JPH05212034A - Circuit for generating ultrasonic transmission pulse for ultrasonic tomography device - Google Patents

Abstract

PURPOSE:To always transmit the input signal as continuous wave transmission at the TTL level with simple and inexpensive construction by connecting diodes in the reverse direction for the polarity of the power supply across the resistances to be connected between the gate and source of one FET. CONSTITUTION:A ultrasonic transmission pulse generation circuit in the ultrasonic diagnostic device used for blood flow measurement is provided with a pair of FETs 11 and 12 of N and P channel type with the drain D connected each other. The source S of one FET 11 is grounded and the source S of the other FET 12 is connected to the power supply +HV. A capacitor C1 is connected between the both gates G. Resistance R1 is connected between the gate B and the source S of the FET 12, and a signal Vin from an FET driver 15 consisting of a reference signal generating circuit 14 and a TTL circuit is inputted to an input terminal IN. The diode D1 is connected across the resistance R1 so as to output a continuous wave signal by means of the input vibration at the TTL level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic tomography apparatus, which receives a signal from a preceding circuit and outputs a transmission signal for driving a probe. The present invention relates to improvement of an ultrasonic transmission pulse generation circuit used.

[0002]

2. Description of the Related Art Generally, an ultrasonic tomography apparatus transmits an ultrasonic wave toward a subject and a probe which receives the ultrasonic wave from the subject and a probe which drives the probe to transmit the ultrasonic wave. For transmitting and receiving the ultrasonic reception signal received by the probe and amplifying and processing the signal, and after the signal from this ultrasonic transmission / reception circuit is digitized and written in the memory , A digital scan converter for reading and converting into a video signal, and a display device for displaying the video signal from the digital scan converter as an image. Here, in the probe, a large number of transducers each formed in a strip shape are arranged, and ultrasonic waves are transmitted and received by these transducers.

The Doppler measurement of blood flow using such an ultrasonic tomography apparatus mainly includes a pulse Doppler method and a continuous wave Doppler method. Since the pulse Doppler method has distance resolution, the Doppler sample point can be accurately aligned with the examination site of the subject, but the maximum detectable speed is limited by the pulse repetition frequency. On the other hand, the continuous wave Doppler method
There is no limit to the maximum blood flow velocity that can be detected, but it has no range resolution. For this reason, conventionally, the pulse Doppler method and the continuous wave Doppler method have been selectively used according to the inspection situation.

As shown in FIG. 2, the ultrasonic transmission / reception circuit of the ultrasonic tomography apparatus used for the blood flow measurement by the Doppler method has a pulse transmission circuit 3, a continuous wave transmission circuit 4,
Transmission / reception separation circuit 5, oscillator switching circuit 6, first-stage amplification circuit 7
And a phasing circuit 8.

The ultrasonic wave transmitting / receiving circuit 2 configured as described above operates as follows during continuous wave transmission. First, a large number of transducers in the probe 1 are divided into a transmitting transducer group and a receiving transducer group by the transducer switching circuit 6. Of these, the transmission oscillator group is supplied with transmission signals from the continuous wave transmission circuit 4 having different phases through the transmission / reception separation circuit 5 and the oscillator switching circuit 6. At the same time, the reception transducer group is used for reception,
After passing through the transducer switching circuit 6 and the transmission / reception separation circuit 5, the first stage amplification circuit 7 amplifies the signal, and then the phasing circuit 8 changes the delay amount of the reception signal of each reception transducer to change the scanning direction of the ultrasonic reception beam. .. The above operation is performed by the ultrasonic wave transmitting / receiving circuit 2, and thereafter, an image is displayed on the CRT of the display device through a digital scan converter (not shown).

FIG. 3 shows an LC resonance transmission signal generation circuit which constitutes the final stage of the continuous wave transmission circuit 4. In FIG. 3, IN is a signal input end, OUT is a transmission signal output end, and + HV is a + power supply. As shown in the figure, this LC resonance transmission signal generation circuit includes a capacitor C2 and a coil L1.
A resonant circuit formed by connecting in parallel with F
It is composed of ET13.

In this LC resonance transmission signal generating circuit, the frequencies of the ultrasonic waves that can be emitted are fixed by the values of the capacitor C2 and the coil L1, so that ultrasonic waves of other frequencies cannot be emitted. Therefore, a separate resonance circuit is required for each frequency, which makes the circuit itself large and impractical.

