JPS6036032B2 - Ultrasonic measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultrasonic measuring device that is used for medical, industrial, fishing, etc. purposes and measures various items using ultrasonic waves.

Most of the transmitting pulse generation circuits in conventional ultrasonic measurement equipment use the SC
The voltage was applied to the vibrator in the probe using an electronic switch such as R, thyratron, or transistor.

A summary of these characteristics is that the voltage across the charging/discharging capacitor has a sawtooth waveform. However, this "sawtooth wave type" transmission pulse generation circuit has the following drawbacks. That is, [a} A current source using a relatively high voltage or an equivalent function is required.

{b} If the above current source is realized with a high voltage power supply and high resistance,
Poor energy efficiency.

Moreover, in order to improve this problem, instead of a resistor, several hundred series inductors are required. [c- The impedance seen from the probe of the transmitting pulse generation circuit is low when the pulse is generated, and high when receiving the echo between pulses.Therefore, the way the probe is damped is different when transmitting and receiving waves. Ru.

'd} For the same reason, there is no other way to connect the transmit pulse generation circuit, probe, and receiver input circuits other than to connect them in parallel.

Therefore, it was necessary to connect a limiter in parallel to prevent the transmitted pulse from affecting the receiver. Therefore, the energy of the transmitting pulse is shunted to the receiving coupling circuit and consumed, resulting in poor energy efficiency. Furthermore, if this shunt ratio is reduced, the coupling between the probe and the receiver will not be optimal during echo reception, and reception with a good noise figure will not be possible. (c' If the electronic switch is turned off at the wrong time, it will produce echoes and confusing noises.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and uses a square wave type transmission pulse generation circuit instead of the sawtooth wave type, and generates a pulse with a different polarity for each ultrasonic wave. The purpose is to provide a measuring device.

According to one embodiment of the present invention, echoes with different polarities are received for each shot, so when handling the echoes, only moving targets are displayed (MT1 (MOVINGTA)).
RGETmDICATION) system (September 1960)
(See pages 712 to 715 of the Pulse Technology Handbook published by Nikkan Kogyo Shimbun on March 20th) or a new method can be adopted in configuring a signal processing system using line correlation. That is, as a transmission pulse generation circuit, a square wave voltage source whose polarity or logic level is inverted at each transmission trigger time is used, and this, the probe, and the receiver are connected in series in a circuit. .

Furthermore, if two of the above three terminals are single-wire grounded, both terminals of the other one must be floating, but if necessary, this can be converted to single-wire grounding using a quasi-ideal transformer. In order to prevent or suppress energy from being shunted to the receiver during transmission, an anti-parallel clamping diode may be included in the receiver circuit.

On the other hand, during reception, this diode becomes high impedance, while the square wave source that is a "voltage source" has little loss between the receiver and the probe, and serves as a return path to receive the energy of the received echo under optimal impedance matching conditions. This makes it possible to introduce it into a machine. The present invention will be explained in detail below using the drawings. The figure is a block diagram of an ultrasonic measuring device according to an embodiment of the present invention. In the figure, 0t is, for example, several KHz.
The transmit trigger pulse is provided by a reference oscillator (not shown). This signal t is frequency-divided by the flip-flop 2 and becomes a square wave signal. Furthermore, this square wave signal is, for example, C
The MOS is amplified by a binary logic power amplifier 4 configured by connecting several TTL line drivers in parallel.
The bifilar transformer T is for converting the coupling to the receiver into a single wire ground, but at the time of the transmission pulse, it is short-circuited by the limiter formed by the diodes D and D2.

That is, the respective rising and falling "shocks" of the square wave transmitted through the coupling capacitor C2 are converted into ultrasonic pulses by the probe TD. Therefore, transmission pulses of equal size and opposite polarity are generated at the rising edge and the falling edge. Note that the coupling capacitor C2 is different from a sawtooth wave type charging/discharging capacitor and is only used to block direct current, so it should have a sufficiently large value. On the other hand, when an echo is received, the echo signal is sufficiently weak that the diodes D and D2 do not reach conduction, and the amplifier 4 receives the moment when its output voltage transitions between the positive and negative maximum amplitude values, that is, the transmission pulse. At flat times other than the moment of transmission, that is, during the time period when echoes should be received, capacitor C2
Since a return path is provided through which one end of the bifilar transformer T is equivalently grounded with a sufficiently low high frequency impedance, the echo signal is transmitted toward the receiving amplifier 12 without energy loss.

Here, the purpose is to match the circuit network 14 formed by the resistors R, coils L and L, and the capacitor C, and the probe TD to optimal conditions including the cable.

Further, the circuit 16 formed by the capacitor C3, the resistor R3, and the diodes D3 and D4 is a bifilar transformer T.
This is to further suppress transients during wave transmission on the secondary side of . In addition, in both the positive and negative power supply paths of the amplifier 4, since this becomes the signal return path during reception, capacitors C4 and C5 and coil L4,
L5 provides strict bypass and filtering to prevent interference from the power supply. On the other hand, the gain of the receiving amplifier 12 can be increased when receiving distant echoes by the TGC function generator 18, thereby compensating for soot loss and the inverse square term in the radar equation. are doing. Such a method is well known. The undetected output signal of the receiving amplifier 12 is divided into two parts, one of which is supplied via the delay line 22 and the other directly to an adder 24 and a subtracter 26, respectively. The delay line 22 has a delay time precisely equal to the period of the transmitted pulse, and therefore an echo signal from one period before appears at its output. As mentioned above, since the polarity of the transmitted pulse is reversed each time, the polarity of the echo signal is also reversed, and by adding echo signals that differ by one cycle at the exit of the delay line 22, the fixed echo is canceled. The erased residue represents an echo of an object that has moved during that time, thus resulting in a so-called MTI system. On the other hand, if subtraction is performed, correlated components are particularly emphasized, and an echo signal related to a fixed target is obtained in which uncorrelated noise and the echo of the moving object described above are suppressed. These relationships are completely opposite to those in a system that constantly transmits pulses of the same polarity. The delay line 22 may be made of crystal or quartz glass with a fixed delay time, but may be made of BBD or CC.
It may be of a type that transfers sample values using a lock made of a D-type semiconductor, or it may be a digital memory or a shift register using AD and DA converters.

In the case of a method that is tuned using these clocks, is there a transmission trigger? t the clock for this delay function? If the clock frequency is divided by o, it is effective because a delay of one period can always be obtained without worrying about the mutual time relationship, even if the clock frequency fluctuates somewhat. As explained above, according to the present invention, it is possible to realize an ultrasonic measurement device that has good energy efficiency in both transmission and reception, and therefore has a good noise figure, and requires less irradiated ultrasonic energy to obtain the same receiver output. .

[Brief explanation of the drawing]

The figure is a block diagram of an ultrasonic measuring device according to an embodiment of the present invention, in which TD: Dipstick, T: /Gifira Trans,
4: binary logic power amplifier, 12: receiving amplifier.

Claims (1)

[Scope of Claims] 1. Square wave signal generating means for outputting a square wave signal, pulse generating means for generating pulses of opposite polarity in response to rising and falling edges of the square wave signal, and a pulse generating means for generating pulses of opposite polarity in response to the pulses. a probe that irradiates an ultrasonic pulse to a target area and receives an echo related to the ultrasonic pulse from the target area; a storage unit that stores a signal related to the echo received by the probe; An ultrasonic measuring device comprising calculation means for calculating the sum or difference between a previously stored signal related to the echo and a signal related to a subsequently received echo. 2. The ultrasonic measuring device according to claim 1, wherein the storage means is a delay line.