close

Вход

Забыли?

вход по аккаунту

?

DESCRIPTION JP2014212413

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 JP2014212413
Abstract: To provide an ultrasonic transducer capable of widening a frequency band in which
impedance matching can be performed. An ultrasonic transducer (100) includes a piezoelectric
element (1) generating ultrasonic waves and receiving and outputting a reflected wave from an
object, and a resistive element (2) and a resistive element (3) connected to the piezoelectric
element (1). And an inductor 4, and a constant resistance circuit is configured by the
piezoelectric element 1, the resistance element 2, the resistance element 3 and the inductor 4.
[Selected figure] Figure 1
Ultrasonic transducer
[0001]
The present invention relates to an ultrasonic transducer, and more particularly to an ultrasonic
transducer comprising a piezoelectric element.
[0002]
Conventionally, an ultrasonic transducer provided with a piezoelectric element is known (see, for
example, Patent Document 1).
In the patent document 1, the piezoelectric element is provided as a part of the band pass filter
circuit, and the resistance component of the impedance characteristic of the band pass filter
circuit is in a predetermined frequency band (passing region) passing through the band pass
11-04-2019
1
filter circuit. The reactance component is configured to be substantially zero (for example, 50 Ω).
That is, the ultrasonic transducer described in Patent Document 1 has impedance matching with
a circuit (for example, an electrical transmission path) connected to the ultrasonic transducer in a
frequency band near the center frequency (resonance frequency of the piezoelectric element).
(Impedance matching) is configured to be possible.
[0003]
Unexamined-Japanese-Patent No. 2001-86587
[0004]
However, the ultrasonic transducer described in Patent Document 1 has a disadvantage that the
resistance component of the impedance characteristic is not substantially constant and the
reactance component is not substantially zero in a frequency band out of the center frequency.
Specifically, in the frequency band out of the center frequency, there is a disadvantage that
reflection noise (reflection noise from a circuit (for example, an electrical transmission line)
connected to the ultrasonic transducer) occurs. That is, the ultrasonic transducer described in
Patent Document 1 has a problem that the frequency band in which impedance matching can be
performed is limited (narrow).
[0005]
The present invention has been made to solve the problems as described above, and one object of
the present invention is to provide an ultrasonic transducer capable of widening the frequency
band in which impedance matching can be performed. It is.
[0006]
In order to achieve the above object, an ultrasonic transducer according to one aspect of the
present invention is connected to a piezoelectric element that generates an ultrasonic wave and
receives and outputs a reflected wave from a subject, and is connected to the piezoelectric
element to provide resistance An electric element including at least one of an element, an
inductor, and a capacitor is provided, and the piezoelectric element and the electric element
constitute a constant resistance circuit.
11-04-2019
2
[0007]
In the ultrasonic transducer according to this one aspect, as described above, the impedance of
the ultrasonic transducer can be made substantially equivalent to pure resistance by configuring
the constant resistance circuit by the piezoelectric element and the electric element, so The
impedance of the acoustic transducer can be made substantially constant regardless of the
frequency.
As a result, it is possible to widen the frequency band in which impedance matching can be
performed.
[0008]
In addition, since the impedance of the ultrasonic transducer can be made substantially
equivalent to pure resistance, the ultrasonic transducer can be handled as a resistive element, so
design of the entire system using the ultrasonic transducer can be facilitated. .
In particular, the burden of consideration and design of the transmission path length and the
input / output impedance of the transmission / reception circuit can be reduced.
[0009]
Furthermore, even in the case where a plurality of ultrasonic transducers are provided for one
transmission / reception circuit, the ultrasonic transducers can be treated as resistive elements,
so that voltage, current and power, reflectance, etc. It can be easily calculated by calculation
based on calculation (calculation in which the ultrasonic transducer is treated as a resistive
element).
[0010]
In the ultrasonic transducer according to the aforementioned one aspect, preferably, the
resistance element includes a first resistance element and a second resistance element, and the
constant resistance circuit has a complex impedance Z1 connected in series or in parallel with
the first resistance element. And a circuit including a piezoelectric element and a circuit having a
11-04-2019
3
complex impedance Z2 connected in series or in parallel with the second resistance element,
wherein the product Z1 · Z2 of the complex impedance Z1 and the complex impedance Z2 is a
first resistance element It is configured to be substantially the same as the product R <2> of the
resistance value R of the second resistance element and the resistance value R of the second
resistance element.
According to this structure, the constant resistance circuit can be easily formed by the circuit
including the first resistance element, the second resistance element, and the complex
impedances Z1 and Z2. Therefore, impedance matching can be easily performed. The frequency
band can be broadened.
[0011]
In the ultrasonic transducer according to the aforementioned one aspect, preferably, the constant
resistance circuit includes an electrical element whose characteristic value can be adjusted.
According to this structure, the constant resistance circuit can be configured by adjusting the
characteristic value of the electric element even when the characteristic value of the piezoelectric
element included in the constant resistance circuit varies. Further, by configuring the constant
resistance circuit to include an electric element whose characteristic value can be adjusted, the
characteristic value of the electric element is adjusted in a state in which the ultrasonic
transducer is maintained as a constant resistance circuit. The frequency characteristics of the
applied voltage can be controlled. As a result, for example, when the filter circuit is included in
the constant resistance circuit, the filter circuit and the reverse circuit of the filter circuit can be
adjusted by adjusting the characteristic value of the electric element. The ultrasonic transducer
can be maintained as a constant resistance circuit while adjusting (changing) the characteristics.
