A signal conditioning circuit for sonar receiver

Abstract

The present invention discloses a signal conditioning circuit for a sonar receiver in the field of sonar system electronic circuit design, including a high-gain preamplifier circuit, a Butterworth bandpass filter circuit, and an operational amplifier follower circuit. The sonar receiver signal conditioning circuit is directly connected to a hydrophone, and can realize preprocessing of weak signals received by the hydrophone. The present invention has a high-gain passband flat signal conditioning circuit, which is constructed with core components such as rail-to-rail operational amplifiers, TPS7A3001, and TPS7A4901, and outputs a signal with a high-quality signal-to-noise ratio, thereby meeting the requirements of a precision analog-to-digital converter of a subsequent signal acquisition circuit. The circuit is suitable for various sonar systems such as navigation sonar, positioning sonar, and communication sonar.

Description

Technical Field

[0001] The invention relates to the technical field of sonar system electronic circuit design, and in particular to a signal conditioning circuit for a sonar receiver. Background Art

[0002] Sonar is an important device for detecting and locating underwater targets and conducting underwater acoustic communications. The signal conditioning circuit of the sonar receiver can amplify and filter the weak signals received by the hydrophone, improve the circuit's receiving signal-to-noise ratio, and improve the circuit's load capacity through the op amp follower circuit to support the subsequent high-quality analog-to-digital conversion and digital signal processing of the signal acquisition circuit. The sonar receiver signal conditioning circuit is an important part of the sonar circuit system, and is related to the entire sonar system's ability to process weak signals received by the hydrophone. Good signal amplification, filtering, and load capacity are important technical indicators of this type of circuit.

[0003] The weak signals received by the sonar receiver are easily affected by the external environment and the circuit itself. How to pre-process the weak signals received by the hydrophone is related to the subsequent signal acquisition, storage and digital signal processing. Traditional signal conditioning circuits usually include multi-stage fixed gain amplifier circuits, multi-stage filter circuits, and multi-stage variable gain amplifier circuits. Although they can achieve good signal conditioning effects, the circuits are relatively complex and large in scale, which is not conducive to the miniaturization and integration requirements of the circuits. Traditional circuits are easily affected by external noise interference, which is not conducive to high-performance digital signal processing in subsequent signal acquisition and storage circuits, and cannot support the requirements for the development of high-performance portable sonar systems. Summary of the invention

[0004] To this end, the present invention provides a signal conditioning circuit for a sonar receiver to solve the problem in the prior art that the sonar receiver is easily interfered by external noise.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A signal conditioning circuit for a sonar receiver comprises a preamplifier circuit, a bandpass filter circuit and an operational amplifier follower circuit; the preamplifier circuit is directly connected to a hydrophone to realize preprocessing of weak signals, improve impedance matching capability, and realize amplification of weak signals; the Butterworth bandpass filter circuit filters the signal output by the preamplifier circuit; the linear voltage regulator circuit provides a stable voltage input for the positive and negative power input terminals of the operational amplifier; the operational amplifier follower circuit has high input impedance and low output impedance, improves the circuit's load carrying capacity, and outputs to an analog-to-digital conversion ADC circuit in a rear-end signal acquisition circuit for high-precision analog-to-digital conversion;

[0007] The linear voltage stabilization circuit uses TPS3A4901 and TPS3A3001 chips to provide stable power input for four groups of operational amplifiers, so that the four groups of operational amplifiers work in a stable state; for the circuit that provides a positive 5V power supply for the operational amplifier, a positive 12V common power supply is used to power the TPS3A4901 chip, and a capacitor C1 is connected in parallel to the positive 12V power supply end, which plays a role in smoothing voltage mutations and filtering high-frequency noise; for the circuit that provides a negative 5V power supply for the operational amplifier, a negative 12V power supply is used to power the TPS7A3001 chip, and a capacitor C5 is connected in parallel to the negative 12V power supply end, which also plays a role in smoothing voltage mutations and filtering high-frequency noise;

