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Description 1, title of the invention
Stereo modulation device
3. Detailed Description of the Invention The present invention relates to controlling the occupied
bandwidth of a stereo modulation device. Heretofore, the following has been known as a stereo
modulation device. That is, a first signal (hereinafter referred to as R signal (right signal)) and a
second signal (hereinafter referred to as left signal) constituting a stereo signal are input, and the
input After phase modulation (hereinafter referred to as PM modulation) of the carrier wave with
the difference signal (L, R,) of the signals, amplitude modulation (hereinafter referred to as AM
modulation) is carried out with a signal obtained by shifting the sum signal (L + R) of the input
signal by 90 ░. It is something like that. The signal thus modulated can be reproduced by
detecting the sum signal (L + Pt.) By the AM detector and the difference signal (LR) by the IPM
detector and taking the sum and difference by the matrix circuit. . As described above, this stereo
modulation scheme is characterized in that the configuration of the aftertone modulation is
simplified. However, in order to put this to practical use in radio broadcasting etc., PM
modulation is performed on the first-stage modulation on what side to use (specially to restrain
the spread of A device is necessary. For this reason, a method has been proposed in which the
side EndPage: 1 band expansion is suppressed by inserting a low-pass filter at the input of the
PM modulator to suppress the spectrum of the modulation signal applied to the PM modulator.
However, in this case, the bandwidth of the low pass filter must be set relatively narrow in order
to effectively suppress the side band spread, so stereo characteristics are obtained in the
modulation frequency region higher than the cutoff frequency of the low pass filter. There is a
problem that broadband stereo broadcasting can not be performed. The present invention has
been made in view of the above points, and in consideration of the spectrum distribution of
music, voice or the like applied as a modulation signal, the modulation is usually performed with
a faithful modulation signal, and the high frequency component of the modulation signal is high
peak value The amplitude modulation of the modulation signal is restricted according to a certain
rule to limit the modulation degree only when is shown, and stereo modulation can be performed
over a wide modulation signal range in order to suppress the spread of the spectrum. A stereo
modulation device is provided.
Stereo modulation device
Hereinafter, the present invention will be described in detail based on the drawings. (100) is a
rule that limits the peak value of the high frequency component of the signal applied as a
modulation signal in the limiting amplification unit by this rule, (200) is the output of the limiting
amplification unit (100) in the modulation unit It receives the signal and performs stereo
modulation. In the limiting amplification unit (100), (111) is an L signal input terminal for
inputting an L signal, (112) is an R signal input terminal for inputting an R signal, and (121) is an
L signal differentiating circuit for L (122) extracts the high frequency component of the R signal
with the delta signal differentiating circuit (1 field is the difference component between the high
frequency components of the signal and the R signal with the matrix circuit (151) is a multiplier,
(152) is a squaring circuit, (171), (172) are first and second resistances, and are integrated with
an operational amplifier (174). What constitutes an addition circuit that adds the output signals
of the multiplication circuit (151) and the squaring circuit (152) by applying a predetermined
gain, (173) is a reference voltage application terminal, and the addition voltage becomes a
predetermined setting value Control from the operational amplifier (174) (181) and (182) are an
L signal delay circuit and an R signal delay circuit, respectively, for giving a predetermined delay
to the L signal and the R signal, (181) and (182) respectively z9x) and (192) are an L signal
limiting amplifier and an R signal limiting amplifier, respectively, to generate L signal and ?
signal passing through each amplitude limiting amplifier (i91), (192) according to a control
signal from the operational amplifier (174) Add a predetermined amplitude limit. Further, in the
modulation section (200), (211) and (212) are L signal modulation input terminals and R signal
modulation input terminals, terminals for inputting L signal and R signal to the modulator, ? is
a) IJ box circuit Forming a sum signal (L + R) and a difference signal (LR) from the L signal and
the R signal applied to the modulation signal modulation input terminal (211) and the R signal
modulation input terminal (212), (2 ) Is a carrier signal generation circuit that generates a carrier
signal that carries a modulation signal (L signal and ? signal) 1 (24 is a PM modulator that
phase modulates the carrier signal with a difference signal (LR), ??? is to shift the sum signal
(L + R) by 90 ░ at 90 ░ shim, (the company) is an amplitude modulator and a PM modulated
signal output from the PM modulator (b) by the sum signal (L + R) AM modulation, (2 outputs It
is a terminal. The operation is described in t.