[0012]
In this case, preferably, the constant resistance circuit is configured such that at least one of the
inductance of the inductor and the capacitance of the capacitor can be adjusted. According to this
structure, even when the characteristic value of the piezoelectric element included in the
constant resistance circuit is dispersed, the constant resistance circuit can be easily configured
by adjusting at least one of the inductance of the inductor and the capacitance of the capacitor.
can do.
11-04-2019
4
[0013]
The ultrasonic transducer according to the above aspect preferably further comprises an
impedance converter connected to the constant resistance circuit and converting an impedance
of the constant resistance circuit. According to this structure, even when the resistance value of
the constant resistance circuit is small, the power gain of the ultrasonic transducer can be
improved by converting the impedance by the impedance conversion unit.
[0014]
In this case, preferably, the impedance converter includes a transformer connected to the
constant resistance circuit to convert the impedance of the constant resistance circuit. With such
a configuration, the transformer can easily improve the power gain of the ultrasonic transducer.
[0015]
In the ultrasonic transducer according to the above aspect, preferably, the electric element
includes an inductor provided in parallel with the piezoelectric element to adjust a peak of
voltage gain of the ultrasonic transducer. According to this structure, since the peak (frequency
characteristic) of the voltage gain of the ultrasonic transducer can be adjusted, the voltage gain
in a desired frequency band can be increased.
[0016]
According to the present invention, as described above, it is possible to widen the frequency band
in which impedance matching can be performed.
[0017]
FIG. 1 is a circuit diagram of an ultrasonic transducer according to a first embodiment of the
present invention.
It is a circuit diagram for demonstrating the general constant resistance circuit in which the
11-04-2019
5
resistance element and the circuit which has complex impedance were connected in parallel. It is
a circuit diagram for demonstrating the general constant resistance circuit in which the
resistance element and the circuit which has complex impedance were connected in series. It is a
figure for demonstrating the impedance of the ultrasonic transducer by 1st Embodiment of this
invention. FIG. 7 is a circuit diagram of an ultrasonic transducer according to a second
embodiment of the present invention. It is a figure which shows the equivalent circuit of FIG. It is
a figure for demonstrating the impedance of the ultrasonic transducer by 2nd Embodiment of
this invention. FIG. 7 is a circuit diagram of an ultrasonic transducer according to a third
embodiment of the present invention. It is a figure for demonstrating the impedance of the
ultrasonic transducer by 3rd Embodiment of this invention. It is a figure for demonstrating the
voltage gain of the ultrasonic transducer by 3rd Embodiment of this invention. FIG. 7 is a circuit
diagram of an ultrasonic transducer according to a fourth embodiment of the present invention.
It is a figure for demonstrating the impedance (real number component) of the ultrasonic
transducer by 4th Embodiment of this invention. It is a figure for demonstrating the reflectance
of the ultrasonic transducer by 4th Embodiment of this invention. FIG. 10 is a circuit diagram of
an ultrasonic transducer according to a fifth embodiment of the present invention. It is a figure
for demonstrating the voltage gain of the ultrasonic transducer by 5th Embodiment of this
invention. FIG. 10 is a circuit diagram of an ultrasonic transducer according to a sixth
embodiment of the present invention. It is an equivalent circuit schematic of the ultrasonic
transducer by 5th Embodiment of this invention shown in FIG. It is a figure for demonstrating the
power gain of the ultrasonic transducer by 6th Embodiment of this invention.
[0018]
Hereinafter, an embodiment of the present invention will be described based on the drawings.
[0019]
First Embodiment With reference to FIG. 1, the configuration of an ultrasonic transducer 100
according to a first embodiment will be described in comparison with general constant resistance
circuits 200 and 210 shown in FIGS. 2 and 3.
[0020]
As shown in FIG. 2, the general constant resistance circuit 200 includes a resistance element 201
having a resistance value R, a resistance element 202 having a resistance value R, a first circuit
203 having a complex impedance Z1, and a complex impedance Z2. And a second circuit 204
having
11-04-2019
6
The resistive element 201 and the first circuit 203 are connected in parallel, and the resistive
element 202 and the second circuit 204 are connected in parallel.
Further, one side of the resistive element 201 and the first circuit 203 is connected to the
terminal p1, and the other side is connected to one side of the resistive element 202 and the
second circuit 204. The other side of the resistive element 202 and the second circuit 204 is
connected to the terminal p2. Here, in the constant resistance circuit 200, the complex
impedances Z1 and Z2 and the resistance value R have a relationship of Z1 · Z2 = R <2>. At this
time, the impedance between the terminal p1 and the terminal p2 is equivalent to a pure
resistance. That is, the resistance value is R, and the impedance does not depend on frequency.
As described above, when there is a relationship of Z1 · Z2 = R <2>, one of the first circuit 203
and the second circuit 204 constitutes the other reverse circuit in the resistance value R.