[0008] The preamplifier circuit includes a first operational amplifier, resistors R5-R7 and capacitors C9-C14; the signal received from the hydrophone is connected to the non-inverting input terminal of the first operational amplifier through C10, and a resistor R7 is connected in series between the non-inverting input terminal of the first operational amplifier and the ground; a resistor R5 and a capacitor C9 are connected in series between the inverting input terminal of the first operational amplifier and the ground; a resistor R6 is connected in series between the output terminal and the inverting input terminal of the first operational amplifier as a negative feedback resistor; the positive 5V output of the linear voltage-stabilized power supply is connected to the positive power input terminal of the first operational amplifier, and two parallel capacitors C11 and C12 are connected in series between the positive power input terminal of the first operational amplifier and the ground; the negative 5V output of the linear voltage-stabilized power supply is connected to the negative power input terminal of the first operational amplifier, and two parallel capacitors C13 and C14 are connected in series between the negative power input terminal of the first operational amplifier and the ground; the negative feedback circuit part of the preamplifier circuit constitutes an amplifier circuit;

[0009] The bandpass filter circuit is composed of a high-pass filter circuit and a low-pass filter circuit; the high-pass filter circuit is composed of a second operational amplifier, a third operational amplifier, capacitors C15-C20 and resistors R8-R9; the low-pass filter circuit is composed of an operational amplifier and C21-C26 and resistors R10-R11;

[0010] The operational amplifier follower circuit includes a fourth operational amplifier, the signal of the Butterworth bandpass filter circuit is input to the in-phase input terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is fed back to the inverting input terminal of the operational amplifier; two parallel capacitors C27 and C28 are connected in series between the positive power supply input terminal and the ground of the fourth operational amplifier, and the positive power supply input terminal is connected to the positive 5V output of the linear voltage-regulated power supply; two parallel capacitors C29 and C30 are connected in series between the negative power supply input terminal and the ground of the fourth operational amplifier, and the negative power supply input terminal is connected to the negative 5V output of the linear voltage-regulated power supply; thereby forming an operational amplifier follower circuit.

[0011] As a further solution of the present invention: the positive 12V power supply is connected to the power supply access terminal IN and the enable terminal EN of the TPS7A4901 chip. When the enable terminal EN is connected to the positive 12V voltage, the regulator chip TPS7A4901 is turned on; the NR terminal of the TPS7A4901 chip is connected to the capacitor C3, the OUT terminal and the FB terminal are connected in series with a capacitor C2, the two ends of C2 are connected in parallel with a resistor R2, a resistor R1 is connected in series between the FB terminal and the ground, and a capacitor C4 is connected in series between the OUT terminal and the ground. By adjusting the resistance between R1 and R2, the desired output voltage is obtained.

[0012] As a further solution of the present invention: the negative 12V power supply is connected to the power supply access terminal IN and the enable terminal EN of the TPS7A3001 chip. When the enable terminal EN is connected to the negative 12V voltage, the regulator chip TPS7A3001 is turned on; a capacitor C7 is connected between the NR terminal and the ground of the TPS7A3001 chip, a capacitor C6 is connected in series between the OUT terminal and the FB terminal, a resistor R3 is connected in series between the FB terminal and the ground, a resistor R4 is connected in parallel at both ends of C6, and a capacitor C8 is connected in series between the OUT terminal and the ground. The output voltage value is changed by adjusting the resistance value between R3 and R4.

[0013] As a further solution of the present invention: in the linear voltage stabilization circuit, R1 uses a 4.99K resistor and R2 uses a 16K resistor; the resistance value of R3 is 4.99K and the resistance value of R4 is 16.2K.

[0014] As a further solution of the present invention: in the preamplifier circuit, the voltage gain is Where G is the gain, and R5 and R6 are the resistance values ​​of the corresponding resistors in the designed circuit.

[0015] As a further solution of the present invention: the amplified signal output by the preamplifier circuit is first input into the high-pass filter circuit, and the signal enters the in-phase input terminal of the second operational amplifier through C15 and C16, a resistor R8 is connected between the in-phase input terminal and the ground, a resistor R9 is connected between C15 and C16 and the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is directly connected to the inverting input terminal; two parallel resistors C17 and C18 are connected in series between the positive power input terminal of the second operational amplifier and the ground; two parallel capacitors C19 and C20 are connected in series between the negative power input terminal of the second operational amplifier and the ground; the positive power input terminal of the second operational amplifier is connected to the positive 5V output of the linear voltage-stabilized power supply; the negative power input terminal of the second operational amplifier is connected to the negative 5V output of the linear voltage-stabilized power supply;

