High-frequency weak echo signal detection circuit for CMUT sensor

Abstract

The utility model discloses a high-frequency weak echo signal detection circuit for a CMUT sensor. A forward voltage input module is connected with a power supply port of a forward input end of a power supply of an echo signal I-V conversion primary amplification module and a power supply port of a forward input end of a power supply of a same-direction proportion secondary amplification module; the reverse voltage input module is sequentially connected with a power supply port of a reverse input end of a power supply of the echo signal I-V conversion primary amplification module and a power supply port of a reverse input end of a power supply of the same-direction proportion secondary amplification module; an output port of the echo signal I-V conversion primary amplification module is connected to a forward port of the in-phase proportion secondary amplification module through filtering; and the output port of the same-direction proportion secondary amplification module is connected to the noise processing filtering module. By means of deep negative feedback formed in the circuit, serious self-oscillation and trailing phenomena existing in circuit signals are eliminated, and weak high-frequency ultrasonic echo signals are more visually detected from noise.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of MEMS electronic measurement technology, mainly relates to the field based on CMUT (Capacitive Micromachined Ultrasonic Transducer, capacitive micromachined ultrasonic transducer) echo signal detection, specifically relates to a kind of high-frequency weak echo signal detection circuit for CMUT sensor. BACKGROUND

[0002] With the wide application of ultrasonic detection technology in medical field, nondestructive testing field, submarine topography detection and other scenes, higher requirements are put forward to the frequency, bandwidth and volume of its key component transducer.The progress of microfabrication technology promotes the development of high-performance capacitive micromachined ultrasonic sensor, which not only overcomes the difficulty of coupling between piezoelectric material and air, but also has the characteristics of wide frequency band, high energy conversion efficiency, high receiving sensitivity, high detection accuracy, easy array, small volume and low noise, becoming the main development direction of future high-frequency ultrasonic sensor.

[0003] When capacitive micro ultrasonic sensor receives external ultrasonic excitation, the change of its own capacitance is only in the order of fF, which is much smaller than the stray capacitance in the circuit.At the same time, due to self-oscillation and signal tailing, the ultrasonic echo signal is submerged in circuit noise flow and space environmental noise.The resonant frequency of capacitive sensor is MHz level, and the echo signal current is only nA level, belonging to the category of weak high-frequency capacitive signal, which is difficult to measure, but the detection of capacitance change is very high, so it is necessary to detect the weak high-frequency echo signal.

[0004] At present, the widely used weak current detection technology mainly includes the following: first, time integration method, which converts the weak current signal into frequency by charging a known capacitor to accumulate charge, and then detects the weak current signal to be measured, which is usually used for low-frequency weak signal detection;Second, AC bridge method, which is more suitable for low-frequency weak signal detection;The last one is I-V conversion method, which converts the input weak current into a voltage signal proportional to it through a precise feedback resistor, which can more intuitively detect the weak high-frequency ultrasonic echo signal from noise.Although this method is commonly used for high-frequency weak signal detection, the existing scheme often lacks amplification and cannot easily detect nA level current.

[0005] In summary, it is necessary to study a high-performance high-frequency weak signal detection method to realize anti-stray, eliminate self-oscillation and improve tailing phenomenon, which is of great significance to obtain effective echo signal in noise. UTILITY MODEL CONTENT

[0006] In order to overcome the shortcomings of the prior art, the utility model provides a high frequency weak echo signal detection circuit for CMUT sensor aims at solving the problem of high frequency weak echo signal detection, so that echo current signal still can effectively solve the problem of harmonic interference and noise flood weak signal under the condition of nA level.

[0007] The technical scheme adopted to solve the key technical problems is:

[0008] A high frequency weak echo signal detection circuit for CMUT sensor, comprising: forward voltage input module, reverse voltage input module, echo signal I-V conversion first stage amplification module, same direction proportional second stage amplification module, noise processing filter module.

