Weak signal detection method and circuit based on Ljung-Box test

Abstract

The invention provides a weak signal detection method and circuit based on Ljung-Box detection, and belongs to the field of signal detection. The method comprises the following steps: S1, obtaining Gaussian white noise and a to-be-detected analog signal, and carrying out direct current isolation on the Gaussian white noise and the to-be-detected analog signal through a capacitor; s2, superposing the Gaussian white noise after direct current isolation and the analog signal to be detected after direct current isolation, and mixing with a direct current voltage signal provided by a low-noise voltage-stabilized power supply VCC to obtain a mixed signal; and S3, sending the mixed signal to a digital circuit to obtain a detection result of the weak signal. In addition, the invention also provides two weak signal detection circuits based on Ljung-Box detection for realizing the method. According to the method provided by the invention, the influence of low-quality noise on a weak signal detection technology can be effectively avoided, and the correlation and statistical characteristics of Gaussian white noise can be effectively utilized.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal detection, and in particular relates to a weak signal detection method and circuit based on Ljung-Box test. Background Art

[0002] A weak signal is a signal that is submerged in noise. Its amplitude is usually much smaller than the noise amplitude, and the characteristics of the signal are often masked by the noise. In long-distance wireless communications, the signal becomes weak after being transmitted over a long distance. Weak signal detection technology can be used to improve the quality of received signals. For example, in deep space communications, the signal strength sent back by the detector is extremely low. The weak signal detection method can effectively extract the signal and achieve reliable data reception.

[0003] In modern communications, radar and electronic system applications, weak signal detection is a key issue. Especially in complex noise environments, separating useful weak signals from strong noise is a core problem. The amplitude of weak signals is much lower than the background noise, making them difficult to extract effectively. Especially in the field of lidar, the complex working environment and signal propagation characteristics make the echo signal extremely weak, making it difficult to distinguish it from the background noise, which increases the difficulty of signal recognition.

[0004] A common weak signal detection method is based on energy detection. This method collects the energy characteristics of the signal and uses the power of the signal to determine the presence of a weak signal. Specifically, the method first samples the signal through an analog-to-digital converter (ADC) to convert the analog signal into a digital signal, and then calculates the energy of the sampled data to determine whether the energy change is significant, thereby detecting the presence of the signal. However, this method has certain limitations in a low signal-to-noise ratio environment. Due to the randomness of the noise signal, especially when the noise power is strong, the energy detection method is easily affected by low-quality noise, resulting in a high false detection rate. In addition, this method cannot effectively utilize the correlation of weak signals and ignores the statistical characteristics of Gaussian white noise. Summary of the invention

[0005] The present invention aims to provide a weak signal detection method and circuit based on Ljung–Box test, which effectively utilizes the correlation of Gaussian white noise and its statistical characteristics to solve the technical problems in the prior art that the false detection rate of weak signal detection is high and the correlation between the statistical characteristics of Gaussian white noise and the weak signal is not effectively utilized.

[0006] In order to solve the above technical problems, the present invention proposes a weak signal detection method based on Ljung–Box test, which comprises the following steps:

[0007] Step S1: obtaining Gaussian white noise and an analog signal to be measured, and isolating the Gaussian white noise and the analog signal to be measured from direct current through capacitors respectively;

[0008] Step S2: superimposing the Gaussian white noise after isolating the DC and the analog signal to be measured after isolating the DC, and mixing them with the DC voltage signal provided by the low-noise regulated power supply VCC to obtain a mixed signal;

[0009] Step S3: Send the mixed signal to the digital circuit to obtain the detection result of the weak signal.

[0010] Furthermore, in step S2, the DC voltage signal is obtained by dividing the low noise regulated power supply VCC by the first resistor R1 and the second resistor R2.

[0011] Furthermore, in step S3, the digital circuit includes an analog-to-digital converter ADC, a calculation module and an estimation module; the mixed signal is sent to the digital circuit and sampled by a one-bit or multi-bit analog-to-digital converter ADC to obtain sampling data; the sampling data is calculated by the calculation module in the digital circuit to obtain a correlation coefficient and a Q statistic; then the estimation module is used to perform detection and signal-to-noise ratio estimation to obtain a detection result of a weak signal.

