Non-linear correction method and system for frequency-modulated continuous wave laser

Abstract

The embodiment of the invention discloses a nonlinear correction method and system for a frequency-modulated continuous wave laser, and the method comprises the steps: obtaining a phase curve of a to-be-corrected beat frequency signal based on an nth voltage signal, determining the frequency modulation nonlinearity according to the phase curve, carrying out the sampling processing of a plurality of phase points in the phase curve, and obtaining a plurality of target phase points, and finally, an (n + 1) th voltage signal is determined according to the multiple target phase points and the nth voltage signal, the (n + 1) th voltage signal is used for nonlinear correction of a frequency modulation continuous wave laser in the system, and n is an integer greater than 0 in sequence until the frequency modulation nonlinearity is smaller than or equal to a frequency modulation nonlinearity threshold value. Therefore, the nonlinear correction of the frequency-modulated continuous wave laser in the nonlinear correction system of the frequency-modulated continuous wave laser is realized, the distance measurement and speed measurement precision can be prevented from being damaged, and the performance of an FMCW radar is remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of frequency modulated continuous wave radar, and in particular to a nonlinear correction method and system for a frequency modulated continuous wave laser. Background Art

[0002] Frequency Modulated Continuous Wave (FMCW) radar technology has been widely used in many fields such as automotive radar, meteorological observation, aerospace, and industrial automation due to its excellent ranging and speed measurement accuracy. However, in practical applications, FMCW radar is often interfered by a variety of nonlinear factors, which causes its ranging and speed measurement accuracy to be impaired, greatly reducing the performance of FMCW radar. Therefore, the research and development of nonlinear correction technology for FMCW radar is particularly important. Summary of the invention

[0003] Based on this, it is necessary to propose a nonlinear correction method and system for frequency modulated continuous wave laser to address the above problems, which realizes the nonlinear correction of the frequency modulated continuous wave laser in the nonlinear correction system of the frequency modulated continuous wave laser, can avoid the damage to its ranging and speed measurement accuracy, and significantly improve the performance of FMCW radar.

[0004] To achieve the above object, the present invention provides, in a first aspect, a nonlinear correction method for a frequency modulated continuous wave laser, the method being applied to a nonlinear correction system for a frequency modulated continuous wave laser, the method comprising:

[0005] Based on the nth voltage signal, obtaining a phase curve of the beat frequency signal to be corrected;

[0006] determining frequency modulation nonlinearity according to the phase curve;

[0007] Sampling a plurality of phase points in the phase curve to obtain a plurality of target phase points;

[0008] Determine an n+1th voltage signal according to a plurality of target phase points and an nth voltage signal, wherein the n+1th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system;

[0009] Among them, n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold.

[0010] Optionally, acquiring a phase curve of the beat frequency signal to be corrected based on the nth voltage signal includes:

[0011] Based on the nth voltage signal, obtaining the beat frequency signal to be corrected;

[0012] The beat frequency signal to be corrected is subjected to Hilbert transform processing to obtain the phase curve.

[0013] Optionally, performing Hilbert transform processing on the beat frequency signal to be corrected to obtain the phase curve includes:

[0014] Performing bandpass filtering on the beat frequency signal to be corrected to obtain the target beat frequency signal;

[0015] The target beat frequency signal is subjected to Hilbert transform processing to obtain the phase curve.

[0016] Optionally, determining the frequency modulation nonlinearity according to the phase curve includes:

[0017] Determining a maximum offset of the phase curve, and determining an endpoint distance between two endpoints of the phase curve in the y-axis direction;

[0018] The frequency modulation nonlinearity is determined according to the maximum offset and the endpoint distance.

[0019] Optionally, the sampling process is performed on a plurality of phase points in the phase curve to obtain a plurality of target phase points, including:

[0020] Downsampling the multiple phase points in the phase curve to obtain multiple downsampled phase points;

[0021] The multiple phase reduction points are uniformly resampled to obtain multiple target phase points.