[0009] The forward voltage input module is sequentially connected with the power supply positive input end power supply port of the echo signal I-V conversion first stage amplification module and the power supply positive input end power supply port of the same direction proportional second stage amplification module, the reverse voltage input module is sequentially connected with the power supply reverse input end power supply port of the echo signal I-V conversion first stage amplification module and the power supply reverse input end power supply port of the same direction proportional second stage amplification module, the output port of the echo signal I-V conversion first stage amplification module is connected to the positive port of the same phase proportional second stage amplification module through filtering, and the output port of the same direction proportional second stage amplification module is connected to the noise processing filter module.

[0010] The forward voltage input module comprises a VCC input port, capacitors C4, C5, C9 and C10, the VCC input port is connected to the forward voltage input port 6 of the first stage amplification chip U1 and the forward voltage input port 6 of the second stage amplification chip U2 respectively, capacitors C4 and C5 are connected in parallel, a first end is connected to the forward voltage input port 6 of the first stage amplification chip U1, and a second end is connected to the ground, capacitors C9 and C10 are connected in parallel, a first end is connected to the forward voltage input port 6 of the second stage amplification chip U2, and a second end is connected to the ground.

[0011] The reverse voltage input module comprises a VDD input port, capacitors C6, C7, C11 and C12, the VDD input port is connected to the reverse voltage input port 2 of the first stage amplification chip U1 and the reverse voltage input port 2 of the second stage amplification chip U2 respectively, capacitors C6 and C7 are connected in parallel, a first end is connected to the reverse voltage input port 2 of the first stage amplification chip U1, and a second end is connected to the ground, capacitors C11 and C12 are connected in parallel, a first end is connected to the reverse voltage input port 2 of the second stage amplification chip U2, and a second end is connected to the ground.

[0012] The echo signal I-V conversion first-stage amplification module comprises resistance R1, resistance R2, capacitor C2, capacitor C3, an echo signal input port and capacitor C1; the resistance R1 is connected in parallel with the capacitor C2, the first end is connected with the positive input end of the 3rd port of the first-stage amplification chip U1, and the second end is grounded; the resistance R2 is connected in parallel with the capacitor C3, the first end is connected with the reverse input end of the first-stage amplification chip U1, and the second end is connected with the output end Vout1 of the first-stage amplification chip U1; the first end of the capacitor C1 is connected with the echo signal input port, and the second end is connected with the reverse input end of the first-stage amplification chip U1.

[0013] The same-direction proportional second-stage amplification module comprises resistance R3, resistance R4, resistance R5 and capacitor C8; the first end of the capacitor C8 is connected with the output end Vout1 of the first-stage amplification chip U1, and the second end of the capacitor C8 is connected with the positive input end of the second-stage amplification chip U2; the first end of the resistance R3 is connected with the positive input end of the second-stage amplification chip U2, and the second end of the resistance R3 is grounded; the first end of the resistance R4 is connected with the reverse input end of the second-stage amplification chip U2, and the second end of the resistance R4 is connected with the ground; the first end of the resistance R5 is connected with the reverse input end of the second-stage amplification chip U2, and the second end of the resistance R5 is connected with the output end of the second-stage amplification chip U2.

[0014] The noise processing filter module comprises resistance R6, resistance R7, capacitor C13 and capacitor C14; the first end of the capacitor C13 is connected with the second-stage amplification output port, the second end of the capacitor C13 is connected with the first end of the resistance R7 and the first end of the capacitor R6; the second end of the resistance R6 is grounded, the second end of the resistance R7 is connected with the output end Vout2, the first end of the capacitor C14 is connected with the output end Vout2, and the second end of the capacitor C14 is grounded.

[0015] Compared with the prior art, the utility model patent has the following advantages:

[0016] (1) Compared with the traditional I-V conversion circuit, the input bias voltage and current are as small as possible, the power consumption is reduced, the input resistance is as large as possible, the load of the signal source is reduced, and the gain bandwidth product meets the range requirements of ultrasonic detection.

[0017] (2) Compared with the traditional I-V conversion circuit, the second-stage same-direction proportional amplification circuit is introduced, the problem of too small pre-output voltage signal is solved, the amplification multiple of the circuit is improved as much as possible under the premise of reducing noise, and the design requirements are met.

