JP2001119786A - Ultrasonic wave transmission/reception system and reverberation eliminating method for the ultrasonic wave transmission/reception system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultrasonic wave transmission/reception system that can reduce the effect of reverberation. SOLUTION: The ultrasonic wave transmission/reception system is provided with a transmission means 12 that outputs a transmission signal, an ultrasonic wave sensor 14 that converts a transmission signal from the transmission means 12 into an ultrasonic wave, transmits the ultrasonic wave, receives an ultrasonic wave and converts in into a reception signal, a reception means 16 that receives the received signal, a transmission/reception changeover circuit 18 that is placed between the transmission means 12 and the reception means 16, connected to the ultrasonic wave sensor 14 via a feeder 17, mainly transmits the transmission signal from the transmission means 12 to the ultrasonic wave sensor 14 at transmission, and transmits the received signal from the ultrasonic wave sensor 14 mainly to the reception means 16, the impedance of the ultrasonic wave sensor 14 is made to match approximately a constant, value in a bandwidth BWSU, and respective bandwidths are selected so as to satisfy a relation of BWDP>BWSU>BWT>BWR, where BWT is a transmission bandwidth of the transmission means 12, BWR is a reception bandwidth of the reception means 14, and BWDP is a pass bandwidth of the transmission reception changeover circuit 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transmission / reception system which can be used in, for example, an ultrasonic flaw detector, an ultrasonic flow meter, an ultrasonic medical device, and the like, and a method for removing reverberation in the system.

[0002]

2. Description of the Related Art Conventional ultrasonic transmission / reception systems include:
A transmitter that outputs a transmission signal, an ultrasonic sensor that converts a transmission signal from the transmitter into an ultrasonic wave, transmits the ultrasonic wave, receives the ultrasonic wave, and converts the ultrasonic wave into a reception signal, and a receiver that receives the reception signal, It is provided between the transmitter and the receiver and is connected to the ultrasonic sensor via a feeder, and mainly transmits a transmission signal from the transmitter at the time of transmission to the ultrasonic sensor, and receives a signal from the ultrasonic sensor at the time of reception. A transmission / reception switching circuit for mainly transmitting a signal to a receiver is known.

In such a conventional ultrasonic transmission / reception system, when a transmitter outputs a transmission signal, the transmission signal is sent to an ultrasonic sensor via a feeder through a transmission / reception switching circuit and is converted into ultrasonic waves. Radiated. Next, when no signal is output from the transmitter, the ultrasonic signal received by the ultrasonic sensor is converted into an electric signal as a received signal, and is transmitted to the receiver by the transmission / reception switching circuit. When using a pulse signal as a transmission signal to measure distance by measuring the ultrasonic propagation time from transmission to reflection on the object to be measured and reception again, the dead zone is reduced, and In order to enable measurement, it is essential to suppress reverberation after transmission pulse output. In a conventional ultrasonic transmission / reception system, instead of darely suppressing reverberation, a configuration is generally employed in which a delay member is provided in an ultrasonic sensor to delay reception time so as not to be affected by reverberation.

[0004]

However, the conventional method using the delay member has a problem that the size of the ultrasonic sensor is increased.

The cause of reverberation is that a transmission signal from a transmitter is reflected by an ultrasonic sensor due to an electrical impedance mismatch with a feeder, or the inductance or capacitance included in a transmission / reception switching circuit temporarily causes a reverberation. Part of the stored energy is swept out, and among them, the noise at the corner at the low frequency side of the pass bandwidth of the transmission / reception switching circuit reaches the receiver and influences it. Conceivable.

In order to avoid the electrical impedance mismatch of the ultrasonic sensor, an inductance and a capacitance are connected in series or in parallel with the piezoelectric element of the ultrasonic sensor to cancel the reactance and to match the resistance. It is conceivable that this will provide a very good impedance match for a single frequency, but will prevent reflection of signals at unmatched frequencies when dealing with signals with a wide frequency band. Can not.

Further, it is conceivable to remove the noise finally input to the receiver by a band-pass filter in the receiver. However, if the noise level to be removed is high, the noise may be saturated. Since the load on the pass filter is large, the band pass filter itself may emit new noise.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide an ultrasonic transmission / reception system capable of reducing the influence of reverberation and a method for removing reverberation in the system.

