Low-noise receiver of multi-beam depth sounding sonar

Abstract

The utility model discloses a low-noise receiver of a multi-beam depth sounding sonar, which belongs to the technical field of sonar and comprises a front-end amplifying circuit, a fourth-order band-pass filter circuit, a variable gain amplifying circuit and a second-order band-pass filter circuit which are connected in sequence. A low-noise chip with stable performance is selected as a chip of each module circuit, and a fully differential circuit with strong common mode resistance is adopted as a circuit structure. After signals are processed by each module circuit, even small signals can be output in a measuring range, and high-precision adjustment and low-distortion amplification of the signals are realized. In the receiver system, a front-end amplification circuit is composed of a chip with the model of ADA4807-2, a band-pass filter circuit is composed of a chip with the model of THS4561, and a variable gain amplification circuit is composed of a chip with the model of AD8338.

Description

Technical Field

[0001] The utility model provides a low-noise receiver for a multi-beam depth sounding sonar, belonging to the technical field of sonar. Background Art

[0002] With the development of underwater acoustic communication technology, the requirements for receiver performance are getting higher and higher. Especially in applications such as deep-sea exploration, underwater target identification, and underwater navigation, higher requirements are placed on the sensitivity and anti-interference ability of the receiver. As one of the important factors affecting the performance of the receiver, circuit noise is particularly important to study and suppress it in depth.

[0003] The circuit noise of the underwater acoustic receiver mainly comes from electronic components, power supply, grounding system and signal processing circuit. The interference generated by these noise sources will affect the normal operation of the receiver, resulting in signal distortion, increased bit error rate, and even completely submerging useful signals. This will greatly affect the accuracy of the underwater acoustic receiving system, and in severe cases will affect the entire sonar system. The dual test of theory and practice tells us that exploring the source of noise in the underwater acoustic receiving system and effectively reducing or even suppressing noise without affecting the operation of the system are the directions that the receiver system will strive to develop now and in the future. Through the study of noise, effective measures can be taken to suppress circuit noise and reduce its interference with the signal, thereby improving the quality of analog signals and the anti-interference ability of the receiver. Utility Model Content

[0004] In view of the above technical problems, the utility model provides a low-noise receiver for multi-beam depth sounding sonar, comprising a front-end amplifier circuit, a fourth-order band-pass filter circuit, a variable gain amplifier circuit and a second-order band-pass filter circuit connected in sequence;

[0005] The front-end amplifier circuit is composed of the ADA4807-2 chip, powered by ±3.3V, and has a gain of 32dB.

[0006] The bandpass filter circuit is composed of the THS4561 chip, which is divided into a fourth-order bandpass filter circuit and a second-order bandpass filter circuit. The fourth-order bandpass filter circuit is powered by ±3.3V, and the gain is 0dB; the second-order bandpass filter circuit is powered by +5V and -3.3V, and the gain is 12dB.

[0007] The variable gain amplifier circuit is composed of the AD8338 chip, powered by 3.3V, and has a gain range of -12dB to 68dB.

[0008] The utility model selects low-noise and stable chips for each module circuit chip selection, and the circuit structure adopts a fully differential circuit with strong anti-common mode capability. After the signal is processed by each module circuit, even a very small signal can be output within the range, achieving high-precision signal regulation and low-distortion amplification. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is the overall framework diagram of the utility model;

[0010] Figure 2 A front-end amplifier circuit composed of ADA4807-2 of the utility model;

[0011] Figure 3 This is the internal structure diagram of the THS4561 chip of the utility model;

[0012] Figure 4 This is a schematic diagram of a fourth-order bandpass filter circuit of the utility model;

[0013] Figure 5 This is a schematic diagram of the second-order bandpass filter circuit of the utility model;

[0014] Figure 6 This is the functional block diagram of the AD8338 chip of the utility model;

[0015] Figure 7 This is a schematic diagram of a variable gain amplifier circuit of the utility model. DETAILED DESCRIPTION

[0016] The specific technical solution of the utility model is explained in conjunction with the embodiments.

[0017] A low-noise receiver for multi-beam depth sounding sonar, with fewer system components, all of which are low-noise and high-performance components. Specifically, it includes a front-end amplifier circuit, a fourth-order bandpass filter circuit, a variable gain amplifier circuit and a second-order bandpass filter circuit connected in sequence;

[0018] The front-end amplifier circuit is composed of the ADA4807-2 chip, powered by ±3.3V, and has a gain of 32dB.

[0019] The bandpass filter circuit is composed of the THS4561 chip, which is divided into a fourth-order bandpass filter circuit and a second-order bandpass filter circuit. The fourth-order bandpass filter circuit is powered by ±3.3V, and the gain is 0dB; the second-order bandpass filter circuit is powered by +5V and -3.3V, and the gain is 12dB.

[0020] The variable gain amplifier circuit is composed of the AD8338 chip, powered by 3.3V, and has a gain range of -12dB to 68dB.