[0018] (3) Compared with the traditional I-V conversion circuit, the low-pass filter circuit and the high-pass filter circuit form a band-pass filter circuit, which can well suppress noise signals out of the range and improve the signal-to-noise ratio of the final output signal. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The schematic diagram of the I-V conversion amplification circuit with adjustable bandwidth gain;

[0020] Figure 2 The schematic diagram of the post-positioned proportional two-stage amplification circuit and the band-pass filter circuit;

[0021] Figure 3 The gain Bode simulation diagram of the designed circuit. DETAILED DESCRIPTION

[0022] The utility model will be explained in detail below in combination with the drawings and specific embodiments.

[0023] A high-frequency weak echo signal detection circuit for a CMUT sensor, comprising: a forward voltage input module, a reverse voltage input module, an echo signal I-V conversion first-stage amplification module, a same-direction proportional second-stage amplification module, and a noise processing filter module.

[0024] The forward voltage input module is sequentially connected to a power supply forward input end power supply port of the echo signal I-V conversion first-stage amplification module and a power supply forward input end power supply port of the same-direction proportional second-stage amplification module; the reverse voltage input module is sequentially connected to a power supply reverse input end power supply port of the echo signal I-V conversion first-stage amplification module and a power supply reverse input end power supply port of the same-direction proportional second-stage amplification module; an output port of the echo signal I-V conversion first-stage amplification module is connected to a forward port of the same-phase proportional second-stage amplification module through filtering; and an output port of the same-direction proportional second-stage amplification module is connected to the noise processing filter module.

[0025] The forward voltage input module comprises a VCC input port, a capacitor C4, a capacitor C5, a capacitor C9, and a capacitor C10; the VCC input port is respectively connected to a forward voltage input port 6 of an amplification chip U1 and a forward voltage input port 6 of an amplification chip U2; a first end of the capacitor C4 and a first end of the capacitor C5 are connected to a connection position of a VCC and the forward voltage input port 6 of the first-stage amplification chip U1; a second end of the capacitor C4 and a second end of the capacitor C5 are connected to the ground; a first end of the capacitor C9 and a first end of the capacitor C10 are connected to a connection position of the VCC and the forward voltage input port 6 of the second-stage amplification chip U2; and a second end of the capacitor C9 and a second end of the capacitor C10 are connected to the ground.

[0026] The reverse voltage input module comprises a VDD input port, capacitors C6, C7, C11 and C12, the VDD input port is connected to the reverse voltage input port 2 of the amplification chip U1 and the reverse voltage input port 2 of the amplification chip U2 respectively, the first ends of the capacitors C6 and C7 are connected to the connection between VDD and the reverse voltage input port 2 of the first-stage amplification chip U1, the second ends of the capacitors C6 and C7 are connected to the ground, the first ends of the capacitors C11 and C12 are connected to the connection between VDD and the reverse voltage input port 2 of the second-stage amplification chip U2, and the second ends of the capacitors C11 and C12 are connected to the ground.

[0027] The echo signal I-V conversion first-stage amplification module comprises resistors R1 and R2, capacitors C2 and C3, a high-frequency weak echo signal input port and a capacitor C1; the first end of the resistor R1 is connected to the positive input end of the 3rd port of the first-stage amplification chip U1, the second end of the resistor R1 is connected to the ground, the first end of the capacitor C2 is connected to the positive input end of the 3rd port of the first-stage amplification chip U1, the second end of the resistor R1 is connected to the ground, the resistor R1 is connected in parallel with the capacitor C2, the first end of the resistor R2 is connected to the reverse input end of the first-stage amplification chip U1, the second end of the resistor R2 is connected to the output end of the first-stage amplification chip U1, the first end of the resistor R2 is connected to the reverse input end of the first-stage amplification chip U1, the second end of the resistor R2 is connected to the output end Vout1 of the first-stage amplification chip U1, and the resistor R2 is connected in parallel with the capacitor C2. The first end of the capacitor C1 is connected to the high-frequency weak echo signal input port, and the second end of the capacitor C1 is connected to the reverse input end of the first-stage amplification chip U1.

