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Claims  |
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What is claimed is:
1. An ultrasonic transducer apparatus comprising:
1) a probe including an ultrasonic transducer having:
a series connection of an inductor, a resistor, and a capacitor; and
a capacitive component for providing a capacitive susceptance connected in
parallel with said series connection;
2) a driving unit separate from said probe and detachably connected to said
probe, said driving unit including means for supplying to said ultrasonic
transducer a driving signal having a frequency, said driving signal being
such that a phase difference between a voltage applied to said ultrasonic
transducer and a current supplied through said ultrasonic transducer is
substantially zero; and
3) matching means including:
first means arranged in said driving unit; and
second means separate from said first means and arranged in said probe for
causing varying of an impedance of said first means in accordance with the
capacitive susceptance of the probe when said probe is connected to said
driving unit;
said first means of said matching means including a variable impedance
component which is variable by means of said second means when said probe
is connected to said driving unit so as to have an impedance value
corresponding to the capacitive susceptance provided by said capacitive
component of said probe;
said impedance component of said first means comprising an inductive
element;
said first means further including a plurality of capacitors having
different capacitances, each capacitor having one terminal connected to
one terminal of said inductive element; and
said second means comprising means for connecting another terminal of one
of said capacitors to another terminal of said inductive element in
accordance with said capacitive susceptance.
2. An apparatus according to claim 1, in which:
said second means comprises a capacitor having a capacitance in accordance
with said capacitive susceptance, said capacitor being coupled in parallel
to said ultrasonic transducer; and
said impedance component of said first means comprises an inductive
element.
3. An apparatus according to claim 2, in which said capacitor is a variable
capacitor.
4. An ultrasonic transducer apparatus comprising:
1) a probe including an ultrasonic transducer having:
a series connection of an inductor, a resistor and a capacitor; and
a capacitive component for providing a capacitive susceptance connected in
parallel with said series connection;
2) a driving unit separate from said probe and detachably connected to said
probe, said driving unit including means for supplying to said ultrasonic
transducer a driving signal having a frequency, said driving signal being
such that a phase difference between a voltage applied to said ultrasonic
transducer and a current supplied through said ultrasonic transducer is
substantially zero; and
3) matching means including:
first means arranged in said driving unit; and
second means separate from said first means and arranged in said probe for
causing varying of an impedance of said first means in accordance with the
capacitive susceptance of the probe when said probe is connected to said
driving unit;
said first means of said matching means including a variable impedance
component which is variable by means of said second means when said probe
is connected to said driving unit so as to have an impedance value
corresponding to the capacitive susceptance provided by said capacitive
component of said probe;
said impedance component of said first means comprising an inductive
element;
said first means further including a plurality of capacitors having the
same capacitance, each capacitor having one terminal connected to one
terminal of said inductive element; and
said second means comprising means for connecting another terminal of each
of a number of said capacitors, the number corresponding to said
capacitive susceptance, to another terminal of said inductive element.
5. An apparatus according to claim 4, in which:
said second means comprises a capacitor having a capacitance in accordance
with said capacitive susceptance, said capacitor being coupled in parallel
to said ultrasonic transducer; and
said impedance component of said first means comprises an inductive
element.
6. An apparatus according to claim 5, in which said capacitor is a variable
capacitor.
7. An ultrasonic transducer apparatus comprising:
1) a probe including an ultrasonic transducer having:
a series connection of an inductor, a resistor, and a capacitor; and
a capacitive component for providing a capacitive susceptance connected in
parallel with said series connection;
2) a driving unit separate from said probe and detachably connected to said
probe, said driving unit including means for supplying to said ultrasonic
transducer a driving signal having a frequency, said driving signal being
such that a phase difference between a voltage applied to said ultrasonic
transducer and a current supplied through said ultrasonic transducer is
substantially zero; and
3) matching means including:
first means arranged in said driving unit; and
second means separate from said first means and arranged in said probe for
causing varying of an impedance of said first means in accordance with the
capacitive susceptance of the probe when said probe is connected to said
driving unit;
said first means of said matching means including a variable impedance
component which is variable by means of said second means when said probe
is connected to said driving unit so as to have an impedance value
corresponding to the capacitive susceptance provided by said capacitive
component of said probe;
said second means comprising a series circuit formed of a capacitor and a
resistor having a resistance corresponding to said capacitive susceptance,
said series circuit being coupled in parallel to said ultrasonic
transducer; and
said impedance component of said first means comprising an inductive
element.