[0021] like Figure 2As shown in the figure, in the front-end amplifier circuit composed of ADA4807-2, the chip is a low-noise, rail-to-rail input and output voltage feedback amplifier. It combines low power consumption, low noise, high speed and DC precision, and provides an excellent solution for a wide range of applications from high-resolution data acquisition instruments to high-performance battery-powered and high-component density systems. The chip can have differential input and differential output, and has a large gain. When the power supply is input, the resistors and capacitors form a passive low-pass filter, which can filter out part of the power supply noise. At the same time, the magnetic beads are placed to absorb specific frequency signals and filter out high-frequency noise. After the differential signal passes through the passive high-pass filter, the circuit gain can be changed by changing the resistance values ​​of R5, R7 and R10, which is 32dB in this state.

[0022] like Figure 3 As shown in the figure, in the bandpass filter circuit composed of THS4561, the chip has excellent performance, low power consumption, and a quiescent current of 775μA in working mode; it has low noise performance and can provide 4nV / √Hz input voltage noise; as a fully differential amplifier, the bandwidth is 60MHz, the slew rate is 315V / μs, the gain bandwidth product is 68MHz, and the 0.01% stabilization time is 90ns; its power supply operating voltage range is 2.85V to 12.6V, and it can achieve rail-to-rail output.

[0023] When the power is input, the resistor and capacitor form a passive low-pass filter, which can filter out some power supply noise. At the same time, the magnetic beads are placed to absorb specific frequency signals and filter out high-frequency noise. Figure 4 As shown in the figure, the passive filter composed of R44, R45 and C65 and R48, R49 and C70 in the circuit is used to filter out differential mode noise and reduce interference; R157, R158, R161, R165, R166, R177, R178, R182, R185 and R186 in the circuit are filter resistors, and C25, C26, C29, C30, C92, C93 and C96 are filter capacitors. Changing their sizes can change the center frequency, bandwidth and gain of the system. Under this parameter configuration, the center frequency of the filter circuit is 150kHz, the bandwidth is 60kHz and the gain is 0dB.

[0024] Since the chip has rail-to-rail output, in order to ensure the normal operation of subsequent acquisition chips, such as Figure 5As shown, the positive power input in the second-order bandpass filter circuit is +5V. In the power input, the resistors and capacitors form a passive low-pass filter, which can filter out some power supply noise. At the same time, the magnetic beads are placed to absorb specific frequency signals and filter out high-frequency noise. R300R302 R329R333 R334 in the circuit are filter resistors, and C154 C155 C158 C159 are filter capacitors. Changing their sizes can change the center frequency, bandwidth, and gain of the system. Under this parameter configuration, the center frequency of the filter circuit is 150kHz, the bandwidth is 60kHz, and the gain is 12dB.

[0025] like Figure 6 As shown in the figure, the variable gain amplifier circuit composed of AD8338 has a dynamic range of 80dB and is controlled by voltage control. The gain is adjusted by an externally set voltage. The initial gain can be changed by changing the resistance value of the input terminal in the peripheral circuit. AD8338 is a low-noise, low-power variable gain amplifier with a power supply range of 3V to 5V, a power supply current of only 3mA, and an input voltage noise of 4.5nV / √Hz.

[0026] like Figure 7 As shown in the figure, a passive RC network is used at the input end for filtering and DC isolation in order to filter out the interference of DC noise and filter out the common-mode and differential-mode noise outside the band. Since the maximum gain of AD8338 is 80dB, even very weak signals will produce great interference after amplification, so it is critical to add a passive filter at the input end.

[0027] The MODE pin of AD8338 is used to configure the positive and negative gradient of the gain. In this design, this pin is grounded and the gain is set to a negative gradient. That is, the larger the external input voltage, the smaller the gain, and the smaller the input voltage, the larger the gain.

[0028] The GAIN pin is the control voltage input, ranging from 0.1V to 1.1V. The gain can be changed by changing the voltage input. In this design, a negative gradient gain is used, and the gain formula is as follows:

[0029] G(dB)=(1.1-V GAIN )×80+20×log(R FBK / R IN )-26

[0030] Where V GAIN is the control voltage, R FBK The output resistance is 9.5kΩ, R IN is the input resistance. From the formula, we can know that when V GAIN When the gain is 1.1V, the gain is minimum. By changing R INThe size of R can change the starting gain value. According to the formula, when the starting gain is -12dB, R IN The value is 1.91kΩ.

Claims

1. A low-noise receiver for multi-beam bathymetric sonar, characterized in that: The invention comprises a front-end amplifier circuit, a fourth-order band-pass filter circuit, a variable gain amplifier circuit and a second-order band-pass filter circuit which are connected in sequence.

2. A low-noise receiver for multi-beam bathymetric sonar according to claim 1, characterized in that: The front-end amplifier circuit is composed of an ADA4807-2 chip, powered by ±3.3V, and has a gain of 32dB.

3. A low-noise receiver for multi-beam bathymetric sonar according to claim 1, characterized in that: The bandpass filter circuit is composed of the THS4561 chip, which is divided into a fourth-order bandpass filter circuit and a second-order bandpass filter circuit. The fourth-order bandpass filter circuit is powered by ±3.3V and has a gain of 0dB; the second-order bandpass filter circuit is powered by +5V and -3.3V and has a gain of 12dB.

4. A low-noise receiver for multi-beam bathymetric sonar according to claim 1, characterized in that: The variable gain amplifier circuit is composed of an AD8338 chip, powered by 3.3V, and has a gain range of -12dB to 68dB.

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