close

Вход

Забыли?

вход по аккаунту

?

JP2015222889

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 JP2015222889
An object of the present invention is to provide a variable directional electret condenser
microphone capable of simplifying a circuit configuration and performing balanced output of
audio signals. SOLUTION: First and second fixed poles 1f and 1b are disposed back to back in a
non-conductive state, and the first and second fixed poles are spaced apart by a predetermined
distance from each other. , 2b face each other, electrically independent first and second electret
condenser microphone units Uf, Ub, a first impedance converter F1 whose input terminal is
connected to the first fixed pole, and a first impedance A first buffer circuit E1 connected to the
converter, a second impedance converter F2 whose input terminal is connected to the second
fixed pole, and a second buffer circuit E2 selectively connected to the second impedance
converter; And directional variable switches SW1 and SW2 capable of alternatively selecting the
first to third directional modes. [Selected figure] Figure 1
Variable directivity electret condenser microphone
[0001]
The present invention relates to a condenser microphone having a variable directivity function by
providing two microphone units back to back, and in particular, a variable directivity electret that
uses an electret for the condenser microphone unit and outputs a balanced audio signal. It relates
to a condenser microphone.
[0002]
As microphones whose directivity can be varied, microphones each having a cardioid
03-05-2019
1
characteristic are disposed back to back in back and forth.
In general, condenser microphones are more suitable for wide-band sound collection than
dynamic microphones, and are excellent in directional frequency response. Non-Patent Document
1 discloses that variable directivity is realized by adjusting the polarization voltage applied to
each condenser microphone unit by utilizing such characteristics of the condenser microphone.
[0003]
On the other hand, the applicant of the present invention has previously filed a patent application
for a variable directional condenser microphone which has solved the technical problem in the
condenser microphone disclosed in the above-mentioned Non-Patent Document 1, which is
disclosed in Patent Document 1 There is. According to the condenser microphone disclosed in
Patent Document 1, as in the condenser microphone disclosed in Non-patent Document 1, the
decrease in output sensitivity and the deterioration in S / N caused by AC coupling of the front
and rear diaphragms It can be prevented.
[0004]
In the case of using two capacitor microphone units requiring the polarization voltage disclosed
in Non-Patent Document 1 and Patent Document 1 described above, a DC power supply of about
5 to 20 V is used to operate a circuit such as an impedance converter. Therefore, it is necessary
to configure so that a polarization voltage of 60 V or more can be obtained by a DC-DC converter
or the like. According to this, it is necessary to provide an additional configuration such as the
DC-DC converter described above in the condenser microphone unit, which inevitably increases
the cost.
[0005]
Accordingly, the applicant of the present invention has also filed a patent application for a
variable directional condenser microphone using an electret dielectric film in two condenser
microphone units, which is disclosed in Patent Document 2. According to the variable directional
condenser microphone disclosed in Patent Document 2, the directivity can be changed
continuously by combining the outputs of the two condenser microphone units by the variable
03-05-2019
2
capacitance condenser (varicon). Can be realized.
[0006]
"Condenser microphone with variable polar response" by Michael Gayford Microphone
Engineering Handbook (p32, Figure 1.18)
[0007]
JP, 2012-65147, A JP, 2008-118260, A
[0008]
Incidentally, Patent Document 1 mentioned above also discloses an example of a variable
directional condenser microphone using an electret condenser microphone unit which does not
require a polarization voltage.
According to an example using the electret condenser microphone unit disclosed in this patent
document 1, it has a phase inverting amplifier whose gain is “1” and the phase of the input
and output is reversed, and the gain is “1” and the phase of the input and output is not The
output of the inverting non-inverting amplifier is also used to select phase adjustment means for
selecting these outputs.
Therefore, providing the above-described phase adjustment means has a problem of complicating
the circuit configuration, and there is room for improvement.