[0016] The output signal of the high-pass filter circuit is input into the low-pass filter circuit. The signal obtained by the high-pass filter circuit first passes through the resistors R10 and R11 and enters the non-inverting input terminal of the third operational amplifier. A capacitor C22 is connected in series between the non-inverting input terminal of the third operational amplifier and the ground. A capacitor C21 is connected in series between the resistors R10 and R11 and the output terminal of the third operational amplifier. The output terminal of the third operational amplifier is directly connected to the inverting input terminal of the operational amplifier, forming a low-pass filter circuit; two parallel capacitors C23 and C24 are connected in series between the positive power input terminal of the third operational amplifier and the ground; two parallel capacitors C25 and C26 are connected in series between the negative power input terminal of the third operational amplifier and the ground; the positive power input terminal of the third operational amplifier is connected to the positive 5V output of the linear regulated power supply; and the negative power input terminal of the third operational amplifier is connected to the negative 5V output of the linear regulated power supply.

[0017] As a further solution of the present invention: the topological structure of the high-pass filter circuit and the topological structure of the low-pass filter circuit are both Sallen-Key structures; the high-pass filter circuit and the low-pass filter circuit are connected in series to form a band-pass filter circuit, and the high-pass filter circuit and the low-pass filter circuit are both Butterworth filter types, and the entire band-pass filter circuit constitutes a Butterworth band-pass filter circuit.

[0018] As a further solution of the present invention: the operational amplifier follower circuit has an output voltage that is equal to the input voltage, can match the output load impedance, and has a strong load-carrying capacity.

[0019] As a further solution of the present invention: the small signal received by the hydrophone is input into the non-inverting input terminal of the preamplifier circuit through the capacitor C10 and the resistor R7, the capacitor C10 and R7 play a role in improving the performance and stability of the circuit, the negative feedback resistor R6 and the resistor R5 play a role in amplifying the circuit signal, and the capacitor C9 connected in series with the inverting input terminal plays a role in blocking the DC signal, suppressing the interference signal and noise, and preventing the self-oscillation of the operational amplifier; the signal amplified by the preamplifier circuit enters the bandpass filter circuit composed of capacitors C15-C26, resistors R8-R11 and two operational amplifiers, which mainly filters out low-frequency and high-frequency noise and improves the signal-to-noise ratio of the signal; the filtered signal enters the operational amplifier follower circuit, the high input impedance and low output impedance of the operational amplifier follower circuit can achieve impedance matching with the back-end circuit, and at the same time improve the load capacity of the circuit, and the output signal enters the signal acquisition circuit for analog-to-digital conversion.

[0020] As a further solution of the present invention: the signal conditioning circuit outputs the conditioned signal to the analog-to-digital converter of the signal acquisition and storage circuit for ADC conversion, and then performs subsequent digital signal processing.

[0021] As a further solution of the present invention: R represents the resistance value, C represents the capacitance value, R1-R11, C1-C30 correspond to the numbers of the resistors and capacitors in the circuit in the drawings of the specification, the operational amplifier is a rail-to-rail voltage feedback operational amplifier, the first operational amplifier, the second operational amplifier, the third operational amplifier, and the fourth operational amplifier are respectively operational amplifiers in the preamplifier circuit, the high-pass filter circuit, the low-pass filter circuit, and the operational amplifier follower circuit, TPS7A4901 and TPS7A3001 are linear regulators, and their pins include IN pin, EN pin, DNC pin, NC pin, PWPD pin, GND pin, OUT pin, FB pin, and NR pin. The letters only represent the pin names and have no other meanings. ADC represents a precision analog-to-digital converter.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention adopts a high-gain circuit design scheme, through reasonable selection of devices, careful optimization of circuit topology, and selection of appropriate filter structure, which significantly improves the performance of the signal conditioning circuit. When designing the positive and negative power supply voltages of the operational amplifier, the TPS7A4901 and TPS7A3001 linear regulator chips are used. These two chips have high voltage stability performance, wide input and output voltage ranges, and high output voltage accuracy. The amplification gain of the preamplifier circuit is stable, the noise is very small, and by optimizing the circuit design, the circuit and the front-end hydrophone can achieve good impedance matching. The operational amplifier is selected as the OPA140 rail-to-rail voltage feedback operational amplifier, and the output voltage is large, which meets the signal requirements of the subsequent signal acquisition and storage circuit. The nonlinear distortion of the circuit is very small, the accuracy is high, and the error is very low. It is a good amplifier circuit structure. The bandpass filter circuit has a large bandwidth, and the passband cutoff frequency of the filter can be designed as needed. The passband ripple of the filter is small, the transition band is steep, the noise filtering is relatively clean, the output signal-to-noise ratio is high, and the passband is the frequency band of the commonly used underwater acoustic signal, which can meet the filtering processing of a variety of underwater acoustic signals. The op amp follower circuit has the function of stabilizing the output signal voltage, and at the same time plays the role of impedance matching with the circuit at the signal output end. The low output impedance can improve the circuit's load capacity. The entire circuit has a strong signal amplification capability, a strong signal filtering function, and a strong matching capability for the front-end and back-end circuits of the signal. It is an excellent signal conditioning circuit.