[0022] Optionally, determining the (n+1)th voltage signal according to the multiple target phase points and the (n)th voltage signal includes:

[0023] According to the multiple target phase points, the nth voltage signal is interpolated to obtain the (n+1)th voltage signal.

[0024] To achieve the above object, the present invention provides a nonlinear correction system for a frequency modulated continuous wave laser in a second aspect, the system comprising a frequency modulated continuous wave laser, an optical path module, a circuit module and a processor;

[0025] The frequency modulated continuous wave laser is connected to the optical path module and the circuit module respectively, and the optical path module and the circuit module are both connected to the processor;

[0026] The circuit module is used to generate a triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser;

[0027] The frequency modulated continuous wave laser is used to modulate the driving current of the frequency modulated continuous wave laser according to the triangular wave signal to generate an optical signal, and transmit the optical signal to the optical path module;

[0028] The optical path module is used to generate a beat signal according to the optical signal, and transmit the beat signal to the circuit module;

[0029] The circuit module is used for converting the beat frequency signal into a beat frequency signal to be corrected, and transmitting the beat frequency signal to be corrected to the processor;

[0030] The processor is configured to execute the method as described in any one of the first aspects.

[0031] Optionally, the optical path module includes an isolator, an adjustable optical attenuator, a Mach-Zehnder interferometer and a balanced detector connected in sequence;

[0032] The frequency modulated continuous wave laser is connected to the isolator, and the balanced detector is connected to the circuit module;

[0033] The frequency modulated continuous wave laser is used to transmit the optical signal to the adjustable optical attenuator through the isolator;

[0034] The adjustable optical attenuator is used to adjust the signal strength of the optical signal to obtain an adjusted optical signal, and transmit the adjusted optical signal to the Mach-Zehnder interferometer;

[0035] The Mach-Zehnder interferometer is used to generate the initial beat signal according to the adjusted optical signal, and transmit the initial beat signal to the balanced detector;

[0036] The balanced detector is used to detect the initial beat frequency signal, obtain the beat frequency signal, and transmit the beat frequency signal to the circuit module.

[0037] Optionally, the circuit module includes a programmable gate array signal processing circuit and a digital-to-analog converter connected in sequence;

[0038] The frequency modulated continuous wave laser is connected to the digital-to-analog converter, and the programmable gate array signal processing circuit is connected to the processor;

[0039] The programmable gate array signal processing circuit is used to drive the digital-to-analog converter to generate the triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser.

[0040] Optionally, the circuit module includes an analog-to-digital converter;

[0041] The analog-to-digital converter is connected to the optical path module and the processor respectively;

[0042] The optical path module is used to transmit the beat frequency signal to the analog-to-digital converter;

[0043] The analog-to-digital converter is used to convert the beat frequency signal into the beat frequency signal to be corrected, and transmit the beat frequency signal to be corrected to the processor.

[0044] To achieve the above object, the present invention provides a nonlinear correction device for a frequency modulated continuous wave laser in a third aspect, the device is applied to a nonlinear correction system for a frequency modulated continuous wave laser, and the device comprises:

[0045] An acquisition module, used for acquiring a phase curve of the beat frequency signal to be corrected based on the nth voltage signal;

[0046] A first determination module, used to determine the frequency modulation nonlinearity according to the phase curve;

[0047] A processing module, used for sampling and processing a plurality of phase points in the phase curve to obtain a plurality of target phase points;

[0048] A second determination module is used to determine the (n+1)th voltage signal according to the multiple target phase points and the (n)th voltage signal, wherein the (n+1)th voltage signal is used for nonlinear correction of the frequency modulated continuous wave laser in the system;

[0049] Among them, n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold.

[0050] To achieve the above-mentioned objective, the present invention provides in a fourth aspect a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes a method as described in any one of the first aspects.

