Design method of three-order active filtering automatic test system

Abstract

The invention discloses a design method of a three-order active filtering automatic test system, and the method comprises the steps: controlling a PXI platform through LabVIEW programming to achieve the generation of a sweep frequency signal and the collection of filtering response, and completing the signal processing, characteristic analysis and result visualization. The system integrates six core technologies, namely a modularized hardware architecture, automatic process control, frequency domain parameter precision measurement, multi-order characteristic synchronous detection, software and hardware collaborative linkage and simulation data comparison. On the basis of retaining traditional functions such as setting waveform type, amplitude, sweep frequency range, sampling rate, trigger mode, recording cut-off frequency, gain and other parameters, exponential sweep frequency accurate excitation and adaptive signal acquisition are innovatively realized, link interference is reduced through matrix switch multi-channel scheduling, a LabVIEW parallel thread and a feedback node mechanism are combined, and the adaptive signal acquisition is realized. And closed-loop analysis of amplitude-frequency / phase-frequency characteristics and real-time drawing of a Bode diagram are completed.

Description

Technical Field

[0001] This invention belongs to the fields of automated measurement and control and electronic circuit testing technology. It is a design method for an intelligent test system for filter performance that integrates the advantages of PXI modular hardware platform and LabVIEW graphical programming. Specifically, it is a design method for an automated test system for a third-order active filter, which is particularly suitable for scenarios such as electronic circuit R&D verification, industrial batch quality inspection, high-frequency signal processing equipment testing, and electronic technology experiments in universities. Background Technology

[0002] Traditional filter characteristic testing systems typically rely on manual connection of test circuits and point-by-point measurements using independent signal generators, oscilloscopes, and other instruments. This approach suffers from inherent drawbacks such as long testing cycles, susceptibility to data recording errors, and poor consistency of test results. Although existing technologies include graphical test interfaces based on LabVIEW and PXI modular hardware platforms, in the complete frequency response testing scenario of a third-order active low-pass filter, signal excitation, response acquisition, and channel switching still generally employ a separate operation mode, lacking a deep collaborative mechanism. This traditional technical system has three core limitations: First, testing the frequency domain characteristics of filters requires manual adjustment of the signal frequency and recording of the response at each frequency point, which is extremely inefficient when acquiring complete amplitude and phase frequency characteristic curves and makes it difficult to guarantee the continuity and accuracy of the frequency sweep process. Second, existing test systems mostly adopt fixed sampling strategies, which cannot dynamically adjust the oscilloscope sampling rate and recording length according to the current test frequency, resulting in insufficient resolution in the low-frequency band or aliasing distortion in the high-frequency band, which seriously affects the measurement accuracy of key parameters such as the cutoff frequency. Third, independent testing of the parameters of each order of a third-order filter requires frequent reconstruction of the test circuit. Existing solutions lack intelligent collaborative control between matrix switches and test instruments, making it impossible to achieve automatic switching and synchronous acquisition of the input signal and the output of each stage, and making it difficult to build a complete and accurate multi-order filter system model. To address the aforementioned bottlenecks, this invention innovatively constructs a fully closed-loop test architecture encompassing signal generation, filtering and transmission, data acquisition, and analysis and calculation. Through unified scheduling using LabVIEW, combined with an exponential sweep frequency algorithm and an adaptive sampling strategy, it achieves full automation of the test process, dynamic parameter optimization, and real-time calibration of phase-frequency characteristics, significantly improving the efficiency, accuracy, and engineering practicality of third-order active low-pass filter testing.

[0003] 1. A search revealed Chinese invention patent CN115981612A, which discloses a Python-based automated data verification platform and method for filters. The platform includes the following components: a data source generation unit that runs MATLAB code to store the sampling points of the signal to be filtered into text files with different filenames using filewriting functions such as `fwrite`, thus obtaining different parameter data sources; a platform control center that uses a Python module to control the reading of CSV files and transmits them to the MATLAB and VCS modules in the form of CSV configuration parameters; a comparison data generation unit that determines the correctness of the output data by subtracting the output data from the MATLAB and VCS modules to see if the result is zero; and a result storage unit that stores the comparison results of the MATLAB and VCS modules. Therefore, this invention not only enables highly automated data comparison by comparing output results with different configurations in a single program run, but also allows configuration parameters to be written into a CSV file in tabular form, enabling quick and accurate configuration of various parameter information.

[0004] The technical comparison between this application and the patent "A Python-based automated data verification platform and method for filters" is as follows:

[0005] The patent "A Python-based Automated Data Verification Platform and Method for Filters" is positioned for the field of digital signal processing, particularly for algorithm function verification in FPGA engineering. It aims to verify the correctness of the hardware implementation by automatically comparing output results under two different simulation environments: MATLAB and VCS. This patent, however, is positioned in the field of analog circuits and hardware testing. Its core objective is to perform end-to-end performance characterization of a physically existing third-order active filter, directly measuring its actual amplitude-frequency and phase-frequency responses. The application scenarios of the two are fundamentally different: the former is virtual, pre-silicon verification, while the latter is physical, post-silicon testing.

[0006] The core mechanism of the patent "A Python-based Automated Data Verification Platform and Method for Filters" is "parameter-driven automated comparison verification." It relies on a CSV configuration file to manage different test vectors, automatically schedules MATLAB and VCS execution via Python scripts, and subtracts the pure data files output by both point-by-point to determine complete consistency. In contrast, the core mechanism of this patent is "hardware-in-the-loop real-time closed-loop frequency sweep measurement." It uses software to control a physical signal generator to produce an excitation signal, which passes through the hardware filter under test. The input / output waveforms are acquired by a physical oscilloscope, and the gain (dB) and phase difference are calculated in real-time in the software, ultimately plotting a continuous frequency response curve. The former focuses on logical correctness, while the latter focuses on physical performance indicators.

[0007] The patent "A Python-based Automated Data Verification Platform and Method for Filters" features a system architecture built around a software simulation toolchain. Its core components are a Python control center, a MATLAB module, and a VCS module. The entire process is completed within the computer and does not involve real physical instruments. In contrast, the system architecture of this patent is a typical Automated Test Equipment (ATE) platform. Its core is the integration of physical hardware instruments via a PXI bus, with unified scheduling and data processing handled by LabVIEW software. The two systems have significantly different compositions: the former is a pure software simulation verification platform, while the latter is a hardware-software integrated physical test platform.

[0008] 2. A search revealed Chinese invention patent CN114371356A, which discloses a method and system for real-time monitoring of low-frequency, high-precision conducted injection voltage. This method employs a high-pass filter to effectively filter out the power supply voltage during the test, improving test safety. A high-precision, high-sampling-rate voltage sampling module acquires low-frequency injected voltage signals to obtain time-domain data, which is then processed to obtain frequency-domain data, improving the dynamic range of the test system. This invention enables rapid and accurate testing of small signals superimposed on AC signals during low-frequency injection interference tests in AC power systems. This invention is applicable to wide-bandwidth small-signal testing in various AC / DC power supply systems. Because the test system operates at a low frequency, a data acquisition card can be used to acquire the low-frequency voltage signal, eliminating the need for a high-sampling-rate, high-bandwidth oscilloscope. This significantly reduces the requirements for the oscilloscope, effectively lowering costs and facilitating the miniaturization of the test system, thus enabling easier completion of electromagnetic compatibility standard assessment tests.