[0024] 2. The circuit of the present invention adopts an innovative circuit design structure, which greatly simplifies the complexity of the circuit, thus improving the reliability of the circuit, reducing the scale of the circuit, improving the integration of the circuit, and reducing the power consumption of the circuit. The operational amplifier chip of the preamplifier circuit and the bandpass filter circuit uses the same chip, which helps to reduce the types of devices, prevent the performance differences caused by different devices, and improve the reliability of the circuit. The selection of the entire circuit structure has been simulated. Each part of the circuit has completed functional testing and system simulation, and has high reliability and stability. Careful device selection has been carried out for each module of the entire circuit. The devices for simulation are all actual devices, which ensures the consistency between the final design result and the actual simulation, making the circuit have high reliability. The device selection of the entire circuit is all commonly used devices, and it is easy to design the circuit board, which also greatly reduces the cost of the circuit and improves the value and practicality of the circuit.

[0025] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practicing the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more intuitively illustrate the prior art and the present application, exemplary drawings are given below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing the present application; for example, those skilled in the art are capable of easily making conventional adjustments or further optimizations to the addition / reduction / attribution division, specific shapes, positional relationships, connection methods, dimensional ratios, etc. of certain units (components) based on the technical concepts and exemplary drawings disclosed in the present application.

[0027] Figure 1 The present invention is an application diagram of a signal conditioning circuit for a sonar receiver.

[0028] Figure 2 A diagram showing the connection relationship of the operational amplifier power supply voltage using TPS7A4901 in the signal conditioning circuit provided in an embodiment of the present invention.

[0029] Figure 3 A diagram showing the connection relationship of the operational amplifier power supply voltage using TPS7A3001 in the signal conditioning circuit provided in an embodiment of the present invention.

[0030] Figure 4 A connection diagram of a preamplifier circuit in a signal conditioning circuit provided in an embodiment of the present invention.

[0031] Figure 5 A connection diagram of a bandpass filter circuit in a signal conditioning circuit provided in an embodiment of the present invention.

[0032] Figure 6A connection diagram of an operational amplifier follower circuit in a signal conditioning circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following is an explanation of the implementation of the present invention by specific specific examples. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of them. It should be understood that these embodiments are only to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical engineers in this field can make some non-essential improvements and adjustments to the present invention based on the contents of the above invention; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] See also Figure 1-Figure 6 A signal conditioning circuit for a sonar receiver comprises an operational amplifier power supply circuit, a preamplifier circuit, a bandpass filter circuit and an operational amplifier follower circuit; the operational amplifier power supply circuit provides a power supply voltage for the operational amplifier chip in the signal conditioning circuit of the present invention; the preamplifier circuit is directly connected to the output signal of the front-end hydrophone, realizes the amplification function of the small signal received by the hydrophone, and can block the DC component in the received signal, and can achieve impedance matching with the front-end hydrophone; the bandpass filter circuit filters the amplified signal of the preamplifier circuit, filters out the noise in the signal, and improves the signal-to-noise ratio of the signal; the operational amplifier follower circuit provides impedance matching for the back-end circuit, and has a strong load capacity due to the low output impedance, and the output signal is converted to digital by the precision analog-to-digital converter ADC.

