A low-noise and high-precision signal processing system for multi-beam echo sounder

Abstract

The invention discloses a low-noise and high-precision signal processing system for a multi-beam depth sounder. The system includes an RF transformer connected to a transducer, the RF transformer is connected to a preamplifier circuit, the preamplifier circuit is connected to a controllable gain circuit, the controllable gain circuit is connected to an anti-aliasing filter, the anti-aliasing filter is connected to an ADC drive circuit, and the ADC drive circuit is connected to an ADC conversion circuit. The processing loop of the invention adopts a fully differential design, which effectively avoids the influence of common-mode interference and other environmental noises, improves the signal-to-noise ratio of the signal, is conducive to the collection and processing of tiny signals, adopts a passive RF transformer for input impedance matching, does not cause system noise, and adopts a low-noise, low-power consumption device for the preamplifier circuit to avoid generating large noise before the preamplifier circuit; on the other hand, by improving the power supply module, it is ensured that the noise of the power supply at the first-stage amplifier circuit is the lowest, which is conducive to improving the signal-to-noise ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of multi-beam echo sounders, and in particular to a low-noise and high-precision signal processing system for a multi-beam echo sounder. Background Art

[0002] The multi-beam bathymetry system can achieve high-precision seabed depth measurement with ultra-wide coverage. It is a seabed topography measurement equipment with high measurement efficiency, high measurement accuracy and high resolution. It is particularly suitable for large-area sea sweeping measurement operations and has a wide range of applications in marine surveying and mapping and other fields.

[0003] When the system is working, the transmitting transducer emits sound waves to illuminate a narrow area of ​​water below the measuring ship. The sound waves propagate in the water and are reflected when they hit the interface of the bottom of the water such as mud and sand. The sound waves reaching the receiving transducer contain information such as the ups and downs of the underwater terrain. By performing a series of processing such as fixed-direction beam forming, energy accumulation, amplitude phase detection, etc. on the echo signal, strip-type high-density water depth data perpendicular to the ship's heading can be obtained to measure the seabed terrain characteristics within the strip along the route.

[0004] After the sound waves emitted by the transmitting transducer are absorbed, scattered, and reflected by the water, the signal strength reaching the receiving transducer is very weak, only a few millivolts or even microvolts. How to amplify these signals with low noise and high precision is a key difficulty.

[0005] The existing technology generally adopts the following methods to achieve the design purpose. First, although the signal from the receiving transducer is a differential signal, there is still a certain common-mode noise. Generally, the differential to single-ended method is used to eliminate the front-end noise. Secondly, the filter circuit is generally implemented with a dedicated chip, which generally has a relatively high power consumption. In addition, the high-precision requirements of the receiving channel, that is, the amplitude and phase consistency of the channel have a greater impact on the system performance. The current traditional design needs to further improve the consistency requirements. Although the existing circuit design can realize the function of the product, the performance of the final product is unsatisfactory, and the existing traditional technology cannot further improve the performance of the product. Summary of the invention

[0006] The object of the present invention is to provide a low-noise and high-precision signal processing system for a multi-beam echo sounder in view of the deficiencies in the prior art.

[0007] To achieve the above-mentioned object, the present invention provides a low-noise and high-precision signal processing system for a multi-beam echo sounder, comprising an RF transformer connected to a transducer, the RF transformer being connected to a preamplifier circuit, the preamplifier circuit being connected to a controllable gain circuit, the controllable gain circuit being connected to an anti-aliasing filter, the anti-aliasing filter being connected to an ADC driving circuit, and the ADC driving circuit being connected to an ADC conversion circuit.

[0008] Furthermore, it also includes a power supply module, which includes a first DC-DC module and a second DC-DC module connected to an external power supply, the first DC-DC module and the second DC-DC module are used to output a positive 5V voltage and a negative 5V voltage respectively, the first DC-DC module is connected to a first LDO module and a second LDO module, the first LDO module and the second LDO module are used to output positive 4.5V and 3.3V voltages respectively, the second DC-DC module is connected to a third LDO module, the third LDO module is used to output a negative 4.5V voltage, the first LDO module and the third LDO module are respectively connected to a preamplifier circuit, a controllable gain circuit, an anti-aliasing filter and an ADC drive circuit, and the second LDO module is connected to an ADC conversion circuit.