[0009] The technical comparison between this application and "A method and system for real-time monitoring of low-frequency, high-precision conducted injection voltage" is as follows:

[0010] The patent "A Low-Frequency High-Precision Conducted Injection Voltage Real-Time Monitoring Method and System" is positioned in the field of electromagnetic compatibility testing, specifically addressing the challenge of accurately monitoring weak interference signals superimposed on high voltage during low-frequency interference injection tests on AC power lines. Its core innovation lies in using a high-pass filter to isolate the high-voltage fundamental wave, thereby safely and accurately capturing small signals. In contrast, this patent aims to comprehensively evaluate the performance of an independent functional analog filter circuit, focusing on the filter's attenuation and phase shift characteristics for signals of different frequencies, rather than extracting specific signals from complex background noise. The two patents have entirely different application purposes.

[0011] The core mechanism of the patent "A Method and System for Real-Time Monitoring of Low-Frequency High-Precision Conducted Injection Voltage" is "signal separation and high-precision acquisition." It uses a specially designed high-pass filter as a front end to physically filter out the 50 / 400Hz power supply fundamental frequency, allowing the subsequent high-resolution, high-sampling-rate acquisition card to focus on capturing the low-frequency injection signal of interest, and then converting it to the frequency domain for analysis using FFT. The core mechanism of this patent, however, is "dual-channel synchronous excitation and response analysis." It requires simultaneous and precise acquisition of the filter's input (Ch1) and output (Ch2) signals, and obtains the frequency response by calculating their RMS ratio and phase difference. The former focuses on the pure extraction of a single-channel signal, while the latter focuses on the correlation analysis of the dual-channel signals.

[0012] The system architecture of the patent "A Low-Frequency High-Precision Real-Time Monitoring Method and System for Conducted Injection Voltage" is customized for a specific EMC testing scenario, including specialized components such as high-pass filters, coupling transformers, and power amplifiers to form a complete closed loop for conducted interference injection and monitoring. In contrast, the system architecture of this patent is a general-purpose, reconfigurable analog circuit testing platform. It utilizes the flexibility of matrix switches to easily switch between different devices under test or test topologies, and its core instruments are also general-purpose laboratory equipment. The two systems differ in their versatility and design philosophy: the former is a highly specialized solution, while the latter is a flexible platform for general analog circuit testing. Summary of the Invention

[0013] To address the aforementioned technical problems, this invention proposes a design method for an automated testing system for third-order active filters. This method enables developers to efficiently control signal generators, oscilloscopes, matrix switches, and programmable power supply modules in a PXI platform through a unified LabVIEW graphical program, thereby achieving automated measurement and intelligent analysis of the full-band amplitude-frequency characteristics, phase-frequency characteristics, and key parameters of each order of a third-order active low-pass filter.

[0014] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0015] A design method for an automated testing system for a third-order active filter, characterized by the following steps:

[0016] S1. Hardware platform setup and standardized connections;

[0017] S2. Software environment configuration and program initialization;

[0018] S3. Test parameter setting and signal generation: Configure PXI-FGEN and use LabVIEW to design the program block diagram;

[0019] S4. Filtered signal acquisition and hardware coordination, configure PXI-SCOPE and use LabVIEW for program block diagram design;

[0020] S5. Signal Processing and Characteristic Analysis;

[0021] S6. Results Comparison and System Closure.

[0022] As a preferred technical solution of the present invention, step S1 is specifically as follows:

[0023] A modular test link was constructed using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction board.

[0024] The input, outputs of each stage, ±15V power supply, and ground of the third-order active low-pass filter are mapped to the column channels of the SCB-264X terminal block according to predefined pins. The PXIe-5402 signal generator and the PXIe-5114 digital oscilloscope are connected to the row channels accordingly. Hardware timing synchronization of FGEN excitation, SCOPE acquisition, and Switch channel switching is achieved based on the backplane bus of the PXI-4110 programmable DC power supply.

[0025] As a preferred technical solution of the present invention, step S2 is specifically as follows:

[0026] Load the test project in LabVIEW and create the main task. Call FGEN, SCOPE, Switch and DC Power driver APIs to bind resources and reset the status of each PXI module.

[0027] Outside the test loop, the FGEN signal is executed to terminate the operation and the matrix switches are completely disconnected. A 50ms delay is inserted to ensure the stability of the switch state, thus completing the initial ready state of hardware and software collaboration.

[0028] As a preferred technical solution of the present invention, step S3 is as follows:

[0029] Configure the frequency sweep test parameters on the LabVIEW user interface, including the excitation waveform type, signal amplitude, bias voltage and frequency range, and use a nonlinear frequency sweep strategy to control the PXIe-5402 signal generator to output a test excitation signal with variable frequency point by point according to a predetermined rule, which is used as the input of the filter under test.

[0030] As a preferred technical solution of the present invention: the method for setting test parameters and generating signals in step S3 requires configuring FGEN, and the specific steps are as follows:

[0031] S31: Prepare a modular test link using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction box as supporting hardware, and LabVIEW, FGEN, SCOPE, Switch, and DC Power driver as supporting software.

[0032] S32: Create a new [FGEN]Set Frequency.VI and save it to the Exercise folder;

[0033] S33: Locate the FGEN function toolkit in the block diagram and place the device initialization VI and termination VI;

[0034] S34: Configure core parameters for FGEN;

[0035] S35: Use local variables and attribute nodes to modify the FGEN output waveform;

[0036] S36: Press the stop button to stop the waveform output of the FGEN board and close the session with the device to release resources;

[0037] The steps of the FGEN main VI function are as follows:

[0038] S331: Place input and output controls on the front panel;

[0039] S332: Call the function to increment the increment by 1 and then divide by 2;

[0040] S333: Call the function to add the above result to the previous frequency;

[0041] S334: Call the function to perform exponentiation;

[0042] S335: Call the function, determine the range of the result and perform a type conversion, and output the result according to the different results.

[0043] As a preferred technical solution of the present invention, step S4 is specifically as follows:

[0044] At each excitation frequency point, the PXIe-5114 digital oscilloscope is synchronously triggered to acquire the input signal and the filtered output signal of the current gating order. The sampling rate is adaptively adjusted according to the signal frequency to ensure that a stable waveform with a sufficient number of cycles is captured.

[0045] By dynamically switching the internal connection path using the PXIe-2532 matrix switch, different orders of filter outputs are sequentially connected to the acquisition channel, enabling automatic and orderly measurement of multi-level response characteristics.

