A design method for high-performance sonar bandpass filters

Abstract

The present invention discloses a high-performance sonar bandpass filter design method. The method uses a dual-channel operational amplifier and two universal filter chips in cascade, configures the peripheral resistors and peripheral capacitors of each second-order filter module according to system indicator requirements, and then performs fine-tuning through simulation to achieve the design of an ultra-high-order bandpass filter that can meet the ultra-high performance bandpass filter requirements of most sonars. At the same time, the number of configured peripheral components is relatively small, which facilitates design and debugging.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a design method for a high-performance sonar bandpass filter. Background Art

[0002] In sonar signal transmission and processing, the filter is a very important component, and its performance directly affects the quality of signal processing.

[0003] To achieve low noise, in-band flatness, and rapid out-of-band attenuation within the filter's passband, a bandpass filter is typically constructed by cascading multiple second-order active filter modules. Since the required attenuation is primarily determined by the filter order, the general filter simulation software FilterCAD can only implement filter circuits composed of general-purpose filter chips with an order of 16 or less, failing to meet the requirements for ultra-high-performance bandpass filters. Bandpass filter circuits based on operational amplifiers require numerous peripheral components, and at high center frequencies, the chip's ideal gain-bandwidth product must exceed 1GHz, making it difficult to achieve near-ideal chips. Summary of the Invention

[0004] In response to the above problems, the inventors provide a high-performance sonar bandpass filter design method, which can realize the design of a 20th-order ultra-high-order bandpass filter.

[0005] The present invention provides a method for designing a high-performance sonar bandpass filter. The high-performance sonar bandpass filter is composed of a dual-channel operational amplifier and two universal filter chips in cascade connection. The dual-channel operational amplifier includes two groups of second-order filter modules, and each universal filter chip includes four groups of second-order filter modules.

[0006] The method comprises:

[0007] Step 1: Calculate the center frequency, quality factor, and channel gain parameters of each set of second-order filter modules;

[0008] Step 2: Configure the peripheral resistors and capacitors of each second-order filter module according to the center frequency, quality factor, and channel gain parameters. Complete the configuration of the dual-channel operational amplifier and two universal filter chips respectively. After cascading, the initial bandpass filter is obtained. Among them, the two universal filter chips constitute eight groups of second-order filter modules.

[0009] The dual-channel operational amplifiers form two sets of second-order filter modules;

[0010] Step 3: Simulate the initial bandpass filter obtained in step 2, and adjust the peripheral resistors and capacitors according to the simulation curve until the index requirements are met;

[0011] Step 4: Power on the circuit for debugging, and adjust the peripheral resistors and capacitors according to the actual results to meet the index requirements.

[0012] Furthermore, the center frequency f0 is:

[0013]

[0014] Wherein, R2 is the first peripheral resistor.

[0015] Furthermore, the quality factor Q is:

[0016]

[0017] Among them, R Q is the second peripheral resistor.

[0018] Furthermore, the channel gain parameter H B for:

[0019]

[0020]

[0021] Among them, R IN is the third peripheral resistor, C IN For external capacitors.

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

[0023] (1) A hybrid structure combining a general filter and an operational amplifier is used to design a bandpass filter, achieving a 20th-order filter design that can meet the ultra-high performance bandpass filter requirements of most sonars.

[0024] (2) The designed bandpass filter has fewer overall peripheral components, which is convenient for design and debugging. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an existing second-order voltage-controlled voltage source bandpass filter circuit;

[0026] Figure 2 The simulated amplitude-frequency curve of the 20th-order op-amp-based bandpass filter designed for the control group;

[0027] Figure 3 The experimental group used the LTC1562I-2 universal filter chip with a basic bandpass configuration;

[0028] Figure 4 Amplitude-frequency curve of the experimental group. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings.

[0030] Project indicator requirements: 75kHz as the center frequency, -3dB bandwidth of 10kHz, attenuation at 85kHz is above 50dB, phase consistency is high, the highest quality factor is less than 50, and a Butterworth filter is required.

[0031] Control group:

[0032] With the existing second-order voltage-controlled voltage source bandpass filter circuit (such as Figure 1 As shown in the figure, a 20th-order bandpass filter based on an op amp is designed. The maximum quality factor of 10 second-order filter modules is 48.060, the center frequency is 80.101kHz, the required gain-bandwidth product is 2.467GHz, the minimum quality factor is 7.594, the center frequency is 74.22kHz, and the required gain-bandwidth product is 57.067MHz. The simulated amplitude-frequency curve is shown in the figure. Figure 2 As shown in the figure, the attenuation at 85kHz is about -62.2dB. This solution requires too high a gain-bandwidth product of the chip, making it difficult to implement.

