阅读说明：本技术 一种超声波接收电路 (Ultrasonic receiving circuit ) 是由 高强 高云飞 李栋 宋雨 毛泽民 于 2021-09-14 设计创作，主要内容包括：本发明涉及一种超声波接收电路,包括：滤波放大电路、整流电路和波形变换电路；滤波放大电路,用于接受超声波回波信号,并将其进行滤波和放大生成滤波放大后的超声波回波信号；整流电路,用于对滤波放大后的超声波回波信号进行整流生成尖脉冲超声波回波信号；波形变换电路,用于将尖脉冲超声波回波信号变换成方脉冲信号,并将方脉冲信号传输到超声波采集装置。本发明通过利用滤波放大电路、整流电路和波形变换电路对超声波回波信号进行滤波、放大、整流后变换成方脉冲信号,并将其传输到超声波采集装置,可以将原超声波回波信号变换成便于被超声波采集装置识别捕捉的方脉冲信号,大大提高超声波收发系统的灵敏度。(The present invention relates to an ultrasonic receiving circuit, comprising: the filter amplifier circuit, the rectifier circuit and the waveform conversion circuit; the filtering and amplifying circuit is used for receiving the ultrasonic echo signal, filtering and amplifying the ultrasonic echo signal to generate a filtered and amplified ultrasonic echo signal; the rectification circuit is used for rectifying the filtered and amplified ultrasonic echo signal to generate a sharp pulse ultrasonic echo signal; and the waveform conversion circuit is used for converting the sharp pulse ultrasonic echo signal into a square pulse signal and transmitting the square pulse signal to the ultrasonic acquisition device. The ultrasonic wave receiving and transmitting system utilizes the filtering amplifying circuit, the rectifying circuit and the waveform converting circuit to filter, amplify and rectify the ultrasonic wave echo signals and then convert the ultrasonic wave echo signals into square pulse signals, and transmits the square pulse signals to the ultrasonic wave collecting device, so that the original ultrasonic wave echo signals can be converted into the square pulse signals which are conveniently identified and captured by the ultrasonic wave collecting device, and the sensitivity of the ultrasonic wave receiving and transmitting system is greatly improved.)

1. An ultrasonic receiving circuit, comprising:

the filtering and amplifying circuit is used for receiving the ultrasonic echo signal, filtering and amplifying the ultrasonic echo signal and generating a filtered and amplified ultrasonic echo signal;

the rectifying circuit is connected with the filtering and amplifying circuit and is used for rectifying the ultrasonic echo signals after filtering and amplifying to generate sharp pulse ultrasonic echo signals;

and the waveform conversion circuit is respectively connected with the rectification circuit and the ultrasonic acquisition device and is used for converting the sharp pulse ultrasonic echo signal into a square pulse signal and transmitting the square pulse signal to the ultrasonic acquisition device.

2. The ultrasonic receiving circuit according to claim 1, wherein the filter amplifying circuit comprises:

the first-order filtering and amplifying circuit is connected with the ultrasonic probe through an aviation plug and is used for receiving the ultrasonic echo signal and performing first-order filtering and amplifying on the ultrasonic echo signal to generate a first-order filtering and amplifying ultrasonic echo signal;

the second-order filtering and amplifying circuit is connected with the first-order filtering and amplifying circuit and is used for performing second-order filtering and amplifying on the ultrasonic echo signal subjected to the first-order filtering and amplifying to generate a second-order filtering and amplifying ultrasonic echo signal;

and the third-order filtering and amplifying circuit is connected with the second-order filtering and amplifying circuit and is used for carrying out third-order filtering and amplifying on the ultrasonic echo signal after the second-order filtering and amplifying to generate the ultrasonic echo signal after the filtering and amplifying.

3. An ultrasonic receiving circuit according to claim 2, wherein the first-order filter amplifying circuit comprises: the current feedback amplifier comprises a first capacitor, a fifth capacitor, a sixth capacitor, a first resistor, a second resistor, a first adjustable resistor and a current feedback amplifier;

a second pin of the current feedback amplifier is connected with one end of the second resistor and one end of the first adjustable resistor respectively, a third pin of the current feedback amplifier is connected with one end of the first capacitor and one end of the first resistor respectively, a fourth pin of the current feedback amplifier is connected with one end of the fifth capacitor, a sixth pin of the current feedback amplifier is connected with the other end of the first adjustable resistor, and a seventh pin of the current feedback amplifier is connected with one end of the sixth capacitor;

the other end of the first resistor, the other end of the second resistor, the other end of the fifth capacitor and the other end of the sixth capacitor are all grounded;

the other end of the first capacitor is connected with the aviation plug.