[0046] As a preferred technical solution of the present invention: the method of filtering signal acquisition and hardware coordination in step S4 requires SCOPE configuration, and the specific steps are as follows:

[0047] S41: Create a new [SCOPE]Set Sample Rate.VI and save it to the Exercise folder;

[0048] S42: Locate the SCOPE function toolkit in the block diagram and place the device initialization VI and termination VI;

[0049] S43: Configure the parameters of SCOPE in the loop;

[0050] S44: Configure the triggering method for SCOPE;

[0051] S45: Add a function to shut down the device and release resources;

[0052] The steps of the SCOPE main VI function are as follows:

[0053] S421: Place input and output controls on the front panel;

[0054] S422: Set the maximum and minimum sampling rate constants;

[0055] S423: Call the function to multiply the frequency by 20;

[0056] S424: Call the function to determine the frequency range and force conversion to obtain the sampling rate, and output the calculated sampling rate;

[0057] S425: Call the function to take the reciprocal of the frequency, multiply the reciprocal by 5 to get the acquisition time, and output the acquisition time;

[0058] S426: Call the function to multiply the sampling rate by the acquisition time to obtain the minimum number of data points, output the result and pass it to the main program.

[0059] As a preferred technical solution of the present invention, step S5 is as follows:

[0060] The acquired dual-channel time-domain waveform data is analyzed to extract amplitude and phase information, calculate the gain and phase difference at the corresponding frequency points, and normalize the phase results.

[0061] Using LabVIEW's data flow mechanism, frequency-gain and frequency-phase data are accumulated in real time to dynamically generate amplitude-frequency response curves and phase-frequency response curves.

[0062] As a preferred technical solution of the present invention: the signal processing and characteristic analysis method in step S5 requires configuring a signal processing sub-VI, and the specific steps are as follows:

[0063] The steps for measuring the amplitude and phase frequency main VI functions are as follows:

[0064] S51: Create a new Measure Gain and Phase.VI file and save it to the Exercise folder;

[0065] S52: Place input and output controls on the front panel;

[0066] S53: The amplitudes of Ch1 and Ch2 are labeled as "Ch1 Amp" and "Ch2 Amp" respectively;

[0067] S54: Call the function to divide "Ch1 Amp" and "Ch2 Amp" to obtain the voltage gain;

[0068] S55: Call the function to perform a logarithmic operation on the voltage gain;

[0069] S56: Call the function to multiply the above result by 20, convert it to decibels, and output the voltage gain;

[0070] S57: Call the function to subtract "Ch1 Amp" from "Ch2 Amp" to obtain the phase difference;

[0071] S58: Call the function, perform condition comparison, make corrections, and output the corrected result;

[0072] S59: Connect “error in input” to the error input ports of all sub-VIs and functions to form a complete error chain.

[0073] As a preferred technical solution of the present invention, step S6 is specifically as follows:

[0074] The key parameters in the measured frequency response characteristics are automatically compared with preset theoretical values ​​or simulation data to evaluate whether the performance of the filter under test meets the design expectations.

[0075] After the test is completed, turn off the signal output, disconnect the power supply, release the switch connection, and safely release all instrument resource references in sequence to complete the entire automated test process.

[0076] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0077] 1. This invention encapsulates the complex processes of signal generation, channel switching, data acquisition, and characteristic analysis of a third-order active low-pass filter using LabVIEW. Users only need to configure key information such as the sweep range, signal amplitude, and sampling parameters on the graphical front panel, and the system can automatically complete the entire process of testing and result visualization. This completely eliminates the cumbersome manual wiring, point-by-point frequency tuning, and manual data recording required in traditional testing, significantly reducing the operational threshold and greatly improving testing efficiency and convenience.

[0078] 2. It achieves flexible adaptation to test scenarios, supports custom configuration of parameters such as exponential sweep frequency parameters, sampling rate range, and number of acquisition cycles, and is compatible with the test requirements of active low-pass filters of different orders and cutoff frequencies. It can be quickly adapted to multiple scenarios such as R&D verification, industrial batch quality inspection, and university experimental teaching, improving the system's versatility and engineering adaptability.

[0079] 3. Adopting a multi-task collaborative architecture, the signal generator, oscilloscope, and matrix switch are synchronously triggered at the microsecond level through the PXI high-speed backplane bus, and the signal output, data acquisition, characteristic calculation and log storage tasks are processed in parallel to ensure that each module works together efficiently and without blocking each other; at the same time, phase correction, over-range protection and equipment anomaly diagnosis mechanisms are embedded, which significantly enhances the stability and fault tolerance of the system in scenarios such as long-term batch testing and high-frequency signal measurement.

[0080] 4. Leveraging the high precision of PXI modular hardware and the precise control capabilities of LabVIEW, combined with exponential sweep frequency algorithm and adaptive sampling strategy, it effectively avoids problems such as insufficient resolution in the low-frequency band and aliasing distortion in the high-frequency band. It accurately identifies key parameters such as filter amplitude-frequency gain, phase delay, and multiple cutoff frequencies. The measurement accuracy and repeatability far exceed those of traditional manual testing schemes, meeting the stringent requirements of high-frequency and high-precision filter characteristic testing.

[0081] 5. Automatically generates standardized reports containing instrument configuration parameters, frequency sweep data, amplitude / phase frequency characteristic curves, and comparison results of various indexes, and fully records the entire test process log. This not only facilitates subsequent performance traceability and data analysis, but also enables rapid reproduction of the test process, providing reliable data support for filter design optimization and quality control. Attached Figure Description

[0082] Figure 1 The front panel of the design method for an automated testing system for third-order active filters;

[0083] Figure 2 A flowchart illustrating the design method for an automated testing system for a third-order active filter;

[0084] Figure 3 The main VI of the signal generator is used in the design method of an automated testing system for third-order active filters.

[0085] Figure 4 The front panel of the sub-VI of the signal generator for the design method of a third-order active filter automated test system;

[0086] Figure 5 The program panel of the sub-VI of the signal generator for the design method of a third-order active filter automated test system;

[0087] Figure 6 The main VI of an oscilloscope for designing an automated testing system for a third-order active filter;

[0088] Figure 7 The front panel of a sub-VI of an oscilloscope for designing an automated test system for a third-order active filter;

[0089] Figure 8 The program panel of a sub-VI of an oscilloscope for designing an automated test system for a third-order active filter;

[0090] Figure 9 The main VI for the switching switch of the design method of the third-order active filter automated test system;

[0091] Figure 10 The main VI for real-time measurement and result display of the design method of the automated test system for third-order active filters;

[0092] Figure 11 The front panel of the sub-VI for real-time measurement and result display of the design method of the third-order active filter automated test system;

[0093] Figure 12 The flowchart of the sub-VI for real-time measurement and result display of the design method of the automated test system for third-order active filters;

[0094] Figure 13 A design method for an automated testing system for third-order active filters using DC Power's soft panel;

[0095] Figure 14 Example 1: Design method for an automated testing system for a third-order active filter;

[0096] Figure 15 Example 2: Design method of an automated testing system for a third-order active filter;

[0097] Figure 16 Example 3: Design method for an automated testing system for a third-order active filter. Detailed Implementation

[0098] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0099] The present invention proposes a design method for an automated testing system for third-order active filters, which enables developers to efficiently control signal generators, oscilloscopes, matrix switches, and programmable power supply modules in a PXI platform through a unified LabVIEW graphical program, thereby achieving automated measurement and intelligent analysis of the amplitude-frequency characteristics, phase-frequency characteristics, and key parameters of each order of a third-order active low-pass filter across the entire frequency band.

