JPS58206989A - Sound wave transmitter and receiver - Google Patents

Abstract

PURPOSE:To suppress a shunt of energy of a transmitting pulse to a receiving circuit side, and to secure coupling of a sufficiently tight signal path, by coupling a transducer and a receiving circuit by use of a variable capacity diode. CONSTITUTION:A waveform in case when a pulse generating circuit 1 applies a positive pulse electric signal to a piezoelectric transducer 4 consists of a positive pulse waveform part (a) and a high voltage waveform part (b) of its dynamic current. In case when a transistor 3 is turned on in a moment only and a pulse is applied to the transducer 4, in the waveform part (a) and (b), capacity of a variable capacity diode 5 is reduced, for instance, to several PF or ten and several PF or so in case of 1SV100, and coupling of the transducer 4 and a receiving circuit 6 becomes loose, therefore, it is suppressed sufficiently that energy of a pulse waveform from the pulse generating circuit 1 is shunted to the receiving circuit 6 side. When the transistor 3 is returned to off and a tail part (b) of a high voltage waveform is attenuated gradually, capacity of the variable capacity diode 5 increases, and coupling of the transducer 4 and the receiving circuit 6 becomes tight gradually, therefore, a transfer signal is scarcely attenuated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a sonic wave transmitter/receiver in a sonar, an ultrasonic diagnostic apparatus, or the like.

[Description of prior art]

This type of device converts a pulsed electrical signal generated by a pulse generation circuit into a sound wave by applying it to a transducer.
This beam is irradiated toward a target object, and the reflected wave from the target object is received by the transducer and converted into an electrical signal, which is then amplified and detected by the receiving circuit.

In the above-mentioned apparatus, when applying a Noculus electric signal to the transducer, it is necessary to prevent the /< pulse electric signal from being shunted to the receiving circuit side. Conventionally, a /R switch limiter or a dedicated time-controlled shunt switch has been used for this purpose, but these devices increase the number of components and complicate the circuit. .

Furthermore, these devices require a so-called TGC (time gain control) function that changes the magnitude of the received reflected wave over time.

[Purpose of the invention]

The present invention provides a T
The purpose of the present invention is to provide a sonic wave transmitting/receiving rock having a simple and inexpensive configuration and also having a GC function.

[Key points of the invention]

The present invention transforms the coupling between the transducer and the receiver circuitry from traditional fixed components such as coils, capacitors, resistors, etc. to non-linear (parametric) coupling.
By using an IMBD Damme element, specifically a variable capacitance diode, it is possible to suppress the energy of the transmitted pulse from being shunted to the receiving circuit side, and to ensure that the signal path is sufficiently dense during the reception of reflected waves. A variable capacitance diode is connected between the transducer and the receiving circuit with a polarity that is reverse biased by the pulsed electrical signal generated by the pulse generating circuit. Features.

[Explanation based on examples] Hereinafter, the present invention will be explained based on the drawings.

v! , 1 is a circuit diagram of a device according to a first embodiment of the present invention.

In the figure, a pulse generation circuit 1 includes a pulser 2 and a transistor 3, and generates a positive pulse electric signal.

The output pulse electric signal of the pulse generation circuit 1 is guided to the piezoelectric transducer 4, where it is converted into a sound wave and irradiated toward the target object. The reflected wave from the target object is converted into a lightning signal by a transducer 4, and then guided to a receiving circuit 6 via a variable capacitance diode 5, where it is amplified and detected.

The freezeable capacitance diode 5 is, for example, 18 V 100, and its polarity is determined by the pulse generation circuit 1.
It is connected in the direction in which it is biased by a positive pulse electric signal.

Next, the operation of the apparatus of this embodiment will be explained.

First, the pulse generation circuit 1 generates a positive pulse electric signal,
This is applied to the piezoelectric transducer 4. The applied voltage and pressure waveforms consist of a positive pulse waveform portion a and a high voltage waveform portion following the positive pulse waveform portion a as shown by Ha(a)K in FIG.

