuit 1o under the control of the trigger circuits 6 and 6, and the
first pilot signal is supplied to the first switching circuit 1o. When present, a rectangular wave
signal having a fundamental wave of 1 in ?st is supplied, and the second switching circuit 11
and the third switching circuit 12 receive the first and second switching circuits. Supplying a
square wave signal having a basic wave Cas?lIt when the pilot signal is present. 1st, 2nd. The
third switching circuit 10, 11 ░ 12 becomes a conducting element when the rectangular wave
signal is not supplied. The first switching circuit 10.1 has a stereo composite signal and can
automatically demodulate monaural, 2-channel stereo and 4-channel stereo by the above
automatic switching operation. However, in order to complete the degree of separation in the 2
channel, 4 channel stereo demodulation, by the separation level adjustment circuit 13, the
composite signal from the output signal of the second switching circuit 11 and the third
switching circuit 8. The main channel signal component in the signal is subtracted by the same
amount. In the above-described configuration, the demodulation process will be described as a
mathematical expression. A square wave signal having a fundamental wave of 5ina + st is 51 (t)
? + sin L sin started ? -8 '(t)! H + 'Fmo-ri 11'ifnxt12n1 Also, the rectangular wave signal which
is aomcmmt @ fundamental wave has a width of B2 (t) -h + gx-1) a184 <-1y-1?n-12n-1s4 <t) -h"-r Strike-"! ????????????????????????????? Demodulation of L
is 8. (T) X82 (t) X ? t is calculated, and the subadjustment amount of the separation degree
adjustment circuit 13, 4? / (?-2), is subtracted to obtain a low frequency component to obtain /
2?. Similarly, the combination of B1 (t), S'1 (t), 52 (t) and S'2 (t) enables demodulation of LB, RF
and RB, with EndPage: 27 vanes. If the second subchannel and the second pilot signal are not
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included in the composite signal, that is, if the composite signal of the 4-3-4 system is used, the
second switching circuit becomes a conductive element, 52 (t) -'AS' 2 (t)-can be written as a bar.
Therefore, the low frequency components of the outputs of the second switching circuit 11 and
the third switching circuit 12 have a degree of separation ii! By subtracting the saw order of the
IN circuit 13, (LF + LB) / 2? (2) (Ri? 10 RB) / 2?... (?, and demodulation of 2 channel nenon
stereo is performed. The stereo composite signal is also applied to the synchronous detection
circuit 141. A rectangular wave signal having oos? it as a fundamental wave is applied from the
subcarrier recovery circuit 2 to the synchronous detection circuit 14 to detect the second sub
channel signal, and the detection of the second sub channel signal is disclosed in JP-A-5l-45902
(3) LF, R, (Ly-LB + Ry-RB) / 4?... (4) LB for the output terminal, and (Ly-LB + Ry-RBI / 4?. 5)
Supply. However, the synchronous detection circuit 14 performs the above function when only
the first pilot signal is present under the control of the trigger circuit 6, and does not have the
detection function of the second subchannel signal in other cases. According to the equation (4),
the output terminal is (SLy + LB + Ry-RB) / 4? (6) (2), the equation (5) the LB output terminal
(3La + Ly + LB-Ry) / '..... (7) ((2) Formula, from (4) Formula R, the output terminal is (3Ry + Ly +
RB-LB) / 4?. ... (8) (saliva type, rough each signal (5) the RB output from the equation (3 RBs ten
LB + Ry-Ly) / 4? иииииииии (9), so-called Demodulation in the 4-3-4 system is j. FIG. 2 is a circuit
diagram of the first switching circuit 10 of FIG. 1, the switching circuit 11 of vJ2, the third
switching circuit 12, the synchronous detection circuit 14, and the switch circuit 9. Transistors
30, 31, 32, 33, 34 and 3B, resistors 36 and 3 constitute a first switching circuit U transistors 52,
53, 54, 55, 58 and 57, resistors 58 and E59 a second switching circuit The transistors 80, 81,
62, 63, 84, 65, and the resistor 86. 87 constitute a third switching circuit. A stereo composite
signal is applied to terminal 16 and terminals 15. The same DC bias is applied to the terminal 16.
??????????????? The circuit consisting of the resistors 43, 42, 43 and 44 is a
circuit for coupling the first switching circuit and the third switching circuit.
The circuit consisting of the resistors 4s and 49.51 is a circuit for coupling the first switching
circuit and the second switching circuit. As for the above-mentioned tunnel, и и и configuration,
since it is known, detailed description will be omitted. Transistors 68, 66, completion 0, 71, 74,
75, 76 ░ 1 o-777, 7B, 79, 80, 81, 82, 83. The circuit consisting of resistors 72 and 73 ░ 102 is
a synchronous detection circuit for detecting the second subchannel signal, and a rectangular
wave signal having a fundamental wave of oos? at is supplied from the subcarrier recovery
circuit between terminals 19 and 20. . The circuit consisting of the transistors 68.degree. 89.70,
71, 74, 75, 76.77 and the resistor 72, 73.degree. 102 is a well-known multiplying circuit, and the
collector connection point of the transistor 74. 76, the collector connection of the transistor 715.