[0009] Furthermore, a primary filtering circuit is connected between the first LDO module and the third LDO module and the ADC driving circuit, and a secondary filtering circuit is connected between them and the anti-aliasing filter, a third filtering circuit is connected between the first LDO module and the third LDO module and the controllable gain circuit, and a fourth filtering circuit is connected between them and the preamplifier circuit.

[0010] Furthermore, inductors are connected between the first DC-DC module and the first LDO module and the second LDO module, and between the second DC-DC module and the third LDO module.

[0011] Furthermore, the ADC conversion circuit includes an AD chip, the AD chip is connected to a digital grounding area and an analog grounding area, an isolation area is provided between the digital grounding area and the analog grounding area, and the digital grounding area and the analog grounding area are bridged by a 0 ohm resistor.

[0012] Furthermore, the preamplifier circuit includes a differential amplifier of model LTC6363.

[0013] Beneficial effects: On the one hand, the present invention improves the signal processing circuit and adopts a fully differential design, which effectively avoids the influence of common-mode interference and other environmental noises, improves the signal-to-noise ratio of the signal, is beneficial to the collection and processing of small signals, and adopts a passive RF transformer for input impedance matching, which will not cause system noise. The preamplifier circuit adopts low-noise and low-power devices to avoid generating large noise before the preamplifier circuit; on the other hand, by improving the power supply module, it is ensured that the noise of the power supply at the first-stage amplifier circuit is the lowest, which is beneficial to improving the signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is the principle block diagram of the low noise and high precision signal processing system of the multi-beam echo sounder;

[0015] Figure 2 This is the circuit diagram of the RF transformer and preamplifier circuit;

[0016] Figure 3 This is the principle block diagram of the power module;

[0017] Figure 4 It is a schematic diagram of the setting of the digital grounding area and the analog grounding area;

[0018] Figure 5 It is a schematic diagram of the return ground settings of each channel of the multi-beam receiver system. DETAILED DESCRIPTION

[0019] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. The embodiments are implemented based on the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0020] like Figures 1 to 4 As shown, an embodiment of the present invention provides a low-noise and high-precision signal processing system for a multi-beam depth sounder, including an RF transformer 1 connected to a transducer, the RF transformer 1 is connected to a preamplifier circuit 2, the preamplifier circuit 2 is connected to a controllable gain circuit 3, the controllable gain circuit 3 is connected to an anti-aliasing filter 4, the anti-aliasing filter 4 is connected to an ADC drive circuit 5, and the ADC drive circuit 5 is connected to an ADC conversion circuit 6. After the signal is input from the transducer, it first enters the RF transformer 1 for impedance matching. The RF transformer 1 is a passive device and will not introduce system noise, which is particularly important for low-noise systems. Then it enters the preamplifier circuit 2 for pre-amplification. The preamplifier circuit 2 preferably uses a differential amplifier of model LTC6363. The voltage noise density of this device is 2.9nV / Hz, and the quiescent current is 2.0mA. It has low noise and low power consumption, which is very beneficial for amplifying tiny signals. The output signal of the preamplifier circuit 2 enters the controllable gain circuit 3 for time-controlled amplification, which can ensure that the echo energy of the middle and edge beams of the multi-beam system is balanced. Finally, the amplified signal enters the anti-aliasing filter 4 and the ADC driving circuit 5 in sequence, which facilitates the acquisition of the signal without distortion.

[0021] It also includes a power supply module, which includes a first DC-DC module 7 and a second DC-DC module 8 connected to an external power supply, wherein the input voltage of the external power supply is preferably 48V, the first DC-DC module 7 and the second DC-DC module 8 are respectively used to output a positive 5V voltage and a negative 5V voltage, the first DC-DC module 7 is connected to a first LDO module 9 and a second LDO module 10, the first LDO module 9 and the second LDO module 10 are respectively used to output positive 4.5V and 3.3V voltages, the second DC-DC module 8 is connected to a third LDO module 11, the third LDO module 11 is used to output a negative 4.5V voltage, the first LDO module 9 and the third LDO module 11 are respectively connected to the preamplifier circuit 2, the controllable gain circuit 3, the anti-aliasing filter 4 and the ADC drive circuit 5, and the second LDO module 10 is connected to the ADC conversion circuit 6.