First, the modulation unit (20o) will be described. A sum signal (L ? R) and a difference signal
(L?R) are generated from the L signal and the R signal in the I) I Socks path 122), and the PM
modulator After PM modulation with the difference signal (L-R), the sum signal shifted by 90 ░
by the 90 ░ shifter is used to perform AM modulation with the AM modulator (i). The signal V6
(1) is as follows. VO (t) = sin (act + ?5inPt) и (1 + ? cospt) ииииииииииииииииииииииииииии 1 иииииииииииииииииииииииии 1
иииииииииииииииии 1 = K (L + fL) (? 1) ? = K (L-R) (? 1) L: L signal amplitude R: R signal amplitude to:
modulation index EndPage: 2 ? J. (B) sin?1 + ииииииииииииииии Dasoshi 1, Jn (?); from Ru Bessel
function Vo (t) = sin?t next, L signal to right and left side bands and R signals are respectively
arranged. Next, I will consider m: и in the spread of the sideband. Now, looking at the large (? +
2p) component of the amplitude in the sideband spectrum, its amplitude coefficient V21) is
influenced by the amplitude of the equation 4 and the amplitude of the L signal and R signal It
can be considered that the amplitude of the amplitude coefficient Vzp of this (? + 2p)
component is suppressed to a predetermined value vo as a method of suppressing the spread of
the side band. As a method of embodying this idea, the L signal and R signal which are
modulation signals are suppressed so that the modulation input is not further increased when the
amplitude coefficient Vzp of the (? + 2p) component reaches a predetermined value vo
determined in advance. You should do it. The amplitude limiting section (100) shown in the
figure is based on such a concept to limit the amplitude and suppress the spread of the side
band. That is, the (L + R) signal and the (L-R) signal are generated by the matrix circuit (I31), and
the 2 (L-R) signal is generated by squaring the (L-R) signal by the square detector (152). Also, by
multiplying the (L + R) signal and the (L-R) signal by a multiplier (151), a 2 (L + R) (L-R) signal is
obtained. These signals are added by an adder circuit (174) composed of an operational amplifier
(174) and first and second resistors (171) and (172) for weighting to obtain a signal
corresponding to the Vtp. After that, compare V2p with the reference voltage applied to the
reference signal terminal (173), and control to limit the passing signal amplitude of each limiting
amplifier (191) (192) when 2p exceeds this reference voltage. .
Each delay circuit (181), (182) compensates for the control delay due to the time delay until the
limiting control signal arrives at the limiting amplifier. The delay is made in accordance with the
delay amount of the control signal. Since the limiting amplification unit (100) is feedforward
controlled, the output level of the limiting amplifier can be set to any of soft limiting, critical
limiting, and over limiting. In the above, focusing on (?-2p) and controlling the spread of the
spectrum by the method of adding the amplitude limitation so that the spectrum of this
frequency component does not become a predetermined value or more has been described. The
circuit that performs the control can be configured based on the same idea. Further, in addition
to the case of using a simple differentiation circuit for extraction of high-frequency components,
it is preferable to weight and extract specific high-frequency components according to the nature
of the modulation signal, thereby performing amplitude limit control. Can. For example, when
applied to a modulation signal where high frequency components have low probability but high
level may occur, stereo modulation is performed in most cases, and amplitude limitation is
performed at high frequency peaks that occur with low probability. As a result, it is possible to
obtain an effect that EndPage: 3 etc. and the occupied bandwidth can be controlled in a
predetermined amount while the modulation is deep on average. As described above, according
to the present invention, when the difference component between the high frequency
components of the first signal and the second signal constituting the stereo signal becomes equal
to or more than a predetermined value, the first and second signals applied to the modulation
section Since the amplitude is limited, it is possible to provide a stereo modulation device capable
of performing stereo modulation over a wide range of modulation signal in which spectrum
spreading can be suppressed.
4 is a block diagram showing an embodiment of the present invention. (1, 00) иии Limited
amplification unit, (200) иии modulation unit, (11), иии L signal input terminal, (112) иии R signal input
terminal, (121) и и и и L signal differentiation circuit, (122) и и и R signal input terminal, (? и и и
matrix circuit, (151) и и и multiplication circuit, (152) и и и и square circuit, (171) и и и 1 resistance,
(172) ... second resistance, (173) ... reference voltage application terminal, (17-1) ... operational
amplifier, (181) ... L signal delay circuit, (182 ) ... R signal delay circuit, (191) ... L signal
amplitude limiting amplifier, (192) ... R signal amplitude limiting amplifier, (211) ... L signal
modulation input terminal, (212) ... и R signal modulation input terminal, solid и и и matrix circuit,
123 и и и (carrier number g generation circuit, (24) и PM modulator, (2 (g) ... 90 'shifter, Cobi иии AM
modulator, (21j иии modulator output terminal. Agent Shinno-EndPage: ?
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