8. An apparatus according to claim 7, in which said resistor is a variable
resistor.
9. An ultrasonic transducer apparatus comprising:
1) a probe including an ultrasonic transducer having:
a series connection of an inductor, a resistor, and a capacitor; and
a capacitive component for providing a capacitive susceptance connected in
parallel with said series connection;
2) a driving unit separate from said probe and detachably connected to said
probe, said driving unit including means for supplying to said ultrasonic
transducer a driving signal having a frequency, said driving signal being
such that a phase difference between a voltage applied to said ultrasonic
transducer and a current supplied through said ultrasonic transducer is
substantially zero, said driving unit comprising:
a voltage-controlled oscillator for supplying an oscillation signal to said
ultrasonic transducer;
means for detecting a voltage applied to said ultrasonic transducer, and
for detecting a current supplied to said ultrasonic transducer;
means for detecting a phase difference between the detected voltage and the
detected current; and
means for controlling a voltage applied to said voltage-controlled
oscillator in accordance with the detected phase difference; and
3) matching means including:
first means arranged in said driving unit; and
second means separate from said first means and arranged in said probe for
causing varying of an impedance of said first means in accordance with the
capacitive susceptance of the probe when said probe is connected to said
driving unit;
said first means of said matching means including a variable impedance
component which is variable by means of said second means when said probe
is connected to said driving unit so as to have an impedance value
corresponding to the capacitive susceptance provided by said capacitive
component of said probe.
10. An ultrasonic transducer apparatus comprising:
a probe including an ultrasonic transducer having:
a series connection of an inductor, a resistor, and a capacitor; and
a capacitive element for providing a capacitive susceptance connected in
parallel with said series connection;
a driving unit detachably connected to said probe and including means for
supplying to said ultrasonic transducer a driving signal having a
frequency, said driving signal being such that a phase difference between
a voltage applied to said ultrasonic transducer and a current supplied
through said ultrasonic transducer is substantially zero; and
matching means arranged in said driving unit and including means for
identifying the type of the probe when the probe is connected to the
driving unit and a variable impedance element whose impedance value is
variable as a function of the type of the probe, and wherein said
impedance value of said variable impedance element is varied in accordance
with the capacitive susceptance provided by said capacitive susceptance of
said capacitive element of said probe, in response to said probe being
connected to said driving unit.
11. An apparatus according to claim 10, in which said variable impedance
element comprises an inductive element connected in parallel with said
ultrasonic transducer.
12. An apparatus according to claim 10, in which said variable impedance
element of said matching means comprises a variable capacitor arranged
parallel to said ultrasonic transducer and having a capacitance in
accordance with said capacitive susceptance.
13. An apparatus according to claim 10, in which said driving unit
comprises:
a voltage-controlled oscillator for supplying an oscillation signal to said
ultrasonic transducer;
means for detecting a voltage applied to said ultrasonic transducer, and
for detecting a current supplied to said ultrasonic transducer;
means for detecting a phase difference between the detected voltage and the
detected current; and
means for controlling a voltage applied to said voltage-controlled
oscillator in accordance with the detected phase difference.
14. An apparatus according to claim 11, in which:
said inductive element comprises a plurality of intermediate taps having
different inductances; and
said probe comprises means for selectively connecting one of said
intermediate taps to said ultrasonic transducer in accordance with said
capacitive susceptance when said probe is connected to said driving unit. |
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Claims |
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Description |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ultrasonic transducer apparatus for
breaking a calculus or eliminating a tumor utilizing ultrasonic
oscillations.
2. Description of the Related Art
As shown in FIG. 1, a conventional ultrasonic transducer apparatus of this
type includes a driving unit 1 having a driving circuit 2, and an
ultrasonic transducer probe 3 which has an ultrasonic transducer 4 and
which is detachable from the driving unit 1.
As shown in FIG. 2, an equivalent circuit of the ultrasonic transducer 4
includes an LCR series resonance circuit formed of an inductor 5, a
capacitor 6, and a resistor 7, and a dumping capacitor Cd connected in
parallel with the LCR series resonance circuit. When a voltage is applied
to the ultrasonic transducer 4, currents il and id are supplied through
the LCR series resonance circuit and the dumping capacitor Cd,
respectively. Of the currents il and id, only the current il is converted
into ultrasonic oscillations. Therefore, it is most efficient to drive the
ultrasonic transducer 4 at a resonance frequency of the LCR series
resonance circuit. The resonance frequency of the series resonance circuit
is referred to as a mechanical resonance frequency ft for the ultrasonic
transducer 4 hereinafter.
