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DESCRIPTION JP2004312479

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DESCRIPTION JP2004312479
The present invention provides a modulation degree control device in which a change in
modulation degree based on a set threshold of a VOX circuit is absorbed. A modulation degree
control apparatus in a wireless communication device including a VOX circuit, which supplies a
signal based on the VOX threshold set in the VOX threshold setting circuit 3 to the inverting
amplifier 8 to operate the VOX circuit, The signal based on the VOX threshold is inverted and
amplified by the inverting amplifier 8, the output signal amplified by the inverting amplifier 8 is
multiplied by the microphone output sound signal, and the multiplication output is supplied to
the modulation circuit as a modulation signal. [Selected figure] Figure 1
Modulation control unit
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
modulation degree control apparatus in a wireless communication device. Conventionally, an
audio signal output from a microphone in a wireless communication device is input to a
modulation circuit via an amplification circuit, a mute circuit, and the like. The degree of
modulation increases in proportion to the audio signal input level to the modulation circuit. The
degree of modulation with respect to the audio signal input level is called the degree of
modulation. As a parameter for determining this degree, there is an index of sound pressure
sensitivity of the microphone. The sound pressure sensitivity of the microphone may be fixed by
a wireless communication device or may be fixed by a user by means of a volume or the like so
that the output sound signal level of the microphone can be substantially changed. FIG. 2 is a
conventional block diagram when adjusting the sound pressure sensitivity of the microphone.
The audio signal output from the microphone is multiplied by the microphone gain signal
corresponding to the sound pressure sensitivity of the microphone set by the user by the
multiplier 21 and the multiplication output is sent to the modulation circuit as a modulation
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signal. In addition to the sound pressure sensitivity adjustment of the microphone, an automatic
gain control circuit may be provided to set a signal corresponding to the microphone gain value
as a reference value of the automatic gain control. On the other hand, when an emergency
condition is instructed, the amplifier and the VOX circuit are activated for a predetermined
period, the microphone output audio signal is amplified by the amplifier, and the amplified
output audio signal is output. It is supplied to the VOX circuit to detect the presence of the
output voice signal from the microphone, and is switched to the transmission prior to the
reception in the wireless communication device, so that the voice in the vehicle compartment in
the emergency can be detected and transmitted early. A wireless communication device is known
(see, for example, Patent Document 1). However, the above-mentioned Patent Document 1 is to
detect the presence of the amplified microphone output sound signal by the VOX circuit when
instructed to be in the emergency state, and the VOX circuit The sound pressure sensitivity of the
microphone is substantially increased in an emergency state without changing the VOX threshold
value for operating the sound, and the sound in the passenger compartment is detected and
transmitted early. Patent Document 1: Japanese Patent Application Laid-Open No. 2001-287599
(page 3, FIG. 1). SUMMARY OF THE INVENTION However, in the above-described prior art, the
user manually controls the sound pressure sensitivity of the microphone according to the
magnitude of the sound pressure of the speech to the microphone in order to control the
modulation degree. The communication is adjusted according to the optimum sensitivity.
On the other hand, there is a VOX function that is automatically set to the transmission state
according to the sound pressure of the voice speaking to the microphone. In this case, it is also
necessary to set a VOX threshold for setting a sound pressure for operating the VOX circuit.
When the set threshold is large, the radio communication device is in the transmission state
when a large sound pressure is input, and when the set threshold is small, the radio
communication device is in the transmission state even with a small sound pressure. In the case
of the VOX threshold set corresponding to the small sound pressure, on the receiver side that
receives the modulated wave transmitted from the wireless communication device, the voice
signal with small sound pressure is demodulated by the demodulation circuit, and transmission is
performed There is a problem that the sound pressure based on the audio signal output from the
receiver changes according to the VOX threshold value on the side. An object of the present
invention is to provide a modulation degree control device in which changes in modulation
degree based on a set threshold of a VOX circuit are absorbed. The modulation degree control
device of the present invention is a modulation degree control device in a radio communication
apparatus provided with a VOX circuit, and the VOX threshold value set to operate the VOX
circuit. The microphone output sound signal is amplified on the basis of the above, and the
amplified microphone output sound signal is supplied as a modulation signal to the modulation
circuit. According to the modulation degree control device of the present invention, even if the
VOX threshold value is changed, the level of the output sound signal from the microphone is
controlled based on the VOX threshold value. Absorbed and the audio output is relatively
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constant at the receiver side. Therefore, it is not necessary to adjust the audio output adjustment
volume of the receiver, and the manual operation on the receiver side is eliminated. BEST MODE
FOR CARRYING OUT THE INVENTION Hereinafter, a modulation degree control apparatus
according to the present invention will be described by way of an embodiment. FIG. 1 is a block
diagram showing the configuration of a modulation degree control apparatus according to an
embodiment of the present invention. The modulation degree control device 10 according to the
embodiment of the present invention rectifies the output sound signal from the microphone by
the rectification circuit 1, and the output sound signal rectified by the rectification circuit 1 is
converted to the low pass filter 2. By supplying and integrating, the output voice signal from the
microphone is converted to a DC level. On the other hand, the preset VOX threshold signal
output from the VOX threshold setting circuit 3 is added by the adder circuit 5 with the fixed
level hysteresis signal output from the hysteresis circuit 4.