[0028] The same-direction proportional second-stage amplification module comprises resistors R3, R4 and R5, and capacitors C8, the first end of the capacitor C8 is connected to the output end Vout1 of the first-stage amplification chip U1, the second end of the capacitor C8 is connected to the positive input end of the second-stage amplification chip U2, the first end of the resistor R3 is connected to the positive input end of the second-stage amplification chip U2, the second end of the resistor R3 is connected to the ground, the first end of the resistor R4 is connected to the reverse input end of the second-stage amplification chip U2, the second end of the resistor R4 is connected to the ground, the first end of the resistor R5 is connected to the reverse input end of the second-stage amplification chip U2, and the second end of the resistor R5 is connected to the output end of the second-stage amplification chip U2.

[0029] The noise processing filter module comprises resistors R6, R7, capacitors C13 and C14, the first end of the capacitor C13 is connected with the secondary amplification output port, the second end of the capacitor C13 is connected with the first end of the resistor R7 and the first end of the capacitor R6, the first end of the resistor R6 is connected with the second end of the capacitor C13 and the first end of the resistor R7, the second end of the resistor R6 is grounded, the first end of the resistor R7 is connected with the second end of the capacitor C13 and the first end of the resistor R6, the second end of the resistor R7 is connected with the output end Vout2, the first end of the capacitor C14 is connected with the output end Vout2, and the second end of the capacitor C14 is grounded.

[0030] The high-frequency weak echo current signal input is used for receiving an input current signal and transmitting the current signal to the echo signal I-V conversion processing first amplification unit.

[0031] The echo signal I-V conversion first amplification module is formed by using ADA4895 as a preamplification circuit, inputting a feedback resistor at the input end and the output end, forming deep negative feedback in the circuit, converting a weak current signal under the action of ultrasonic into a voltage output signal, and parallelly connecting a feedback capacitor at both ends of the feedback resistor, so that serious self-oscillation and tailing phenomena existing in the circuit signal can be well eliminated, and a weak high-frequency ultrasonic echo signal can be more intuitively detected from noise.

[0032] The value of the feedback resistor of the I-V conversion circuit can be calculated by formula (1):

[0033] (1)

[0034] Further, the maximum output voltage is output, the minimum output voltage is represented, the maximum input current is represented

[0035] The value of the feedback capacitor of the I-V conversion circuit can be calculated by formula (2):

[0036] (2)

[0037] In the formula, Rf is the feedback resistor, Cf is the feedback capacitor, f0 is the resonance frequency.

[0038] Further, when the feedback resistor is large enough, the input current and the input current noise of the ADA4895 amplification circuit will cause a larger bias and output current noise at the output end, and a pull-down resistor is connected to the positive port of the amplifier, so that the bandwidth of the circuit can be better configured.

[0039] Further, when the pull-down resistor is connected, a pole is connected in a loop of the circuit, which can cause system peak and instability, and self-oscillation of the circuit.

[0040] The output voltage value of the I-V conversion circuit can be calculated by formula (3)

[0041] (3)

[0042] Further, in the formula R1 is a forward access resistor, R2 is a capacitor connected in parallel to the pull-down resistor.

[0043] The secondary amplification unit uses ADA4851 as the core unit of the amplification circuit, and the initial signal is a weak current signal of 30nA. After the first amplification by the I-V conversion circuit, the proportional voltage weak signal obtained is only in the mV level, and the signal still cannot meet the voltage requirement of subsequent analog-to-digital conversion. Therefore, the echo weak signal needs to be amplified twice.

[0044] Further, a coupling capacitor is connected between the primary amplification and the secondary amplification, which functions as a direct current isolation and alternating current transmission, filters out the direct current component in the input signal, ensures that the input signal of the operational amplifier only contains alternating current components, and avoids the influence of the direct current bias voltage generated by the primary amplification port on the working state of the amplifier.

[0045] Further, a bias resistor is connected to the forward port of the amplifier to provide a stable direct current reference level. This ensures that the operational amplifier works within the correct voltage range and avoids the drift problem caused by the floating input end.

[0046] The amplification factor of the low-noise amplifier can be calculated by formula (4):

[0047] (4)

[0048] Further, R4 represents a lower bias resistor, and R5 represents a lower bias resistor.

[0049] The filter unit is a series combination of a low-pass filter and a high-pass filter, which can not only filter out the resonance noise generated after the secondary amplification, but also filter out the signals beyond the detection range generated by the ultrasonic resonance point and the anti-resonance point.