[0012] Furthermore, the autocorrelation coefficient is calculated as follows:

[0013]

[0014] Among them, n is the number of data points contained in the sampled data sequence, k is the lag period, and y t is the tth data value of the data sequence, y t-k is the tkth data value of the data sequence, is the mean of the data series, ρ k is the autocorrelation coefficient with lag period k.

[0015] Furthermore, the Q statistic is calculated as follows:

[0016]

[0017] h is the maximum lag considered in the test.

[0018] Furthermore, the estimation module sets a threshold as needed. If the Q statistic is greater than 0 and less than or equal to the threshold, there is no weak signal; if the Q statistic is greater than the threshold, there is a weak signal; the signal-to-noise ratio is estimated based on the degree of deviation of the Q statistic from 0. The larger the Q statistic, the larger the signal-to-noise ratio, and the smaller the Q statistic, the smaller the signal-to-noise ratio.

[0019] The present invention also proposes a weak signal detection circuit based on Ljung–Box test, which is used to implement the above-mentioned weak signal detection method based on Ljung–Box test, and the circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, an analog-to-digital converter ADC, a calculation module and an estimation module.

[0020] Furthermore, the analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and is connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the analog-to-digital converter ADC, the digital-to-analog converter ADC is connected to the calculation module, and the calculation module is connected to the estimation module; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to the low-noise regulated power supply VCC.

[0021] The present invention also proposes another weak signal detection circuit based on Ljung–Box test, which is used to implement the above-mentioned weak signal detection method based on Ljung–Box test. The circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, and a field programmable gate array FPGA.

[0022] Furthermore, the analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and then connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the field programmable gate array FPGA; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to a low-noise regulated power supply VCC; the field programmable gate array FPGA includes a sampling module, a calculation module and an estimation module.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects: the present invention firstly isolates the analog signal to be measured from the Gaussian white noise by capacitor DC and then mixes it, then uses one or more ADCs for sampling, and finally, based on the Ljung–Box test, uses the correlation of the sampled data to detect weak signals and estimate the signal-to-noise ratio. The method of the present invention can effectively avoid the influence of low-quality noise on weak signal detection technology, and can effectively use the correlation information and statistical characteristics of Gaussian white noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0025] Figure 1 This is a flow chart of the weak signal detection method based on Ljung–Box test of the present invention.

[0026] Figure 2 Schematic diagram of a weak signal detection circuit based on Ljung–Box test of the present invention.

[0027] Figure 3 Schematic diagram of another weak signal detection circuit based on Ljung–Box test of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In order to avoid the influence of low-quality noise on weak signal detection, high-quality noise can be mixed with the signal to be detected. High-quality Gaussian white noise has almost no autocorrelation, while weak periodic signals often have certain correlation. In order to effectively utilize the non-correlated characteristics of Gaussian white noise and its statistical characteristics, the present invention proposes a weak signal detection method based on the Ljung–Box test, which is also called the Q test.

[0030] like Figure 1 As shown, the present invention proposes a weak signal detection method based on Ljung–Box test, comprising the following steps:

[0031] Step S1: Gaussian white noise and an analog signal to be measured are obtained, and direct current isolating the Gaussian white noise and the analog signal to be measured respectively through capacitors.

[0032] Step S2: Superimpose the Gaussian white noise after isolating the DC and the analog signal to be measured after isolating the DC, and mix them with the DC voltage signal provided by the low-noise regulated power supply VCC to obtain a mixed signal. The DC voltage signal is obtained by dividing the low-noise regulated power supply VCC by the first resistor R1 and the second resistor R2.

[0033] Step S3: Send the mixed signal to the digital circuit to obtain the detection result of the weak signal.

[0034] The digital circuit includes an analog-to-digital converter (ADC), a calculation module and an estimation module. Specifically, the mixed signal is sent to the digital circuit and sampled by a one-bit or multi-bit analog-to-digital converter (ADC) to obtain sampled data; the sampled data is calculated by the calculation module in the digital circuit to obtain the correlation coefficient and Q statistic; and then the estimation module is used to perform detection and signal-to-noise ratio estimation to obtain the detection result of the weak signal.