The output voice signal from the low pass filter 2 and the output signal from the addition circuit
5 are input to the comparison circuit 6, and when the output voice signal level from the low pass
filter 2 exceeds the output signal level from the addition circuit 5, The output of circuit 6 is
activated. The output signal of the comparison circuit 6 is sent as a VOX detection signal for
operating the VOX circuit to a computer that controls a wireless communication device (not
shown), and the computer receives the activated VOX detection signal and the wireless
communication device receives Control to send state. Here, the VOX threshold signal is preset
corresponding to the threshold for operating the VOX circuit. Further, the hysteresis circuit 4 is
for changing the threshold based on the VOX threshold signal according to the transmission /
reception state so that the VOX detection signal does not repeat active / non-active in a short
period due to fluctuation of the audio signal level. . On the other hand, the output voice signal
from the microphone is multiplied by the amplification output from the inverting amplifier 8
which multiplies the VOX threshold signal output from the VOX threshold setting circuit 3 by α
in the multiplication circuit 7 to obtain the output voice from the microphone The signal is
substantially multiplied based on the VOX threshold, and the multiplication output is sent as a
modulation signal to a modulation circuit (not shown). As described above, in the modulation
factor control device 10, the output sound signal level from the microphone is converted to a DC
voltage, and the converted DC voltage level exceeds the level of the VOX threshold signal to
which the hysteresis voltage signal is added. At the same time, the VOX circuit is operated, and
the multiplication signal of the inverted amplified output signal obtained by multiplying the VOX
threshold signal by α by α by the inverted amplifier 8 and the output sound signal from the
microphone is converted to a modulation signal and sent out to the modulation circuit. . The VOX
threshold can be set as appropriate by the user of the wireless communication device. For
example, when the VOX threshold is set low, it is a case where you want to make the
surroundings quiet and talk with a small voice as a whole and make the transmission state,
conversely, if the VOX threshold is set high, the noise etc. It can be inferred that this is the case
where it is the first time to speak in a loud voice overall and want to be in the transmission state
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for the first time. As described above, in many cases, the VOX threshold value and the
modulation degree are in a proportional relationship, and the setting of the VOX threshold value
causes the received audio output signal level to increase or decrease at the receiver side.
However, in the modulation degree control device 10, the VOX threshold signal is supplied to the
inverting amplifier 8 to be inverted and amplified, and the output sound signal from the
microphone is gain controlled by multiplying this inverted amplification output with the output
sound signal from the microphone. The modulation degree is increased when the VOX threshold
is low, and the modulation degree is decreased when the VOX threshold is high, and the
modulation degree is controlled in conjunction with the set VOX threshold. Ru.
As a result, since the level of the output sound signal from the microphone is controlled based on
the VOX threshold, the change of the modulation degree due to the change of the VOX threshold
is absorbed, and the audio output becomes relatively constant on the receiver side . Therefore,
there is no need to adjust the audio output adjustment volume of the receiver, and there is an
effect that the manual operation on the receiver side is eliminated. Note that the modulation
degree control device 10 can also be performed by digital signal processing using a digital signal
processing circuit etc. by A / D converting an audio signal. As described above, according to the
modulation degree control device of the present invention, the level of the output sound signal
from the microphone is controlled based on the VOX threshold, and the output sound signal level
is controlled. In order for the signal to be a modulated signal, changes in modulation due to
changes in the set VOX threshold will be absorbed. BRIEF DESCRIPTION OF THE DRAWINGS FIG.
1 is a block diagram showing a configuration of a modulation degree control device according to
an embodiment of the present invention. FIG. 2 is a block diagram for microphone sound
pressure sensitivity adjustment in the prior art. [Description of the code] 1 rectification circuit 2
low pass filter 3 VOX threshold setting circuit 4 hysteresis circuit 5 addition circuit 6 comparison
circuit 7 multiplication circuit 8 inversion amplifier 10 modulation degree control device
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