[0021]
As shown in FIG. 3, in the general constant resistance circuit 210, the resistance element 201
and the first circuit 203 are connected in series, and the resistance element 202 and the second
circuit 204 are connected in series. . Moreover, one side of the resistive element 201 and the
resistive element 202 is connected to the terminal p1. Further, one side of the first circuit 203
and the second circuit 204 is connected to the terminal p2. Here, in the constant resistance
circuit 210, there is a relationship of Z1 · Z2 = R <2> between the complex impedances Z1 and
Z2 and the resistance value R, and the impedance between the terminal p1 and the terminal p2 is
, Equivalent to pure resistance.
[0022]
Further, in FIGS. 2 and 3, the first circuit 203 (Z1) is a capacitive element having a capacitance C,
and the second circuit 204 (Z2) is an inductive element having an inductance L. The complex
impedances of the first circuit 203 and the second circuit 204 are Z1 = 1 / jωC and Z2 = jωL.
Here, ω = 2πf, and f is a frequency. That is, when Z1 · Z2 = L / C = R <2> is satisfied, the
constant resistance circuit 200 (see FIG. 2) and the constant resistance circuit 210 (see FIG. 3)
are constant resistance circuits. That is, the capacitive element and the inductive element are
reverse circuits with respect to each other in the resistance value R.
11-04-2019
7
[0023]
In addition, it is possible to form a constant resistance circuit as long as Z1 · Z2 = R <2> can be
satisfied by a circuit constituted by elements other than capacitive elements and inductive
elements. . When one of the first circuit 203 (Z1) and the second circuit 204 (Z2) is a resonant
circuit, the other is configured by an antiresonant circuit having the same resonant frequency as
that of one circuit.
[0024]
Here, in the first embodiment, as shown in FIG. 1, the ultrasonic transducer 100 generates an
ultrasonic wave and receives and outputs a reflected wave from an object, and a resistive element
2 and the resistive element 2. The resistor element 3 and the inductor 4 are provided, and the
piezoelectric element 1, the resistor element 2, the resistor element 3 and the inductor 4
constitute a constant resistance circuit. The piezoelectric element 1 has mechanical resonance
with a resonance frequency of about 200 MHz, and the frequency of electrical resonance is also
about 200 MHz. When the Q value of resonance (the value obtained by dividing the frequency f0
at the resonance peak by the width f2-f1 of the frequency at which the resonance peak is half) is
small, the piezoelectric element 1 is regarded as equivalent to a capacitor Good. Therefore, in FIG.
1, the piezoelectric element 1 is described as a capacitor, and the capacitance of the piezoelectric
element 1 (capacitor) is about 11 [pF]. The resistance element 2 is an example of the “first
resistance element” or the “electric element” in the present invention. The resistance element
3 is an example of the “second resistance element” or the “electric element” in the present
invention. The inductor 4 is an example of the “electric element” in the present invention.
[0025]
Further, in the ultrasonic transducer 100, the resistance value of the resistance element 2 is 50
[Ω], and the resistance value of the resistance element 3 is 50 [Ω]. また、インダクタ4のインダ
クタンスは、27[nH]である。 The inductor 4 is a reverse circuit to the piezoelectric
element 1 at a resistance value of 50 [Ω].
[0026]
11-04-2019
8
Specifically, in the first embodiment, the inductor 4 (complex impedance Z1) connected in series
with the resistive element 2 and the piezoelectric element 1 (complex in series connected with
the resistive element 3 and forming an inverse circuit of the inductor 4 The constant resistance
circuit is configured to include the impedance Z2). The product Z1 · Z2 of the complex
impedance Z1 of the inductor 4 and the complex impedance Z2 of the piezoelectric element 1 is
substantially the same as the product R <2> of the resistance value R of the resistance element 2
and the resistance value R of the resistance element 3 (Z1 · Z2 = L / C = R <2>) to be satisfied.
[0027]
Next, referring to FIG. 4, the frequency characteristics of the impedance of the ultrasonic
transducer 100 will be described. The frequency characteristics of the impedance of the
ultrasonic transducer 100 are obtained by simulation using a circuit simulator. In addition, it is
possible to obtain the frequency characteristic of the impedance by expressing the impedance of
the constant resistance circuit as a function of the characteristic value of each electric element
and differentiating the function of the impedance. It is more efficient to obtain frequency
characteristics.
[0028]
As shown in FIG. 4, the real component of the impedance is approximately 50 [Ω] over the
frequency range of 10 [MHz] to 400 [MHz], and the imaginary component is approximately 0
[Ω]. It turned out that it was. In order to improve impedance matching, it is preferable that the
real component of the impedance of the constant resistance circuit be in the range of 70% to
140% of the value of the characteristic impedance. Further, the imaginary component of the
impedance of the constant resistance circuit is preferably within ± 30% of the value of the
characteristic impedance. Then, when the real and imaginary components of the impedance of
the constant resistance circuit are within the above range, the maximum value of the reflectance
is only 0.25, and it is possible to perform better impedance matching.
[0029]
Also, while the characteristic values of the respective electric elements (piezoelectric element 1,
resistance element 2, resistance element 3 and inductor 4) constituting the constant resistance
circuit have an error with respect to the ideal characteristic values in practice, the result It is
good to select each electric element in the range where an error does not become a problem.