[0009]
Further, according to the variable directional condenser microphone disclosed in Patent
Document 2 described above, the output of the two electret condenser microphone units is
coupled by the variable capacitance condenser (varicon), so that the external vibration is variable.
When added to the capacitive capacitor, the capacitance changes, which causes noise. Therefore,
it is necessary to take measures against the external vibration acting on the above-mentioned
variable capacitance capacitor, and there is room for improvement in this respect.
03-05-2019
3
[0010]
On the other hand, in this type of microphone, when it is necessary to use a microphone cord of a
considerable length, such as when used in a hall or an event hall, etc., or in a studio etc., the tone
is made more faithful and high S / N. When using it as a collect to collect noise, a balanced
shielded cable is used as a microphone cord.
[0011]
Therefore, the audio output of the microphone used for this adopts a balanced (balanced) output
system, and the audio signal from the microphone is sent out to a mixer etc. via the abovementioned balanced shield cable.
Then, on the mixer side, an audio signal with common mode noise reduced can be obtained by
extracting an audio signal using a differential amplifier or a microphone transformer.
[0012]
Therefore, the present invention solves the above-mentioned problems of an electret condenser
microphone in which two microphone units are arranged back to back so as to change directivity,
and a variable directivity electret condenser which outputs audio signals in balance. It is an
object to provide a microphone.
[0013]
One preferable form of the variable directional electret condenser microphone according to the
present invention, which has been made to solve the above-mentioned problems, is characterized
in that the first and second fixed poles are disposed back to back in a nonconductive state.
Electrically independent first and second electret condenser microphone units in which first and
second diaphragms are disposed at predetermined intervals in the second fixed pole and opposed
to the first and second fixed poles, and A first impedance converter whose input terminal is
connected to the first fixed pole, a first buffer circuit connected to the first impedance converter,
and a second impedance converter whose input terminal is connected to the second fixed pole
And a second buffer circuit selectively connected to the second impedance converter and the
second impedance converter, and at least a first directivity mode to a third directivity mode are
selected. And a directional variable switch, and when the first directional mode is selected by the
directional variable switch, the second buffer circuit is connected to the output terminal of the
second impedance converter, and the directional switch is selected. When the second directivity
03-05-2019
4
mode is selected by the variable property switch, the input terminal of the second buffer circuit is
grounded, and when the third directivity mode is selected by the directivity variable switch, the
output of the second impedance converter The first diaphragm is connected to the terminal, the
input terminal of the second buffer circuit is grounded, the second diaphragm is always
grounded, and an audio signal is output from the output terminals of the first and second buffer
circuits. Is characterized in that a balanced output of is derived.
[0014]
Moreover, another preferable embodiment of the variable directional electret condenser
microphone according to the present invention made to solve the above-mentioned problems is
that the first and second fixed poles are disposed back to back in a non-conductive state,
Electrically independent first and second electrets in which first and second diaphragms are
disposed to face the first and second fixed poles at predetermined intervals respectively in the
first and second fixed poles. A condenser microphone unit, a first impedance converter having an
input terminal connected to the first diaphragm, a first buffer circuit connected to the first
impedance converter, and an input terminal connected to the second diaphragm A second
impedance converter and a second buffer circuit selectively connected to the second impedance
converter; and at least a first directivity mode to a third directivity mode And a directivity
variable switch capable of alternatively selecting a diode, and when the first directivity mode is
selected by the directivity variable switch, the second buffer circuit is connected to the output
terminal of the second impedance converter. When the second directivity mode is selected by the
directivity variable switch, the input terminal of the second buffer circuit is grounded, and the
third directivity mode is selected by the directivity variable switch. The first fixed pole is
connected to the output terminal of the impedance converter, the input terminal of the second
buffer circuit is grounded, the second fixed pole is always grounded, and the first and second
buffer circuits are connected. A balanced output of the audio signal is derived from the output
terminal.
[0015]
In this case, in any of the above-described modes, a two-link three-contact switch can be suitably
used as the directivity variable switch.
