close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JPH05114870

код для вставкиСкачать
Patent Translate
Powered by EPO and Google
Notice
This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JPH05114870
[0001]
FIELD OF THE INVENTION This invention relates to a receiver for a wireless microphone.
[0002]
2. Description of the Related Art A tone squelch wireless microphone and its receiver are
configured as shown in, for example, FIGS. That is, FIG. 4 shows the wireless microphone, and the
audio signal S1 from the microphone unit 1 is supplied to the addition circuit 4 through the band
pass amplifier 2 and the pre-emphasis circuit 3 whose passband is the audio frequency band.
[0003]
At this time, in the crystal oscillation circuit 5, a tone signal (oscillation signal) S5 having a
constant frequency and amplitude outside the audible frequency band, for example, a tone signal
S5 having a frequency of 32.768 kHz is formed. 4 is supplied.
[0004]
Therefore, the addition circuit 4 takes out the addition signal S4 in which the tone signal S5 is
superimposed on the audio signal S1.
[0005]
10-04-2019
1
Then, the addition signal S4 is supplied to the FM modulation circuit 6 to be, for example, an FM
signal S6 of 800 MHz band, and this FM signal S6 is supplied to the antenna 8 through the
output amplifier 7 and transmitted to the receiver. .
[0006]
FIG. 5 shows the receiver, and the FM signal S6 from the wireless microphone is received by the
antenna 11, and the received signal S6 is supplied to the reception circuit (tuner circuit) 12.
Although not shown, the receiving circuit 12 is configured in a double super heterodyne system
and includes an antenna tuning circuit to an FM demodulation circuit. When the FM signal S6 is
received, the original addition signal S4 is demodulated. Output.
Then, the signal S4 is supplied to the low pass filter 13 whose cutoff frequency is, for example,
20 kHz to extract the audio signal S1, and this signal S1 is output from the switch circuit 14 for
muting → the de-emphasis circuit 15 → the output amplifier 16 It is taken out to the terminal 17
through the signal line.
[0007]
In this case, the detection circuit 20 detects the presence or absence of the tone signal S5, and
muting control is performed by the detection signal.
That is, the addition signal S4 from the reception circuit 12 is supplied to a narrow band
bandpass filter, in this example, a quartz oscillator 21 equivalent to the quartz oscillator
constituting the oscillation circuit 5, and the tone signal S5 is The signal S5 is taken out and
supplied to the amplitude detection circuit 23 through the amplifier 22 to take out the DC
voltage V23 of a level corresponding to the amplitude of the signal S5.
[0008]
The voltage V23 is supplied to the voltage comparison circuit 24, and the reference voltage V25
is supplied from the reference voltage source 25 to the comparison circuit 24. When V23 比較
V25, "H", V23 < The comparison output S24 which becomes "L" at V25 is taken out, and this
10-04-2019
2
signal S24 is supplied to the switch circuit 14 as its control signal, and the switch circuit 14 is on
when S24 = "H", S24 = "L" When you are off.
[0009]
According to such a configuration, when the receiver receives the FM signal S6, the voice signal
S1 is obtained from the low pass filter 13, and at the same time, the tone signal S5 is obtained
from the crystal oscillator 21; The switch circuit 14 is turned on as it becomes "H".
Therefore, as described above, the audio signal S1 from the filter 13 is taken out to the terminal
17 through the switch circuit 14.
[0010]
On the other hand, when the receiver can not receive the FM signal S6, the filter 13 outputs
limiter noise in place of the audio signal S1. However, at this time, the tone signal S5 is not
obtained from the crystal oscillator 21, and the switch circuit 14 is turned off since S24 = "L".
Therefore, in the switch circuit 14, limiter noise is blocked and is not output to the terminal 17.
[0011]
Thus, according to this wireless microphone and receiver, the presence or absence of the tone
signal S5 obtained simultaneously with the audio signal S1 is detected, and the muting is
controlled by the detection output, so that reliable muting can be performed.
[0012]
However, in the case of the detection circuit 20 described above, the detection circuit 20 may
malfunction due to the reception characteristics of the receiver, and muting may not be correct.
[0013]
That is, FIG. 6 is a measurement example showing the relationship between the antenna input
voltage of the receiver of FIG. 5 and the demodulation output of the receiving circuit 12.