4. An ultrasonic receiving circuit according to claim 3, wherein the current feedback amplifier is of type AD 811.

5. An ultrasonic receiving circuit according to claim 1, wherein the rectifying circuit comprises: the circuit comprises a fourth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a seventh resistor, a second adjustable resistor, a third adjustable resistor, a first diode, a second diode and a feedback amplifier;

a second pin of the feedback amplifier is connected with one end of the seventh resistor, one end of the second adjustable resistor and an anode of the first diode respectively, a third pin of the feedback amplifier is grounded, a fourth pin of the feedback amplifier is connected with one end of the eleventh capacitor, a sixth pin of the feedback amplifier is connected with a cathode of the first diode and an anode of the second diode respectively, and a seventh pin of the feedback amplifier is connected with one end of the twelfth capacitor;

one end of the fourth capacitor is connected with the output end of the filtering amplification circuit, and the other end of the fourth capacitor is connected with the other end of the seventh resistor;

the cathode of the second diode, one end of the thirteenth capacitor and one end of the third adjustable resistor are connected with the other end of the second adjustable resistor;

the other end of the eleventh capacitor, the other end of the twelfth capacitor, one end of the thirteenth capacitor and the other end of the third adjustable resistor are all grounded.

6. An ultrasonic receiving circuit according to claim 5, wherein the feedback amplifier is of type LM 7171.

7. An ultrasonic receiving circuit according to claim 1, wherein the waveform converting circuit comprises: the circuit comprises a monostable trigger, a fourteenth capacitor, a fourth adjustable resistor, a fifth adjustable resistor and a voltage regulator tube;

a fifth pin of the monostable trigger is connected with an output end of the rectifying circuit, a third pin, a fourth pin and a seventh pin of the monostable trigger are all grounded, a sixth pin of the monostable trigger is connected with one end of the fifth adjustable resistor, a ninth pin of the monostable trigger is connected with one end of the fourth adjustable resistor, a tenth pin of the monostable trigger is connected with one end of the fourteenth capacitor, an eleventh pin of the monostable trigger is connected with the other end of the fourteenth capacitor, and a fourteenth pin of the monostable trigger is connected with the other end of the fourth adjustable resistor;

the other end of the fifth adjustable resistor is connected with one end of the voltage stabilizing tube, and the other end of the voltage stabilizing tube is grounded.

8. An ultrasound receiving circuit according to claim 7, wherein the monostable flip-flop is model number 74121.

Technical Field

The invention relates to the technical field of ultrasonic waves, in particular to an ultrasonic receiving circuit.

Background

In the ultrasonic transmission/reception system, the ultrasonic probe receives ultrasonic waves (mechanical vibration waves) and converts the waves into electric signals by using the piezoelectric effect of a piezoelectric material. When the dielectric medium is deformed by an external force in a certain direction, polarization occurs in the dielectric medium, and charges of opposite polarities occur on two opposite surfaces of the dielectric medium. Most of existing ultrasonic wave transceiving systems on the market are constructed based on piezoelectric materials, and due to the fact that the energy of reflected echoes is very small, converted alternating current signals are also very weak, usually in the milliampere level, and whether the echoes exist in subsequent processing equipment is not facilitated. Therefore, the conventional ultrasonic wave transmission/reception system has a disadvantage of low echo reception sensitivity. And the existing ultrasonic receiving circuit is too redundant and complex, and the product developed according to the ultrasonic receiving circuit is too large in size, too heavy in weight and very inconvenient in actual use.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide an ultrasonic receiving circuit to improve the sensitivity of an ultrasonic receiving and transmitting system.