Next, FIG. 4 shows an ultrasonic transmission pulse generation circuit which constitutes the final stage of the pulse transmission circuit 3. This Figure 4
In, IN, OUT and + HV are the same as in FIG. In this ultrasonic transmission pulse generation circuit, a pair of N and P channel type FETs 11 and 12 are connected to each other at their drains D to be led out as a transmission signal output terminal OUT, and one gate 11 is set to a gate G as an input terminal IN. Is grounded, the source S of the other FET 12 is connected to the + power source + HV, and the capacitor C1 is connected between the gates G of both FETs 11 and 12, and the gate G and the source S of the other FET 12 are connected to each other. A resistor R1 is connected therebetween, and the signal Vin from the preceding circuit is input to the input terminal IN.

In this ultrasonic transmission pulse generation circuit, different frequencies can be transmitted depending on the frequency of the input signal Vin. However, when the preceding circuit is composed of the TTL circuit and the drive signal Vin at the TTL level is input to the input terminal IN, the pulse transmission may be performed but the continuous wave transmission may not be performed.

For example, it is assumed that the gate and source cutoff voltages of the FET 11 and FET 12 turn on between the source and drain from around + 3V and -3V. In the case of pulse transmission, the input signal S1 (Vin) 5 shown in FIG.
When V is input, the gate voltage of FET 12 is
As shown in the gate signal S2 of (b), and the voltage between the gate and the source becomes -5V, the transmission signal output terminal OUT
Outputs a transmission signal S3 shown in FIG. 5 (c).

In the case of continuous wave transmission, when the input signal S4 (Vin) 5V shown in FIG. 5 (d) is input, the gate voltage of the FET 12 becomes + as shown by the gate signal S5 in FIG. 5 (e).
It becomes ± 2.5V centering on HV. Therefore, the voltage between the gate and the source is applied only up to 2.5 V, so that the FET 12 is not turned on. Therefore, the transmission signal S7 as shown in FIG. 5 (g) cannot be obtained. That is, the input signal Vin
Depending on the amplitude of, continuous wave transmission is not possible (continuous wave transmission signal is not output).

[0012]

As described above, the LC resonance transmission signal generating circuit shown in FIG. 3 cannot transmit continuous waves at different frequencies. Further, the ultrasonic wave transmission pulse generating circuit shown in FIG. 4 cannot perform continuous wave transmission depending on the voltage of the input level of the input signal Vin.

Therefore, conventionally, a transmission circuit (a pulse transmission circuit 3 and a continuous wave transmission circuit 4) having both of them has been constructed, and the pulse Doppler method and the continuous wave Doppler method can be selectively used by appropriately selecting and using them. However, this has a problem that the structure becomes large and expensive.

In the ultrasonic transmission pulse generation circuit,
Regarding the point that continuous wave transmission is not possible depending on the amplitude of the input signal Vin, the input signal Vin may be sufficiently amplified to a voltage at which the FET can be switched and then input to the ultrasonic transmission pulse generation circuit. There were similar problems.

An object of the present invention is to provide a supersonic ultrasonic tomography apparatus which has a very simple structure (small size) and is inexpensive, is capable of pulse transmission and continuous wave transmission, and is applicable to both the pulse Doppler method and the continuous wave Doppler method. An object is to provide a sound wave transmission pulse generation circuit.

[0016]

SUMMARY OF THE INVENTION The above-mentioned object is to realize the source of one FET in which the drains of a pair of N-channel and P-channel FETs are connected to each other to be led out as a transmission signal output terminal and whose gate is an input terminal. Is grounded, the source of the other FET is connected to the power supply, and a capacitor is connected between the gates of both FETs and the other FET is connected.
In the ultrasonic transmission pulse generating circuit of the ultrasonic tomography apparatus, in which a resistor is connected between the gate and the source of the This is accomplished by connecting a diode across the opposite direction of the polarity of the power supply.

[0017]

The above diode works so as not to exceed + HV voltage. As a result, when a TTL level signal is input,
The gate-source voltage of the other FET becomes a switchable voltage. Therefore, continuous wave transmission can be performed even when the input signal is at the TTL level, and an ultrasonic wave transmission pulse generation circuit applicable to both the pulse Doppler method and the continuous wave Doppler method can be realized extremely easily (small size) and at low cost. become.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an example of a transmission circuit to which an ultrasonic transmission pulse generation circuit of an ultrasonic tomography apparatus according to the present invention is applied. In FIG. 1, IN, OUT, + H
V, 11, 12, C1 and R1 are the same as in FIG.