[0050] Further, to calculate the passing range of signal frequency, ensure the effectiveness of the signal, the low pass filter and the high pass filter have lower limit cutoff frequency and upper limit cutoff frequency respectively, the capacitance resistance parameter directly determines the passing range of effective signal, the signal bandwidth can be calculated by the difference between the two.

[0051] The frequency signal range that the low pass filter can pass can be calculated by formula (5):

[0052] (5)

[0053] Further, represents the low pass filter resistance size, represents the low pass filter capacitance size.

[0054] The frequency signal range that the high pass filter can pass can be calculated by formula (6):

[0055] (6)

[0056] Further, represents the high pass filter resistance size, represents the high pass filter capacitance size.

[0057] The frequency range that can pass can be calculated by formula (7)

[0058] (7)

[0059] Further, represents the band pass filter bandwidth, represents the high pass frequency lower limit value, represents the low pass frequency upper limit value.

[0060] Embodiment:

[0061] In the embodiments of the present disclosure, a multi-stage amplification filter circuit for high-frequency weak echo signals based on a CMUT sensor is provided, which combines Figure 1 and Figure 2 As shown in the drawings, the echo signal multi-stage amplification circuit includes a power module unit, a high-frequency weak echo signal input unit, an echo signal I-V conversion method processing first-stage amplification unit, a high-frequency high-gain processing second-stage amplification unit, a filtering processing unit, and an output unit.

[0062] The power module is directly powered by the VCC and VDD ports of the CMUT sensor-based system to supply 5V and -5V to the high-frequency weak echo signal detection module, respectively. The modular design can greatly reduce the size of the ultrasonic flaw detection system.

[0063] The high-frequency weak echo signal input unit, through the 0Ω resistor R3 test port, is connected to the input end of the multi-stage amplification filter circuit of the high-frequency weak echo signal of the CMUT sensor, and receives the current signal I emitted by the ultrasonic echo signal source in , and is connected to the I-V conversion first-stage gain circuit.

[0064] The output point Vout1 of the I-V conversion circuit is connected to the first-stage gain amplification, and a voltage signal is obtained. After Vout1 is connected to the high-pass filter part, it is connected to the in-phase proportional input end through the high-pass filter output end, and the gain of the second-stage amplification unit is obtained as Vout2. Vout2 is connected to the input end of the next-stage filter unit.

[0065] The output node OUT of the filter unit is connected to the output end of the multi-stage amplification filter circuit of the high-frequency weak echo signal of the CMUT sensor, and outputs the voltage signal Vout.

[0066] According to the embodiment of the present disclosure, the I-V conversion circuit comprises: a first input capacitor C1, a matching resistor R1, a matching capacitor C2, a feedback resistor R2, a feedback capacitor C3, a +5V power supply VCC and a -5V power supply VDD, a first filter capacitor C4, a second filter capacitor C5, a third filter capacitor C6, a fourth filter capacitor C7, and an amplifier device unit ADA4895.

[0067] The first input capacitor C1 filters the direct current bias of the input signal, confirms that the input current signal is not affected by the bias, and is connected to the next-stage I-V conversion circuit. The feedback resistor R2 is connected across the signal input end and the output end of the signal amplifier, and the feedback capacitor C3 is connected in parallel across the feedback resistor R2. The entire system is powered by ±5V voltage, the first filter capacitor C4 and the second filter capacitor C5 are connected to the VCC+5V input port, and the third filter capacitor C6 and the fourth filter capacitor C7 are connected to the VDD input port.

[0068] The filter capacitors C4, C5, C6 and C7 are large capacitors connected in parallel with small capacitors for filtering the input power supply, removing ripple, and in specific embodiments, the large capacitor has a value of 10uf and the small capacitor has a value of 100nf.

[0069] The value of the feedback resistor R2 determines the amplification factor of the system. In specific embodiments, the current of 30nA is amplified to 15mA, so in specific examples, the resistance value of the feedback resistor is 500KΩ.