In order to achieve the purpose, the invention provides the following scheme:

an ultrasonic receiving circuit comprising:

the filtering and amplifying circuit is used for receiving the ultrasonic echo signal, filtering and amplifying the ultrasonic echo signal and generating a filtered and amplified ultrasonic echo signal;

the rectifying circuit is connected with the filtering and amplifying circuit and is used for rectifying the ultrasonic echo signals after filtering and amplifying to generate sharp pulse ultrasonic echo signals;

and the waveform conversion circuit is respectively connected with the rectification circuit and the ultrasonic acquisition device and is used for converting the sharp pulse ultrasonic echo signal into a square pulse signal and transmitting the square pulse signal to the ultrasonic acquisition device.

Preferably, the filtering and amplifying circuit includes:

the first-order filtering and amplifying circuit is connected with the ultrasonic probe through an aviation plug and is used for receiving the ultrasonic echo signal and performing first-order filtering and amplifying on the ultrasonic echo signal to generate a first-order filtering and amplifying ultrasonic echo signal;

the second-order filtering and amplifying circuit is connected with the first-order filtering and amplifying circuit and is used for performing second-order filtering and amplifying on the ultrasonic echo signal subjected to the first-order filtering and amplifying to generate a second-order filtering and amplifying ultrasonic echo signal;

and the third-order filtering and amplifying circuit is connected with the second-order filtering and amplifying circuit and is used for carrying out third-order filtering and amplifying on the ultrasonic echo signal after the second-order filtering and amplifying to generate the ultrasonic echo signal after the filtering and amplifying.

Preferably, the first-order filtering and amplifying circuit includes: the current feedback amplifier comprises a first capacitor, a fifth capacitor, a sixth capacitor, a first resistor, a second resistor, a first adjustable resistor and a current feedback amplifier;

a second pin of the current feedback amplifier is connected with one end of the second resistor and one end of the first adjustable resistor respectively, a third pin of the current feedback amplifier is connected with one end of the first capacitor and one end of the first resistor respectively, a fourth pin of the current feedback amplifier is connected with one end of the fifth capacitor, a sixth pin of the current feedback amplifier is connected with the other end of the first adjustable resistor, and a seventh pin of the current feedback amplifier is connected with one end of the sixth capacitor;

the other end of the first resistor, the other end of the second resistor, the other end of the fifth capacitor and the other end of the sixth capacitor are all grounded;

the other end of the first capacitor is connected with the aviation plug.

Preferably, the model of the current feedback amplifier is AD 811.

Preferably, the rectifier circuit includes: the circuit comprises a fourth capacitor, an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a seventh resistor, a second adjustable resistor, a third adjustable resistor, a first diode, a second diode and a feedback amplifier;

a second pin of the feedback amplifier is connected with one end of the seventh resistor, one end of the second adjustable resistor and an anode of the first diode respectively, a third pin of the feedback amplifier is grounded, a fourth pin of the feedback amplifier is connected with one end of the eleventh capacitor, a sixth pin of the feedback amplifier is connected with a cathode of the first diode and an anode of the second diode respectively, and a seventh pin of the feedback amplifier is connected with one end of the twelfth capacitor;

one end of the fourth capacitor is connected with the output end of the filtering amplification circuit, and the other end of the fourth capacitor is connected with the other end of the seventh resistor;

the cathode of the second diode, one end of the thirteenth capacitor and one end of the third adjustable resistor are connected with the other end of the second adjustable resistor;

the other end of the eleventh capacitor, the other end of the twelfth capacitor, one end of the thirteenth capacitor and the other end of the third adjustable resistor are all grounded.

Preferably, the feedback amplifier is LM 7171.

Preferably, the waveform conversion circuit includes: the circuit comprises a monostable trigger, a fourteenth capacitor, a fourth adjustable resistor, a fifth adjustable resistor and a voltage regulator tube;

a fifth pin of the monostable trigger is connected with an output end of the rectifying circuit, a third pin, a fourth pin and a seventh pin of the monostable trigger are all grounded, a sixth pin of the monostable trigger is connected with one end of the fifth adjustable resistor, a ninth pin of the monostable trigger is connected with one end of the fourth adjustable resistor, a tenth pin of the monostable trigger is connected with one end of the fourteenth capacitor, an eleventh pin of the monostable trigger is connected with the other end of the fourteenth capacitor, and a fourteenth pin of the monostable trigger is connected with the other end of the fourth adjustable resistor;

the other end of the fifth adjustable resistor is connected with one end of the voltage stabilizing tube, and the other end of the voltage stabilizing tube is grounded.