11-04-2019
9
[0030]
For example, even if the maximum self-resonant frequency of the inductor 4 shown in FIG. 1 is 2
GHz and the ideal characteristic of the inductor deviates from the frequency around 2 GHz, the
center frequency of the ultrasonic transducer 100 is Designing at 200 MHz and using a
frequency around 200 MHz, the inductor 4 has a nearly ideal inductance at frequencies around
200 MHz, so there is a problem with self-resonance characteristics. It turns out that it can be
avoided.
[0031]
Further, for example, even when the resistance value of resistance element 2 (resistance element
3) shown in FIG. 1 is 49 [.OMEGA.] Or 51 [.OMEGA.] Instead of 50 [.OMEGA. It was confirmed
that the characteristic value (impedance) was not affected.
[0032]
In the first embodiment, as described above, by constituting a constant resistance circuit by the
piezoelectric element 1, the resistance element 2, the resistance element 3, and the inductor 4,
the impedance of the ultrasonic transducer 100 is substantially reduced to a pure resistance.
Since the impedances can be equalized, the impedance of the ultrasonic transducer 100 can be
made substantially constant regardless of the frequency.
As a result, it is possible to widen the frequency band in which impedance matching can be
performed.
[0033]
In the first embodiment, as described above, the constant resistance circuit is an inductor 4
having a complex impedance Z1 connected in series to the resistance element 2 and a
piezoelectric having a complex impedance Z2 connected in series to the resistance element 3.
Element 1 is included so that product Z1 · Z2 of complex impedance Z1 of inductor 4 and
complex impedance Z2 of piezoelectric element 1 is product of resistance value R of resistance
element 2 and resistance value R of resistance element 3 It is configured to be substantially the
same as R <2>.
11-04-2019
10
Thus, the constant resistance circuit can be easily formed by the resistance element 2, the
resistance element 3, the inductor 4 and the piezoelectric element 1, so that the frequency band
in which impedance matching can be easily performed can be widened. .
[0034]
Also, since the impedance of the ultrasonic transducer 100 can be made substantially equivalent
to a pure resistance, the ultrasonic transducer 100 can be handled as a resistance element,
thereby facilitating the design of the entire system using the ultrasonic transducer 100. be able
to.
In particular, the burden of consideration and design of the transmission path length and the
input / output impedance of the transmission / reception circuit can be reduced.
[0035]
Furthermore, even when a plurality of ultrasonic transducers 100 are provided for one
transmission / reception circuit, the ultrasonic transducer 100 can be treated as a resistive
element, so that voltage, current and power, or reflectance etc. It can be easily calculated by
connection-based calculation (calculation in which the ultrasonic transducer is treated as a
resistive element).
[0036]
Second Embodiment Next, the configuration of an ultrasonic transducer 101 according to a
second embodiment will be described with reference to FIGS. 5 and 6.
In the second embodiment, unlike the first embodiment in which the piezoelectric element is
regarded as being equivalent to a capacitor, the piezoelectric element is expressed as an
equivalent circuit including a series resonant circuit and a capacitor. The ultrasonic transducer
101 is composed of two constant resistance circuits (a first constant resistance circuit and a
second constant resistance circuit) as described later.
11-04-2019
11
[0037]
As shown in FIG. 5, the ultrasonic transducer 101 generates a ultrasonic wave and receives and
outputs a reflected wave from the object, a circuit 12 connected in parallel to the piezoelectric
element 11, and a resistance A resistor element 2 having a value of 50 [Ω], a resistor element 15
having a resistance value of 58 [Ω], and an inductor 4 having an inductance of 27 [nH] are
provided.
[0038]
The piezoelectric element 11 includes a capacitor 13 and a series resonant circuit 14 connected
in parallel to the capacitor 13 and exhibiting the resonance characteristic of the piezoelectric
element 11.
The series resonant circuit 14 includes a resistive element 14a having a resistance value of 350
[.OMEGA.], An inductor 14b connected in series to the resistive element 14a and an inductance of
300 [nH], and a series connected to the inductor 14b. And a capacitor 14c.
[0039]
The circuit 12 connected in parallel to the piezoelectric element 11 includes a resistive element
12a having a resistance value of 350 [Ω], a capacitor 12b having a capacitance of 2.4 [pF], and
an inductor 12c having an inductance of 180 [nH]. And. The capacitor 12 b and the inductor 12
c are connected in parallel and connected in series to the resistive element 12 a. The series
resonant circuit 14 and the circuit 12 constitute a constant resistance circuit (first constant
resistance circuit) having a radiation impedance of 350 [Ω].
[0040]
In addition, a constant resistance circuit constituted by the series resonant circuit 14 having a
radiation impedance of 350 [Ω] and the circuit 12 is connected in parallel to the resistance
element 15 having a resistance value of 58 [Ω]. The combined impedance of the resistance
element 15 and the resistance element 15 is about 50 [Ω].
[0041]
11-04-2019
12
In FIG. 6 (the equivalent circuit of the ultrasonic transducer 101 shown in FIG. 5), the constant
resistance circuit whose combined impedance is approximately 50 [Ω] is represented by the
resistance element 16.
As shown in FIG. 6, the ultrasonic transducer 101 has a relationship of 27 [nH] × 1/11 [pF] ≒
50 [Ω] × 50 [Ω], and the ultrasonic transducer 101 has a constant resistance circuit The second
constant resistance circuit is configured. The resistance element 16 is an example of the
“second resistance element” or the “electric element” in the present invention.