Since a conductance G of the ultrasonic transducer 4 is maximum at the
mechanical resonance frequency ft, the frequency ft is a rightmost point
in a graph of an admittance Y (=G+jB) of the ultrasonic transducer 4, as
shown in FIG. 3. FIG. 3 shows a locus of the admittance Y obtained when an
angular frequency .omega. is a variable. Reference symbol B denotes a
susceptance; and .omega., a driving angular frequency (=2.pi.f).
The conventional driving circuit 2 includes a phase-locked loop (PLL)
circuit to lock the driving frequency when the conductance is maximum. The
PLL circuit controls the driving frequency to make a phase difference
between a voltage applied to the ultrasonic transducer 4 and a current
supplied to the ultrasonic transducer 4, i.e., a susceptance, zero. As
shown in FIG. 3, however, the center of an admittance characteristic
circle of the ultrasonic transducer 4 is shifted in the positive direction
of the susceptance by a capacitive susceptance .omega.Cd of the dumping
capacitor Cd. Therefore, a lock point (point at which a susceptance is
zero) PR obtained by the PLL does not coincide with the mechanical
resonance point ft (point at which a conductance is maximum), i.e., the
transducer 4 cannot be driven at the mechanical resonance frequency even
if a phase difference between the voltage and the current is set to be
zero. As a result, conversion efficiency of a driving signal into
ultrasonic oscillations is poor.
An apparatus to eliminate the above drawback is disclosed in Published
Unexamined Japanese Utility Model Application No. 54-136943. As shown in
FIG. 4, in this apparatus, the driving unit 1 includes an inductor Ld
arranged in parallel with the ultrasonic transducer 4 besides the driving
circuit 2. According to this apparatus, as shown in FIG. 5, a capacitive
susceptance .omega.Cd of the dumping capacitor Cd included in the
ultrasonic transducer 4 can be canceled by an inductive susceptance
(=1/.omega.Ld) of the inductor Ld. As a result, as shown in FIG. 5, the
center of the admittance characteristic circle of the equivalent circuit
of the ultrasonic transducer 4 is positioned on the axis where the
susceptance is zero, and the lock point PR obtained by the PLL coincides
with the mechanical resonance point ft. Therefore, the ultrasonic
transducer 4 can be efficiently driven.
A capacitive susceptance of the dumping capacitor in the ultrasonic
transducer probe is varied depending on its shape or the characteristics
of the ultrasonic transducer included in the probe. For this reason, in
the ultrasonic transducer apparatus in which different types of ultrasonic
transducer probes can be connected to the above-mentioned driving unit
shown in FIG. 4, capacitive susceptances of dumping capacitors in the
ultrasonic transducers of all probes cannot be canceled. In other words,
in a driving unit including only one inductor Ld, capacitive susceptances
of different dumping capacitors cannot be perfectly canceled. Therefore,
when various ultrasonic transducer probes are selectively connected to a
driving unit as in an ultrasonic medical treatment apparatus in accordance
with a target to be treated, various ultrasonic transducers cannot be
driven at respective optimal mechanical resonance points. As a result,
driving efficiency is poor.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ultrasonic
transducer apparatus which reliably drives an ultrasonic transducer at its
mechanical resonance frequency even when types of ultrasonic transducer in
an ultrasonic transducer probe connected to a driving unit are different
so that capacitive susceptances of dumping capacitors are different,
thereby efficiently converting a driving signal into ultrasonic
oscillations.
According to the present invention, there is provided an ultrasonic
transducer apparatus comprising a probe including an ultrasonic transducer
formed of a series connection of an inductor, a resistor, and a capacitor,
and a dumping capacitor connected in parallel with the series connection;
a driving unit detachably connected to the probe and including a driving
circuit for supplying to the ultrasonic transducer a driving signal having
a frequency where a phase difference between a voltage applied to the
ultrasonic transducer and a current supplied to the ultrasonic transducer
is substantially zero, and an inductor connected in parallel with the
ultrasonic transducer; and an impedance matching element arranged in at
least one of the probe and the driving unit and having an impedance
corresponding to a capacitive susceptance of the dumping capacitance.