Preferably, the type of the monostable flip-flop is 74121.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention provides an ultrasonic receiving circuit, which can convert an ultrasonic echo signal into a square pulse signal after filtering, amplifying and rectifying by using a filtering and amplifying circuit, a rectifying circuit and a waveform converting circuit, and transmit the square pulse signal to an ultrasonic acquisition device, so that the original ultrasonic echo signal can be converted into the square pulse signal which is convenient to be identified and captured by the ultrasonic acquisition device, and the sensitivity of an ultrasonic receiving and transmitting system is greatly improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

Fig. 1 is a circuit diagram of an ultrasonic receiving circuit in an embodiment provided in the present invention.

Fig. 2 is a first-order filtering amplifying circuit diagram in the embodiment of the invention.

Fig. 3 is a rectification circuit diagram in an embodiment provided by the present invention.

Fig. 4 is a diagram of a waveform conversion circuit according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide an ultrasonic receiving circuit to improve the sensitivity of an ultrasonic receiving and transmitting system.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

Fig. 1 is a circuit diagram of an ultrasonic receiving circuit in an embodiment of the present invention, and as shown in fig. 1, an ultrasonic receiving circuit includes: a filter amplifying circuit, a rectifying circuit and a waveform converting circuit. The filtering and amplifying circuit is used for receiving the ultrasonic echo signal, filtering and amplifying the ultrasonic echo signal and generating a filtered and amplified ultrasonic echo signal; the rectifying circuit is connected with the filtering and amplifying circuit and is used for rectifying the ultrasonic echo signals after filtering and amplifying to generate sharp pulse ultrasonic echo signals; and the waveform conversion circuit is respectively connected with the rectification circuit and the ultrasonic acquisition device and is used for converting the sharp pulse ultrasonic echo signal into a square pulse signal and transmitting the square pulse signal to the ultrasonic acquisition device.

The ultrasonic receiving circuit in the invention mainly comprises three parts: the first is a filter amplifying circuit, the second is a rectifying circuit, and the third is a waveform converting circuit.

1. And the filtering and amplifying circuit is used for carrying out multi-stage filtering and amplifying on the received weak echo signal and outputting an attenuation oscillating wave pattern which can be identified by the acquisition device and has no clutter interference. The filter amplifying circuit comprises the following components:

an aviation plug receive is connected with a capacitor C1 in series and then connected with the 3 rd pin of the U6 of the AD811 chip, and is grounded through a resistor R1; the 2 nd pin of the AD811 chip U6 is connected with the resistor R2 and grounded; the 2 nd pin of the AD811 chip U6 is connected with an adjustable resistor First, then connected with a capacitor C2 and then connected to the 3 rd pin of the AD811 chip U7; the 6 th pin of the AD811 chip U6 is connected with the capacitor C2, then is connected to the 3 rd pin of the AD811 chip U7, and is grounded through the resistor R3; the 4 th pin of the AD811 chip U6 is connected to ground through a capacitor C5; the 7 th pin of the AD811 chip U6 is connected to ground through a capacitor C6.

The 2 nd pin of the AD811 chip U7 is connected with the resistor R4 and grounded; the 2 nd pin of the AD811 chip U7 is connected with an adjustable resistor Second, then is connected with a capacitor C3 and then is connected to the 3 rd pin of the AD811 chip U8; the 6 th pin of the AD811 chip U7 is connected with the capacitor C3, then is connected to the 3 rd pin of the AD811 chip U8, and is grounded through the resistor R5; the No. 4 pin of the AD811 chip U7 is connected with the ground through a capacitor C7; the No. 7 pin of the AD811 chip U7 is connected to ground through a capacitor C8.

The 2 nd pin of the AD811 chip U8 is connected with the resistor R6 and grounded; the 2 nd pin of the AD811 chip U8 is connected with an adjustable resistor Third, then is connected with the 6 th pin, a capacitor C4 and a resistor R7, and then is connected to the 2 nd pin of the LM7171 chip; the 4 th pin of the AD811 chip U8 is connected to ground through a capacitor C9; the 7 th pin of the AD811 chip U8 is connected to ground through a capacitor C10.