[0035] By adopting the above technical scheme, the sonar receiver signal conditioning circuit of the present invention calculates the gain of the sonar receiver and sets a suitable fixed gain; the bandpass filter can set the upper and lower cut-off frequencies of the filter according to the actual received signal frequency range; the signal passes through the preamplifier circuit, the bandpass filter circuit and the operational amplifier follower circuit in sequence; the small signal received by the hydrophone is amplified and filtered in sequence through the circuit, and a signal with a high signal-to-noise ratio is output, thereby meeting the requirements of the back-end high-precision analog-to-digital converter ADC.

[0036] In this embodiment, the signal conditioning circuit is used to amplify and filter the small signal received by the hydrophone, improve the signal-to-noise ratio of the system signal, and provide the output high quantization signal-to-noise ratio signal to the back-end precision analog-to-digital converter ADC for signal conversion, facilitating subsequent high-quality digital signal processing.

[0037] The preamplifier circuit provides a high-gain amplification function for the circuit, amplifies the signal received by the front-end hydrophone, and facilitates subsequent filtering processing.

[0038] See also Figure 4 , the amplification process of the preamplifier circuit includes the following steps:

[0039] First, after the signal is input, it enters the non-inverting input terminal of the first operational amplifier OPA140 (OPA140 operational amplifier) ​​through the capacitor C10. A resistor R7 is connected in series between the non-inverting input terminal of the first operational amplifier and the ground. The capacitor C10 and the resistor R7 play the role of impedance matching.

[0040] After the signal enters the operational amplifier, the output terminal is fed back to the inverting input terminal of the operational amplifier through resistor R6. Resistor R5 and capacitor C9 are connected in series between the inverting input terminal and the ground. Capacitor C9 plays the role of introducing the AC signal into the ground. The amplification gain of the amplifier circuit is Where G represents gain, R5 and R6 represent the resistance values ​​of the corresponding resistors. The amplification factor of the circuit can be changed by adjusting the resistance values ​​of R5 and R6.

[0041] Capacitors C11 and C12 are connected in parallel and then connected in series between the negative power input terminal and ground of the first operational amplifier, mainly to filter out noise in the power supply and improve the stability of the power supply voltage; capacitors C13 and C14 are connected in parallel and then connected in series between the positive power input terminal and ground of the first operational amplifier, and their function is the same as that of capacitors C11 and C12.

[0042] Among them, the signal input terminal of the pre-operational amplifier circuit is connected with a resistor and a capacitor to play a certain filtering and impedance matching role. The first operational amplifier adopts a rail-to-rail voltage feedback operational amplifier with the characteristics of high gain, high precision, high output voltage swing, low distortion, low noise, etc.; two parallel capacitors are connected in series between the power supply terminal and the ground of the rail-to-rail voltage feedback operational amplifier to filter out high-frequency noise and stabilize the power supply voltage; the circuit has a large fixed gain and can stably amplify the weak signal received by the front-end hydrophone.

[0043] The bandpass filter circuit includes a second operational amplifier OPA140, a third operational amplifier OPA140, resistors R8-R11 and capacitors C15-C26; R8, R9, capacitors C15-C20 and the second operational amplifier OPA140 constitute a high-pass filter circuit; R10, R11, C21-C26 and the third operational amplifier OPA140 constitute a low-pass filter circuit; the high-pass filter circuit and the low-pass filter circuit are connected in series to constitute a bandpass filter circuit.

[0044] The second operational amplifier OPA140 has a non-inverting input terminal, an inverting input terminal, an output terminal, a positive power input terminal, and a negative power input terminal; the amplified signal output by the preamplifier circuit is input to the non-inverting input terminal of the second operational amplifier OPA140 through capacitors C15 and C16, a resistor R9 is connected in series between the capacitors C15 and C16 and the output terminal of the second operational amplifier OPA140, a resistor R8 is connected in series between the non-inverting input terminal of the second operational amplifier OPA140 and the ground, the output terminal and the inverting terminal of the second operational amplifier OPA140 are directly connected, capacitors C17 and C18 are connected in parallel and then connected in series between the positive power input terminal and the ground of the second operational amplifier OPA140, capacitors C19 and C20 are connected in parallel and then connected in series between the negative power input terminal and the ground of the second operational amplifier OPA140, so as to filter out high-frequency noise, thus forming a high-pass filter circuit.

