JPS5937466B2 - Ultrasonic transmitter/receiver circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention uses one piezoelectric vibrator to transmit ultrasonic waves,
Furthermore, regarding the ultrasonic transmitting/receiving circuit that receives the ultrasonic waves, it is possible to faithfully apply a drive signal to a piezoelectric vibrator, especially in response to a human input signal, and to also apply human input to a detection circuit that faithfully detects changes in the impedance of the piezoelectric vibrator using current values, etc. This invention relates to ultrasonic transmitting and receiving circuits.

Generally, in the medical and flaw detection fields, it is known to detect the tomographic structure of a medium by transmitting and receiving ultrasonic signals, and in order to reduce the transmitting and receiving wave surface due to manufacturing costs, one piezoelectric vibrator is used for both transmitting and receiving. It is being used as a transducer.

In addition, when one piezoelectric element is used for both transmission and reception in this way, the circuit that starts the transmission biases the path of the received signal to a predetermined value in order to prevent the signal component of the received wave from being lost. By switching V), the piezoelectric element is prompted to oscillate and drive at the rising edge of the switching.

However, in these conventional ultrasonic transmitter/receiver circuits, the piezoelectric vibrator is generated by using the signal component at the resonant frequency of the piezoelectric vibrator among the signal components in a wide frequency band generated during switching, so the so-called ultrasonic burst can only be output.

For this reason, a transducer that uses one transducer for both transmission and reception has the disadvantage that it cannot transmit continuous ultrasound signals (continuous waves) or modulated ultrasound signals. SUMMARY OF THE INVENTION In order to eliminate this drawback, it is an object of the present invention to provide an ultrasonic transmitter/receiver circuit that can generate continuous waves or modulated ultrasonic signals without adversely affecting the received signal. In order to achieve the above object, the present invention uses a switching element whose output changes according to the level of a signal that drives a piezoelectric element, and whose impedance is small on the side to which a received signal is manually applied. V) Examples will be described in detail below.

Figures 1 and 2 are an ultrasonic transmitting/receiving circuit diagram and a time chart of an embodiment of the present invention, in which AT is an ultrasonic transducer, Ampl and Amp2 are amplifiers, T is a coupling transformer, and Q
,, Q2 are transistors constructed as AB class complementary push-pull circuits, D1 to D are diodes, R1 to R are resistors, and -VEO and +VOO are power supplies. Also, Fig. 2 A, b, c, d are points A, b, c, d in Fig. 1,
The signals of c and d are shown. The bases of the transistors Ql and Q2 are connected to diodes D, D, and a resistor R to the power source -V1, so that the transistor Q2 operates as a constant current circuit.

In addition, diodes D and D are connected to transistors Q1 and Q.
The base potential of the transistor Q1 is clamped and applied to the base of the transistor Q, so that one of the transistors Q2 is always turned on. Resistors R1 and R2 are inserted between the terminal of each transistor Q1 and the emitter of transistor Q2 in order to prevent thermal runaway of transistors Q1 and Q2.

The operation of FIG. 1 will be explained assuming that the drive signal of FIG. 2a is input to the amplifier Ampl.

The amplifier Ampl amplifies the drive signal a and inputs the amplified signal to the transistor Q1. Since the transistor Q2 has the emitter of the transistor Q1 grounded, the transistor Q1 supplies the ultrasonic transducer AT with a signal similar to the signal inputted to the amplifier with the emitter grounded. The ultrasonic transducer AT is oscillated by this signal and sends an ultrasonic signal to the test medium at the timing TO. Ultrasonic waves reflected from the tomographic plane of the test medium are attenuated,
The ultrasonic transducer AT is delayed by the travel time,
For example, it is received at position tl in FIG. 2b. Note that amplifier A
The input signal a to mpl is set to, for example, 0v01t at least until the ultrasound signal is received. When the ultrasonic transducer AT receives an ultrasonic signal, its diimpedance changes and the output current changes.