Additional objects and advantages of the invention will be set forth in the
description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention. The objects
and advantages of the invention may be realized and obtained by means of
the instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part
of the specification, illustrate presently preferred embodiments of the
invention and, together with the general description given above and the
detailed description of the preferred embodiments given below, serve to
explain the principles of the invention.
FIG. 1 is a block diagram of a conventional ultrasonic transducer
apparatus;
FIG. 2 is an equivalent circuit diagram of an ultrasonic transducer;
FIG. 3 is a graph of an admittance characteristic for explaining an
operation of the conventional apparatus shown in FIG. 1;
FIG. 4 is a block diagram of another conventional ultrasonic transducer
apparatus;
FIG. 5 is a graph of an admittance characteristic for explaining an
operation of the conventional apparatus shown in FIG. 4;
FIG. 6 is a block diagram of an ultrasonic transducer apparatus according
to a first embodiment of the present invention;
FIG. 7 is a block diagram showing the first embodiment with another
ultrasonic transducer probe;
FIG. 8 is a block diagram of a driving circuit for the first embodiment;
FIG. 9 is a block diagram of an ultrasonic transducer apparatus according
to a second embodiment of the present invention;
FIG. 10 is a block diagram of the second embodiment with another ultrasonic
transducer probe;
FIG. 11 is a block diagram of an ultrasonic transducer apparatus according
to a third embodiment of the present invention;
FIG. 12 is a block diagram of the third embodiment with another ultrasonic
transducer probe;
FIG. 13 is a block diagram of an ultrasonic transducer apparatus according
to a fourth embodiment of the present invention;
FIG. 14 is a block diagram of an ultrasonic transducer apparatus according
to a fifth embodiment of the present invention;
FIG. 15 is a block diagram of the fifth embodiment with another ultrasonic
transducer probe;
FIG. 16 is a block diagram of an ultrasonic transducer apparatus according
to a sixth embodiment of the present invention;
FIG. 17 is a block diagram of the sixth embodiment with another ultrasonic
transducer probe;
FIG. 18 is a block diagram of an ultrasonic transducer apparatus according
to a seventh embodiment of the present invention;
FIG. 19 is a block diagram of the seventh embodiment with another
ultrasonic transducer probe;
FIG. 20 is a block diagram of an ultrasonic transducer apparatus according
to a eighth embodiment of the present invention;
FIG. 21 is a block diagram of an ultrasonic transducer apparatus according
to a ninth embodiment of the present invention; and
FIG. 22 is a graph of an admittance for explaining an operation of the
apparatus in the ninth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An ultrasonic transducer apparatus according to preferred embodiments of
the present invention will be described hereinafter with reference to the
accompanying drawings.
FIG. 6 is a block diagram showing an arrangement of the first embodiment. A
driving unit 12 includes a driving circuit 14, an inductor 16, and
connection terminals 18, 20, 22, and 24. Output terminals of the driving
circuit 14 are respectively connected to the connection terminals 18 and
24. The inductor 16 is connected between the connection terminals 18 and
24. An inductance of the inductor 16 is constant, i.e., L1. The inductor
16 includes intermediate taps at positions corresponding to inductances L2
and L3 (L1>L2>L3), respectively. The intermediate taps corresponding to
the inductances L2 and L3 are connected to the connection terminals 20 and
22, respectively. More specifically, the inductances between the terminals
18 and 24 can be switched to the inductance L1, L2, or L3.
An ultrasonic transducer probe 26 includes an ultrasonic transducer 28
having an equivalent circuit shown in FIG. 2, and a connector 30 connected
to the driving unit 12 through the connection terminals 18, 20, 22, and
24.
When this embodiment is applied to an ultrasonic medical treatment
apparatus, the probe includes a horn or a pipe (not shown) for efficiently
transmitting ultrasonic oscillations of the ultrasonic transducer 28 to a
morbid part. Such a probe is known as a Langevin-type transducer probe.
The ultrasonic transducer 28 is connected between the connection terminals
18 and 24. It is assumed that a capacitance of a dumping capacitor in the
ultrasonic transducer 28 is Cd1. The probe 26 is detachably connected to
the driving unit 12 through the connector 30. More specifically, another
ultrasonic transducer probe 26a of another type having an ultrasonic
transducer 28a as shown in FIG. 7 can be connected to the driving unit 12.