[0045] The signal output by the high-pass filter circuit is input to the non-inverting input terminal of the third operational amplifier OPA140 through R10 and R11, a capacitor C21 is connected in series between R10 and R11 and the output terminal of the third operational amplifier OPA140, a capacitor C22 is connected to the ground at the non-inverting input terminal of the third operational amplifier OPA140, the output terminal and the inverting input terminal of the third operational amplifier OPA140 are directly connected, capacitor C23 and capacitor C24 are connected in parallel and connected between the positive power input terminal of the third operational amplifier OPA140 and the ground, capacitor C25 and capacitor C26 are connected in parallel and connected between the negative power input terminal of the third operational amplifier OPA140 and the ground, so as to filter out high-frequency noise, thereby forming a low-pass filter circuit.

[0046] The bandpass filter is formed by connecting a high-pass filter and a low-pass filter in series. The cutoff frequency is easy to determine and can be adjusted according to actual needs. Two parallel capacitors are connected in series between the power input terminal and the ground of the operational amplifier OPA140 to filter out high-frequency noise and stabilize the power supply voltage. The bandpass filter is a Butterworth bandpass filter and the topology is a Sallen-Key circuit structure. The Sallen-Key circuit has a small passband ripple, is relatively flat, and has a steep transition band. It has good filtering performance and can effectively improve the output signal-to-noise ratio of the signal, making good preparations for the high-precision analog-to-digital conversion ADC of the subsequent signal acquisition circuit.

[0047] The operational amplifier follower circuit is used for applications where the signal output by the filtering circuit needs to be coupled to a precision analog-to-digital converter ADC, and signal stabilization and impedance matching with the back-end circuit are required; the signal output from the filtering circuit enters the in-phase input terminal of the fourth operational amplifier OPA140, the output terminal and the inverting input terminal of the fourth operational amplifier OPA140 are directly connected, capacitors C27 and C28 are connected in parallel and then connected in series between the negative power input terminal and ground of the fourth operational amplifier OPA140, capacitors C29 and C30 are connected in parallel and then connected in series between the positive power input terminal and ground of the fourth operational amplifier OPA140, so as to filter out high-frequency noise in the power supply and stabilize the power supply voltage.

[0048] The op amp follower circuit has a simple structure and uses fewer components, which can effectively reduce the size of the circuit; the op amp power supply end uses two parallel capacitors connected between the power input end and the ground, which can effectively filter out the noise at the power supply end; the op amp follower circuit has a high input impedance and a low output impedance, which can achieve a good impedance matching function with the back-end circuit and has a strong load capacity.

[0049] The signal conditioning circuit outputs the conditioned signal to the precision analog-to-digital converter ADC in the back-end signal acquisition circuit for analog-to-digital conversion, and then performs subsequent digital signal processing.

[0050] In this embodiment, in order to meet the needs of current miniaturized and portable sonar for processing small signals received by hydrophones, a signal conditioning circuit is constructed with rail-to-rail voltage feedback operational amplifiers and linear regulator chips as core components to condition the weak signals received by the hydrophones and output signals with a high quantization signal-to-noise ratio, thereby meeting the needs of high-precision analog-to-digital converters ADC, and is suitable for various sonar systems such as positioning, communication, and navigation sonars.