[0100] The PXI modular hardware architecture employs a high-precision, highly synchronized instrument module design. All modules achieve microsecond-level synchronous triggering and data interaction via the PXI high-speed backplane bus. This not only completely eliminates the cumbersome manual wiring, manual frequency adjustment, and step-by-step data recording operations of traditional filter testing, but also dynamically optimizes signal parameters and acquisition configurations based on the current test frequency through an innovative exponential sweep frequency algorithm and adaptive sampling strategy, ensuring the continuity and accuracy of test data across the entire frequency band. The system's built-in multi-order characteristic analysis engine can automatically complete gain conversion, phase correction, cutoff frequency identification, and theoretical value comparison, significantly improving the measurement accuracy, efficiency, and repeatability of third-order filter testing across the entire low-to-high frequency range. This provides a highly reliable and intelligent integrated testing solution for electronic circuit design verification, filter mass production quality inspection, communication system front-end optimization, and electronic experimental teaching in universities.

[0101] The specific technical solution of the present invention is as follows:

[0102] A design method for an automated testing system for a third-order active filter includes the following steps:

[0103] S1. Hardware platform setup and standardized connections;

[0104] A modular test link was constructed using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction board.

[0105] The input, outputs of each stage, ±15V power supply, and ground of the third-order active low-pass filter are mapped to the column channels of the SCB-264X terminal block according to predefined pins. The PXIe-5402 signal generator and the PXIe-5114 digital oscilloscope are connected to the row channels accordingly. The hardware timing synchronization of FGEN excitation, SCOPE acquisition, and Switch channel switching is realized based on the backplane bus of the PXI-4110 programmable DC power supply, ensuring a low-latency and high-consistency measurement path.

[0106] S2. Software environment configuration and program initialization;

[0107] Load the test project in LabVIEW and create the main task. Call FGEN, SCOPE, Switch and DC Power driver APIs to bind resources and reset the status of each PXI module.

[0108] Outside the test loop, the FGEN signal is executed to terminate the operation and the matrix switches are completely disconnected. A 50ms delay is inserted to ensure the stability of the switch state, thus completing the initial ready state of hardware and software collaboration.

[0109] S3. Test parameter setting and signal generation: Configure PXI-FGEN and use LabVIEW to design the program block diagram;

[0110] Configure the frequency sweep test parameters on the LabVIEW user interface, including the excitation waveform type, signal amplitude, bias voltage and frequency range, and use a nonlinear frequency sweep strategy to control the PXIe-5402 signal generator to output a test excitation signal with variable frequency point by point according to a predetermined rule, which is used as the input of the filter under test.

[0111] The test parameter setting and signal generation method in step S3 requires configuring FGEN. The specific steps are as follows:

[0112] S31: Prepare a modular test link using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction box as supporting hardware, and LabVIEW, FGEN, SCOPE, Switch, and DC Power driver as supporting software.

[0113] S32: Create a new [FGEN]Set Frequency.VI and save it to the Exercise folder;

[0114] S33: Locate the FGEN function toolkit in the block diagram and place the device initialization VI and termination VI;

[0115] S34: Configure core parameters for FGEN;

[0116] S35: Use local variables and attribute nodes to modify the FGEN output waveform;

[0117] S36: Press the stop button to stop the waveform output of the FGEN board and close the session with the device to release resources;

[0118] The steps of the FGEN main VI function are as follows:

[0119] S331: Place input and output controls on the front panel;

[0120] S332: Call the function to increment the increment by 1 and then divide by 2;

[0121] S333: Call the function to add the above result to the previous frequency;

[0122] S334: Call the function to perform exponentiation;

[0123] S335: Call the function, determine the range of the result and perform a type conversion, and output the result according to the different results.

[0124] S4. Filtered signal acquisition and hardware coordination, configure PXI-SCOPE and use LabVIEW for program block diagram design;

[0125] At each excitation frequency point, the PXIe-5114 digital oscilloscope is synchronously triggered to acquire the input signal and the filtered output signal of the current gating order. The sampling rate is adaptively adjusted according to the signal frequency to ensure that a stable waveform with a sufficient number of cycles is captured.

[0126] By dynamically switching the internal connection path using the PXIe-2532 matrix switch, different orders of filter outputs are sequentially connected to the acquisition channel, enabling automatic and orderly measurement of multi-level response characteristics.

[0127] The method of coordinating the acquisition of filtered signals with hardware in step S4 requires configuring SCOPE. The specific steps are as follows:

[0128] S41: Create a new [SCOPE]Set Sample Rate.VI and save it to the Exercise folder;

[0129] S42: Locate the SCOPE function toolkit in the block diagram and place the device initialization VI and termination VI;

[0130] S43: Configure the parameters of SCOPE in the loop;

[0131] S44: Configure the triggering method for SCOPE;

[0132] S45: Add a function to shut down the device and release resources;

[0133] The steps of the SCOPE main VI function are as follows:

[0134] S421: Place input and output controls on the front panel;

[0135] S422: Set the maximum and minimum sampling rate constants;

[0136] S423: Call the function to multiply the frequency by 20;

[0137] S424: Call the function to determine the frequency range and force conversion to obtain the sampling rate, and output the calculated sampling rate;

[0138] S425: Call the function to take the reciprocal of the frequency, multiply the reciprocal by 5 to get the acquisition time, and output the acquisition time;

[0139] S426: Call the function to multiply the sampling rate by the acquisition time to obtain the minimum number of data points, output the result and pass it to the main program.

[0140] S5. Signal Processing and Characteristic Analysis;

[0141] The acquired dual-channel time-domain waveform data is analyzed to extract amplitude and phase information, calculate the gain and phase difference at the corresponding frequency points, and normalize the phase results.

[0142] Using LabVIEW's data flow mechanism, frequency-gain and frequency-phase data are accumulated in real time to dynamically generate amplitude-frequency response curves and phase-frequency response curves.

[0143] The signal processing and characteristic analysis method in step S5 requires configuring a signal processing sub-VI. The specific steps are as follows:

[0144] The steps for measuring the amplitude and phase frequency main VI functions are as follows:

[0145] S51: Create a new Measure Gain and Phase.VI file and save it to the Exercise folder;

[0146] S52: Place input and output controls on the front panel;

[0147] S53: The amplitudes of Ch1 and Ch2 are labeled as "Ch1 Amp" and "Ch2 Amp" respectively;

[0148] S54: Call the function to divide "Ch1 Amp" and "Ch2 Amp" to obtain the voltage gain;

[0149] S55: Call the function to perform a logarithmic operation on the voltage gain;

[0150] S56: Call the function to multiply the above result by 20, convert it to decibels, and output the voltage gain;

[0151] S57: Call the function to subtract "Ch1 Amp" from "Ch2 Amp" to obtain the phase difference;

[0152] S58: Call the function, perform condition comparison, make corrections, and output the corrected result;

[0153] S59: Connect “error in input” to the error input ports of all sub-VIs and functions to form a complete error chain.