[0035] The sampling bit number of the analog-to-digital converter ADC can be set to 1, that is, a single-bit ADC is used for sampling. Single-bit sampling can effectively reduce the computational complexity of weak signal detection technology.

[0036] The sampled data obtained after sampling by the analog-to-digital converter ADC contains the correlation information of the signal to be measured. The calculation module calculates the autocorrelation coefficient and Q statistics. The autocorrelation coefficient is calculated as follows:

[0037]

[0038] Among them, n is the number of data points contained in the sampled data sequence, k is the lag period, and y t is the tth data value of the data sequence, y t-k is the tkth data value of the data sequence, is the mean of the data series, ρ k is the autocorrelation coefficient with lag period k.

[0039] The Ljung–Box test is a classic method for testing autocorrelation, the core of which is the Q statistic. The Q statistic is calculated as follows:

[0040]

[0041] h is the maximum lag considered in the test. The Q statistic is a statistic used to test whether the autocorrelation coefficient (from lag 1 to lag k) is significantly different from zero.

[0042] The power spectrum of Gaussian white noise is flat and has no autocorrelation. The introduction of weak signals will interfere with the non-correlation characteristics of Gaussian white noise, resulting in the mixed signal having first-order or higher-order autocorrelation. In addition, the sampling data contains the correlation information of the analog signal to be measured. The estimation module verifies the autocorrelation of the sampling data after the analog-to-digital converter ADC sampling, and then determines whether the weak signal exists and further estimates the signal-to-noise ratio.

[0043] The Q statistic of the Ljung–Box test approximately follows a chi-square distribution with the number of lags (h) as the degree of freedom. Therefore, the Q statistic reflects the autocorrelation of multiple lags. If the Q statistic is very small (close to 0), it means that the autocorrelation of the data at multiple lags is very weak, that is, there is no weak signal; if the Q statistic is too large, it means that the data has significant autocorrelation, that is, there is a weak signal.

[0044] Furthermore, the estimation module identifies the presence of weak signals and estimates their signal-to-noise ratio by analyzing the Q statistic calculated by the calculation module. The estimation module sets a threshold value as needed. If the Q statistic is greater than 0 and less than or equal to the threshold value, there is no weak signal; if the Q statistic is greater than the threshold value, there is a weak signal. Furthermore, since the larger the signal-to-noise ratio, the greater the relative power of the weak signal, the greater the correlation of the mixed signal, resulting in a larger Q statistic. Therefore, the signal-to-noise ratio can be estimated based on the degree of deviation of the Q statistic from 0 (the size of the Q statistic). The larger the Q statistic, the greater the signal-to-noise ratio, and the smaller the Q statistic, the smaller the signal-to-noise ratio. When the Q statistic is lower than or equal to the threshold, it means that there is no weak signal.

[0045] The present invention also proposes a weak signal detection circuit based on Ljung–Box test for implementing the above method, such as Figure 2 As shown, the circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, an analog-to-digital converter ADC, a calculation module and an estimation module.

[0046] The analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and then connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the analog-to-digital converter ADC, the digital-to-analog converter ADC is connected to the calculation module, and the calculation module is connected to the estimation module; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to the low-noise regulated power supply VCC.

[0047] The first capacitor C1 and the second capacitor C2 are used for DC isolation; the first resistor R1 and the second resistor R2 are used to divide the DC voltage signal provided by the low-noise regulated power supply VCC; the analog-to-digital converter ADC is used to implement sampling; the calculation module is used to calculate the autocorrelation coefficient and the Q statistic; the estimation module is used for weak signal detection and signal-to-noise ratio estimation.

[0048] In addition, the present invention also proposes another weak signal detection circuit based on Ljung–Box test for implementing the above method, such as Figure 3 As shown, the circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, and a field programmable gate array FPGA.

[0049] The analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and then connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the field programmable gate array FPGA; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to the low-noise regulated power supply VCC.

[0050] The first capacitor C1 and the second capacitor C2 are used for DC isolation; the first resistor R1 and the second resistor R2 are used to divide the DC voltage signal provided by the low-noise regulated power supply VCC; the field programmable gate array FPGA includes a sampling module, a calculation module and an estimation module, the sampling module is used for sampling, and the calculation module is used to calculate the autocorrelation coefficient and the Q statistic; the estimation module is used for weak signal detection and signal-to-noise ratio estimation, and finally outputs the detection result.