[0042]
Next, referring to FIG. 7, the frequency characteristic of the impedance of the ultrasonic
transducer 101 will be described.
[0043]
As shown in FIG. 7, the real component of the impedance is approximately 50 [Ω] (pure
resistance) over a wide range (frequency band) of frequencies from 10 [MHz] to 400 [MHz], and
an imaginary component Was found to be approximately 0 [Ω].
[0044]
The effect of the second embodiment is the same as that of the first embodiment.
[0045]
Third Embodiment Next, the configuration of an ultrasonic transducer 102 according to a third
embodiment will be described with reference to FIG.
In the third embodiment, unlike the first and second embodiments, an inductor is connected in
parallel to the piezoelectric element.
[0046]
11-04-2019
13
As shown in FIG. 8, in the ultrasonic transducer 102 according to the third embodiment, an
inductor 21 for adjusting the peak of the voltage gain of the ultrasonic transducer 102 is
connected in parallel with the piezoelectric element 1.
なお、インダクタ21のインダクタンスは、230[nH]である。
A capacitor 22 is connected in series with the inductor 4 so as to make the ultrasonic transducer
102 a constant resistance circuit. なお、キャパシタ22のキャパシタンスは、100[pF]で
ある。 The inductor 21 and the capacitor 22 are examples of the “electric element” in the
present invention.
[0047]
Next, referring to FIG. 9, the frequency characteristic of the impedance of the ultrasonic
transducer 102 will be described.
[0048]
As shown in FIG. 9, the real component of the impedance is approximately 50 [Ω] (pure
resistance) over a wide range (frequency band) with a frequency of 10 [MHz] to 400 [MHz], and
an imaginary component Was found to be approximately 0 [Ω].
[0049]
Next, referring to FIG. 10, the voltage gain of the ultrasonic transducer will be described.
The voltage gain is a value (20 × Log (Vo / Vi)) obtained by multiplying the logarithm of the
ratio of the voltage Vo applied to the piezoelectric element to the voltage Vi applied to the
ultrasonic transducer by 20.
Also, the voltage gain is obtained by simulation using a circuit simulator.
[0050]
11-04-2019
14
As shown in FIG. 10, the voltage gain of the ultrasonic transducer 101 (see FIG. 5) according to
the second embodiment is in the range of about 3 [dB] over a frequency of 10 [MHz] to 400
[MHz]. There was found. On the other hand, it was found that the voltage gain of the ultrasonic
transducer 102 (see FIG. 8) according to the third embodiment is smaller in the low frequency
region and is maximal at the frequency of 100 MHz. . It has been found that the voltage gain of
the ultrasonic transducer 102 at a frequency of 100 MHz is larger than the voltage gain of the
ultrasonic transducer 101 according to the second embodiment.
[0051]
The result (the difference between the ultrasonic transducer 101 according to the second
embodiment and the ultrasonic transducer 102 according to the third embodiment) that the
frequency at which the voltage gain is maximum (peak) is 100 [MHz] is 11 [pF]. It originates in
the resonant circuit comprised by the piezoelectric element 1 which has a capacitance, and the
inductor 21 which has an inductance of 230 [nH]. That is, it was confirmed that the frequency
characteristic of the voltage gain can be controlled by adjusting the value of the inductance of
the inductor 21 connected in parallel with the piezoelectric element 1. As a result, it was
confirmed that by controlling the voltage gain, the frequency characteristics of the ultrasonic
waves transmitted by the ultrasonic transducer 102 can also be adjusted.
[0052]
Thus, both the ultrasonic transducer 101 according to the second embodiment and the ultrasonic
transducer 102 according to the third embodiment constitute a constant resistance circuit of
about 50 [Ω] (the electrical characteristics as seen from the transmission path are On the other
hand, it was found that the frequency characteristics of the voltage gain are different from each
other.
[0053]
In the third embodiment, as described above, the inductor 21 provided in parallel with the
piezoelectric element 1 for adjusting the peak of the voltage gain of the ultrasonic transducer
102 is provided.
As a result, since the peak (frequency characteristic) of the voltage gain of the ultrasonic
11-04-2019
15
transducer 102 can be adjusted, the voltage gain in a desired frequency band can be increased.
The remaining effects of the third embodiment are similar to those of the aforementioned first
and second embodiments.
[0054]
Fourth Embodiment Next, the configuration of an ultrasonic transducer 103 according to a
fourth embodiment will be described with reference to FIG. In the fourth embodiment, unlike the
first to third embodiments, the inductance of the inductor is configured to be adjustable.
[0055]
As shown in FIG. 11, the ultrasonic transducer 103 includes a piezoelectric element 31, a
resistance element 2, a resistance element 3, an inductor 4, and an inductance adjustment circuit
32. The piezoelectric element 31 is manufactured (dispersed) so that the capacitance is in the
range of 10 [pF] or more and 15 [pF] or less due to the manufacturing process.
[0056]
Here, in the fourth embodiment, the ultrasonic transducer 103 (constant resistance circuit) is
configured to include an electric element whose characteristic value can be adjusted. Specifically,
the ultrasonic transducer 103 (constant resistance circuit) is configured such that the inductance
of the inductor can be adjusted. More specifically, in the ultrasonic transducer 103, the
inductance adjustment circuit 32 is configured to include an inductor 33 and a switch 34
connected in parallel. Further, the inductance adjustment circuit 32 is connected in series to the
inductor 4. The inductance of the inductance adjustment circuit 32 is configured to be adjustable
to 0 [nH] / 10 [nH] by turning the switch 34 ON / OFF. The inductor 33 is an example of the
“electric element” in the present invention.
