JPS61120985A - Ultrasonic wave generation circuit - Google Patents

Abstract

PURPOSE:To generate a burst wave fast in the rising and falling with a small pulse length, by feeding a relatively long burst wave generated with a sine wave oscillator to a shaping circuit adapted to gate according to a pulse contained in the pulse period of a shaped pulse. CONSTITUTION:A burst wave with a relatively long pulse length generated with an oscillator at the preceding stage is inputted into a shaping circuit D. Anode of diodes 14 and 16 of a circuit D are biased DC to the zero potential with choke coils 13 and 19 and with the application of a reverse bias, it is turned OFF. The anodes are turned ON with the application of a forward bias as the shaped pulse EP from a terminal 18 enters the pulse period and exceeds V1. Then, as coils 13 and 19 have a high impedance with respect to a high frequency, a burst wave is outputted corresponding to the pulse period of the pulse EP from an output terminal 20. Thus, the diodes switched according to the pulse EP with a small pulse width to obtain a burst wave with a short pulse length.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an ultrasonic generation circuit, for example, an ultrasonic tomographic image display diagnosis I! Suitable for excitation circuits of vibrators in devices using pulsed ultrasonic waves such as Fi devices.

[Technical Background of the Invention] Generally, various methods are known for generating ultrasonic waves, but for example, in an ultrasonic diagnostic apparatus such as an ultrasonic microscope, several MN
Since a frequency of approximately 10 MHz to 10 MHz is required, a vibrator that utilizes a piezoelectric phenomenon is used.

Ultrasonic diagnostic equipment that uses such sensors may need to generate continuous waves, such as in diagnosis using the Doppler method, but in many cases, it is necessary to generate continuous waves to the target area, which is called the pulse-echo method. A method of emitting ultrasonic waves and detecting the reflected waves is used.

Therefore, the ultrasonic generation circuit that excites the camera element is
For reasons to be described later, an ideal burst signal is required that contains only a few H2 minutes of the signal of the used frequency and that no unnecessary signals are mixed into the no-signal period between the signal periods. Therefore,
Conventional ultrasonic generation circuits obtain desired pulsed ultrasonic waves by successively generating a plurality of single pulses with extremely short widths.

(Problems with the Background Art) However, in view of the need for higher resolution, the method of generating a single pulse as described above has problems with high speed and high output.

Therefore, in order to solve this problem, a method of intermittent continuous waves can be considered. As a configuration based on such a method, for example, there is a configuration in which a sine wave oscillator that generates a sine wave and an electronic switch composed of an analog switch, a diode, etc. are connected in series. According to such a configuration, the sine wave generated by the sine wave oscillator is switched by the electronic switch, and is output only when the electronic switch is in the on state. Therefore, it is considered that a short pulse-like excitation signal can be obtained by controlling the electronic switch at high speed. However, in reality, leakage occurs from the input side even when the electronic switch is in the OFF state, so that in the output waveform, signal components leak and remain in all regions other than the burst period. Such a method is effective when detecting only signals on the surface of a subject with an ultrasound microscope, but it is not effective when extracting signals inside the subject or displaying tomographic images on an ultrasound tomography device. Since the intensity of the reflected signal from the deep part of the object is weak, the received signal is buried in the leaked signal, making it impossible to detect the information in that part.

Further, a circuit is known that controls the oscillation conditions (operation) of an oscillation circuit to obtain a burst-like output. FIG. 3 is a circuit diagram showing an example of the basic configuration of this type of circuit. In the figure, symbol A is a tuning circuit, 1 is an amplification transistor, and B is a tuning circuit.
is a bias resistor, C is an electronic switch, and tuning circuit A
A part of the circuit constitutes the emitter feedback circuit of the transistor 1, which is a positive recirculation sine wave oscillation circuit. The output is taken out from the emitter, and an electronic switch C connected to the emitter is controlled on/off by a control pulse ■ρ.

According to the above configuration, by turning on the electronic switch C with the control pulse ■ρ, the oscillation condition based on the emitter positive feedback effect is satisfied and the circuit oscillates. On the other hand, when the electronic switch C is turned off, the oscillation stops.