Here, if the transistor 3 is turned on only momentarily and a pulse with an amplitude of several tens of volts is applied to the transducer 4, then in the above portions a and b, the capacitance of the variable capacitance diode 5 is, for example, I In the case of S V 100, it is reduced to about several PFs to more than ten PFs, and the coupling between the transducer 4 and the receiving circuit 6 becomes sparse. Therefore, the energy of the pulse waveform from the pulse generating circuit 1 is sufficiently suppressed from being shunted to the receiving circuit 6 (Ill).While the pulse generating circuit 1 is pulling up the transducer 4 in this way, Due to the parametric nature of the variable capacitance diode, the amount of charge flowing into it, and thus the charging current to it, is limited to a limited amount or cumulative value at most. , the capacitor capacity was connected in parallel to the transducer 4, giving an additional 4A load to the pulse generation circuit 1.
With the present invention, such a situation will no longer occur.

Next, when the transistor 3 is turned off and the tail of the high voltage waveform gradually attenuates, the capacitance of the variable capacitance diode 4 increases, and the coupling 1d between the transducer 4 and the receiving circuit 6 increases. As the density gradually increases, the attenuation of the transmitted signal decreases.When the applied voltage approaches Ov, the capacitance reaches about 600 to 1000 PF, and the transmitted signal is hardly attenuated.

In this way, this device functions as a T/R switch, but furthermore, the change from weak coupling when a pulsed electrical signal is applied to tight coupling as time passes is due to the fact that the amplification factor of the receiving circuit 6 changes over time. As a result, it increases and becomes @ = valence, and it also functions as a so-called TGC.

FIG. 2 shows a circuit diagram of the device of the second embodiment, and only the variable capacitance diode portion is shown in the same figure.

In this embodiment, the withstand voltage of the variable capacitance tie-down wire 4 is insufficient for the applied voltage of the applied voltage and voltage signal, and the four variable capacitance tie-down diodes 4a~ 4d to 1
By connecting the diodes in parallel, the voltage applied to each diode can be completely reduced, and the capacity t of the entire circuit can be maintained as much as in the first embodiment.

FIG. 15 is a block diagram of the apparatus of the fifth embodiment.

In this embodiment, the connection point C between the variable diode 5 and the transducer 4 is biased to be pulled by a dog voltage, and after the transient period of application of the electric signal by the pulse generating circuit 1 is over, the is configured so that the variable capacitance diode 5 is further biased in the forward direction beyond zero bias, and in this forward bias state, the capacitance based on the specific standard of the variable capacitance diode 5 is Transducer 4 and receiver circuit 6 regardless
Coupling with the variable capacitor is achieved only through the forward dynamic impedance of the diode, and in that case, it is possible to achieve a state close to a direct connection with a resistance of several ohms.

In this embodiment device, even when the variable capacitance diode 5 is switched from reverse bias to forward bias, the coupling between the transducer 4 and the receiving circuit 6 is not suddenly restarted, and the variable capacitance diode 5 is variable. Since the capacitance diode 5 is coupled with the increasing capacitance, the above-mentioned function as a TGO can also be maintained.

Of course, it is also possible to use an ordinary switching diode instead of the variable capacitance diode 5, and to take into account that the coupling is cut off when the reverse direction is turned on, the connection point C can be sufficiently increased by 9 voltages. It is.

〔Effect of the invention〕

Since the present invention has the above-described structure and operation, T
It is possible to realize a device that has both the function of a /R switch and the 700 function. Since such a device has an extremely simple structure in which the coupling component of the conventional device is replaced with a variable capacitance diode, it is easy to modify from the conventional device, and the effect is great. This is also desirable from the point of view of reducing the number of parts.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a device according to a first embodiment of the present invention. FIG. 2 is a circuit diagram of a device according to a second embodiment of the present invention. FIG. 3 is a block diagram of a device according to a third embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Pulse generation circuit, 4... Piezoelectric transducer, 5... Variable capacitance diode, 6... Receiving circuit. Patent applicant Yokogawa Electric Corporation Representative Patent attorney Koichi Ide (Figure 1)

Claims (1)

[Claims] (1) A pulse generation circuit that generates a pulse electric signal, a transducer that converts the output pulse electric signal of this circuit into a sound wave, and converts the reflected wave from the sound wave into an electric signal, and the output electricity of this transducer. In a sound wave transmitter/receiver equipped with a receiving circuit that amplifies and detects a signal, a variable polarity is connected between the transducer and the receiving circuit so as to be reverse biased by the pulsed electric signal generated by the handwritten pulse generating circuit. A sound wave transmitter/receiver characterized by being equipped with a capacitive diode.