[0057]
Here, for the piezoelectric element 31 whose capacitance is the upper limit 15 [pF], an inductor
having an inductance of 37.5 [nH] is an inverse circuit in design. In this case, by turning off the
11-04-2019
16
switch 34, the inductor 4 (27 [nH]) and the inductor 33 (10 [nH]) are connected in series to
constitute an inductor having an inductance of 37 [nH], An inverse circuit of the piezoelectric
element 31 is configured. In addition, for the piezoelectric element 31 whose capacitance is 10
[pF], which is the lower limit value, an inductor with an inductance of 25 [nH] becomes an
inverse circuit in design. In this case, by turning on the switch 34, an inverse circuit of the
piezoelectric element 31 is formed only by the inductor 4 (27 [nH]).
[0058]
Next, referring to FIG. 12, the frequency characteristic of the impedance of the ultrasonic
transducer 103 will be described. In FIG. 12, the symbol “□” indicates the real component of
the impedance when the capacitance of the piezoelectric element 31 is 10 [pF] and the switch 34
is turned on. The symbol “Δ” indicates the real component of the impedance when the
capacitance of the piezoelectric element 31 is 15 [pF] and the switch 34 is turned on. The symbol
“○” indicates the real component of the impedance when the capacitance of the piezoelectric
element 31 is 15 [pF] and the switch 34 is in the OFF state.
[0059]
As shown in FIG. 12, when the capacitance of the piezoelectric element 31 is 15 [pF] and the
switch 34 is turned on (inductor inductance is 27 [nH], symbol “Δ”), about 40 [Ω When the
characteristic impedance of the transmission line is, for example, 50 [Ω], the reflectance of the
ultrasonic transducer 103 viewed from the transmission line is found to be about 0.1. did.
[0060]
On the other hand, when the capacitance of the piezoelectric element 31 is 15 [pF] and the
switch 34 is turned off (inductor inductance is 37 [nH], symbol "o"), the change in impedance is
about 5 [? If the characteristic impedance of the transmission line is 50 [Ω], the reflectance of
the ultrasonic transducer 103 viewed from the transmission line is approximately 0. 0. It turned
out to be 05.
That is, when the switch 34 is turned off, the reflectance can be reduced to about half (half) as
compared with the case where the switch 34 is turned on (symbol “Δ”). In addition, when the
capacitance of the piezoelectric element 31 is 15 [pF], the capacitance of the piezoelectric
element 31 is 10 [p] by switching the switch 34 from the ON state (symbol “Δ”) to the OFF
11-04-2019
17
state (symbol “o”). pf], and it is confirmed that the switch 34 can be brought close to the
impedance in the ON state (symbol “□”). As described above, it was confirmed that the
consistency with respect to the manufacturing variation of the piezoelectric element 31 can be
secured by turning the switch 34 ON / OFF.
[0061]
Next, the reflectance between the ultrasonic transducer 103 and the transmission path will be
described with reference to FIG. In FIG. 13, the horizontal axis indicates the capacitance of the
piezoelectric element 31. The vertical axis indicates the maximum value of the reflectance for the
transmission path whose characteristic impedance is 50 [Ω] in the frequency range of 10 [MHz]
to 400 [MHz].
[0062]
As shown in FIG. 13, it was found that when the switch 34 is in the ON state (symbol “o”), the
reflectance tends to decrease as the frequency increases. It was also found that when the switch
34 is in the OFF state (symbol “−”), the reflectance tends to increase as the frequency
increases. As a result, when the capacitance of the piezoelectric element 31 is less than 12 pF,
the switch 34 is turned OFF (symbol “−”), and when the capacitance of the piezoelectric
element 31 is 12 pF or more, By turning on the switch 34 (symbol "o"), it was found that the
reflectance can be suppressed to less than 0.06 even when the capacitance of the piezoelectric
element 31 has a manufacturing variation. The range of the frequency for securing the
consistency between the ultrasonic transducer 103 and the transmission path is preferably at
least 1/2 or more and twice or less of the center frequency of the ultrasonic transducer 103, and
this frequency Preferably, the reflectance is at least 0.1 or less.
[0063]
In the fourth embodiment, as described above, the ultrasonic transducer 103 (constant resistance
circuit) is configured to include an electric element (in the fourth embodiment, an inductor)
whose characteristic value can be adjusted. Thereby, even when the characteristic value of the
piezoelectric element 31 included in the constant resistance circuit is dispersed, the constant
resistance circuit can be configured by adjusting the characteristic value of the electric element
(in the fourth embodiment, the inductor) . Further, by configuring the ultrasonic transducer 103
11-04-2019
18
(constant resistance circuit) to include an electric element whose characteristic value can be
adjusted, the characteristic value of the electric element is adjusted in a state where the
ultrasonic transducer 103 is maintained as a constant resistance circuit. By doing this, it is
possible to control the frequency characteristics of the voltage applied to the piezoelectric
element. As a result, for example, when the filter circuit is included in the constant resistance
circuit, the filter circuit and the reverse circuit of the filter circuit can be adjusted by adjusting
the characteristic value of the electric element. The ultrasonic transducer 103 can be maintained
as a constant resistance circuit while adjusting (changing) the characteristics.