[0033] Experimental group:

[0034] Two universal filter chips LTC 1562-2 are used to design eight groups of second-order filter modules. The operational amplifier chip LT6237 (gain bandwidth product 215MHz) is used to design two groups of second-order filter modules. The two different chips are cascaded to form a 20th-order ultra-high-order bandpass filter. The LTC 1562-2 can realize filters with a center frequency of 20 to 300kHz. The 20-100kHz frequency band can meet the filter applications of most sonar receivers. The LTC1562-2 chip is an active filter controlled by external components. It consists of four second-order filter modules internally. The center frequency f0, quality factor Q and gain of each group of second-order filter modules are calculated with the help of TI filter design tools. The center frequency f0, quality factor Q and gain of each group of second-order filter modules can be set by external resistors R or capacitors C. The chip bandpass configuration is as follows Figure 1 shown.

[0035] Wherein, the center frequency f0 is:

[0036]

[0037] The quality factor Q is:

[0038]

[0039] Channel gain parameter H B for:

[0040]

[0041]

[0042] According to formulas (1), (2), (3), and (4), the first peripheral resistor R2 and the second peripheral resistor R Q , the third peripheral resistor R IN and the external capacitor C IN .

[0043] Two universal filter chips, the LTC1562-2, form eight high-quality second-order filter modules, while the LT6237 operational amplifier chip forms two low-quality second-order filter modules. These two components are cascaded to form a 20th-order ultra-high-order bandpass filter. In module allocation, the quality factor (Q) represents the filter's selectivity at the center frequency. A higher Q requires a higher gain-bandwidth product (GBP). The LTC1562-2 is used to design the eight high-quality second-order modules, while the op amp-based filter module is used to design the two low-quality second-order modules. This reduces the op amp's GBP requirements. This design meets the ultra-high-performance bandpass filter requirements of most sonar applications.

[0044] like Figure 1 and Figure 3 As shown, the second-order filter module consists of three peripheral resistors and one peripheral capacitor. The overall peripheral components are only half of the peripheral components of the existing second-order voltage-controlled voltage source bandpass filter circuit, which is convenient for design and debugging.

[0045] The design scheme is simulated using LTspice simulation software, and the amplitude-frequency curve is as follows: Figure 4 As shown, the attenuation at 85kHz is over 62dB, meeting the design requirements. The LTC1562-2's 16th-order filter schematic design ideally achieves around 44dB attenuation. The 20th-order filter, combining the LTC1562-2 and LT6237, achieves over 18dB improvement, demonstrating excellent performance.

[0046] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A high-performance sonar bandpass filter design method, characterized in that: The high-performance sonar bandpass filter is composed of a dual-channel operational amplifier and two universal filter chips in cascade. The dual-channel operational amplifier includes two sets of second-order filter modules, and each universal filter chip contains four sets of second-order filter modules. The method comprises: Step 1: Calculate the center frequency, quality factor, and channel gain parameters of each group of second-order filter modules according to system index requirements; Step 2: Configure the peripheral resistors and capacitors of each second-order filter module according to the center frequency, quality factor, and channel gain parameters. Complete the configuration of the dual-channel operational amplifier and two universal filter chips respectively, and cascade them to obtain the initial bandpass filter; Among them, two universal filter chips constitute 8 groups of second-order filter modules; The dual-channel operational amplifiers form two sets of second-order filter modules; Step 3: Simulate the initial bandpass filter obtained in step 2, and adjust the peripheral resistors and capacitors according to the simulation curve until the index requirements are met; Step 4: Power on the circuit for debugging, and adjust the peripheral resistors and capacitors according to the actual results to meet the index requirements.

2. The high performance sonar bandpass filter design method according to claim 1, wherein: The center frequency is denoted as f0: Wherein, R2 is the first peripheral resistor.

3. The high performance sonar bandpass filter design method according to claim 2, wherein: The quality factor is denoted as Q: Among them, R Q is the second peripheral resistor.

4. The high performance sonar bandpass filter design method according to claim 3, wherein: The channel gain parameter is expressed as H B : Among them, R IN is the third peripheral resistor, C IN For external capacitors.

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