2. A rectifier circuit: the negative voltage is eliminated, the input signal is adjusted to be sharp pulse, and the value of the slide rheostat is changed to adjust the output amplitude. Wherein, the rectifier circuit is as follows:

the No. 2 pin of the LM7171 chip U9 is connected with the anode of a diode D1, then connected with the anode of a diode D2 and simultaneously connected with the No. 5 pin of a 74121 chip U10 through an adjustable resistor RP 7171; after the No. 6 pin of the LM7171 chip U9 is connected with the anode of the diode D2, the adjustable resistor RP is connected with the No. 5 pin of the 74121 chip U10 through the capacitor C13; the capacitor C11 of the 4 th pin of the U9 of the LM7171 chip is connected with the ground; the LM7171 chip U9 pin 7 capacitor C12 is grounded after being connected.

3. The waveform conversion circuit uses the rectified signal as a trigger pulse, and utilizes a multivibrator to generate a standard square pulse with a certain pulse width, so that the standard square pulse is conveniently identified and captured by an acquisition device. The waveform conversion circuit comprises the following components:

74121 chip U10 No. 3, 4, 7 pins are grounded after being connected; 74121 chip U10 pin 10 is connected with capacitor C14 and then connected with pin 11; 74121 chip U10 the 14 th pin is connected with the 9 th pin through adjustable resistance RP 6; the 6 th pin of the U10 of the 74121 chip is connected with an adjustable resistor RP3V 3.

The ultrasonic receiving circuit of the present invention is further described below with reference to specific embodiments:

the filter amplifying circuit of the invention comprises: the circuit comprises a first-order filtering amplifying circuit, a second-order filtering amplifying circuit and a third-order filtering amplifying circuit.

The first-order filtering and amplifying circuit is connected with the ultrasonic probe through an aviation plug and is used for receiving the ultrasonic echo signal and performing first-order filtering and amplifying on the ultrasonic echo signal to generate a first-order filtering and amplifying ultrasonic echo signal; the second-order filtering and amplifying circuit is connected with the first-order filtering and amplifying circuit and is used for performing second-order filtering and amplifying on the ultrasonic echo signal subjected to the first-order filtering and amplifying to generate a second-order filtering and amplifying ultrasonic echo signal; and the third-order filtering and amplifying circuit is connected with the second-order filtering and amplifying circuit and is used for carrying out third-order filtering and amplifying on the ultrasonic echo signal after the second-order filtering and amplifying to generate the ultrasonic echo signal after the filtering and amplifying.

In the invention, after the ultrasonic echo signal is processed by the first-order filtering and amplifying circuit, the extremely weak interference signal which is not filtered can be amplified, and the interference signal can be found and eliminated by the second-order and third-order filtering circuits. The invention adopts the cross arrangement of three filter amplifying circuits, can amplify the ultrasonic echo signal to 2-3V, and simultaneously filters out the interference signal, so that the interference signal does not influence the subsequent signal processing any more.

FIG. 2 is a first-order filtering amplifier circuit according to an embodiment of the present invention. As shown in fig. 2, the first-order filtering and amplifying circuit includes: the circuit comprises a First capacitor C1, a fifth capacitor C5, a sixth capacitor C6, a First resistor R1, a second resistor R2, a First adjustable resistor First and a current feedback amplifier;

a second pin of the current feedback amplifier is connected with one end of the second resistor R2 and one end of the First adjustable resistor First, a third pin of the current feedback amplifier is connected with one end of the First capacitor C1 and one end of the First resistor R1, a fourth pin of the current feedback amplifier is connected with one end of the fifth capacitor C5, a sixth pin of the current feedback amplifier is connected with the other end of the First adjustable resistor First, and a seventh pin of the current feedback amplifier is connected with one end of the sixth capacitor C6; the other end of the first resistor R1, the other end of the second resistor R2, the other end of the fifth capacitor C5 and the other end of the sixth capacitor C6 are all grounded; the other end of the first capacitor C1 is connected with the aviation plug. The current feedback amplifier in the present invention is model AD 811. The fourth pin and the seventh pin of the AD811 chip are used for being connected with a power supply module to supply power.