Further, a configuration is adopted in which the audio signals of balanced outputs respectively
derived from the output terminals of the first and second buffer circuits are mixed and output by
a mixer.
03-05-2019
5
Furthermore, a configuration in which phantom power for the variable directivity electret
condenser microphone is supplied from the output terminals of the first and second buffer
circuits can also be suitably adopted.
[0016]
According to the variable directional electret condenser microphone of the present invention, in
addition to the first and second electret condenser microphone units, the first and second
impedance converters, the first and second buffer circuits, and the directivity changeable A
changeover switch as a switch is provided.
Thus, it is possible to provide a variable directional electret condenser microphone that realizes
balanced output of audio signals. Therefore, according to the variable directional electret
condenser microphone according to the present invention, it is not necessary to provide a special
circuit configuration such as a phase inversion amplifier, as compared with the example disclosed
in Patent Document 1 described above. It can be simplified.
[0017]
Further, according to the variable directional electret condenser microphone according to the
present invention, the problem of noise generation due to vibration caused by adopting the
variable capacitance condenser (varicon) as compared with the example disclosed in the abovementioned Patent Document 2 Can contribute to simplifying the circuit configuration.
[0018]
FIG. 1 is a circuit connection diagram showing a first embodiment of a variable directivity
electret condenser microphone according to the present invention.
It is an equivalent circuit schematic when 1st directivity mode is selected in the structure shown
in FIG. It is an equivalent circuit schematic when the 2nd directivity mode is selected similarly. It
is an equivalent circuit schematic when the 3rd directivity mode is selected similarly. It is a
circuit connection diagram showing the principal part of a 2nd embodiment of a variable
directivity electret condenser microphone concerning the present invention. FIG. 6 is an
03-05-2019
6
equivalent circuit diagram when a first directivity mode is selected in the configuration shown in
FIG. 5; It is an equivalent circuit schematic when the 2nd directivity mode is selected similarly. It
is an equivalent circuit schematic when the 3rd directivity mode is selected similarly.
[0019]
A variable directivity electret condenser microphone according to the present invention will be
described based on an embodiment shown in the drawings. FIG. 1 shows a state in which a mixer
M2 is connected to a variable directivity electret condenser microphone M1 according to the
present invention via a balanced shield cable Ca, and the variable directivity electret condenser
microphone M1 is a phantom on the mixer M2 side. The power supply device is configured to
receive a drive current.
[0020]
First, the variable directional electret condenser microphone indicated by reference numeral M1
is configured to include two electrically independent electret condenser microphone units in
front and back. In the two electret condenser microphone units, the sound collecting axis side
indicated by the arrow 0 deg is referred to as a front unit Uf, and the opposite side is referred to
as a rear unit Ub.
[0021]
The first and second fixed poles 1f and 1b constituting the front unit Uf and the rear unit Ub are
disposed back to back in a non-conductive state, and are fixed to the first and second fixed poles
1f and 1b, respectively. The first and second diaphragms 2f and 2b are disposed to face each
other at an interval. In this embodiment, electret dielectric films 3f and 3b are provided on the
surfaces of the first and second fixed electrodes 1f and 1b facing the respective diaphragms 2f
and 2b, respectively, and back An electret condenser microphone unit according to the electret
method is configured.
[0022]
03-05-2019
7
F1 and F2 shown in FIG. 1 are first and second impedance converters, both of which are formed
by the same circuit configuration. That is, the first and second impedance converters F1 and F2
are respectively provided with FETs Q1 and Q2 with a built-in bias circuit. Diodes D1 and D2 and
a resistor R1 are connected in anti-parallel between the gate and the source of the FET Q1, and
these function to generate a gate bias of the FET Q1. Similarly, diodes D3 and D4 and a resistor
R2 are connected in anti-parallel between the gate and the source of the FET Q2, and these
function to generate a gate bias of the FET Q2.