[0070] The feedback capacitor can well eliminate self-oscillation, and the value of C2 is 10.99pf in theory. In specific embodiments, considering the parasitic capacitance carried by the PCB board itself, the final value of C2 is 1pf, which has better effect on eliminating self-oscillation.

[0071] The matching resistance R1 and the matching capacitance C2 are connected in parallel to the positive port of the amplifier, which can adjust the system gain and bandwidth, and improve the system stability. In specific embodiments, R1 is 50KΩ, and C1 is 100nf.

[0072] According to the embodiments of the present disclosure, the post-circuit comprises: a first input resistance R3, a high-pass capacitance C8, a first voltage division amplification resistance R4, a second voltage division amplification resistance R5, a high-pass filter circuit C13, a R6, a low-pass filter circuit C14, a R7, a +5V power supply VCC and a -5V power supply VDD, a first filter capacitance C9, a second filter capacitance C10, a third filter capacitance C11, and a fourth filter capacitance C12.

[0073] According to the embodiments of the present disclosure, the front output node VOUT is connected to the front end of the in-phase proportional amplification circuit, and the DC component is filtered out by using C8. R3 is connected to the positive port of the amplifier, R4 and R5 are used as feedback resistances and play a role in voltage division amplification. R5 and the output port 1 of the amplifier are the output port of the in-phase proportional amplification circuit. R3, R4, R5 and the amplifier together realize in-phase proportional amplification.

[0074] The output port of the in-phase proportional amplification circuit is connected to a band-pass filter circuit. The capacitance C13 and the resistance R6 together form a high-pass filter, which filters out low-frequency noise signals. The capacitance C14 and the resistance R7 in the low-pass filter together realize a low-pass filter, and the whole forms a band-pass filter circuit, which can filter out most of the external noise.

[0075] The filter capacitances C9, C10, C11 and C12 are used to filter the input power supply. A large capacitance and a small capacitance are usually connected in parallel to remove ripple. In specific embodiments, the value of the large capacitance is 10uf, and the value of the small capacitance is 100nf.

[0076] The coupling capacitance C8 can filter out DC components, and the bias resistance R3 is pulled down to ground, providing a stable DC reference level. This is to ensure that the operational amplifier works in the correct voltage range and avoid the drift problem caused by the floating input terminal.

[0077] In specific embodiments, the coupling capacitance C8 and the bias resistance R3 together form a high-pass filter. The coupling capacitance C8 is 100nf, and the bias resistance R3 is 100k, which realizes the passage of high-frequency signals and solves the noise problem of the first-stage preamplifier circuit.

[0078] In specific embodiments, the value of the amplification forward end resistor R4 is 10kΩ, the value of the amplification feedback resistor R7 is 90kΩ, and a same direction proportional amplification circuit is formed with the amplifier engineering, realizing two-stage amplification, which amplifies the mV level signal, and can meet the subsequent analog-to-digital conversion analog signal requirements.

[0079] In specific embodiments, the value of the filter capacitor C13 is 100nf, the value of the filter resistor R6 is 100kΩ, the value of the filter resistor R7 is 1kΩ, and the value of the filter capacitor C14 is 22pf, which can realize the band-pass filtering effect.

[0080] In specific embodiments, the circuit is simulated and tested by using Cadence PSpice software, the ADA4895 model and the ADA4851 model are downloaded from the ADA official website and loaded into the Cadence PSpice software, the two-stage amplification circuit is built according to the description, the parameters of each component are preset to be consistent with the description in the foregoing, and frequency scanning is performed.

[0081] In specific embodiments, the gain Bode simulation diagram is as shown in Figure 3 The simulation result shows that the gain of the two-stage amplification circuit is 113.72dB under the working frequency of 3.18MHz, and 30nA can be amplified to 14.37mA through calculation, which meets the CMUT array working frequency requirement, and the filtering range of the band-pass filter is 114.81KHz~3.89MHz.

[0082] In summary, the disclosure provides a detection circuit for high-frequency weak echo signals based on a CMUT sensor, which realizes higher gain and bandwidth performance than the conventional transimpedance amplification circuit structure.

