Multi-channel weak signal multi-frequency positioning digital phase-locked loop method and amplifier system

Abstract

This invention discloses a digital phase-locked loop (PLL) method and amplifier system for multi-frequency positioning of multi-channel weak signals. The system includes: a signal input module, a reference signal module, a phase-sensitive detector module, and a detection result display module. The PLL method is as follows: First, multiple channels of signals to be tested are input and summed into a single signal. Then, the frequency of the reference signal is set according to the frequency of the signals to be tested. Next, the merged signal to be tested is input into different phase-sensitive detectors along with different reference signals. The amplitude and phase of the corresponding frequency signal are calculated from the signals obtained by the phase-sensitive detectors. Finally, the calculated signal amplitude is input into the display module for display of the PLL amplification result. This invention can effectively perform multi-frequency positioning of multi-channel weak signals and effectively detect the amplitude and phase of the signals, exhibiting high computational efficiency.

Description

Technical Field

[0001] This invention belongs to the technical field of multi-frequency weak signal detection equipment, and specifically relates to a multi-channel weak signal multi-frequency positioning digital lock-in amplifier. Background Technology

[0002] Lock-in amplifiers (LIPs), as a commonly used method for weak signal detection, have attracted considerable attention from researchers and have wide applications in weak signal detection and weak damage detection. Numerous attempts have been made to improve LIPs. However, due to limitations imposed by the correlation between signals, LIPs cannot achieve satisfactory results in detecting multi-frequency weak signals.

[0003] Currently, digital lock-in amplifiers (LLPs) are widely used for detecting weak single-frequency signals. Among them, dual-channel orthogonal vector digital LLPs are widely used, such as the patent "A Digital Lock-in Amplification Processing Method Based on Precise Automatic Frequency Tracking Using FPGA" (application number: CN201810717251.X) applied for by China University of Geosciences (Wuhan); and the patent "A Digital Lock-in Amplification Processing Method Based on Interpolation DFT Signal Synchronization" (application number: CN202111408144.7) applied for by Hunan Wuling Electric Power Technology Co., Ltd. and Wuling Electric Power Co., Ltd., etc. These methods can only detect weak single-frequency signals. There are also multi-channel digital LLPs, such as the patent "A Synchronous Multi-channel Digital Lock-in Amplifier" (application number: 202010678683.1) applied for by Guangzhou Sain Scientific Instruments Co., Ltd. This method uses multi-channel input and a single reference signal to perform phase-sensitive detection on the signals to be detected from multiple channels sequentially. Although this saves instrument size and reduces instrument manufacturing costs, it greatly increases time costs, which are reflected not only in the frequency matching of the reference signal but also in the time costs incurred by the filter when performing multiple filtering operations. Summary of the Invention

[0004] To address the limitations of digital lock-in amplifiers in rapidly and efficiently detecting the amplitude and phase of weak, multi-channel multi-frequency signals, this invention provides a multi-channel digital lock-in amplifier for weak signal localization. Digital lock-in amplification technology serves as the fundamental method for weak signal detection. Multiple reference signals and phase-sensitive detectors provide a rapid detection method for weak, multi-channel multi-frequency signals. An oscilloscope serves as the final display of amplitude, phase, and detection results, ensuring that weak, multi-channel multi-frequency signals can be detected.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A multi-frequency digital phase-locked loop method for multi-channel weak signals includes the following steps:

[0007] Step 1: Add the L signals to be measured and a white noise signal together to form a single input signal, and then input the input signal into the L phase-sensitive detectors respectively.

[0008] Step 2: Set one reference signal for each signal to be tested. Each reference signal corresponds to the frequency of a signal to be tested. Input the L reference signals and one input signal into a phase-sensitive detector for detection.

[0009] Step 3: After processing the reference signal and the original signal in the phase-sensitive detector, the results are output to the display module to observe the detection results of the amplitude and phase of the signal under test.

[0010] Furthermore, the summation of the L test signals and the white noise signal in step 1 includes the following specific steps:

[0011] Step 11: Simultaneously input L signals to be measured and a randomly generated white noise into a summer to add them together into a single input signal;

[0012] Step 12: Divide the input signal after the summer into several identical signals, input them into a phase-sensitive detector for digital phase-locked amplification, and input them into an oscilloscope for comparison with the detection results.

[0013] Furthermore, step 2 includes the following process:

[0014] Step 21: Set a reference signal with an amplitude of one unit for each signal to be tested, and generate L reference signals. The frequency of each reference signal is the same as the frequency of its corresponding signal to be tested. For each of the L reference signals with different frequencies, construct two in-phase orthogonal reference signals.

[0015] Step 22: Input the two generated reference signals and the input signal into the same phase-sensitive detector;

[0016] Step 23: Perform low-pass filtering on the results of correlation operations between the two reference signals and the signal to be tested to obtain two DC signals;

[0017] Step 24: Square the two DC signals respectively, add them together, and then take the square root of the sum to obtain the amplitude curve of the signal under test;

[0018] Step 25: Calculate the arctangent function value of the quotient of the two DC signals to obtain the phase curve of the signal under test;

[0019] Step 26: Multiply the amplitude detection result by one reference signal to obtain the signal detection result.