[0051] In this embodiment, R represents the resistance value of the resistor, C represents the capacitance value of the capacitor, R1-R11, C1-C30 correspond to the numbers of the resistors and capacitors in the circuit in the drawings of the specification, U1A, U4, U5 and U6 are operational amplifiers OPA140 rail-to-rail voltage feedback operational amplifiers, TPS7A4901 and TPS7A3001 are linear regulators, and their pins include IN pin, EN pin, DNC pin, NC pin, OUT pin, FB pin, NR pin, PWPD pin and GND pin. Letters represent pin names and have no other meanings. ADC represents a precision analog-to-digital converter.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A signal conditioning circuit for a sonar receiver, comprising a linear voltage regulator circuit, a preamplifier circuit, a Butterworth bandpass filter circuit and an operational amplifier follower circuit, characterized in that: The preamplifier circuit is directly connected to the hydrophone to realize the preprocessing of weak signals, improve the impedance matching capability, and realize the amplification function of weak signals; the Butterworth bandpass filter circuit filters the signal output by the preamplifier circuit; the linear voltage regulator circuit provides stable voltage input for the positive and negative power input terminals of the four groups of operational amplifiers; the operational amplifier follower circuit has high input impedance and low output impedance, which improves the circuit's load capacity and outputs to the analog-to-digital conversion ADC circuit in the back-end signal acquisition circuit for high-precision analog-to-digital conversion; The negative feedback circuit part of the preamplifier circuit constitutes an amplifier circuit; The band-pass filter circuit is composed of a high-pass filter circuit and a low-pass filter circuit connected in series; both the high-pass filter circuit and the low-pass filter circuit are Butterworth filter types, and the entire band-pass filter circuit constitutes a Butterworth band-pass filter circuit; the topological structure of the high-pass filter circuit and the topological structure of the low-pass filter circuit are both Sallen-Key structures; The operational amplifier follower circuit is composed of a fourth operational amplifier and capacitors C27-30. The signal passing through the Butterworth bandpass filter circuit is input to the in-phase input terminal of the fourth operational amplifier, and the output terminal of the fourth operational amplifier is fed back to the inverting input terminal of the operational amplifier; two parallel capacitors C27 and C28 are connected in series between the positive power supply input terminal and the ground of the fourth operational amplifier, and the positive power supply input terminal is connected to the positive 5V output of the linear voltage-regulated power supply; two parallel capacitors C29 and C30 are connected in series between the negative power supply input terminal and the ground of the fourth operational amplifier, and the negative power supply input terminal is connected to the negative 5V output of the linear voltage-regulated power supply; thereby forming an operational amplifier follower circuit.

2. A signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: In the linear voltage stabilization circuit, for the circuit that provides a positive 5V power supply for four groups of operational amplifiers, a common positive 12V power supply is used to power the TPS3A4901 chip, and a capacitor C1 is connected in parallel to the positive 12V power supply end, which plays a role in smoothing voltage mutations and filtering high-frequency noise; for the circuit that provides a negative 5V power supply for four groups of operational amplifiers, a negative 12V power supply is used to power the TPS7A3001 chip, and a capacitor C5 is connected in parallel to the negative 12V power supply end, which also plays a role in smoothing voltage mutations and filtering high-frequency noise.

3. A signal conditioning circuit for a sonar receiver according to claim 2, characterized in that: The positive 12V power supply is connected to the power access terminal IN and the enable terminal EN of the TPS7A4901 chip. When the enable terminal EN is connected to the positive 12V voltage, the voltage regulator chip TPS7A4901 is turned on; the NR terminal of the TPS7A4901 chip is connected to the capacitor C3, the OUT terminal and the FB terminal are connected in series with a capacitor C2, the two ends of C2 are connected in parallel with a resistor R2, a resistor R1 is connected in series between the FB terminal and the ground, and a capacitor C4 is connected in series between the OUT terminal and the ground. By adjusting the resistance between R1 and R2, the desired output voltage is obtained.

4. A signal conditioning circuit for a sonar receiver according to claim 2, characterized in that: The negative 12V power supply is connected to the power supply access terminal IN and the enable terminal EN of the TPS7A3001 chip. When the enable terminal EN is connected to the negative 12V voltage, the voltage regulator chip TPS7A3001 is turned on; a capacitor C7 is connected between the NR terminal and the ground of the TPS7A3001 chip, a capacitor C6 is connected in series between the OUT terminal and the FB terminal, a resistor R3 is connected in series between the FB terminal and the ground, a resistor R4 is connected in parallel at both ends of C6, and a capacitor C8 is connected in series between the OUT terminal and the ground. The output voltage value is changed by adjusting the resistance value between R3 and R4.

5. A signal conditioning circuit for a sonar receiver according to any one of claims 1 to 4, characterized in that: In the linear voltage stabilization circuit, R1 uses a 4.99K resistor, and R2 uses a 16K resistor; the resistance value of R3 is 4.99K, and the resistance value of R4 is 16.2K.