[0009]

In order to achieve the above object, an ultrasonic transmission / reception system according to the present invention comprises a transmitting means for outputting a transmission signal, a transmission signal from the transmission means being converted into an ultrasonic wave and transmitted. An ultrasonic sensor that receives an ultrasonic wave and converts it into a reception signal, a reception unit that receives the reception signal, and a transmission unit that is provided between the transmission unit and the reception unit and that is connected to the ultrasonic sensor via a feeder and transmits the ultrasonic wave. And a transmission / reception switching circuit that mainly transmits a transmission signal from the transmission unit to the ultrasonic sensor at the time of reception, and mainly transmits a reception signal from the ultrasonic sensor to the reception unit at the time of reception. Change the sensor impedance to the bandwidth BW _SU
In conjunction with matching the impedance of the feeder, BW _T transmission bandwidth of the transmission means, and BW _R a reception bandwidth of the receiving means, when the pass band width of the transmission and reception switching circuit and the BW _DP,

[0010]

The Equation 3] _{BW DP ⊃BW SU ⊃BW T ⊃BW R} (1) (A⊃B bandwidth indicates that contained within the bandwidth of A in B) each bandwidth to satisfy the It is characterized by setting.

[0011] The band pass filter is provided to the transmitting means may be set so that the transmission bandwidth of the transmission means including the band-pass filter and BW _T, thereby satisfying the expression (1). The bandpass filter can be, for example, a Butterworth type bandpass filter.

[0012] Further, the reverberation removing method in the ultrasonic transmitting / receiving system according to the present invention comprises:
An ultrasonic sensor that converts a transmission signal from a transmission unit into an ultrasonic wave, transmits the ultrasonic wave, receives an ultrasonic wave, and converts the ultrasonic wave into a reception signal, a reception unit that receives a reception signal, and the transmission unit and the reception unit. And is connected to the ultrasonic sensor via a feeder, and mainly transmits a transmission signal from the transmission unit to the ultrasonic sensor at the time of transmission, and mainly transmits a reception signal from the ultrasonic sensor to the reception unit at the time of reception. a dereverberation method for ultrasonic wave transmission and reception system and a transmission and reception switching circuit, the match to the impedance feeder impedance bandwidth BW _SU the ultrasonic sensor, the transmission bandwidth BW _T of the transmission means, and BW _R a reception bandwidth of the receiving means, the pass bandwidth of the transmission and reception switching circuit BW _DP
And when

[0013]

The Equation 4] _{BW DP ⊃BW SU ⊃BW T ⊃BW R} (1) (A⊃B bandwidth indicates that contained within the bandwidth of A in B) each bandwidth to satisfy the Set.

[0014] The ultrasonic sensor is impedance-matched to the feeder with a bandwidth BW _SU , and BW _SU ⊃B
With W _T, over the entire transmission bandwidth BW _T of the transmission means, it becomes possible to perform impedance matching between the ultrasonic sensor, it is possible to prevent the reflection from the ultrasonic sensor of the transmission signal. Furthermore, the most wide pass bandwidth BW _DT of transmission and reception switching circuit, the frequency of the edge portion of the pass band width BW _DT, by away from the most reception bandwidth BW _R receiving means, provided in the receiving means of the influence Not to be.

The impedance of the ultrasonic sensor is set to a bandwidth B
As a means for aligning the feeder in W _SU, can be used any means, for example, be achieved by configuring the band-pass filter having an impedance characteristic having a constant impedance values comprises an ultrasonic transducer Can be. As a bandpass filter,
Preferably, a Butterworth type band pass filter can be used.