[0064]
Fifth Embodiment Next, the configuration of an ultrasonic transducer 104 according to a fifth
embodiment will be described with reference to FIG. In the fifth embodiment, unlike the fourth
embodiment, in addition to the inductance of the inductor, the capacitance of the capacitor is also
adjustable.
[0065]
As shown in FIG. 14, the ultrasonic transducer 104 includes a piezoelectric element 1, a
resistance element 2, a resistance element 3, an inductor 4, a capacitor 41 having a capacitance
of 100 [pF], and a capacitance adjustment circuit 42. An inductor 43 having an inductance of
230 [nH] and an inductance adjustment circuit 44 are provided. The inductor 43 is an example
of the “electric element” in the present invention.
[0066]
Here, in the fifth embodiment, the ultrasonic transducer 104 is configured to be able to adjust
the capacitance of the capacitor in addition to the inductance of the inductor. Specifically, the
capacitance adjustment circuit 42 is configured to include a capacitor 42a and a switch 42b
having a capacitance of 33 [pF] connected in parallel. Also, the capacitance adjustment circuit 42
is connected in series to the capacitor 41. In addition, the inductance adjustment circuit 44 is
configured to include an inductor 44 a and a switch 44 b which have an inductance of 76 [nH]
connected in series. Further, the inductance adjustment circuit 44 is connected in parallel to the
inductor 43. The capacitor 42 a and the inductor 44 a are examples of the “electric element”
in the present invention.
11-04-2019
19
[0067]
When the switch 44b is in the ON state and the switch 42b is in the OFF state (the state K is in
the ON state), or the switch 44b is in the OFF state, When the switch 42 b is in the ON state
(when the state K is in the OFF state), a constant resistance circuit is obtained. That is, when the
switch 44b and the switch 42b are both in the ON state or in the OFF state, the ultrasonic
transducer 104 does not constitute a constant resistance circuit.
[0068]
Next, referring to FIG. 15, the frequency characteristic of the voltage gain of the ultrasonic
transducer 104 will be described. In FIG. 15, the symbol “○” indicates that the state K is in the
OFF state, and the symbol “−” indicates that the state K is in the ON state.
[0069]
As shown in FIG. 15, the voltage gain increases as the frequency increases in both the ON state of
the state K and the OFF state of the state K, and then gradually decreases after reaching the
maximum value. It turned out to be. That is, it was found that the voltage gain has a gentle
convex shape both when the state K is in the ON state and when the state K is in the OFF state. As
a result, it has been confirmed that the ultrasonic transducer 104 can obtain a voltage gain equal
to or greater than a predetermined magnitude in a wide frequency band. In the case where the
state K is in the OFF state (symbol "o"), the voltage gain has a local maximum value in the vicinity
of about 100 [MHz] and the state K is in the ON state (symbol "-"). It was found that the voltage
gain has a maximum value in the vicinity of about 200 MHz. That is, it was confirmed that the
frequency at which the voltage gain is maximized can be adjusted by turning ON / OFF the state
K. In addition, it was found that the maximum value of the voltage gain was 0 [dB] or more both
when the state K was in the ON state and when the state K was in the OFF state. In addition, the
maximum value of the voltage gain when the state K is in the ON state (symbol “−”) is several
percent larger than the maximum value of the voltage gain when the state K is in the OFF state
(symbol “○”) It has been confirmed that the
[0070]
11-04-2019
20
The effect of the fifth embodiment is the same as that of the fourth embodiment.
[0071]
Sixth Embodiment Next, the configuration of an ultrasonic transducer 105 according to a sixth
embodiment will be described with reference to FIG.
In the sixth embodiment, different from the first to fifth embodiments, the constant resistance
circuit is connected to the transformer.
[0072]
As shown in FIG. 16, the ultrasonic transducer 105 according to the sixth embodiment includes a
resistive element 51, a resistive element 52, a capacitor 53, an inductor 54, an inductor 55, a
piezoelectric element 56, and a transformer 57. Resistive element 51 and resistive element 52
both have a resistance value of 25 [Ω]. Also, the capacitor 53 has a capacitance of 80 [pF]. In
addition, inductor 54 and inductor 55 have inductances of 6 [nH] and 50 [nH], respectively. Also,
the piezoelectric element 56 has a capacitance of 11 [pF]. Further, the turns ratio of the primary
side and the secondary side of the transformer 57 is 2.2: 1. The resistance element 51 is an
example of the “first resistance element” or the “electric element” in the present invention.
The resistive element 52 is an example of the “second resistive element” or the “electric
element” in the present invention. The capacitor 53, the inductor 54 and the inductor 55 are
examples of the "electric element" in the present invention. Moreover, the transformer 57 is an
example of the "impedance converter" of this invention.
[0073]
The capacitor 53 and the inductor 54 are connected in series, and the capacitor 53 and the
inductor 54 are connected in parallel to the resistance element 51. Also, the capacitor 53 and the
resistance element 51 are connected to the transformer 57. Further, the resistive element 52, the
piezoelectric element 56, and the inductor 55 are connected in parallel to one another. Further,
one side of the resistive element 52, the piezoelectric element 56 and the inductor 55 is
connected to the resistive element 51 and the inductor 54, and the other side is connected to the
transformer 57.