[0023]
A direct current operating voltage is supplied to each drain of each of the FETs Q1 and Q2 from a
constant voltage circuit described later, and source resistances R3 and R4 are connected to each
source to constitute a source follower circuit. Further, capacitors C1 and C2 are respectively
connected to the first and second impedance converters F1 and F2 constituting a source follower
circuit, and the signals from the front unit Uf and the rear unit Ub which have been impedance
converted are the same as the first and second impedance converters. It is drawn out through
each of the capacitors C1 and C2.
[0024]
A signal from the first impedance converter F1 through the capacitor C1 is supplied to an emitter
follower circuit E1 as a first buffer circuit including a transistor Q3. Further, a signal from the
second impedance converter F2 through the capacitor C2 is selectively supplied to the emitter
follower circuit E2 as a second buffer circuit including the transistor Q4 through a directivity
variable switch described later. .
[0025]
The first emitter follower circuit E1 includes bias setting resistors R5 and R6, and the mixer M2
side via the terminal pin P2 is configured as a load resistor (emitter resistor), and the output of
the emitter follower is a terminal pin It is supplied to P2 as a hot side output. Similarly, the
second emitter follower circuit E2 includes bias setting resistors R7 and R8, and the mixer M2
side via the terminal pin P3 is configured as a load resistor (emitter resistor). The output of this
emitter follower is a terminal It is supplied to pin P3 as a cold side output. The signal output by
the first buffer circuit E1 and the second buffer circuit E2 is balanced and output to the mixer
03-05-2019
8
M2 through the balanced shield cable Ca with the terminal pin P1 as the ground line.
[0026]
On the other hand, phantom power is supplied to the terminal pins P2 and P3 from the mixer M2
side with the terminal pin P1 as a ground line. The collectors of the transistors Q3 and Q4 are
commonly connected and connected to a constant current element Ic, and a constant voltage
element Z1 and an electrolytic capacitor C3 are connected between the constant current element
Ic and the ground line of the terminal pin P1. A voltage circuit is formed.
[0027]
Therefore, the constant voltage by the phantom power generated by the constant voltage circuit
is supplied to the drains of the FETs Q1 and Q2 constituting the first and second impedance
converters F1 and F2. In this embodiment, an electrolytic capacitor C4 for AC coupling bypass is
connected across the series circuit of the constant current element Ic and the constant voltage
element Z1.
[0028]
The symbols SW1 and SW2 shown in FIG. 1 are 2-link three-contact switches, which function as
a directivity variable switch that selects one of the first directivity mode to the third directivity
mode. Then, when the switches SW1 and SW2 select the position indicated by the code BI, they
are set to bi-directional (Bidirectional characteristics), and when the switches SW1 and SW2
select the position indicated by the code C, a single signal is selected. It is set to directivity
(cardioid characteristic). Further, when the switches SW1 and SW2 select the position indicated
by the symbol O, they are set to omnidirectional (Omnidirectional characteristics). The directivity
switching action based on these selections will be described later based on FIGS. 2 to 4.
[0029]
A first diaphragm 2f constituting a front unit Uf is connected to the movable contact of the first
switch SW1 functioning as a directivity variable switch. The movable contact of the second
03-05-2019
9
switch SW2 is connected to the base of the transistor Q4 that constitutes the second emitter
follower circuit E2.
[0030]
The fixed contacts BI and C of the first switch SW1 are connected to the ground line of the
terminal pin P1, and the fixed contacts C and O of the second switch SW2 are also connected to
the ground line of the terminal pin P1. Furthermore, the fixed contact O of the first switch SW1
and the fixed contact BI of the second switch SW2 are connected in common, and the capacitor
C2 from the second impedance converter F2 is connected to this common connection point. That
is, a signal from the rear unit Ub is configured to be applied to a connection point between the
fixed contact O of the first switch SW1 and the fixed contact BI of the second switch SW2.