[0154] S6. Results Comparison and System Closure;

[0155] The key parameters in the measured frequency response characteristics are automatically compared with preset theoretical values ​​or simulation data to evaluate whether the performance of the filter under test meets the design expectations.

[0156] After the test is completed, turn off the signal output, disconnect the power supply, release the switch connection, and safely release all instrument resource references in sequence to complete the entire automated test process.

[0157] The design method of the automated testing system for a third-order active filter proposed in this invention can achieve the following functions:

[0158] 1. Utilize LabVIEW graphical programming to achieve deep collaborative control of signal generators, oscilloscopes, matrix switches, and programmable power supplies in a PXI platform. This enables fully automated testing from excitation signal generation, dynamic switching of test paths, synchronous acquisition of multi-channel signals, amplitude and phase characteristic calculation to result visualization, without the need for manual intervention in wiring and parameter adjustment.

[0159] 2. Supports flexible configuration of key parameters such as sweep frequency mode, frequency range, signal amplitude, and sampling rate. It can dynamically adjust the step and frequency boundary of the exponential sweep frequency according to the design requirements of the third-order active low-pass filter, and simultaneously optimize the oscilloscope sampling rate range and number of acquisition cycles to adapt to test scenarios of filters of different specifications.

[0160] 3. Automatically completes gain conversion, phase correction, multi-order cutoff frequency identification and theoretical value comparison, generates standardized test reports, and fully records instrument configuration parameters, frequency sweep data, amplitude-frequency / phase-frequency characteristic curves, key indicators of each order and operation logs, which facilitates subsequent performance analysis, quality traceability and test process reproduction.

[0161] 4. Based on the PXI high-speed backplane bus, the microsecond-level synchronous triggering and data interaction of each module are realized. The core sub-VI is integrated through LabVIEW to build a closed-loop architecture of "signal generation - filtering transmission - acquisition and analysis - result verification", which meets the high requirements of testing efficiency, accuracy and repeatability in scenarios such as R&D verification of third-order active low-pass filters, batch quality inspection, and teaching experiments.

[0162] Specifically:

[0163] I. Front Panel Design:

[0164] The front panel is the core interface for the software designed in this application to interact with the user. The user sets the test parameters of the third-order active low-pass filter, controls the signal excitation, channel switching and data acquisition process, and displays key measurement results such as time-domain waveform, amplitude frequency response (Gain) and phase frequency response (Phase) in real time.

[0165] The design of the front panel is as follows Figure 1 , Figure 4 , Figure 7 , Figure 11 As shown, it is mainly divided into the following functional areas:

[0166] 1. Signal Generator (FGEN) Parameter Setting Area

[0167] This area is used to configure the basic parameters of the excitation signal to ensure that the output signal meets the filter test requirements. It includes: FGEN Resource Name: A drop-down menu control for selecting the connected PXI signal generator resource, supporting multi-device switching; Standard Waveform: A list control providing various standard waveform options, including Sine, Square, Triangle, Ramp Up / Down, DC, and Noise; Amplitude (Vp-p): A rotary dial control for setting the peak-to-peak voltage of the output signal, ranging from 0 to 12 V; DC Offset (V): A rotary dial control for setting the DC bias of the output signal, ranging from -6 V to +6 V; Start Phase: A numerical input control for setting the starting phase of the sine wave, in degrees.

[0168] 2. SCOPE Digital Oscilloscope Parameter Setting Area

[0169] This area is used to configure the oscilloscope's acquisition parameters to match the signal frequency and dynamic range. It includes: ResourceName: A drop-down menu to select the connected PXI oscilloscope resource. Channel(s): A text input box to specify the acquisition channel, such as "0,1", where Channel 0 is the input signal and Channel 1 is the output signal. Timeout(s): A numerical input control to set the acquisition timeout, defaulting to 5.00 seconds to prevent program crashes due to prolonged waiting. Vertical Offset(V): A numerical input control to set the vertical offset. Vertical Range(V): A numerical input control to set the vertical scale range, covering ±3V signal amplitude. Trigger Modifier: A drop-down menu to select the trigger mode to ensure stable signal capture.

[0170] 3. Matrix Switch Parameter Setting Area

[0171] This area is used to configure the topology and connection paths of the matrix switch, enabling automatic switching between multiple nodes. It includes: Switch Name: a dropdown menu to select the connected PXI switch module; Topology Name: a dropdown menu to select a predefined switch topology; Connection List: a multi-line text box displaying the currently active connection paths, indicating that multiple input ports (r) are connected to the corresponding output ports (c), constructing a test link from FGEN → Filter → SCOPE; and Stop button: a red stop button used to terminate the test process and release all hardware resources.

[0172] 4. Real-time measurement and result display area

[0173] This area contains three graphical display controls for real-time presentation of test results, including: a Time Domain(s) graph (horizontal axis: time (s), vertical axis: voltage (V)); a Gain(dB) vs Frequency(Hz) graph (horizontal axis: frequency (Hz), ranging from 1 Hz to 1 kHz, vertical axis: gain (dB), ranging from 0 dB to -14 dB); and a Phase(deg) vs Frequency(Hz) graph (horizontal axis: frequency (Hz), ranging from 1 Hz to 1 kHz, vertical axis: phase (degrees), ranging from 120° to 180°).

[0174] II. Design of the program flowchart:

[0175] The flowchart is the core logic implementation part of the method of this invention. Based on the LabVIEW graphical programming environment, a design method for an automated test system for third-order active filters is realized through modular design.

[0176] like Figure 2 , Figure 5 , Figure 8 , Figure 12 As shown. According to the technical solution of the present invention, the program flowchart is divided into the following main VI and sub-VI, as detailed below:

[0177] 1. Setting the main VI function of the signal generator

[0178] like Figure 3 The main VI of the signal generator is used in the design method of an automated testing system for third-order active filters.

[0179] The main VI function is primarily used to control the complete excitation signal output process of the signal generator. It connects functional modules such as hardware initialization, waveform parameter configuration, frequency setting, amplitude adjustment, phase control, and output enable in a logical sequence to form an executable signal generation program. The main VI integrates a robust error handling mechanism to ensure the safety and reliability of FGEN hardware operation.

[0180] The steps of the main VI function are as follows:

[0181] Step 1: First, add the following input controls to the front panel: Amplitude (Vp-p), a numerical input control used to set the peak-to-peak value of the output signal; DC Offset (V), a numerical input control used to set the DC bias of the signal; Standard Waveform, a drop-down list control used to select the output waveform type; FGEN Resource Name, a string input control used to specify the signal generator device identifier; Channel, a numerical input control used to select the signal output channel; and Start Phase, a numerical input control used to set the initial phase of the signal.