It is assumed that the dumping capacitance of the ultrasonic transducer
28a is Cd2.
The connector of each probe includes a wiring for connecting the connection
terminal 18 to the connection terminal 20 or 22 or does not include the
wiring so as not to connect the connection terminal 18 to other connection
terminals at all in accordance with the capacitance of the dumping
capacitor of the ultrasonic transducer. More specifically, when the probe
is connected to the driving unit, an inductor for providing an inductive
susceptance having an absolute value equal to that of a capacitive
susceptance of the dumping capacitor in the ultrasonic transducer is
connected in parallel with the ultrasonic transducer, and the capacitive
susceptance (positive) of the ultrasonic transducer is canceled by the
inductive susceptance (negative) of the inductor 16.
A detailed arrangement of the driving circuit 14 is shown in FIG. 8. An
output from a voltage-controlled oscillator 36 is supplied to the
connection terminals 18 and 24 through an amplifier 38 and a transformer
40. Phases of an output voltage and an output current from the amplifier
38 are detected, and detection results are input to a phase comparator 42.
A phase difference between the output voltage and the output current is
applied to the control terminal of the oscillator 36 through a low-pass
filter 44. Thus, the driving circuit 14 includes a PLL circuit for locking
a driving frequency at the mechanical resonance frequency where the
susceptance of the ultrasonic transducer 28 of the ultrasonic probe is
substantially zero, i.e., a conductance is maximum.
As described above, according to the first embodiment, a plurality of
intermediate taps are arranged at the inductor 52 in the driving unit 12
to provide a plurality of inductances, and the wiring in the connector 30
of the probe 26 is varied in accordance with a capacitive susceptance of
the dumping capacitor in the ultrasonic transducer 28. Therefore, an
inductance corresponding to the capacitive susceptance of the dumping
capacitor can be selectively connected in parallel to the ultrasonic
transducer 28. Even if a different kind of probe is connected to the
driving unit 12, a capacitive susceptance of the dumping capacitor can be
perfectly canceled by the inductive inductance of the inductor 16.
Therefore, the ultrasonic transducer has admittance characteristics shown
in FIG. 5, and a lock point obtained by the driving circuit 14 having the
PLL circuit coincides with the mechanical resonance point of the
ultrasonic transducer. As a result, when another ultrasonic oscillator
probe is connected to this driving unit 12, the driving circuit 14 can
reliably drive the ultrasonic transducer 28 at its mechanical resonance
point. This apparatus allows an improvement of efficiency achieved when a
calculus is broken, or a tumor is eliminated. Note that the number of taps
is not limited to three. When the number of types of probe is increased,
the number of taps may be increased in accordance with the number of types
of probe.
FIG. 9 is a block diagram showing the second embodiment. In the second
embodiment, intermediate taps are arranged at an inductor in the same
manner as in the first embodiment, and an inductance is selected upon
selection of the tap. In the second embodiment, each tap is positioned so
that an inductance is multiplied, and the larger number of inductance
levels than the number of taps can be obtained in accordance with a
combination of the inductances between the taps.
A driving unit 50 includes the driving circuit 14, an inductor 52, and
connection terminals 54, 56, 58, 60, 62, 64, and 66. Output terminals of
the driving circuit 14 are respectively connected to the connection
between the connection terminals 54 and 66. A total inductance of the
inductor 52 is 32L, and the intermediate taps are arranged at positions
where the inductances from the connection terminal 66 are L, 2L, 4L, 8L,
and 16L, respectively. The taps corresponding to the inductances 16L, 8L,
4L, 2L, and L are connected to the connection terminals 56, 58, 60, 62,
and 64, respectively.