6. The signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: The preamplifier circuit includes a first operational amplifier, resistors R5-R7 and capacitors C9-C14; the signal received from the hydrophone is connected to the non-inverting input terminal of the first operational amplifier through C10, and a resistor R7 is connected in series between the non-inverting input terminal of the first operational amplifier and the ground; a resistor R5 and a capacitor C9 are connected in series between the inverting input terminal of the first operational amplifier and the ground; a resistor R6 is connected in series between the output terminal and the inverting input terminal of the first operational amplifier as a negative feedback resistor; the positive 5V output of the linear voltage-stabilized power supply is connected to the positive power input terminal of the first operational amplifier, and two parallel capacitors C11 and C12 are connected in series between the positive power input terminal of the first operational amplifier and the ground; the negative 5V output of the linear voltage-stabilized power supply is connected to the negative power input terminal of the first operational amplifier, and two parallel capacitors C13 and C14 are connected in series between the negative power input terminal of the first operational amplifier and the ground.

7. The signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: In the preamplifier circuit, the voltage gain is Where G is the gain, and R5 and R6 are the resistance values ​​of the corresponding resistors in the designed circuit.

8. The signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: The high-pass filter circuit is composed of a second operational amplifier, a third operational amplifier, capacitors C15-C20 and resistors R8-R9; the low-pass filter circuit is composed of an operational amplifier and C21-C26 and resistors R10-R11; the amplified signal output by the preamplifier circuit is first input into the high-pass filter circuit, and the signal enters the in-phase input terminal of the second operational amplifier through C15 and C16, a resistor R8 is connected between the in-phase input terminal and the ground, a resistor R9 is connected between C15 and C16 and the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier is directly connected to the inverting input terminal; two parallel resistors C17 and C18 are connected in series between the positive power input terminal of the second operational amplifier and the ground; two parallel capacitors C19 and C20 are connected in series between the negative power input terminal of the second operational amplifier and the ground; the positive power input terminal of the second operational amplifier is connected to the positive 5V output of the linear voltage-stabilized power supply; the negative power input terminal of the second operational amplifier is connected to the negative 5V output of the linear voltage-stabilized power supply; The output signal of the high-pass filter circuit is input into the low-pass filter circuit. The signal obtained by the high-pass filter circuit first passes through the resistors R10 and R11 and enters the non-inverting input terminal of the third operational amplifier. A capacitor C22 is connected in series between the non-inverting input terminal of the third operational amplifier and the ground. A capacitor C21 is connected in series between the resistors R10 and R11 and the output terminal of the third operational amplifier. The output terminal of the third operational amplifier is directly connected to the inverting input terminal of the operational amplifier, forming a low-pass filter circuit; two parallel capacitors C23 and C24 are connected in series between the positive power input terminal of the third operational amplifier and the ground; two parallel capacitors C25 and C26 are connected in series between the negative power input terminal of the third operational amplifier and the ground; the positive power input terminal of the third operational amplifier is connected to the positive 5V output of the linear regulated power supply; and the negative power input terminal of the third operational amplifier is connected to the negative 5V output of the linear regulated power supply.

9. The signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: The small signal received by the hydrophone is input to the non-inverting input terminal of the preamplifier circuit through capacitor C10 and resistor R7. Capacitor C10 and R7 play a role in improving the performance and stability of the circuit. Negative feedback resistor R6 and resistor R5 play a role in amplifying the circuit signal. The capacitor C9 connected in series to the inverting input terminal plays a role in blocking DC signals, suppressing interference signals and noise, and preventing the operational amplifier from self-oscillating. The signal amplified by the preamplifier circuit enters a bandpass filter circuit composed of capacitors C15-C26, resistors R8-R11 and two operational amplifiers, which mainly filters out low-frequency and high-frequency noise and improves the signal-to-noise ratio of the signal. The filtered signal enters the operational amplifier follower circuit. The high input impedance and low output impedance of the operational amplifier follower circuit can achieve impedance matching with the back-end circuit and improve the load capacity of the circuit. The output signal enters the signal acquisition circuit for analog-to-digital conversion.

10. The signal conditioning circuit for a sonar receiver according to claim 1, characterized in that: The signal conditioned by the signal conditioning circuit is output to the high-precision analog-to-digital converter ADC of the signal acquisition circuit for analog-to-digital conversion and subsequent digital signal processing.

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