[0182] Step 2: Call the Fgen Initialize With Channels VI to initialize the device and open the specified channel;

[0183] Step 3: Call Fgen Abort Generation VI to interrupt the current generation;

[0184] Step 4: Call Fgen Configure Output Mode VI to configure the output mode;

[0185] Step 5: Call Fgen Configure Standard Waveform VI to set the waveform type, amplitude, offset, frequency, phase, etc.;

[0186] Step 6: Call the Fgen Output Enable VI to enable output;

[0187] Step 7: Call Fgen Initiate Generation VI to start signal generation.

[0188] 2. Sub-VI function settings for the signal generator

[0189] like Figure 5 This is the program panel of the sub-VI of the signal generator for the design method of an automated test system for third-order active filters.

[0190] The core function of the sub-VI is to configure the output frequency of the signal generator. The specific process is as follows: This sub-VI receives the current frequency (Last Frequency) and frequency increment (Increment) input by the user, calculates and generates a new target frequency value. Internally, the sub-VI calls a mathematical operation node to add the previous frequency to the increment, achieving a gradual increase or decrease in frequency. Simultaneously, it uses a comparison function to determine if the new frequency is within the valid range (e.g., 0–1000 Hz), ensuring the output frequency meets hardware limitations. The sub-VI then passes the calculated frequency value and range check results to the next module, achieving seamless integration of the frequency sweep test process.

[0191] The steps for sub-VI are as follows:

[0192] Step 1: Create a new file named "[FGEN]Set Frequency.VI" and save it to the Exercise folder.

[0193] Step 2: Add input and output controls to the panel: Last Frequency (numerical control), stores the last frequency value; Increment (numerical control), sets the step size / increment of the exponential sweep; Frequency (numerical control), displays the current sweep frequency; Freq in range? (Boolean control), displays whether the current frequency is within the range of 0~1kHz.

[0194] Step 3: Call the addition function to increment the increment by 1;

[0195] Step 4: Call the division function to divide the increment by 2;

[0196] Step 5: Call the addition function to add the above result to the previous frequency;

[0197] Step 6: Call the exponentiation function to perform exponentiation;

[0198] Step 7: Call the judgment range and force conversion function to determine whether it is in the 0~1 kHz range; if the frequency is greater than 1000, output 1000; if it is less than 0, output 0; otherwise, output the current value.

[0199] 3. Setting the main VI function of the oscilloscope

[0200] like Figure 6 The main VI of an oscilloscope for designing an automated testing system for a third-order active filter;

[0201] The oscilloscope's main VI function is primarily used to control the complete signal acquisition and data preprocessing process of the oscilloscope. It logically connects functional modules such as device initialization, acquisition parameter configuration, multi-channel signal synchronous acquisition, data parsing, and characteristic curve plotting to form an executable filtered signal testing program. The main VI integrates a robust error handling mechanism, capturing issues such as device connection anomalies and acquisition timeouts through a chained error cluster propagation, ensuring the safety and reliability of the oscilloscope hardware operation.

[0202] The steps of the main VI function are as follows:

[0203] Step 1: First, add input and output controls to the front panel: Resource Name (string control), enter the oscilloscope device name; Channel Name (string control), enter the acquisition channel; Vertical Range (numerical control), set the oscilloscope's vertical range; Vertical Offset (numerical control), set the oscilloscope's vertical offset; Timeout(s), numerical control, set the acquisition timeout; Time Domain(s), indicator, display the acquired time domain waveform data.

[0204] Step 2: Call the Scope Initialize VI to connect the Resource Name control to its input.

[0205] The output session is connected to the session input of all subsequent Scope VIs.

[0206] Step 3: Call the Scope Configure Vertical VI: Configure the vertical range and vertical offset;

[0207] Step 4: Call [SCOPE]Set Sample Rate.VI: Set the sampling rate;

[0208] Step 5: Call Scope Configure Trigger and configure the trigger mode to "Instant Trigger".

[0209] Step 6: Call the Scope Initiate Acquisition VI: Start signal acquisition;

[0210] Step 7: Call the Scope Fetch VI to read the collected data.

[0211] 4. Setting up sub-VI functions on the oscilloscope

[0212] like Figure 7 The image shows the front panel of a sub-VI of an oscilloscope for designing an automated test system for a third-order active filter.

[0213] The core function of the sub-VI is to configure the oscilloscope's sampling parameters. The specific process is as follows: This sub-VI receives the user-input current test frequency and, combined with preset minimum and maximum frequency limits (Min Freq and Max Freq), calculates and generates a sampling rate, acquisition time, and minimum record length that match the signal characteristics. Internally, the sub-VI calls a mathematical operation node, multiplying the input frequency by 20 to obtain the recommended sampling rate, ensuring compliance with the Nyquist sampling theorem; simultaneously, it multiplies the reciprocal of the frequency by 5 to obtain the acquisition time, guaranteeing at least 5 complete signal cycles are acquired, thus improving FFT analysis accuracy. The sub-VI then passes the calculated Sample Rate, Acquisition Time, and Min record length to the next module, achieving automatic optimization and dynamic adjustment of the oscilloscope's acquisition configuration.

[0214] The steps for sub-VI are as follows:

[0215] Step 1: Create a new file named "[SCOPE]Set Sample Rate.VI" and save it to the Exercise folder;

[0216] Step 2: Add input and output controls to the front panel: Frequency, a numerical control, to input the frequency of the signal being measured; Max Freq, a numerical constant, set to 1 GHz; Min Freq, a numerical constant, set to 15260 Hz; Sample Rate, a numerical control, to display the final set sampling rate; Min record length, a numerical control, to display the minimum record length; Acquisition Time, a numerical control, to display the acquisition time.

[0217] Step 3: Set the maximum and minimum sampling rate constants;

[0218] Step 4: Call the multiplication function to multiply the frequency by 20;

[0219] Step 5: Call the range determination and forced conversion function to obtain the sampling rate, and output the calculated sampling rate;

[0220] Step 6: Call the reciprocal function to take the reciprocal of the frequency and calculate the period of a single signal;

[0221] Step 7: Call the multiplication function, multiply the reciprocal by 5 to obtain the acquisition time, and output the acquisition time;

[0222] Step 8: Call the multiplication function to multiply the sampling rate by the acquisition time to obtain the minimum number of data points (Min RecordLength), output the result and pass it to the main program.

[0223] 5. Setting the main VI function for the toggle switch

[0224] like Figure 9 The image shows the main VI of the switching switch for the design method of the third-order active filter automated testing system;

[0225] The main VI function is primarily used to control the complete path configuration and channel switching process of the switching switch. It logically connects functional modules such as hardware initialization, topology selection, channel connection configuration, and multi-channel switching execution to form an executable matrix switch control program. The main VI integrates a robust error handling mechanism to ensure the safety and reliability of the switch hardware operation. Furthermore, the main VI supports dynamic parameter configuration, such as selecting specific PXI switching devices, setting the physical topology of the switch matrix, and flexibly configuring the connection relationships of multiple input / output channels to adapt to multi-point measurement needs in different testing scenarios. By calling the SWITCH driver function, the main VI can achieve precise switching and status verification of specified channel combinations and supports batch multi-channel switching operations, improving the automation level of the system in complex applications such as multi-node filter testing and multi-channel signal routing.