10-04-2019
3
Then, the curve receives the noise level of the demodulation output, the curve receives the level
of the demodulated tone signal S5, and the curve receives an FM signal S6 that has been
frequency-modulated so that the frequency shift is ± 5 kHz by the alternating signal S1 having a
frequency of 1 kHz. The level of the demodulated output at that time and the straight line are
levels corresponding to the reference voltage V25 of the tone signal S5.
In the vertical axis, the demodulation output level is 0 dB when the FM signal S6 of the curve is
received at an antenna input voltage of 60 dB.mu.V.
[0014]
Then, according to FIG. 6, when the antenna input voltage becomes 30 dBμV or less, the noise
level becomes higher than the reference level of the tone signal. The noise signal generated at
this time is a wideband noise signal and contains the same 32.768 kHz frequency component as
the tone signal S5. Therefore, the detection circuit 20 erroneously recognizes the 32.768 kHz
component of the wide band noise signal as the tone signal S5, and outputs S24 = "H" regardless
of the presence or absence of the tone signal S5.
[0015]
Therefore, muting does not occur when there is no received radio wave or when it is weak.
[0016]
The present invention seeks to provide a receiver that solves such problems.
[0017]
Therefore, in the present invention, when the reference numerals of the respective parts
correspond to those of the embodiments described later, the tone signal S5 outside the audible
band is added to the audio signal S1, and this addition signal is added. In a receiver for a wireless
microphone for transmitting S4, a switch circuit 14 provided on a signal line of an audio signal
S1 output from the receiver circuit 12 for muting the audio signal S1, and a receiver circuit The
first demodulation circuit 20 is supplied with the 12 demodulation outputs, detects the tone
10-04-2019
4
signal S5 included in the demodulation output, and is supplied with the demodulation output of
the reception circuit 12, and detects the noise signal included in the demodulation output. A
second detection circuit 30 and a logic circuit 41 that performs a logical operation of detection
outputs of the first detection circuit 20 and the second detection circuit 30 are provided.
By supplying the logic output S41 of the logic circuit 41 to the switch circuit 14 as its control
signal, the first detection circuit 20 detects the tone signal S5, and the second detection circuit
30 does not detect the noise signal. Sometimes, when muting by the switch circuit 14 is canceled
and the first detection circuit 20 does not detect the frequency component of the tone signal S5
or when the second detection circuit 30 detects a noise signal, the switch circuit 14 It is intended
to apply muting.
[0018]
The detection circuit 20 detects the presence or absence of the tone signal S5, the detection
circuit 30 detects the presence or absence of the noise signal, the muting is controlled by the
logical output of these detection outputs, and the tone signal S5 is received, , Muting is canceled
only when no noise signal is received, and muting is applied in other states.
[0019]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the receiving
system and detection circuit 20 for the audio signal S1 are constructed in the same manner as
the receiver of FIG. 5, and the output signal S24 of the voltage comparison circuit 24 is supplied
to the exclusive OR circuit 41. .
[0020]
Reference numeral 30 denotes a noise detection circuit for detecting a wide band noise signal.
That is, the output signal of the receiving circuit 12 is supplied to a narrow band bandpass filter,
in this example, the crystal oscillator 31.
In this case, the resonance frequency (passing frequency) of the crystal oscillator 31 is close to
the frequency 32.768 kHz of the tone signal S5, but is a frequency which can sufficiently
separate the signal component of this frequency, for example, 31.468 kHz.
10-04-2019
5
Thus, when the wide band noise signal is output from the receiving circuit 12, the 31.468 kHz
noise component S31 included in the wide band noise signal is extracted from the crystal
oscillator 31.
[0021]
Then, this noise component S31 is supplied to the amplitude detection circuit 33 through the
amplifier 32, and a DC voltage V33 of a level corresponding to the amplitude of the noise
component S31 is taken out, and this voltage V33 is supplied to the voltage comparison circuit
34. A reference voltage V35 is supplied from the reference voltage source 35 to the comparison
circuit 34. In this case, for example, V35 = V25.
[0022]
Then, a comparison output S34 which is "H" when V33 V V35 and "L" when V33 <V35 is taken
out from the comparison circuit 34, and this signal S34 is supplied to the exclusive OR circuit 41,
The output signal S41 of the exclusive OR circuit 41 is supplied to the switch circuit 14 as its
control signal, and the switch circuit 14 is turned on when S41 = "H" and turned off when S41 =
"L".
[0023]
According to such a configuration, 1.
When the FM signal S6 is received at a sufficient level. This corresponds to the case where the
antenna input level is 30 dBμV or more in FIG. 6. In this case, in the detection circuit 20, the
tone signal S5 is obtained at the level of the reference voltage V25 or more, and S24 = "H".