Claims

1. A high frequency weak echo signal detection circuit for a CMUT sensor, characterized by, The utility model relates to a kind of echo signal processing circuit, including: Forward voltage input module, reverse voltage input module, echo signal I-V conversion first-stage amplification module, same direction proportional second-stage amplification module, noise processing filter module; The forward voltage input module is sequentially connected echo signal I-V conversion first-stage amplification module power supply forward input end power supply port, same direction proportional second-stage amplification module power supply forward input end power supply port;Reverse voltage input module is sequentially connected echo signal I-V conversion first-stage amplification module power supply reverse input end power supply port, same direction proportional second-stage amplification module power supply reverse input end power supply port;Echo signal I-V conversion first-stage amplification module's output port is connected to the forward port of same phase proportional second-stage amplification module after filtering;Same direction proportional second-stage amplification module's output port is connected to noise processing filter module.

2. The high frequency weak echo signal detection circuit for CMUT sensors of claim 1, wherein, The forward voltage input module includes: VCC input port, capacitor C4, capacitor C5, capacitor C9 and capacitor C10;VCC input port is connected to the forward voltage input port (6) of first-stage amplification chip U1 and the forward voltage input port (6) of second-stage amplification chip U2 respectively;Capacitor C4 and capacitor C5 are connected in parallel, and the first end is connected to the forward voltage input port (6) of first-stage amplification chip U1, and the second end is connected to ground;Capacitor C9 and capacitor C10 are connected in parallel, and the first end is connected to the forward voltage input port (6) of second-stage amplification chip U2, and the second end is connected to ground.

3. The high frequency weak echo signal detection circuit for CMUT sensors of claim 2, wherein, The reverse voltage input module includes: VDD input port, capacitor C6, capacitor C7, capacitor C11 and capacitor C12;VDD input port is connected to the reverse voltage input port (2) of first-stage amplification chip U1 and the reverse voltage input port (2) of second-stage amplification chip U2 respectively;Capacitor C6 and capacitor C7 are connected in parallel, and the first end is connected to the reverse voltage input port (2) of first-stage amplification chip U1, and the second end is connected to ground;Capacitor C11 and capacitor C12 are connected in parallel, and the first end is connected to the reverse voltage input port (2) of second-stage amplification chip U2, and the second end is connected to ground.

4. The high frequency weak echo signal detection circuit for CMUT sensors of claim 3, wherein, The echo signal I-V conversion first-stage amplification module includes resistance R1, resistance R2, capacitor C2, capacitor C3, echo signal input port and capacitor C1;Resistance R1 and capacitor C2 are connected in parallel, and the first end is connected with the third port forward input end of first-stage amplification chip U1, and the second end is grounded;Resistance R2 and capacitor C3 are connected in parallel, and the first end is connected with the reverse input end of first-stage amplification chip U1, and the second end is connected with the output end Vout1 of first-stage amplification chip U1;The first end of capacitor C1 is connected with echo signal input, and the second end is connected with the reverse input end of first-stage amplification chip U1.

5. The high frequency weak echo signal detection circuit for CMUT sensors of claim 4, wherein, The same direction proportional secondary amplification module comprises resistors R3, R4, R5 and a capacitor C8; the first end of the capacitor C8 is connected with the output end Vout1 of the primary amplification chip U1, and the second end of the capacitor C8 is connected with the positive input end of the secondary amplification chip U2; the first end of the resistor R3 is connected with the positive input end of the secondary amplification chip U2, and the second end of the resistor R3 is grounded; the first end of the resistor R4 is connected with the negative input end of the secondary amplification chip U2, and the second end of the resistor R4 is connected with the ground; the first end of the resistor R5 is connected with the negative input end of the secondary amplification chip U2, and the second end of the resistor R5 is connected with the output end of the secondary amplification chip U2.

6. The high frequency weak echo signal detection circuit for CMUT sensors of claim 5, wherein, The noise processing filter module comprises resistors R6, R7, capacitors C13 and C14; the first end of the capacitor C13 is connected with the secondary amplification output port, the second end of the capacitor C13 is connected with the first end of the resistor R7 and the first end of the capacitor R6; the second end of the resistor R6 is grounded, the second end of the resistor R7 is connected with the output end Vout2, the first end of the capacitor C14 is connected with the output end Vout2, and the second end of the capacitor C14 is grounded.

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