Further, the bandwidth of the transmission / reception switching circuit may be different even if the pass bandwidth BW _DP1 from the transmitting means to the ultrasonic sensor is different from the pass bandwidth BW _DP2 from the ultrasonic sensor to the receiving means. , Both pass bandwidths are BW _SU , BW _T ,
To have a large bandwidth encompasses BW _R. Further, it is preferable that the transmission / reception switching circuit switches signals without including a resistor. Thereby, the influence of thermal noise due to the resistance can be avoided, and the noise level input to the receiving means can be further reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an ultrasonic transmitting / receiving system according to the present invention. The ultrasonic transmission / reception system 10 includes a transmission unit 12 that outputs a transmission signal, an ultrasonic sensor 14 that converts a transmission signal from the transmission unit 12 into an ultrasonic wave, transmits the ultrasonic wave, receives an ultrasonic wave, and converts the ultrasonic wave into a reception signal. Receiving means 16 for receiving a received signal, and an ultrasonic sensor 14 provided between the transmitting means 12 and the receiving means 16.
Via the feeder 17 and the transmitting means 1
2 is provided with a transmission / reception switching circuit 18 for mainly transmitting the transmission signal from the ultrasonic sensor 14 to the ultrasonic sensor 14 and for mainly transmitting the reception signal from the ultrasonic sensor 14 to the reception means 16 during reception.

The transmitting means 12 and the receiving means 16 include band-pass filters 24 and 26 and amplifiers 25 and 27, respectively, in addition to the conventional transmitter 20 and receiver 22, and their respective bandwidths are BW _T , and has a BW _R.

The impedance of the ultrasonic sensor 14 is substantially constant within a predetermined bandwidth, and
It has characteristics matched to the characteristic impedance of FIG. 2 is a specific example of a circuit diagram of the ultrasonic sensor 14 having such characteristics. In this example, the ultrasonic sensor 14
Constitutes a third-order Butterworth band-pass filter including the ultrasonic transducer 30 as a whole.

That is, the equivalent circuit constants of the lead titanate-based ultrasonic transducer 30 include a series inductance L, a series capacitance Ca, and a resistance R, which are connected in series.
These are represented by a parallel capacitance Cb connected in parallel to them. The resistance R of this equivalent circuit constant is used as a load resistance, the series inductance L, the series capacitance Ca, and the parallel capacitance Cb are used as a part of a filter circuit. A third-order T-type Butterworth bandpass filter as a whole is configured as a circuit element that constitutes the part. In the case of the third order, if load resistance = input resistance, L = L1, Ca = C
It becomes 1. Further, the value of L2 can be obtained from a known formula or a numerical table of a Butterworth bandpass filter. The value of C ′ may be such that the combined capacitance with Cb is equal to the required second-stage capacitance from the formula or numerical table. That is, if Cb is smaller than the required capacitance, C 'can be added to substantially increase the value of Cb. Thus, if Cb is equal to the required capacitance, then C 'is unnecessary, while if Cb is greater than the required capacitance, the filter cannot be constructed in 3rd order, so the order of the filter And the fourth order,
By setting the fifth order, any high-order Butterworth filter can be configured.

The Butterworth type filter is also called a maximum flatness characteristic filter, and the pass characteristic of the filter is almost flat in the pass band. In this connection, the resistance component of the impedance characteristic in many parts of the pass band coincides with a constant value, for example, the characteristic impedance of the feeder 17, and the reactance component has a characteristic of approximately 0Ω. Accordingly, a wide band pass characteristic is obtained, and impedance matching is performed over a wide band.

FIG. 3 shows frequency pass characteristics and impedance characteristics when a third-order Butterworth filter is constructed. As shown in FIG. 3, the characteristics are almost flat within the pass band, and a wide band pass characteristic is obtained. In many parts of the pass band, the resistance component of the impedance characteristic is, for example, 50Ω, and the reactance component is It is almost 0Ω. Accordingly, the Butterworth filter cancels out the reactance component, and furthermore, makes the resistance component equal to, for example, 50Ω by using the transformer T to match the characteristic impedance of the feeder 17, thereby achieving impedance matching over a wide band.

[0024] to be larger than the bandwidth BW _T of the band-pass filter 24 in the frequency band BW _SU transmission means 12 substantially constant impedance value of the ultrasonic sensor 14, electrical reflections from the ultrasonic sensor 14 And minimize unnecessary reverberation. The band-pass filter 24 of the transmitting means 12 also can be configured with Butterworth filter, its impedance characteristics are to be flat in the transmission bandwidth BW _T.