11-04-2019
21
[0074]
Further, the electric elements on the secondary side of the transformer 57 (the resistance
element 51, the resistance element 52, the capacitor 53, the inductor 54, the inductor 55, and
the piezoelectric element 56) constitute a 25 [Ω] constant resistance circuit. The constant
resistance circuit includes a resonant circuit having a resonant frequency of 200 MHz. And, in
the sixth embodiment, this constant resistance circuit is connected to the transformer 57 for
converting the impedance of the constant resistance circuit.
[0075]
Next, with reference to FIG. 18, the frequency characteristic of the power gain at the time of
transmission of the piezoelectric element of the ultrasonic transducer 105 will be described in
comparison with the ultrasonic transducer 104 (see FIG. 17) of the fifth embodiment. The power
gain is a value (10 × Log (Wo / Wi)) obtained by multiplying 10 by the logarithm of the ratio of
the power Wo of the piezoelectric element to the power Wi of the ultrasonic transducer. Also, the
power gain is obtained by simulation using a circuit simulator.
[0076]
FIG. 17 is an equivalent circuit in the case where the state K is in the ON state (the switch 44 b is
in the ON state, the switch 42 b is in the OFF state) in the ultrasonic transducer 104 shown in
FIG. Similarly, it includes a resonant circuit having a resonant frequency of 200 MHz.
[0077]
As shown in FIG. 18, both the ultrasonic transducer 105 (symbol “記号”) of the sixth
embodiment and the ultrasonic transducer 104 (symbol “Δ”) of the fifth embodiment increase
as the frequency increases. It was found that the power gain increased and became smaller
gradually after reaching the maximum value.
In addition, it was confirmed that the power gain of the ultrasonic transducer 105 of the sixth
embodiment is larger (improved) by 6 [dB] or more than the power gain of the ultrasonic
11-04-2019
22
transducer 104 of the fifth embodiment. That is, it was confirmed that the power gain was
improved as a result of performing impedance conversion by the transformer 57 with the
resistance value of the constant resistance circuit being 1⁄2 (= 25 [Ω] / 50 [Ω]). That is, if a
constant resistance circuit having a resistance value of, for example, 25 [Ω] is configured as in
the ultrasonic transducer 105, the power gain at transmission can be improved by performing
impedance conversion to 50 [Ω] by the transformer 57. Was confirmed.
[0078]
In the sixth embodiment, as described above, the impedance transformer 57 connected to the
constant resistance circuit is provided to transform the impedance of the constant resistance
circuit. Accordingly, even when the resistance value of the constant resistance circuit is small, the
power gain of the ultrasonic transducer 105 can be easily improved by converting the impedance
of the constant resistance circuit by the transformer 57.
[0079]
It should be understood that the embodiments and examples disclosed herein are illustrative and
non-restrictive in every respect. The scope of the present invention is indicated not by the
description of the embodiments and examples described above but by the claims, and further
includes all modifications within the meaning and scope equivalent to the claims.
[0080]
For example, in the first to sixth embodiments, the constant resistance circuit is constituted by
the piezoelectric element, the resistance element and the inductor (or the piezoelectric element,
the resistance element, the inductor and the capacitor). It is not restricted to this. In the present
invention, as long as the piezoelectric element is included, the constant resistance circuit may be
configured by an electrical element other than the resistive element, the inductor and the
capacitor (or further including the electrical element in the resistive element, the inductor and
the capacitor). .
[0081]
11-04-2019
23
In the fourth embodiment (fifth embodiment), the inductance (the inductance of the inductor and
the capacitance of the capacitor) of the inductor is configured to be adjustable, but the present
invention is not limited to this. For example, the resistance value of the resistive element may be
adjustable. The ultrasonic transducer may also be provided with an electrical element whose
characteristic value can be adjusted, such as a switch, volume control, trimmer capacitor, variable
inductor, or the like. Furthermore, a field effect transistor (FET) or the like may be provided to
make the resistance value of the constant resistance circuit variable by voltage control.
[0082]
In the fourth embodiment (fifth embodiment), an example is shown in which one switch (two) is
provided to adjust the inductance of the inductor (inductor inductance and capacitor
capacitance). It is not restricted to this. For example, three or more switches may be provided to
adjust the characteristic value of the electrical element.
[0083]
Moreover, although the example which uses a transformer as an impedance converter of this
invention was shown in the said 6th Embodiment, this invention is not limited to this. For
example, a voltage dividing circuit may be used, or an active element such as a transistor which
can convert impedance in a relatively wide frequency band at a constant ratio may be used.
[0084]
1, 11, 31, 56 Piezoelectric element 2, 51 Resistance element (first resistance element, electric
element) 3, 21, 33, 43, 44 a, 54, 55 Inductor (electric element) 4, 16, 52 Resistance element
(first 2 resistance element, electric element) 22, 42a, 53 capacitor (electric element) 57
transformer (impedance converter) 100, 101, 102, 103, 104, 105 ultrasonic transducer
11-04-2019
24
Документ
Категория
Без категории
Просмотров
0
Размер файла
37 Кб
Теги
jp2014212413, description
1/--страниц
Пожаловаться на содержимое документа