D1 is a diode connected between both ends of the resistor R1, and is connected in a direction opposite to the polarity of + power source + HV. 14 is a reference signal generating circuit, 15 is T
It is an FET driver (pre-stage circuit) composed of a TL circuit.

Next, the operation will be described. For continuous wave transmission, when the input signal S4 shown in FIG. 5D is input to the input terminal IN, the gate voltage of the FET 12 is as shown in FIG. 5F when the forward drop voltage of the diode D1 is V _D. As shown in the gate signal S6. The gate of the FET 12, the source voltage becomes _{(+ V D) ~ (+} V D -Vin). When the gate and source of the FET 12 are in the ON state at (+ V _D −Vin), the transmission signal S7 shown in FIG. 5 (g) is output to the output terminal OUT.

For example, it is assumed that the gate-source voltages of the FET 11 and the FET 12 start to turn on from around +3 V or more and -3 V or less, respectively. At this time, a continuous wave signal of 5V _PP is input to the input terminal IN and the diode D
When the forward drop voltage of 1 is 0.7V, the gate-source voltage of the FET 12 is +0.7 to -4.3V,
At -4.3V, the FET 12 is turned on. Therefore, the continuous wave signal of + HV _PP (the transmission signal S7 shown in FIG. 5G) is output to the output terminal OUT.

As described above, in the ultrasonic wave transmission pulse generating circuit of the present invention to which the diode D1 is added, it is possible to perform continuous wave transmission with an input signal of TTL level. Also, continuous wave transmission of different frequencies can be performed by changing the frequency of the input signal Vin. Note that pulse transmission is possible as in the conventional circuit.

Further, in the ultrasonic wave transmission pulse generation circuit of the present invention, the + power supply + HV may drop by several volts due to the impedance of the pattern of the substrate constituting the ultrasonic transmission pulse generation circuit. In this case, in the conventional circuit, the gate of the FET 12
The waveform may be deformed by the voltage between the sources. However, if the diode D1 is added as described above, F
Even if the source voltage of the ET12 drops, the gate voltage of the FET12 also drops due to the diode D1. Therefore, the voltage between the gate and source of the FET 12 is + power supply + HV
Is not affected, and the above waveform deformation is prevented.

[0024]

As described above, according to the present invention, a simple and inexpensive structure in which a diode is simply added,
It is possible to always transmit a continuous wave even with an input signal at the TTL level, and therefore, it is possible to provide an ultrasonic wave transmission pulse generating circuit applicable to both the pulse Doppler method and the continuous wave Doppler method at a small size and at a low cost.

In the past, when a pulse was transmitted, the waveform was sometimes deformed due to the impedance of the pattern when the circuit was formed on a substrate, but the circuit of the present invention also has the effect of preventing this.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an example of a transmission circuit to which a circuit of the present invention is applied.

FIG. 2 is a block diagram showing an ultrasonic transmission / reception circuit of an ultrasonic tomography apparatus to which a conventional circuit is applied.

FIG. 3 is a diagram showing an LC resonance transmission signal generation circuit in the continuous wave transmission circuit in FIG.

FIG. 4 is a diagram showing a conventional circuit.

FIG. 5 is a signal waveform diagram for explaining the operation of the ultrasonic transmission pulse generation circuit of the ultrasonic tomography apparatus.

[Explanation of symbols]

IN input terminal OUT output terminal + HV + power supply Vin input signal 11 N-channel type FET 12 P-channel type FET C1 capacitor R1 resistance D1 diode 15 FET driver composed of TTL circuit (pre-stage circuit)

Claims (1)

[Claims] 1. A pair of N-channel and P-channel FETs are connected to each other at their drains to be led out as a transmission signal output terminal, and the source of one FET whose gate is an input terminal is grounded and the other FET is grounded. Is connected to the power source, a capacitor is connected between the gates of both FETs, and a resistor is connected between the gates and sources of the other FETs, and the signal from the preceding circuit is connected to the input terminal. In the ultrasonic transmission pulse generating circuit of the input ultrasonic tomography apparatus, a diode connected in the opposite direction to the polarity of the power source is provided between both ends of the resistance, Sound wave transmission pulse generation circuit.