FIG. 4 shows an ultrasonic sensor 14 according to the present invention.
FIG. 10 is a circuit diagram illustrating another example of the present invention, which is an example applied to a lead niobate-based ultrasonic transducer 31. In the case of a lead niobate-based ultrasonic transducer, its equivalent circuit constant is composed of a resistor R and a parallel capacitance Cb connected in parallel without exhibiting electrical resonance characteristics. The resistance R of this equivalent circuit is defined as the load resistance, and the parallel capacitance C
b is a part of the filter circuit, and the inductance L21, the capacitance C21, and the inductance L2
2. A third-order π-type Butterworth bandpass filter as a whole is constituted by using the capacitance C22 and the inductance L23 as circuit elements constituting the rest of the filter circuit. In the case of the third order, if load resistance = input resistance,
L21 = L23 and C21 = Cb. Also, L21,
The values of L23, L22, and C22 can be obtained from known formulas or numerical tables of Butterworth bandpass filters. If the value of R is too large, the resistance R '
Can be added to substantially reduce the value of R. When it is desired to substantially increase the value of the capacitance Cb, the capacitance C ′ can be connected in parallel as in FIG. The frequency band BW of the ultrasonic sensor 14 having a substantially constant impedance value
_SU is the bandwidth B of the band-pass filter 24 of the transmitting means 12.
As it is larger than W _T, determining the values of the circuit elements are the same as in the example of FIG.

Similarly, the transmission / reception switching circuit 18 has a bandpass filter function as well as a transmission / reception switching function. FIG.
Is a specific example of a circuit diagram of the transmission / reception switching circuit 18. The transmission / reception switching circuit 18 includes a first diode 36 composed of two diode elements connected in series and reversely between the transmission means 12 and the ultrasonic transducer 14, and the ultrasonic sensor 1.
Between the ultrasonic sensor 14 and the second diode 38 between the ultrasonic sensor 14 and the second diode 38; And

Further, the transmitting means 12 and the first diode 3
6, an inductance L31, a capacitance C31, an inductance L32, and a capacitance C3.
2, an inductance L33 and a capacitance C33 are connected, and together with the capacitance C34, constitute a transmission-side bandpass filter 40. Further, an inductance L34, a capacitance C35, and an inductance L35 are connected between the second diode 38 and the receiving unit 16, and these constitute a reception-side bandpass filter 42 together with the capacitance C34.

At the time of transmission, when a large transmission signal is output from the transmission means 12, the transmission signal is transmitted to the ultrasonic sensor 14 through the first diode 36. At this time, a part of the transmission signal passes through the capacitance C34,
Since the second diode 38 is short-circuited, the receiving means 16 is protected without being excessively input to the receiving means 36. In this state, the circuit from the transmission means 12 to the ultrasonic sensor 14 including the capacitance C34 can be rewritten by the circuit shown in FIG. 6, and the transmission-side bandpass filter 40 includes the capacitance C34.
The pass band BT _{DP1 of the} transmission side band pass filter 40
Is the bandwidth B of the band-pass filter 24 of the transmitting means 12.
W _T and the ultrasonic sensor 14 of the impedance-matched frequency band BW _SU each circuit such that the large Butterworth bandpass filter than the element L31, C3
The values of 1, L32, C32, L33, and C3 are respectively set, and the capacitance C34 plays a part of the capacitance of the third stage. The third-order Butterworth bandpass filter has a flat pass characteristic, and therefore can transmit a transmission signal from the transmission unit 12 to the ultrasonic sensor 14 without deteriorating the frequency characteristic. The transmission-side bandpass filter 40 is designed such that its input impedance is substantially equal to the output impedance, which is the internal resistance of the transmission means 12, and its output impedance is substantially equal to the matched impedance of the ultrasonic sensor 14. You can also. In this way, impedance matching between the transmitting means 12 and the ultrasonic sensor 14 can be achieved. However, if the influence on reverberation is small, the matching need not always be achieved.