In the embodiment of the invention, the first capacitor C1 and the first resistor R1 form a high-pass filter circuit. The AD811 chip U6, the second resistor R2, the fifth capacitor C5, the sixth capacitor C6 and the First adjustable resistor First form a gain amplifying circuit. The invention can reduce noise and amplify the ultrasonic signals through the high-pass filter circuit and the gain amplifying circuit, and can highlight the characteristic waveform in the ultrasonic signals. The principle of the first-order filtering amplification circuit is as follows:

the aviation plug receive is connected with an ultrasonic probe to receive ultrasonic echo signals, the ultrasonic echo signals firstly enter a high-pass filter circuit consisting of a capacitor C1 and a resistor R1 to be filtered, low-frequency noise signal interference in the signals is removed, then the ultrasonic echo signals enter an AD811 chip U6 to be subjected to gain amplification, the resistor R2 is used for adjusting the amplification gain of the AD811 chip, an adjustable resistor First is used for adjusting the amplification bandwidth of the AD811 chip, and the adjusted signals are output to a next-stage filter amplification circuit from a 6 th pin of the AD811 chip U6. The capacitors C6 and C5 in the invention play a role of voltage stabilization.

It should be noted that the second-order filtering and amplifying circuit and the third-order filtering and amplifying circuit in the present invention are the same as the first-order filtering and amplifying circuit in the present invention in structure and principle, and therefore, the details thereof are not repeated.

FIG. 3 is a rectifier circuit diagram in an embodiment of the present invention. As shown in fig. 3, the rectifier circuit includes: a fourth capacitor C4, an eleventh capacitor C11, a twelfth capacitor C12, a thirteenth capacitor C13, a seventh resistor R7, a second adjustable resistor RP7171, a third adjustable resistor RP-output, a first diode D1, a second diode D2 and a feedback amplifier;

a second pin of the feedback amplifier is respectively connected with one end of the seventh resistor R7, one end of the second adjustable resistor RP7171 and an anode of the first diode D1, a third pin of the feedback amplifier is grounded, a fourth pin of the feedback amplifier is connected with one end of the eleventh capacitor C11, a sixth pin of the feedback amplifier is respectively connected with a cathode of the first diode D1 and an anode of the second diode D2, and a seventh pin of the feedback amplifier is connected with one end of the twelfth capacitor C12; one end of the fourth capacitor C4 is connected to the output end of the filter amplifying circuit, and the other end of the fourth capacitor C4 is connected to the other end of the seventh resistor R7; a cathode of the second diode D2, one end of the thirteenth capacitor C13, and one end of the third adjustable resistor RP-output are all connected to the other end of the second adjustable resistor RP 7171; the other end of the eleventh capacitor C11, the other end of the twelfth capacitor C12, one end of the thirteenth capacitor C13 and the other end of the third adjustable resistor RP-output are all grounded. In the present invention, the feedback amplifier is model LM 7171.

The principle of the rectifier circuit of the present invention is described below with reference to fig. 3 of the present invention:

the capacitor C4, the resistor R7, the LM7171 chip U9, the capacitor C11, the capacitor C12, the adjustable resistor RP7171, the capacitor C13 and the adjustable resistor RP-output form a half-wave rectification circuit, the capacitor C4 is connected with the resistor R7 in series to attenuate low-frequency signals, which is equivalent to further removing low-frequency signal interference, and then the low-frequency signals enter a No. 2 pin of the LM7171 chip of the feedback amplifier, when an input signal is positive, the D1 is connected, the D2 is disconnected, the circuit is equivalent to a voltage follower, and the output is equal to the input; when the input signal is negative, D1 is turned off, D2 is turned on, the circuit is equivalent to an inverter, the signal is inverted to be output, the signal with the voltage below 0v is removed, only a positive voltage signal is reserved, subsequent processing is facilitated, the resistor RP7171 is used for adjusting the gain of the LM7171, and the resistor C13 is connected with the adjustable resistor RP-output in parallel, so that low-frequency signals are difficult to pass through, high-frequency signals are easy to pass through, and low-frequency noise in the signal is further filtered.

The invention can realize further adjustment of the amplified signal by utilizing the LM7171 and the adjustable resistor in the peripheral circuit. After LM7171, the negative voltage below 0V is removed, and its gain is changed by adjusting RP4, RP5 is used for current limiting. The purpose of this process is to adjust the amplitude to a suitable state so that the received signal meets the triggering requirements for waveform conversion. The minimum requirement of the common mode rejection ratio of the voltage feedback amplifier selected by the invention is 80dB, and the maximum value of the output current is 100 mA. And D1 and D2 are preferably rectifier diodes, model 1N 4148.