At this time, as mentioned above, since the output of the amplifier Ampl is set to the ground potential, the transistor Q1 is connected to the ultrasonic transducer AT.
This is a grounded base circuit with a power source on the human power side, and its input impedance is low.

Therefore, most of the current change in the vibrator AT is transmitted as a current change in the collector of the transistor Q1, causing the primary side current of the coupling transformer T to change. Therefore, the received ultrasonic signal can be extracted by amplifying the current change occurring on the secondary side of the coupling transformer using the amplifier Amp2. The extracted signal is determined, for example, by determining the phase change or the attenuation rate of the signal during the period T (shown in Figure 2) from transmission to reception, and determining which tomographic plane of the examination medium the ultrasonic signal corresponding to the received signal is reflected. It is used to determine the substance present in the medium based on whether the substance has been oxidized and its attenuation rate.
FIG. 3 is a circuit diagram of another embodiment of the present invention.

In the figure, the same components as those used in FIG. 1 are indicated by the same symbols 9, Z1 is a Zener diode, and R, , R5 are resistors. In this embodiment, the transistor Q2 is made into a constant current circuit by the Zener diode Z1 and the resistors R, , R5.

It uses a so-called A-class bushable circuit. As explained using Fig. 1, the operation is such that the transistor Q2 position is a constant current circuit9, and the emitter grounded circuit is used for input signal a, V, and for the signal from ultrasonic transducer AT. becomes a base ground circuit.

Therefore, the input signal a is faithfully amplified and the transistor Q
1 to the ultrasonic transducer AT, and the ultrasonic transducer A
The current variation of T can be faithfully generated on the secondary side of the coupling transformer T via the transistor Q1. In addition, in the embodiment described above, the transistor Q1 is used as a switching element.
is used in the emitter-grounded and base-grounded circuit, but it is not limited to NPN transistors such as transistor Q1.
P transistors and field effect transistors can also be used in the same way. However, in the case of a field effect transistor, the emitter of each embodiment is used as the source, the base as the gate,
A similar effect can be achieved by replacing collector with drain. In addition, the method of biasing the transistor Q2 does not matter whether it is the above-mentioned class AB, B class, or class A, and the emitter grounding circuit on the emitter side of the transistor Q, or on the source side if it is a field effect transistor, is simply a resistor. It does not matter what the load is, or the power supply V.

It goes without saying that the polarity and type of O do not matter. ? As explained above, according to the present invention, when transmitting an ultrasonic transducer, the human input signal and the received signal are relayed by the emitter grounding circuit for the input signal and the base grounding circuit for the received signal. Therefore, the ultrasonic transducer can faithfully oscillate in response to the input signal, and the received signal can also be faithfully guided to the detection circuit.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 3 are circuit diagrams of an embodiment of the present invention, and FIG. 2 is a time chart thereof. In the figure, Ampl and Amp2 are amplifiers, T is a coupling transformer, Ql and Q2 are transistors, and R1 to R5 are diodes.

Claims (1)

[Claims] 1. An ultrasonic transducer comprising an ultrasonic transducer, a transmitting circuit for driving the ultrasonic transducer, and a receiving circuit for detecting a received signal received by the ultrasonic transducer, and an output signal of the transmitting circuit. an ultrasonic transmitting/receiving circuit comprising a signal relay circuit that causes the ultrasonic transducer to oscillate in accordance with the input signal and supplies a received signal of the ultrasonic transducer to the receiving circuit, the signal relay circuit being an input transmitting circuit; An ultrasonic transmitting/receiving circuit, characterized in that the ultrasonic transducer is configured with a circuit that outputs the output signal of the above and has a small input impedance with respect to the signal output from the ultrasonic transducer, and the ultrasonic transducer is used for both transmission and reception. . 2. The signal relay circuit is a common emitter or common source circuit for the transmitting circuit, and is composed of a transistor that serves as a common base or common gate circuit for the ultrasonic transducer, and is configured to detect signal changes at the collector or drain. 2. The ultrasonic transmitting/receiving circuit according to claim 1, wherein the receiving circuit detects the ultrasonic waves.