77 At each point are the calculated outputs of the 43-subchannel signals in antiphase with each
other, respectively, which are divided by W by transistors 78, 79, and 80.81, and the four output
terminals 'y, s' Btrytrg Supplied to The resistor 102 determines the gain of the multiplication
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circuit, and the supply amounts to the four output terminals are determined so as to be the
equations (4) and (6). Although not described in the second FfJ, the output of the isolation si
circuit in FIG. 1 is also supplied to the four output terminals. Transistor 88. . A circuit consisting
of 88, 139, 90, 93, 94, 98 ░ 97, 98, 89, resistors 87, 92, 95, 1oo, 101, 103EndPage: 311 pages
constitutes a switch circuit. A rectangular wave signal having gin?- (1) as a fundamental wave is
supplied between terminals 21 and 22 and a rectangular wave signal having oog?st as a
fundamental wave is supplied between terminals 23. and 24 from a subcarrier recovery circuit.
Also, a voltage (hereinafter referred to as H) for turning on the transistor 86 when there is only
the first pilot signal from the trigger circuit 5 at the terminal 17 is referred to as a voltage for
subsequently turning off the transistor 86 (hereinafter referred to ) Is supplied. On the other
hand, H is supplied from the trigger circuit 6 to the terminal 18 when the first and second pilot
signals are present, and L otherwise. The transistors 82 and F1a control the function of the
synchronous detection circuit, and when both transistors are turned on, the voltage between the
collector and the emitter becomes very small. Therefore, the transistors 68, 69, 74 ░ 75.76.77
The multiplication function is stopped.
Since the current of the direct current source by the ? transistor 70.71 is still supplied from the
output terminal in the path of the transistor 82.83, there is no fluctuation of the output terminal
(a direct current does not fluctuate. When configured as described above, the following three
states can be switched automatically. First, if there is no pilot signal, ie monaural, terminals
17.18 are supplied with a collet L and transistors 86,88.
????????????????????????????????? Accordingly, the
rectangular wave signal is not supplied to the switching circuit of 'N' s' 42, and the function of
the synchronous t It wave circuit is also stopped. Second, when only the 's1 pilot signal is
present, ie, in the case of 2-channel stereo or 4-3-4 stereo, H is supplied to the terminal 17 and L
is supplied to the terminal 19, and the transistor 86 ░ F1a , 89.90 is on, transistor 93,
94.96.degree. 97.98.99 is off. Therefore, the rectangular wave signal is supplied only to the first
switching circuit, and the synchronous detection circuit has a detection function. Third, the first
one. When the second pilot signal is present, that is, in the case of 4-channel stereo, L is supplied
to the terminal 17 and H is supplied to the terminal 19, and 13-=--. The rectangular signal is
supplied to both of the second switching circuits. Also, the synchronous detection circuit will stop
functioning. As described above in the embodiments, according to the present invention, only 4channel stereo broadcasting according to the 4-4-4 system and stereo broadcasting according to
the 4-3-4 system can be automatically switched and received. At that time, there is a feature that
it is only necessary to turn on and off the detection circuit of the second subchannel signal and to
interrupt the regenerated carrier signal to the recovery circuit of the 4-4-4 system, and the
electric field strength is Where the S / N of the received signal is relatively weak, the frequency
of the second pilot signal is high, so the effect of noise is large, and the detection output of the
second pilot signal detection circuit is reduced, automatically 4-3-4. It is possible to switch to the
demodulation circuit to increase 3 / N of the reception signal, and also to have an excellent effect
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such as no DC fluctuation of the circuit at the time of the above switching and no transient height
at the time of switching.
4. Brief Description of the Drawings FIG. 11 is a block diagram of a 4-channel 14-basil stereo
demodulator according to an embodiment of the present invention, and FIG. 2 is a specific circuit
diagram of the device of FIG. 2 ......... Subcarrier regenerating circuit, 9 ... switch circuit, 10 ...
switch circuit of 11 ... jil, 11 ... second switch circuit, 12 ... 3 switch circuits 3, 4 и и и и и и и и и и pilot
signal detection circuit, 5.6 и и и trigger circuit, и и и и synchronous detection circuit, 13 и и и isolation
adjustment circuit. Name of agent Attorney Nakao et al. 1 person EndPage: 4 Fig. 1 6 Inventors
and agents other than the above (1) Inventor address same name vi1t ? address same name \
V1 Windows (2) agent EndPage: ?
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