Therefore, as shown in FIG. 4, the output waveform of this circuit provides a sine output at a specified level during the pulse period T1 of the control pulse Vρ, and exhibits rising and falling levels before and after that. However, as is clear from the same waveform diagram, in this circuit, the rise and fall of the burst wave are blunted, and there is a lower limit to the duration of oscillation, so it is particularly unsuitable for ultrasonic tomography equipment, and it is continuous. Similar to the intermittent wave switching method, this method has the disadvantage of degraded distance resolution.

[Objective of the Invention 1 The object of the present invention is to use extremely short ultrasonic waves without requiring rise and fall times in order to obtain sufficient distance resolution in an ultrasonic tomographic image display diagnostic apparatus that requires pulsed ultrasonic waves. The object of the present invention is to provide an ultrasonic generation circuit that can generate ultrasonic waves.

[Summary of the Invention] In order to achieve the above object, the present invention controls oscillation by a certain sine wave oscillator with a first control pulse to allow a relatively long burst wave to be output. Next, this output is applied to the second control pulse included in the pulse period of the first control pulse.
It is passed through a shaping circuit that gates based on pulses.

[Embodiments of the invention] Hereinafter, the present invention will be described with reference to illustrated embodiments.

FIG. 1 is a circuit diagram showing an embodiment of an ultrasonic generation circuit according to the present invention, and FIG. 2 is a waveform diagram showing signal waveforms obtained by the present invention.

This embodiment shows the emitter feedback type circuit shown in FIG. 3 in more detail, and furthermore, a shaping circuit is provided at the subsequent stage. In the same figure, the same parts as in FIG. Connected via. Further, the collector of the transistor 1 is applied with a voltage source Vcc via a high frequency choke coil 6, and has a capacitor 8 between it and ground, while a voltage source ■ is connected to its base via a resistor 7. Ru. The intersection of the capacitors 3 and 4 of the tuning circuit A is connected to the emitter of the transistor 1 and connected to the electronic switch C via the high frequency choke 9.
It is connected to the collector of the transistor 11 constituting the circuit.

The emitter of this transistor 11 is grounded, and a control pulse ρ is applied to the base from a terminal 10. Incidentally, in the tuned circuit A, the intersection of the coil 2 and the capacitor 4 is grounded.

Next, the output from the emitter of the transistor 1 is supplied to a shaping circuit via a coupling capacitor 12. However, a high frequency choke 13 is connected between the input side of the shaping circuit and ground. The shaping circuit is a coupling capacitor 1
2, a second diode 15 having one end connected to the ground point, and a third diode 16 having one end connected to the output side of the circuit. , 15 and 16 are both connected at one point, and a terminal 18 is connected to the connection point P via a resistor 17.
is connected. This terminal 18 has a control pulse ■ρ
A shaping pulse Eρ, which is a shorter pulse and is included within the pulse period of the pulse Vp, is supplied. This pulse E
ρ is the first. It is a pulse that exceeds the level V1 that turns on the third diode 14, 16 and turns off the second diode 15, for example, becomes negative. Note that one high-frequency choke is connected to one end of the third diode 16, that is, the output end 20, between it and ground.

The operation of the ultrasonic generation circuit having the above configuration will be explained with reference to FIGS. 2 and 4.

The relatively long burst wave shown in FIG. 4 generated by the emitter feedback tuning excavator in the previous stage is caused by the coupling capacitor
After the DC component is removed by step 2, the signal is input to the next stage shaping circuit. Since the shaping pulse Eρ that crosses the level ■1 is input from the terminal 18 of this circuit, during the period when this pulse Ep does not exceed ■1 (outside the pulse period), the first and third diodes are One end of 14.16 is DC biased to zero potential by choke coil 13.19. Therefore, the first. A reverse bias is applied to the third diodes 14 and 16, and the third diodes 14 and 16 are turned off. Also,
Since the second diode 15 is biased in the forward direction, no burst wave can be obtained as an output. Conversely, when the shaping pulse Ep input from the terminal 18 becomes negative (pulse period) and exceeds the ■ level, the first. Third diode 14
and 16, the forward bias is briefly turned on. Also, since the third diode 15 is reverse biased,
The diode 15 is turned off.