An ultrasonic transducer probe 68 includes the ultrasonic transducer 28,
and a connector 70 detachably connected to the driving unit 50 through the
connection terminals 54, 56, 58, 60, 62, 64, and 66. The ultrasonic
transducer 28 is connected between the connection terminals 54 and 66. The
connector 70 includes or does not include wirings for connecting arbitrary
pairs of the connection terminals 54, 56, 58, 60, 62, 64, and 66 to each
other in accordance with a capacitive susceptance of the dumping capacitor
in the ultrasonic transducer 28. For this reason, the inductance of the
inductor 52 can be varied in 32 ways of L to 32L depending on
interconnections of the connection terminals. Thus, the connector 70
includes the wiring for determining an inductance of the inductor 52 so
that the inductive susceptance of the inductor 52 connected in parallel
with the ultrasonic transducer 28, when the probe 68 is connected to the
driving unit 50, is equal to a capacitive susceptance of the ultrasonic
transducer. In the arrangement shown in FIG. 9, the connection terminals
56 and 58, and the connection terminals 60 and 62 are connected to each
other; the inductance of the inductor 52 is set to be 22L. In another
probe 68a shown in FIG. 10, the connection terminals 54 and 56, and the
connection terminals 62 and 64 are connected to each other; the inductance
of the inductor 52 is set to be 14L.
According to the second embodiment, the capacitive susceptance of the
dumping capacitor can be canceled by the inductive inductance of the
inductor in the same manner as in the first embodiment. In addition, the
inductance of the inductor can be varied in a large number of levels.
Therefore, this apparatus can be applied to various ultrasonic probes as
compared with that in the first embodiment. Even if a new type of
ultrasonic oscillator probe is manufactured, the capacitive susceptance of
a dumping capacitor can be reliably canceled by changing wiring in the
connector without increasing the number of intermediate taps of the
inductor and changing the structure of the driving unit.
FIG. 11 is a block diagram showing the third embodiment. In the third
embodiment, an inductance of an inductor is varied in accordance with the
type of probe connected to a driving unit, i.e., a capacitive susceptance
of a dumping capacitor, in the same manner as in the first and second
embodiments. Although the inductance is varied in a stepped manner upon
selection of the tap in the first and second embodiments, a core of a coil
of the inductor is slid to continuously change the inductance in the third
embodiment.
A driving unit 74 includes the driving circuit 14, an inductor 76, and
connection terminals 78 and 80. Output terminals of the driving circuit 14
are respectively connected to the connection terminals 78 and 80, and the
inductor 76 is connected between the connection terminals 78 and 80. A
ferrite core 82 is inserted in a coil of the inductor 76. One end of the
ferrite core 82 is fixed to a part of a housing of the driving unit 74
through a spring 84. The spring 84 is biased in its extending direction,
and the core 82 is biased in the right direction in FIG. 11.
An ultrasonic oscillator probe 86 includes the ultrasonic transducer 28,
and a connector 88 detachably connected to the driving unit 74 through the
connection terminals 78 and 80. The ultrasonic transducer 28 is connected
between the connection terminals 78 and 80. The connector 88 holds a bar
90 for pushing the other end of the ferrite core 82 against a biasing
force of the spring 84 when the probe 86 is connected to the driving unit
74. One end of the bar 90 is fixed in the connector 88. The length of the
bar 90 is determined in accordance with the capacitive susceptance of the
dumping capacitor in the ultrasonic transducer 28. In the arrangement
shown in FIG. 11, the length of the bar 90 is relatively long, and the bar
90 deeply pushes the ferrite core 82 in. In contrast to this, in a probe
86a shown in FIG. 12, the length of the bar 90a is relatively short, and
the bar 90a hardly pushes the ferrite core 82 in. Therefore, the position
of the ferrite core 82 in the coil is varied in accordance with the type
of the probe 86, and the inductance of the inductor 76 is varied in
accordance with a change in position of the core 82. More specifically,
the lengths of the bars 90 and 90a are determined in accordance with the
capacitive susceptance of the dumping capacitor in the ultrasonic
transducer 28, i.e., to move the ferrite core 82 so that an inductive
susceptance of the inductor 76 equal to the capacitive susceptance can be
provided. For this reason, the inductance of the inductor 76 can be
continuously varied.
According to the third embodiment, the capacitive susceptance of the
dumping capacitor can be canceled by the inductive susceptance of the
inductor in the same manner as in the first and second embodiments. In
addition, the infinite number of variations in inductance can be achieved.
Therefore, this apparatus can be applied to various ultrasonic transducer
probes as compared with those in the first and second embodiments. Even if
a new type of ultrasonic transducer probe is manufactured, the capacitive
susceptance of the dumping capacitor can be reliably canceled by only
changing the length of a bar in the connector without changing the
structure of the driving unit.
FIG. 1 | | |