[0226] The steps of the main VI function are as follows:

[0227] Step 1: Add input and output controls to the front panel: resource name (string control, enter the name of the switch device); topology name (string control, enter the switch topology type); connection list (string array control, configure multi-channel connection information); and error control.

[0228] Step 2: Call the SWITCH Initialize VI to initialize the switching device;

[0229] Step 3: Call the SWITCH Disconnect All Channels VI to disconnect all channels and ensure that all channels are disconnected to avoid residual connections affecting the new configuration;

[0230] Step 4: Invoke Switch Connect Channels, configure multi-channel connection, select Multiple mode, and connect the specified channels in sequence;

[0231] Step 5: Call the wait function, set the delay time to 50ms, and wait for the switch mechanical action to complete to ensure that the state is ready;

[0232] Step 6: Call the SWITCH Close VI, add as needed, to release device resources.

[0233] 6. Setting up the main VI function for real-time measurement and result display

[0234] like Figure 10 The main VI for real-time measurement and result display of the design method of the automated test system for third-order active filters;

[0235] The main VI function is primarily used to control the complete signal acquisition and measurement result display process of the oscilloscope. It logically connects functional modules such as channel configuration, sampling parameter setting, trigger mode selection, data acquisition, time-domain waveform processing, and multi-channel data display to form an executable signal measurement and visualization program. The main VI integrates a robust error handling mechanism to ensure the safety and reliability of the oscilloscope hardware operation.

[0236] Step 1: Add input and output controls to the front panel: Ch1 ​​Gain, a numerical control for channel 1 signal gain; Ch2 Gain, a numerical control for channel 2 signal gain.

[0237] Step 2: Add the signal processing core function, the WDT index channel DBL function, which is used to extract the numerical arrays of Ch1 and Ch2 from the 1D WDT waveform. The array operation module performs numerical calculations on the amplitude and phase of the extracted Ch1 and Ch2 arrays.

[0238] Step 3: Link connection and logic implementation. Connect the 1D WDT waveform output terminal to the WDT index channel DBL function to extract the numerical arrays of Ch1 and Ch2 respectively, and connect them to the Ch1 / Ch2 display controls.

[0239] 7. Sub-VI function settings for real-time measurement and result display

[0240] like Figure 12 The flowchart of the sub-VI for real-time measurement and result display of the design method of the automated test system for third-order active filters;

[0241] The core function of sub-VI is to realize real-time measurement and gain / phase calculation of dual-channel signals, and display the results. The specific process is as follows: This sub-VI receives Ch1 and Ch2 waveform data acquired from an oscilloscope, calls the waveform measurement function to extract the effective values ​​(RMS) of the two channels respectively, and calculates the voltage gain ratio (Gain(V)). Then, the gain value is converted to decibels (dB) through the "Convert to dB" node to obtain the Gain(dB) output. Simultaneously, the waveform measurement function obtains the phase information of the two channels, calculates the phase difference (Delta Phase), and performs negative phase correction: if the phase difference is less than -180°, 360° is added to ensure the result falls within the range of [0°, 360°], improving the continuity and readability of the phase display. Sub-VI passes the calculated Gain(dB) and Phase values ​​to the next module and uses an error chain mechanism to uniformly handle and report abnormal states, ensuring the accuracy of the measurement results and the stability of the system.

[0242] Step 1: Create a new document named "Measure Gain and Phase.VI" and save it to the Exercise folder.

[0243] Step 2: Add input and output controls to the front panel: Original signal Ch1, waveform control, the signal before the filter; Filtered signal Ch2, waveform control, the output signal after the filter; Gain (dB), numerical control, displays the gain value in decibels; Phase, numerical control, displays the corrected positive phase difference; Error control, error out, displays program error messages.

[0244] Step 3: The amplitudes of Ch1 and Ch2 are labeled as "Ch1 Amp" and "Ch2 Amp" respectively;

[0245] Step 4: Call the division function to divide "Ch1 Amp" and "Ch2 Amp" to obtain the voltage gain;

[0246] Step 5: Call the logarithmic function to perform a logarithmic operation on the voltage gain;

[0247] Step 6: Call the multiplication function to multiply the above result by 20, convert it to decibel form, and output the voltage gain;

[0248] Step 7: Call the subtraction function to subtract "Ch1 Amp" from "Ch2 Amp" to obtain the phase difference;

[0249] Step 8: Call the selection function, perform condition comparison, make corrections, and output the corrected result;

[0250] Step 9: Connect "error in input" to the error input ports of all sub-VIs and functions to form a complete error chain, and then set "error output" as the output port of the last error cluster to ensure that the exception can be caught by the upper-level program.

[0251] To enable those skilled in the art to better understand the solutions provided by this invention, three examples are given below in conjunction with experimental procedures.

[0252] After opening the software, the user will enter a state such as Figure 1 The user can then follow the steps shown on the interface to perform the operation.

[0253] Example 1:

[0254] Step 1: Select the waveform type as "Sine", set the amplitude to 5 V, the DC bias to 0 V, and the initial phase to 0° to ensure a clean test excitation signal is output;

[0255] Step 2: Set the acquisition channel to "0,1", the vertical range to 6V, and the trigger mode to "Auto Trigger" to ensure complete capture of input and output signals;

[0256] Step 3: Select the topology as "Configured Topology" and establish the following channel connections: r0 → c0, r1 → c1, r2 → c2, r3 → c3, r4 → c6, r5 → c7, r6 → c8, r7 → c9, to construct a complete signal transmission path;

[0257] Step 4: Open the DC Power soft panel, set CH1 and CH2 to +15 V and -15 V respectively, and enable both channels, as shown below. Figure 13 As shown;

[0258] Step 5: Run the program to see the time-domain characteristic curve, achieving the desired effect as follows. Figure 14 As shown.

[0259] Example 2:

[0260] Step 1: Select waveform type "Sine", set amplitude to 5 V, DC bias to 0 V, and initial phase to 0° to ensure a clean test excitation signal output;

[0261] Step 2: Set the acquisition channel to "0,1", the vertical range to 6V, and the trigger mode to "Auto Trigger" to ensure complete capture of input and output signals;

[0262] Step 3: Select the topology as "Configured Topology" and establish the following channel connections: r0 → c0, r1 → c1, r2 → c2, r3 → c3, r4 → c6, r5 → c7, r6 → c8, r7 → c9, to construct a complete signal transmission path;

[0263] Step 4: Open the DC Power soft panel, set CH1 and CH2 to +15 V and -15 V respectively, and enable both channels, as shown below. Figure 13 As shown;

[0264] Step 5: Run the program to see the amplitude-frequency response curve, achieving the desired effect as follows. Figure 15 As shown.