Become. Further, in the detection circuit 30, since the noise component S31 has a level equal to
or lower than the reference voltage V35, S34 = "L".
[0024]
10-04-2019
6
Therefore, since S41 = "H", the switch circuit 14 is turned on and muting is not performed, and
the audio signal S1 is output to the terminal 17 through the switch circuit 14. 2. When the FM
signal S6 is not received at a sufficient level. This corresponds to the case where the antenna
input level is 30 dBμV or less in FIG. 6. In this case, a wideband noise signal is output from the
reception circuit 12, and as described above, the detection circuit 20 detects the wideband noise
signal. 32.768 kHz component is erroneously recognized as the tone signal S5, and S24 = "H" is
output regardless of the presence or absence of the tone signal S5. Further, in the detection
circuit 30, the noise component S31 is obtained at a level equal to or higher than the reference
voltage V35, and S34 = "H".
[0025]
Therefore, since S41 = “L”, the switch circuit 14 is turned off and muting is performed, so the
noise signal is not output to the terminal 17.
[0026]
In addition to this, although the tone signal S5 can not be obtained as a combination of the
output signals of the receiving circuit 12, the wide band noise signal can not be output, and the
tone signal S5 can be obtained, the wide band noise signal is also output. However, since S24 =
“L” and S34 = “L” in the former case, S41 = “L” in the latter case, and S24 = “H” and
S34 = “H” in the latter case. Therefore, S41 = “L”, and in either case, the switch circuit 14 is
turned on and muting is applied.
[0027]
Thus, according to the present invention, the switch circuit 14 is turned on to release muting
only when the tone signal S5 is obtained above the prescribed level and the broadband noise
signal is below the prescribed level. In the case, the switch circuit 14 is turned off and muting is
performed.
[0028]
Therefore, when the reception state of the FM signal S6 at the receiver is poor, for example,
when there is no received radio wave or when it is weak, when the radio wave of a frequency
different from the original FM signal S6 is received in the detuned state, the disturbance wave is
When received, muting can be applied reliably, and no muting is applied to the audio signal S1.
[0029]
FIG. 2 shows a specific example of the above-mentioned detection circuits 20 and 30, and
10-04-2019
7
reference numeral 29 denotes a buffer amplifier which doubles as a band pass filter.
[0030]
FIG. 3 shows the case where the output signals S24 and S34 of the detection circuits 20 and 30
are supplied to the three-state buffer 42 to form a muting control signal S41.
Then, in this case, when S34 = “L”, S41 = S24.
Further, when S34 = "H", the output of the buffer 42 becomes high impedance, but since the
output is pulled down by the resistor 43, S41 = "L" regardless of the signal S24.
Therefore, also in this case, the muting operation similar to the example of FIG. 1 is performed on
the tone signal S5 and the wide-band noise signal.
[0031]
Then, according to this example, the degree of freedom in design of the detection circuits 20 and
30 is higher than in the example of FIG.
That is, in the example of FIG. 1, since the exclusive OR circuit 41 is used, the detection circuit 20
needs to act as a detection circuit of the tone signal S5 and also as a detection circuit of the wide
band noise signal. is there.
Also, the noise detection capability of the detection circuit 20 and the noise detection capability
of the detection circuit 30 need to be equivalent.
[0032]
However, in the case of the example of FIG. 3, the detection circuit 20 is not required to operate
10-04-2019
8
as a detection circuit of the wideband noise signal. Further, the noise detection capability and the
circuit configuration of the detection circuit 30 can be designed independently of the detection
circuit 20.
[0033]
Therefore, according to the example of FIG. 3, the degree of freedom in design of the detection
circuits 20 and 30 is higher than in the example of FIG.
[0034]
According to the present invention, the switch circuit 14 is turned on to release muting only
when the tone signal S5 is obtained at a specified level or higher and the broadband noise signal
is lower than the specified level. In the case of (3), the switch circuit 14 is turned off to apply
muting.
[0035]
Therefore, when the reception state of the FM signal S6 in the receiver is poor, for example,
when there is no received radio wave or when it is weak, when the radio wave of a frequency
different from the original FM signal S6 is received in the detuned state, the disturbance wave is
When received, muting can be applied reliably, and no muting is applied to the audio signal S1.
10-04-2019
9
Документ
Категория
Без категории
Просмотров
0
Размер файла
17 Кб
Теги
description, jph05114870
1/--страниц
Пожаловаться на содержимое документа