[0031]
The variable directional electret condenser microphone M1 is connected to the mixer M2 by the
balanced shield cable Ca via the terminal pins P1 to P3 as described above. A subtractor circuit
OP1 of operational amplifier is mounted on the mixer M2, and a signal from the terminal pin P2
is supplied to the non-inverted input terminal of the subtractor circuit OP1 through a capacitor
C11, and a signal from the terminal pin P3 is a capacitor It is supplied to the inverting input
terminal of the subtraction circuit OP1 via C12. With this configuration, the audio signals of
balanced outputs from the terminal pins P2 and P3 are mixed by the mixer M2, and the
subtraction output by the subtraction circuit OP1 is provided to the output terminal OUT as an
audio signal by the microphone M1.
[0032]
The mixer M2 side is provided with, for example, a 48 V DC power supply E0 functioning as a
phantom power supply, and this DC power supply E0 is sent to the terminal pins P2 and P3
described above via the 6.8 KΩ resistors R11 and R12, respectively. .
[0033]
2 to 4 show the first and second switches SW1 and SW2 as directivity variable switches in the
configuration of the variable directivity electret condenser microphone M1 shown in FIG. The
03-05-2019
10
equivalent circuit schematic at the time of selecting to sex C and nondirectional O is shown,
respectively.
Further, in addition to the equivalent circuit diagram, addition and subtraction of polar patterns
obtained by the front unit Uf and the rear unit Ub are shown.
[0034]
That is, when the directivity variable switch selects BI which is the first directivity mode, as
shown in FIG. 2, the input terminal of the second buffer circuit E2 is connected to the output
terminal of the second impedance converter F2. Connected As a result, the signals of the polar
pattern shown in FIG. 2 are respectively supplied to the second terminal pin P2 and the third
terminal pin P3, and these are subtracted in the subtraction circuit OP1 of the mixer M2, and as
a result, bi-directional It is possible to obtain an audio signal having sex.
[0035]
Next, when the variable directivity switch selects the single directivity C which is the second
directivity mode, as shown in FIG. 3, the input terminal of the second buffer circuit E2 is
grounded. As a result, while the signal of the polar pattern shown in the figure is supplied to the
second terminal pin P2, the third terminal pin P3 becomes non-signal. As a result, an audio signal
having unidirectionality is provided as a subtraction output by the subtraction circuit OP1 of the
mixer M2.
[0036]
In addition, when the directivity variable switch selects the nondirectional O which is the third
directivity mode, as shown in FIG. 4, the first diaphragm 2f is connected to the output terminal of
the second impedance converter F2. While being connected, the input terminal of the second
buffer circuit E2 is grounded. Thereby, a signal from the second impedance converter F2 by the
rear unit Ub is applied to the first diaphragm 2f of the front unit Uf, and the polar pattern by the
rear unit Ub and the polar pattern by the front unit Uf are As a result, the second terminal pin P2
is supplied with a signal having an omnidirectional polar pattern as shown in the figure.
03-05-2019
11
[0037]
On the other hand, since the input terminal of the second buffer circuit E2 is grounded, the third
terminal pin P3 has no signal. As a result, a nondirectional audio signal shown in FIG. 4 is
provided as a subtraction output by the subtraction circuit OP1 of the mixer M2.
[0038]
FIG. 5 shows a second embodiment of a variable directional electret condenser microphone
according to the present invention, and FIG. 5 is a main alternative to the variable directional
electret condenser microphone M1 already described based on FIG. It shows only the
department. In the example shown in FIG. 5, the first fixed electrode 1 f and the first diaphragm
2 f in the front unit Uf are alternately connected to each other and the rear unit Ub is connected
to the example shown in FIG. 1 already described. The second fixed electrode 1b and the second
diaphragm 2b are alternately connected to each other.