When the transmission from the transmission means 12 is completed and the ultrasonic wave is transmitted from the ultrasonic sensor 14, thereafter, a weak reception signal by the ultrasonic wave received by the ultrasonic sensor 14 is transmitted to the transmission / reception switching circuit 18. Is entered. Since this received signal is lower than the blocking voltage of the first diode 16, it is not sent to the transmitting means 12 side, passes through the capacitance C34, and is also lower than the blocking voltage of the second diode 38, so that no short circuit occurs. In this state, the ultrasonic sensor 1
7 can be rewritten by the circuit shown in FIG. 7, and the receiving side band-pass filter receiving side 42 including the capacitance C34 is configured. The reception-side bandpass filter 42 has a passband BT _DP2 of the reception-side bandpass filter 42 that is larger than a frequency band BW _{SU in} which the impedance of the ultrasonic sensor 14 can be matched. bandwidth BW _R each circuit element so that the second-order Butterworth bandpass filter greater than C34 of, L34,
The values of C35 and L35 are set, and the capacitance C34 serves as the first-stage capacitance. The second-order Butterworth band-pass filter has a relatively flat pass characteristic, although not as high as the third order, and therefore receives the reception signal from the ultrasonic sensor 14 without deteriorating the frequency characteristic. Can be sent to the means 16. Also, the receiving-side bandpass filter 42 can be designed such that its input impedance is substantially equal to the matched impedance of the ultrasonic sensor 14 and its output impedance is substantially equal to the input impedance of the receiving means 16. In this way, impedance matching between the ultrasonic sensor 14 and the receiving means 16 can be achieved. However, if the influence on reverberation is small, the matching need not always be achieved.

The receiving-side band-pass filter 42 has a 2
Although the following Butterworth type is used, the present invention is not limited to this, and a third-order or higher-order Butterworth-type band-pass filter can be used similarly to the transmission-side band-pass filter 40. A Butterworth bandpass filter of a higher order than the second or third order may be used. Further, an inductance may be used instead of the capacitance C34. In such a case, a capacitance can be used instead of the inductance L34. Alternatively, a Chebyshev type filter other than the Butterworth type filter can be formed by changing the values of the capacitance and the inductance.

Thus, as shown in FIG. 8, the ultrasonic transmission / reception system as a whole has the impedance matching bandwidth BW _{SU of} the ultrasonic sensor 14, the transmission bandwidth of the transmission means 14 as BW _T , and the reception bandwidth of the reception means 16. width passband width BW _R and duplexer circuit 18 when the BW _DP,

[0032]

Equation 5] is _{BW DP1, BW DP2 ⊃BW SU ⊃BW} T ⊃BW R (1) and so as to set. Then, to be able to ensure bandwidth required for measurement bandwidth BW _R receiving means 16. Specifically, when the impedance matching bandwidth BW _SU of the ultrasonic sensor 14 is set to 1, BW
_DP1, BW _DP2 is 1.5, BW _T is 0.9, BW _R 0.8
It can be set so that

The ultrasonic sensor 14 is shown in FIG.
Although not limited to the configuration described above, FIG. 2 or FIG.
As described above, the equivalent circuit by the ultrasonic transducer 30
The degree of freedom is small because the constant is automatically determined.
Generally, impedance matching bandwidth BW_SUIs to widen
Although it is difficult, the transmission / reception switching circuit 18
Although not limited to the configuration of FIG.
The inductance and inductance can be set relatively freely.
Bandwidth BW_DP1, BW_DP2Can be widely taken.
Therefore, BW_DP1, BW_DP2⊃BW_SUBy doing
Bandwidth BW of ultrasonic sensor 14_SUEffective use of the entire area of
I am able to do it. At the same time, BW _SU⊃BW_TToss
The bandwidth BW transmitted from the transmitting means_TInside
Signal is not reflected by the ultrasonic sensor 14.
And is efficiently converted to ultrasonic waves. Further, receiving means 1
Bandwidth BW at 6_RIs the smallest, extra
Naturally, it is possible to remove the reverberation, but that alone
By satisfying the above inequality (1),
Side bandpass filter 40 and reception side bandpass filter
Bandwidth BW of data 42_DP1, BW_DP2Low-frequency side
From the receiver part, the receiving bandwidth BW of the receiving means_RThe most distant
Can be opened. Thus, the pass bandwidth BW_DP1, B
W_DP2Of the noise corresponding to the low frequency corner of
Sound can be avoided. At the same time, the inequality of (1) above
Satisfies the expression to obtain the reverberation level before being input to the receiving means 16.
Because the bell has been suppressed to some extent,
The load on the band-pass filter 26 can be reduced.
You.