[0020] Furthermore, step 3, after processing the reference signal and the original signal in the phase-sensitive detector, outputs the result to the display module to display the amplitude, phase, and detection result, including the following specific steps:

[0021] Step 31: Input the L amplitudes and phases of the signal to be tested obtained above into the oscilloscope to display the results;

[0022] Step 32: Add the L signal processing results of the signal to be tested obtained above, merge them into one signal, input it into the oscilloscope, and compare it with the original signal input into the oscilloscope.

[0023] This application also provides a multi-channel weak signal multi-frequency positioning digital lock-in amplifier system, the amplifier system comprising:

[0024] The input signal module sums L test signals and a white noise signal, and combines them into a single input signal.

[0025] A reference signal module is provided, wherein each signal under test is provided with one reference signal, and the reference signal has the same frequency as the corresponding signal under test.

[0026] A phase-sensitive detector module is used to receive the input signal and the reference signal generation module to obtain the detection results of the amplitude and phase of the signal under test;

[0027] The result display module is used to observe the detection results of the amplitude and phase of the signal under test.

[0028] Compared with existing technologies, the present invention has the following advantages:

[0029] This invention utilizes multi-channel reference signals to simultaneously detect multi-channel signals under test. Employing multiple phase-sensitive detectors and low-pass filters, it enables the simultaneous detection of the amplitude and phase of multiple frequency components of the multi-frequency signal, improving the efficiency of multi-channel weak signal detection. By adding the signals from multiple channels and merging them into a single signal, the number of input lock-in amplifier interfaces is reduced, making it applicable to single-channel weak multi-frequency signals as well, thus expanding its applicability. This invention can effectively detect multiple frequencies of multi-channel weak signals and effectively detect the amplitude and phase of each frequency signal. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the principle framework of the present invention;

[0031] Figure 2 It is the amplitude of the frequency corresponding to the mixed signal detected in this invention;

[0032] Figure 3 It is the phase of the frequency corresponding to the mixed signal detected in this invention;

[0033] Figure 4 This is a comparison diagram of the detection results and the original input signal in this invention;

[0034] Figure 5 This is a schematic diagram of the circuit structure of the phase-sensitive detector module. Detailed Implementation

[0035] The present invention will be further described below with reference to embodiments.

[0036] Example 1

[0037] This embodiment is a multi-channel, multi-frequency positioning digital lock-in amplifier system for weak signals, such as... Figure 1 As shown, the system includes a signal input module, a reference signal module, a phase-sensitive detection module, and a detection result display module. The amplifier system includes:

[0038] The input signal module sums L test signals and a white noise signal, and combines them into a single input signal.

[0039] A reference signal module is provided, wherein each signal under test is provided with one reference signal, and the reference signal has the same frequency as the corresponding signal under test.

[0040] A phase-sensitive detector module is used to receive the input signal and the reference signal generation module to obtain the detection results of the amplitude and phase of the signal under test;

[0041] The result display module is used to observe the detection results of the amplitude and phase of the signal under test.

[0042] Example 2

[0043] Based on the above-mentioned multi-channel weak signal multi-frequency positioning digital phase-locked amplifier system, this invention proposes a multi-channel weak signal multi-frequency positioning digital phase-locked method, the specific steps of which are as follows:

[0044] Step 1: Add the L signals to be measured and a white noise signal together to form a single signal, and input the sum into the L phase-sensitive detectors respectively.

[0045] L signals to be measured and a randomly generated white noise are synchronously input into a summer and added together to form a single channel signal.

[0046] Suppose that the mixed signal contains L different frequency components, with frequencies f1 = n1 × f, f2 = n2 × f, ..., f L =n L×f(n1≠n2≠…≠n L The amplitudes are A1, A2, ..., A L The phases are Φ1, Φ2, ..., Φ L Sampling frequency f s = N×f(N>2max(n1,n2,…,n) L The number of sampling periods is q, and the total number of sampling points is M = N × q.

[0047] Let the input signal V s (k) is:

[0048]

[0049] Step 2: Set up L reference signals with the same frequency as the original signal. Input these L reference signals into the phase-sensitive detectors that input the original signal at the corresponding frequency.

[0050] L reference signals are generated, each with the same frequency as the L signals to be detected. For each of the L different frequency components, two in-phase orthogonal reference signals are constructed respectively.

[0051]

[0052] The two generated reference signals and the test signal of the same frequency are input into the same phase-sensitive detector;

[0053] The results of correlation operations between the two reference signals and the signal to be tested are low-pass filtered to obtain two DC signals.

[0054] Then V s (k) and The cross-correlation functions are respectively V s (k) and The cross-correlation functions are respectively

[0055]

[0056]

[0057] …

[0058]

[0059] and These represent in-phase output and quadrature output, respectively.

[0060] Square the two DC signals separately, add them together, and then take the square root of the sum to obtain the amplitude of the signal under test. Calculate the arctangent function value of the quotient of the two DC signals to obtain the phase of the signal under test. Therefore, the amplitude and phase at each frequency are:

[0061]

[0062] The amplitude detection result is multiplied by a generated reference signal to obtain the signal detection result.