[0039]
That is, the first diaphragm 2f constituting the front unit Uf is connected to the input terminal of
the first impedance converter F1, and the first fixed pole 1f is connected to the movable contact
of the first switch SW1. The second diaphragm 2b of the rear unit Ub is connected to the input
terminal of the second impedance converter F2, and the second fixed pole 1b is connected to the
ground line formed by the terminal pin P1. The other configuration is the same as that shown in
FIG. According to the configuration shown in FIG. 5, the sound collection axis shown by the
arrow 0 deg differs from the variable directivity electret condenser microphone shown in FIG. 1
in that the sound collection axis is located on the front side of the rear unit Ub.
[0040]
FIGS. 6 to 8 show the first and second switches SW1 and SW2 as directivity variable switches in
the second embodiment shown in FIG. 5 as bi-directional BI, uni-directional C, non-directional
The equivalent circuit diagram at the time of each selecting to O is shown. In addition to the
equivalent circuit diagram, addition and subtraction of polar patterns obtained by the front unit
03-05-2019
12
Uf and the rear unit Ub are shown. 6 to 8 correspond to the equivalent circuit diagrams of the
first embodiment shown in FIGS. 2 to 4 described above.
[0041]
In the second embodiment shown in FIG. 5, when the variable directivity switch selects BI which
is the first directivity mode, as shown in FIG. 6, the output terminal of the second impedance
converter F2 is selected. The input terminal of the second buffer circuit E2 is connected. As a
result, the signals of the polar pattern shown in FIG. 6 are respectively supplied to the second
terminal pin P2 and the third terminal pin P3, and these are subtracted in the subtraction circuit
OP1 of the mixer M2, and as a result, bi-directional It is possible to obtain an audio signal having
sex.
[0042]
Next, when the directivity variable switch selects the single directivity C which is the second
directivity mode, as shown in FIG. 7, the input terminal of the second buffer circuit E2 is
grounded. As a result, while the signal of the polar pattern shown in the figure is supplied to the
second terminal pin P2, the third terminal pin P3 becomes non-signal. As a result, an audio signal
having unidirectionality is provided as a subtraction output by the subtraction circuit OP1 of the
mixer M2.
[0043]
In addition, when the directivity variable switch selects the nondirectional O which is the third
directivity mode, as shown in FIG. 8, the first fixed pole 1f is connected to the output terminal of
the second impedance converter F2. While being connected, the input terminal of the second
buffer circuit E2 is grounded. Thereby, the signal from the second impedance converter F2 by
the rear unit Ub is added to the first fixed pole 1f of the front unit Uf, and the polar pattern by
the rear unit Ub and the polar pattern by the front unit Uf are As a result, the second terminal pin
P2 is supplied with a signal having an omnidirectional polar pattern as shown in the figure.
[0044]
03-05-2019
13
On the other hand, since the input terminal of the second buffer circuit E2 is grounded, the third
terminal pin P3 has no signal. As a result, a nondirectional audio signal shown in FIG. 8 is
provided as a subtraction output by the subtraction circuit OP1 of the mixer M2.
[0045]
1f 1st fixed pole 1b 2nd fixed pole 2f 1st diaphragm 2b 2nd diaphragm 3f electret dielectric film
3b electret dielectric film Uf front unit (first electret condenser microphone unit) Ub rear unit
(second electret condenser Microphone unit) F1 first impedance converter F2 second impedance
converter E1 first buffer circuit (first emitter follower circuit) E2 second buffer circuit (second
emitter follower circuit) SW1 first switch (variable directivity switch) SW2 Second switch
(variable directivity switch) OUT Audio signal output terminal P1 first terminal pin (ground line)
P2 second terminal pin (hot side terminal) P3 third terminal pin (cold side terminal) M1 variable
directional electret condenser microphone M2 Miki Over OP1 subtracting circuit (operational
amplifier) Ca equilibrium shielded cable
03-05-2019
14
Документ
Категория
Без категории
Просмотров
0
Размер файла
25 Кб
Теги
jp2015222889
1/--страниц
Пожаловаться на содержимое документа