[0034]

As described above, according to the present invention,
By satisfying the above expression (1), it is possible to reduce the influence of reverberation as compared with the case where the respective bandwidths of the transmission means, the reception means, and the transmission / reception switching circuit are the same. Therefore, it is possible to perform short-range measurement with high sensitivity from the ultrasonic sensor without increasing the size of the ultrasonic sensor.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an embodiment of an ultrasonic transmission / reception system of the present invention.

FIG. 2 is a specific example of a circuit diagram of the ultrasonic sensor of FIG. 1;

FIG. 3 is a graph showing frequency pass characteristics and impedance characteristics of the ultrasonic sensor of FIG. 2;

FIG. 4 is another specific example of a circuit diagram of the ultrasonic sensor of FIG. 1;

FIG. 5 is a specific example of a circuit diagram of the transmission / reception switching circuit of FIG. 1;

FIG. 6 is an explanatory diagram at the time of transmission of the transmission / reception switching circuit of FIG. 5;

FIG. 7 is an explanatory diagram at the time of reception of the transmission / reception switching circuit of FIG. 5;

FIG. 8 shows an impedance matching band of the ultrasonic sensor of FIG. 1;
Width BW_SU, The transmission bandwidth BW of the transmission means_T, Receiving means
BW for communication bandwidth_R, And the transmission / reception switching circuit
W _DPFIG. 7 is a frequency characteristic diagram showing the relationship of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Ultrasonic transmission / reception system 12 Transmission means 14 Ultrasonic sensor 16 Receiving means 17 Feeder 18 Transmission / reception switching circuit 24 Bandpass filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04R 17/00 330

Claims (3)

[Claims] 1. A transmitting means for outputting a transmission signal, an ultrasonic sensor for converting a transmission signal from the transmission means into an ultrasonic wave, transmitting the ultrasonic wave, receiving the ultrasonic wave and converting the ultrasonic wave into a reception signal, and receiving the reception signal. Receiving means, which is provided between the transmitting means and the receiving means and is connected to the ultrasonic sensor via a feeder, and mainly transmits a transmission signal from the transmitting means to the ultrasonic sensor at the time of transmission and an ultrasonic signal at the time of reception. A transmission / reception switching circuit that mainly sends a reception signal from the acoustic wave sensor to a reception unit,
In the ultrasonic transmitting and receiving system having a, with matching the impedance feeder impedance bandwidth BW _SU the ultrasonic sensor, BW _T transmission bandwidth of the transmission means, and BW _R a reception bandwidth of the receiving means, transmitting and receiving the passband width of the switching circuit when the BW _DP, Equation 1] _{BW DP ⊃BW SU ⊃BW T ⊃BW R} (1) (A⊃B the bandwidth of B contained within the bandwidth of the a The ultrasonic transmission and reception system is characterized in that each bandwidth is set so as to satisfy the above. 2. A band pass filter is provided in a transmitting means,
Ultrasonic wave transmission and reception system according to claim 1, wherein the transmission bandwidth of the transmission means including the band-pass filter is set such that BW _T satisfying the formula (1). 3. A transmission means for outputting a transmission signal, an ultrasonic sensor for converting a transmission signal from the transmission means into an ultrasonic wave, transmitting the ultrasonic wave, receiving the ultrasonic wave and converting the ultrasonic wave into a reception signal, and receiving the reception signal. Receiving means, which is provided between the transmitting means and the receiving means and is connected to the ultrasonic sensor via a feeder, and mainly transmits a transmission signal from the transmitting means to the ultrasonic sensor at the time of transmission and an ultrasonic signal at the time of reception. A transmission / reception switching circuit that mainly sends a reception signal from the acoustic wave sensor to a reception unit,
A dereverberation method for ultrasonic wave transmission and reception system comprising a, with matching the impedance of the feeder impedance bandwidth BW _SU ultrasonic sensor, the reception band of BW _T, and receiving means to transmit bandwidth of the transmission means width BW _R, when the pass band width of the transmission and reception switching circuit and the BW _DP, Equation 2] _{BW DP ⊃BW SU ⊃BW T ⊃BW R} (1) (A⊃B the bandwidth B is a A reverberation method in the ultrasonic transmission / reception system, wherein the respective bandwidths are set so as to satisfy the following.