Furthermore, since the high frequency choke coil 13 and the first one have sufficiently high impedance to high frequencies, the output terminal 2
0, a burst wave corresponding to the pulse period of the shaped pulse Ep is output. Therefore, each diode 14=15. By switching j6, a burst wave $1 with a fast rise and short pulse length can be obtained. Actually, the above 1. Since there is leakage from the oscillator even when the third diodes 14 and 16 are in the off state, leakage components 82 and 82 remain near the resulting burst wave, as shown in FIG. However, the reflected waves detected near the burst wave are reflected waves from something that is close to the vibrator.
Since it is usually detected as a strong reflected wave, the influence of the leakage component S2 is small.

Note that the circuit of the present invention is not limited to one that excites a piezoelectric vibrator.

[Effects of the Invention] As explained above, according to the present invention, it is possible to generate a burst wave with a high frequency, a fast rise, and a short pulse length, and by exciting an ultrasonic transducer with this burst wave, excellent results can be obtained. The present invention contributes to the provision of an ultrasonic tomographic image display device that has excellent distance resolution and can display tomographic images of minute structures and tissues that were conventionally considered impossible to resolve.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the ultrasonic generation circuit according to the present invention, FIG. 2 is a waveform diagram showing the output waveform of an excitation signal obtained by the same circuit, and FIG. FIG. 4 is a principle circuit diagram showing an example of a related oscillator, and FIG. 4 is a waveform diagram showing the output waveform obtained by FIG. 3. 1.11... Transistor 2... Tuning coil 3.4... Tuning capacitor 6.9.13.19... High frequency choke coil 7.1
7... Resistor 10.18... Terminal 12... Coupling capacitor 14.15.16... Diode 20... Output terminal ■ρ... Control pulse Eρ... Shaping pulse Figure 1 Fig. 2 Fig. 3 1-T, -1 Voluntary writing of Procedure Neho Sho 1) October 1985 188 1. Indication of the case 1988 Patent Application No. 242975
No. 2, Title of the invention Ultrasonic generation circuit 3, Relationship with the case of the person making the amendment Representative of the patent applicant Satoshi Shimoyama Department 6, Subject of the amendment Detailed explanation of the invention column 7 in the specification ≧ 7, Amendment Contents As shown in the attached document 1, "Ultrasonic microscope, etc." in the first line of the second page of the Memorandum is deleted. 2. Delete "There is a Doppler method..." in the 6th and 7th lines of the second page of Akira Il@. 3. Delete "Therefore, it is requested." from lines 10 to 14 on the second page of the statement. 4゜In the second line of page 5 of the specification, the phrase [...as is clear from the figure...] will be corrected to [...as shown in the figure...]. 5. In the 14th line of the 6th page of the specification, [...VC
Correct the statement "C is applied..." to "...Vcc is connected...". 6. In the 9th line of the 7th page of the clear book, the phrase "... has one end..." has been replaced with "... has an anode..."
” will be corrected. 7. In the 10th line of page 7 of the specification, the statement "...one end..." should be corrected to "the cathode...". 8. In the 11th line of page 7 of the specification, the statement ``One end is on...'' will be corrected to ``The anode is on...''. 9. In the first and second lines of page 8 of the specification, “
``...one end...'' is replaced with ``...anode...''
” will be corrected. 10. In the 8th page of the specification, from the 9th line to the 15th line, [This circuit...is biased]. therefore,·
``...'' is [No. 1. The anode of the third diode 14.16 is DC biased to zero potential by the choke coil 13.19, so...] is corrected. 11. Delete "However, there is no limitation..." in the first and second lines of page 10 of the statement.

Claims (1)

[Claims] An ultrasonic generation circuit that excites a transducer by generating pulsed ultrasonic waves, which includes an oscillation section that generates a predetermined frequency, and an oscillation operation of the oscillation section based on a first pulse of a predetermined width during the pulse period. A control unit that controls the oscillation state; and a signal from the oscillation unit is supplied, and gates this signal based on a second pulse included in the pulse period to generate a burst shorter than the first pulse period. An ultrasonic generation circuit comprising a shaping section that shapes signals.