[0022] A primary filter circuit is connected between the first LDO module 9 and the third LDO module 11 and the ADC driving circuit 5, and a secondary filter circuit is connected between it and the anti-aliasing filter 4, a third filter circuit is connected between the first LDO module 9 and the third LDO module 11 and the controllable gain circuit 3, and a fourth filter circuit is connected between it and the preamplifier circuit 2. In supplying power to the amplifier circuits at each level of the channel, we adopt a method in which the power supply direction is opposite to the signal flow direction, so that the power supply of the amplifier circuits at each level can be filtered step by step to ensure that the noise of the power supply at the first-stage amplifier circuit is the lowest, which is conducive to improving the signal-to-noise ratio. It should be noted that the filter circuit is an RC filter circuit, the primary filter circuit uses a group of RC filter circuits, the secondary filter circuit uses two groups of RC filter circuits, and so on.

[0023] Inductors are connected between the first DC-DC module 7 and the first LDO module 9 and the second LDO module 10, and between the second DC-DC module 8 and the third LDO module 11. This helps clean the power supply and does not interfere with the subsequent analog processing circuits.

[0024] The ADC conversion circuit 6 includes an AD chip, and the AD chip is connected to a digital grounding area and an analog grounding area. An isolation area is provided between the digital grounding area and the analog grounding area. The isolation area is artificially isolated when drawing the PCB, and the isolation area is not paved with copper (there is no reference ground, and it is best not to pass through the middle of the analog or digital signal line). The digital grounding area and the analog grounding area are separated to ensure their own independent return paths, and the digital grounding area and the analog grounding area are bridged by a 0 ohm resistor to ensure the consistency of the potential.

[0025] In addition, the receiving circuit of the existing multi-beam receiver system consists of 64 channels. In order to ensure the isolation between channels, Figure 5As shown, the present invention adopts the method of isolating the return ground of each channel and merging them at the LDO, which can ensure the independence of the return paths between channels and reduce the mutual interference of signal return. In addition, in the component layout layer of the circuit board, each channel is shielded with a shielding cover to further reduce the signal crosstalk between channels and improve the isolation of the channels.

[0026] The above is only a preferred embodiment of the present invention. It should be noted that for ordinary technicians in this technical field, other parts not specifically described belong to the prior art or common knowledge. Several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention.

Claims

1. A low-noise and high-precision signal processing system for a multi-beam echo sounder, characterized in that: comprising an RF transformer connected to the transducer, the RF transformer being connected to a preamplifier circuit, the preamplifier circuit being connected to a controllable gain circuit, the controllable gain circuit being connected to an anti-aliasing filter, the anti-aliasing filter being connected to an ADC drive circuit, and the ADC drive circuit being connected to an ADC conversion circuit; It also includes a power supply module, the power supply module includes a first DC-DC module and a second DC-DC module connected to an external power supply, the first DC-DC module and the second DC-DC module are respectively used to output a positive 5V voltage and a negative 5V voltage, the first DC-DC module is connected to a first LDO module and a second LDO module, the first LDO module and the second LDO module are respectively used to output positive 4.5V and 3.3V voltages, the second DC-DC module is connected to a third LDO module, the third LDO module is used to output a negative 4.5V voltage, the first LDO module and the third LDO module are respectively connected to a preamplifier circuit, a controllable gain circuit, an anti-aliasing filter and an ADC driving circuit, and the second LDO module is connected to an ADC conversion circuit; A primary filtering circuit is connected between the first LDO module and the third LDO module and the ADC driving circuit, and a secondary filtering circuit is connected between them and the anti-aliasing filter, a third filtering circuit is connected between the first LDO module and the third LDO module and the controllable gain circuit, and a fourth filtering circuit is connected between them and the preamplifier circuit; Inductors are connected between the first DC-DC module and the first LDO module and the second LDO module, and between the second DC-DC module and the third LDO module.

2. The low-noise and high-precision signal processing system for a multi-beam echo sounder according to claim 1, characterized in that: The ADC conversion circuit includes an AD chip, the AD chip is connected to a digital grounding area and an analog grounding area, an isolation area is provided between the digital grounding area and the analog grounding area, and the digital grounding area and the analog grounding area are bridged by a 0 ohm resistor.

3. The low-noise and high-precision signal processing system for a multi-beam echo sounder according to claim 1, characterized in that: The preamplifier circuit includes a differential amplifier of model LTC6363.

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