Fig. 4 is a diagram of a waveform conversion circuit according to an embodiment of the present invention. As shown in fig. 4, in the embodiment of the present invention, the waveform converting circuit includes: the circuit comprises a monostable trigger, a fourteenth capacitor C14, a fourth adjustable resistor RP6, a fifth adjustable resistor RP3V3 and a voltage regulator tube D3;

a fifth pin of the monostable trigger is connected with an output end of the rectifying circuit, a third pin, a fourth pin and a seventh pin of the monostable trigger are all grounded, a sixth pin of the monostable trigger is connected with one end of a fifth adjustable resistor RP3V3, a ninth pin of the monostable trigger is connected with one end of a fourth adjustable resistor RP6, a tenth pin of the monostable trigger is connected with one end of a fourteenth capacitor C14, an eleventh pin of the monostable trigger is connected with the other end of the fourteenth capacitor C14, and a fourteenth pin of the monostable trigger is connected with the other end of the fourth adjustable resistor RP 6; the other end of the fifth adjustable resistor RP3V3 is connected with one end of the voltage regulator tube D3, and the other end of the voltage regulator tube D3 is grounded.

The principle of the waveform conversion circuit of the present invention is described below with reference to fig. 4 of the present invention:

74121 chip U10, electric capacity C10, adjustable resistance RP6, adjustable resistance 3v3, stabilivolt D3 constitute monostable trigger circuit. The signal processed by the rectifying circuit enters a 5 th pin of an 74121 chip, when a 74121 chip detects that an input signal has a rising edge, a trigger signal is generated, a standard square wave pulse signal is output to be convenient for subsequent processing, the width of the signal is determined by RP6 and a capacitor C14 (the pulse width of a 74121 output signal can be equal to 0.7RC by adjusting the resistance value of Rp 6), the pulse signal is output from a 6 th pin of an 74121 chip, the voltage is limited to about 3.3v and then output after being limited by a resistor RP3v3, and a voltage stabilizing tube D3 plays a role in stabilizing voltage. Furthermore, the waveform conversion circuit of the invention also has a filtering function, because the 74121 input rising edge level can be triggered only when reaching about 3v, and only the voltage of the characteristic signal (useful signal) can reach the level through the previous filtering and gain amplification, and the voltage of the interference signal cannot reach the level requirement.

The waveform conversion circuit of the invention comprises an oscillator output and a limiting part. The rectified sharp pulse ultrasonic echo signal is connected with the input end of the 74121 chip, and when a rising edge is detected, the 74121 chip immediately outputs a square pulse signal, so that the subsequent processing is facilitated. The invention can adjust the pulse width by changing the values of the slide rheostat RP6 and the C14, so that the signal can be stably captured without changing the normal trigger of the next-stage echo signal. RP3v3, D3 was used for clipping. The invention can adjust the value of RP3v3 to change the amplitude of the output signal, thereby ensuring that the acquisition equipment is not damaged due to overhigh amplitude. The monostable trigger model of the invention is preferably 74121, the propagation delay time is 80ns, the working temperature is 0-70 ℃, the low-level output current is 16mA, and the power supply voltage is 4.75V-5.25V. It should be noted that the R1 resistance value of the present invention is 330 ohms, the R2 resistance value is 68 ohms, and the R7 resistance value is 330 ohms.

According to the specific embodiment provided by the invention, the invention discloses the following technical effects:

the invention provides an ultrasonic receiving circuit, which can convert an ultrasonic echo signal into a square pulse signal after filtering, amplifying and rectifying by using a filtering and amplifying circuit, a rectifying circuit and a waveform converting circuit, and transmit the square pulse signal to an ultrasonic acquisition device, so that the original ultrasonic echo signal can be converted into the square pulse signal which is convenient to be identified and captured by the ultrasonic acquisition device, and the sensitivity of an ultrasonic receiving and transmitting system is greatly improved. And the circuit has simple structure, small size and low weight, and realizes the miniaturization and light weight of the application process of the receiving circuit.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.