[0063]

[0064] Step 3: After processing the reference signal and the original signal in the phase-sensitive detector, the results are output to the display module to display the amplitude and detection results.

[0065] The L amplitudes and phases of the signal to be tested obtained above are input into an oscilloscope for display of the results, such as... Figure 2 The amplitude detection results are displayed. Figure 3 The phase detection results are shown. In this example, we choose L=4, that is, a 4-channel weak signal 4-frequency positioning phase-locked amplification, to simultaneously detect the amplitude and phase of 4 weak signals of different frequencies;

[0066] The L processed signals of the signal under test obtained above are added together and combined into one signal, which is then input into an oscilloscope for comparison and display with the original signal input into the oscilloscope. Figure 4 The signal detection results shown are as follows: the black line represents the original four input signals plus white noise, which are then input into the lock-in amplifier; the red line represents the result after detection by the lock-in amplifier. This demonstrates that the method provided by this invention can effectively detect the amplitude and phase of four frequency signals under noise conditions.

[0067] The above description is merely an example of a 4-channel weak signal digital lock-in amplifier selected by the present invention. It should be noted that for those skilled in the art, without departing from the principle of the present invention, the method of the present invention can be applied to other similar multi-channel weak signal processing and some improvements and modifications can be made. These improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A multi-frequency digital phase-locked loop method for multi-channel weak signals, characterized in that, Includes the following steps: Step 1: Add the L signals to be measured and a white noise signal together to form a single input signal, and then input the input signal into the L phase-sensitive detectors respectively. Suppose that the mixing signal contains different There are several frequency components, with frequencies of respectively , … , The amplitudes are respectively , … The phases are respectively , … Sampling frequency , The number of sampling periods is The total number of sampling points is ; Let the input signal be for: ； Step 2: Set one reference signal for each signal to be tested. Each reference signal corresponds to a frequency of the signal to be tested. Input L reference signals and one input signal into a phase-sensitive detector for detection. Step 2 includes the following process: Step 21: Set a reference signal with an amplitude of one unit for each signal to be tested, and generate L reference signals. The frequency of each reference signal is the same as the frequency of its corresponding signal to be tested. For each of the L reference signals with different frequencies, construct two in-phase orthogonal reference signals. Step 22: Input the two generated reference signals and the input signal into the same phase-sensitive detector; Set up L reference signals, which have the same frequency as the original signal, and input these L reference signals into the phase-sensitive detectors into which the original signal is input at the corresponding frequencies. L reference signals are generated, each with the same frequency as the L signals to be detected. For each of the L different frequency components, two in-phase orthogonal reference signals are constructed respectively. ； The two generated reference signals and the test signal of the same frequency are input into the same phase-sensitive detector; Step 23: Perform low-pass filtering on the results of correlation operations between the two reference signals and the signal to be tested to obtain two DC signals; Step 24: Square the two DC signals respectively, add them together, and then take the square root of the sum to obtain the amplitude curve of the signal under test; Step 25: Calculate the arctangent function value of the quotient of the two DC signals to obtain the phase curve of the signal under test; Step 26: Multiply the amplitude detection result by one reference signal to obtain the signal detection result; Step 3: After processing the reference signal and the original signal in the phase-sensitive detector, the results are output to the display module to observe the detection results of the amplitude and phase of the signal under test.

2. The multi-channel weak signal multi-frequency positioning digital phase-locked loop method according to claim 1, characterized in that, The specific steps for summing the L signals to be measured and a white noise signal in step 1 include the following: Step 11: Simultaneously input L signals to be measured and a randomly generated white noise into a summer to add them together into a single input signal; Step 12: Divide the input signal after the summer into several identical signals, input them into a phase-sensitive detector for digital phase-locked amplification, and input them into an oscilloscope for comparison with the detection results.

3. The multi-channel weak signal multi-frequency positioning digital phase-locked loop method according to claim 1, characterized in that, Step 3, after processing the reference signal and the original signal in the phase-sensitive detector, outputs the result to the display module to display the amplitude, phase, and detection result. This includes the following specific steps: Step 31: Input the L amplitudes and phases of the signal to be tested obtained above into the oscilloscope to display the results; Step 32: Add the L signal processing results of the signal to be tested obtained above, merge them into one signal, input it into the oscilloscope, and compare it with the original signal input into the oscilloscope.

4. A multi-channel weak signal multi-frequency positioning digital phase-locked amplifier system, the system being used to implement the multi-channel weak signal multi-frequency positioning digital phase-locked method as described in claim 1, characterized in that, The amplifier system includes: The input signal module sums L test signals and a white noise signal, and combines them into a single input signal. A reference signal module is provided, wherein each signal under test is provided with one reference signal, and the reference signal has the same frequency as the corresponding signal under test. A phase-sensitive detector module is used to receive the input signal and the reference signal generation module to obtain the detection results of the amplitude and phase of the signal under test; The result display module is used to observe the detection results of the amplitude and phase of the signal under test.

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