[0265] Example 3:

[0266] Step 1: Select the waveform type as "Sine", set the amplitude to 5 V, the DC bias to 0 V, and the initial phase to 0° to ensure a clean test excitation signal is output;

[0267] Step 2: Set the acquisition channel to "0,1", the vertical range to 6V, and the trigger mode to "Auto Trigger" to ensure complete capture of input and output signals;

[0268] Step 3: Select the topology as "Configured Topology" and establish the following channel connections: r0 → c0, r1 → c1, r2 → c2, r3 → c3, r4 → c6, r5 → c7, r6 → c8, r7 → c9, to construct a complete signal transmission path;

[0269] Step 4: Open the DC Power soft panel, set CH1 and CH2 to +15 V and -15 V respectively, and enable both channels, as shown below. Figure 13 As shown;

[0270] Step 5: Run the program to view the phase frequency response curve, achieving the desired effect as shown below. Figure 16 As shown.

[0271] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A design method for an automated testing system for a third-order active filter, characterized in that, Includes the following steps: S1. Hardware platform setup and standardized connections; S2. Software environment configuration and program initialization; S3. Test parameter setting and signal generation: Configure PXI-FGEN and use LabVIEW to design the program block diagram; S4. Filtered signal acquisition and hardware coordination, PXI-SCOPE configuration and LabVIEW for program block diagram design; S5. Signal Processing and Characteristic Analysis; S6. Results Comparison and System Closure.

2. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S1 is as follows: A modular test link was constructed using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction board. The input, outputs of each stage, ±15V power supply, and ground of the third-order active low-pass filter are mapped to the column channels of the SCB-264X terminal block according to predefined pins. The PXIe-5402 signal generator and the PXIe-5114 digital oscilloscope are connected to the row channels accordingly. Hardware timing synchronization of FGEN excitation, SCOPE acquisition, and Switch channel switching is achieved based on the backplane bus of the PXI-4110 programmable DC power supply.

3. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S2 is as follows: Load the test project in LabVIEW and create the main task. Call FGEN, SCOPE, Switch and DC Power driver APIs to bind resources and reset the status of each PXI module. Outside the test loop, the FGEN signal is executed to terminate the operation and the matrix switches are completely disconnected. A 50ms delay is inserted to ensure the stability of the switch state, thus completing the initial ready state of hardware and software collaboration.

4. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S3 is as follows: Configure the frequency sweep test parameters on the LabVIEW user interface, including the excitation waveform type, signal amplitude, bias voltage and frequency range, and use a nonlinear frequency sweep strategy to control the PXIe-5402 signal generator to output a test excitation signal with variable frequency point by point according to a predetermined rule, which is used as the input of the filter under test.

5. The design method of a third-order active filter automated testing system according to claim 4, characterized in that, The test parameter setting and signal generation method in step S3 requires configuring FGEN. The specific steps are as follows: S31: Prepare a modular test link using a PXIe-5402 signal generator, a PXIe-5114 digital oscilloscope, a PXIe-2532 matrix switch, a PXI-4110 programmable DC power supply, a TB-2641B junction box, and an SCB-264X junction box as supporting hardware, and LabVIEW, FGEN, SCOPE, Switch, and DC Power driver as supporting software. S32: Create a new [FGEN]Set Frequency.VI and save it to the Exercise folder; S33: Locate the FGEN function toolkit in the block diagram and place the device initialization VI and termination VI; S34: Configure core parameters for FGEN; S35: Use local variables and attribute nodes to modify the FGEN output waveform; S36: Press the stop button to stop the waveform output of the FGEN board and close the session with the device to release resources; The steps of the FGEN main VI function are as follows: S331: Place input and output controls on the front panel; S332: Call the function to increment the increment by 1 and then divide by 2; S333: Call the function to add the above result to the previous frequency; S334: Call the function to perform exponentiation; S335: Call the function, determine the range of the result and perform a type conversion, and output the result according to the different results.

6. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S4 is as follows: At each excitation frequency point, the PXIe-5114 digital oscilloscope is synchronously triggered to acquire the input signal and the filtered output signal of the current gating order. The sampling rate is adaptively adjusted according to the signal frequency to ensure that a stable waveform with a sufficient number of cycles is captured. By dynamically switching the internal connection path using the PXIe-2532 matrix switch, different orders of filter outputs are sequentially connected to the acquisition channel, enabling automatic and orderly measurement of multi-level response characteristics.

7. The design method of a third-order active filter automated testing system according to claim 6, characterized in that, The method of coordinating the acquisition of filtered signals with hardware in step S4 requires configuring SCOPE. The specific steps are as follows: S41: Create a new [SCOPE]Set Sample Rate.VI and save it to the Exercise folder; S42: Locate the SCOPE function toolkit in the block diagram and place the device initialization VI and termination VI; S43: Configure the parameters of SCOPE in the loop; S44: Configure the triggering method for SCOPE; S45: Add a function to shut down the device and release resources; The steps of the SCOPE main VI function are as follows: S421: Place input and output controls on the front panel; S422: Set the maximum and minimum sampling rate constants; S423: Call the function to multiply the frequency by 20; S424: Call the function to determine the frequency range and force conversion to obtain the sampling rate, and output the calculated sampling rate; S425: Call the function to take the reciprocal of the frequency, multiply the reciprocal by 5 to get the acquisition time, and output the acquisition time; S426: Call the function to multiply the sampling rate by the acquisition time to obtain the minimum number of data points, output the result and pass it to the main program.

8. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S5 is as follows: The acquired dual-channel time-domain waveform data is analyzed to extract amplitude and phase information, calculate the gain and phase difference at the corresponding frequency points, and normalize the phase results. Using LabVIEW's data flow mechanism, frequency-gain and frequency-phase data are accumulated in real time to dynamically generate amplitude-frequency response curves and phase-frequency response curves.

9. The design method of a third-order active filter automated testing system according to claim 8, characterized in that, The signal processing and characteristic analysis method in step S5 requires configuring a signal processing sub-VI. The specific steps are as follows: The steps for measuring the amplitude and phase frequency main VI functions are as follows: S51: Create a new Measure Gain and Phase.VI file and save it to the Exercise folder; S52: Place input and output controls on the front panel; S53: The amplitudes of Ch1 and Ch2 are labeled as "Ch1 Amp" and "Ch2 Amp" respectively; S54: Call the function to divide "Ch1 Amp" and "Ch2 Amp" to obtain the voltage gain; S55: Call the function to perform a logarithmic operation on the voltage gain; S56: Call the function to multiply the above result by 20, convert it to decibels, and output the voltage gain; S57: Call the function to subtract "Ch1 Amp" from "Ch2 Amp" to obtain the phase difference; S58: Call the function, perform condition comparison, make corrections, and output the corrected result; S59: Connect "error in input" to the error input ports of all sub-VIs and functions to form a complete error chain.

10. The design method of a third-order active filter automated testing system according to claim 1, characterized in that, Step S6 is as follows: The key parameters in the measured frequency response characteristics are automatically compared with preset theoretical values ​​or simulation data to evaluate whether the performance of the filter under test meets the design expectations. After the test is completed, turn off the signal output, disconnect the power supply, release the switch connection, and safely release all instrument resource references in sequence to complete the entire automated test process.

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