[0051] The method of the present invention can effectively avoid the influence of low-quality noise on weak signal detection technology, and can effectively utilize the correlation and statistical characteristics of Gaussian white noise.

[0052] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A weak signal detection method based on Ljung–Box test, characterized in that: The steps include: Step S1: obtaining Gaussian white noise and an analog signal to be measured, and isolating the Gaussian white noise and the analog signal to be measured from direct current through capacitors respectively; Step S2: superimposing the Gaussian white noise after isolating the DC and the analog signal to be measured after isolating the DC, and mixing them with the DC voltage signal provided by the low-noise regulated power supply VCC to obtain a mixed signal; Step S3: Send the mixed signal to the digital circuit to obtain the detection result of the weak signal.

2. The weak signal detection method based on Ljung–Box test according to claim 1, characterized in that: In step S2, a DC voltage signal is obtained by dividing the low noise regulated power supply VCC by the first resistor R1 and the second resistor R2.

3. The weak signal detection method based on Ljung–Box test according to claim 1, characterized in that: In step S3, the digital circuit includes an analog-to-digital converter ADC, a calculation module and an estimation module; the mixed signal is sent to the digital circuit and sampled by a one-bit or multi-bit analog-to-digital converter ADC to obtain sampling data; the sampling data is calculated by the calculation module in the digital circuit to obtain the correlation coefficient and the Q statistic; then the estimation module is used to perform detection and signal-to-noise ratio estimation to obtain the detection result of the weak signal.

4. The weak signal detection method based on Ljung–Box test according to claim 3, characterized in that: The autocorrelation coefficient is calculated as follows: Among them, n is the number of data points contained in the sampled data sequence, k is the lag period, and y t is the tth data value of the data sequence, y t-k is the tkth data value of the data sequence, is the mean of the data series, ρ k is the autocorrelation coefficient with lag period k.

5. The weak signal detection method based on Ljung–Box test according to claim 4, characterized in that: The Q statistic is calculated as follows: h is the maximum lag considered in the test.

6. The weak signal detection method based on Ljung–Box test according to claim 5, characterized in that: The estimation module sets the threshold as needed. If the Q statistic is greater than 0 and less than or equal to the threshold, there is no weak signal; if the Q statistic is greater than the threshold, there is a weak signal; the signal-to-noise ratio is estimated based on the degree of deviation of the Q statistic from 0. The larger the Q statistic, the larger the signal-to-noise ratio, and the smaller the Q statistic, the smaller the signal-to-noise ratio.

7. A weak signal detection circuit based on Ljung–Box test, characterized in that: Used to implement the weak signal detection method based on Ljung–Box test as described in any one of claims 1 to 6, the circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, an analog-to-digital converter ADC, a calculation module and an estimation module.

8. The weak signal detection circuit based on Ljung–Box test according to claim 7, characterized in that: The analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and then connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the analog-to-digital converter ADC, the digital-to-analog converter ADC is connected to the calculation module, and the calculation module is connected to the estimation module; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to the low-noise regulated power supply VCC.

9. A weak signal detection circuit based on Ljung–Box test, characterized in that: Used to implement the weak signal detection method based on Ljung-Box test as described in any one of claims 1 to 6, the circuit includes a first capacitor C1, a second capacitor C2, a first resistor R1, a second resistor R2, and a field programmable gate array FPGA.

10. The weak signal detection circuit based on Ljung–Box test according to claim 9, characterized in that: The analog signal to be measured is connected to one end of the first capacitor C1, and the Gaussian white noise is connected to one end of the second capacitor C2 to form a parallel circuit; the other end of the first capacitor C1 is connected in parallel with the other end of the second capacitor C2, and then connected to one end of the second resistor R2 and one end of the first resistor R1, and then connected to the field programmable gate array FPGA; the other end of the second resistor R2 is grounded, and the other end of the first resistor R1 is connected to a low-noise regulated power supply VCC; the field programmable gate array FPGA includes a sampling module, a calculation module and an estimation module.

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