[0051] To achieve the above-mentioned purpose, the present invention provides a computer device in a fifth aspect, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the method as described in any one of the first aspects.

[0052] The embodiment of the present invention has the following beneficial effects: the method is applied to a nonlinear correction system of a frequency modulated continuous wave laser, and the phase curve of the beat frequency signal to be corrected is obtained based on the nth voltage signal, and then the frequency modulation nonlinearity is determined according to the phase curve, and a plurality of phase points in the phase curve are sampled and processed to obtain a plurality of target phase points, and finally the n+1th voltage signal is determined according to the plurality of target phase points and the nth voltage signal, and the n+1th voltage signal is used for the nonlinear correction of the frequency modulated continuous wave laser in the system, wherein n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold; that is, the nonlinear correction of the frequency modulated continuous wave laser in the nonlinear correction system of the frequency modulated continuous wave laser is realized, and the range and speed measurement accuracy thereof can be prevented from being damaged, and the performance of the FMCW radar is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0054] in:

[0055] Figure 1 A schematic diagram of a nonlinear correction method for a frequency modulated continuous wave laser in an embodiment of the present application;

[0056] Figure 2 A schematic diagram of a nonlinear correction system for a frequency modulated continuous wave laser in an embodiment of the present application;

[0057] Figure 3 Another schematic diagram of a nonlinear correction system for a frequency modulated continuous wave laser according to an embodiment of the present application;

[0058] Figure 4 This is a schematic diagram of a down-sweep frequency spectrum of a beat frequency signal before correction in an embodiment of the present application;

[0059] Figure 5 A schematic diagram of a downward sweep frequency spectrum of a corrected beat frequency signal in an embodiment of the present application;

[0060] Figure 6 Schematic diagram of the instantaneous frequency of the beat signal before correction in an embodiment of the present application;

[0061] Figure 7 Schematic diagram of the instantaneous frequency of the corrected beat signal in an embodiment of the present application;

[0062] Figure 8A schematic diagram of the phase of the down-sweep frequency of the beat frequency signal before correction in an embodiment of the present application;

[0063] Fig. 9 A schematic diagram of the phase of the downward sweep frequency of the beat frequency signal after correction in an embodiment of the present application;

[0064] Fig.10 A schematic diagram of a nonlinear correction device for a frequency modulated continuous wave laser in an embodiment of the present application;

[0065] Fig.11 1 is a diagram of the internal structure of a computer device in some embodiments. DETAILED DESCRIPTION

[0066] 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.

[0067] Frequency Modulated Continuous Wave (FMCW) radar technology has been widely used in many fields such as automotive radar, meteorological observation, aerospace, and industrial automation due to its excellent ranging and speed measurement accuracy. However, in practical applications, FMCW radar is often interfered by a variety of nonlinear factors, which causes its ranging and speed measurement accuracy to be impaired, greatly reducing the performance of FMCW radar. Therefore, the research and development of nonlinear correction technology for FMCW radar is particularly important.

[0068] It should be noted that the performance of FMCW radar is highly dependent on the frequency modulation linearity of the laser. Ideally, the laser of FMCW radar should exhibit linear frequency modulation characteristics to ensure the accuracy of ranging and speed measurement and high spatial resolution. However, in actual operation, the frequency modulation process of the laser is often affected by nonlinear factors, resulting in signal waveform distortion, which in turn affects the ranging and speed measurement accuracy and resolution of the radar, greatly reducing the performance of the FMCW radar. Therefore, it is necessary to implement effective nonlinear correction measures to avoid damage to its ranging and speed measurement accuracy, thereby significantly improving the performance of the FMCW radar.

[0069] In view of the above problems, the present application proposes a nonlinear correction method and system for a frequency modulated continuous wave laser, which realizes the nonlinear correction of the frequency modulated continuous wave laser in the nonlinear correction system of the frequency modulated continuous wave laser, can avoid the loss of its ranging and speed measurement accuracy, and significantly improve the performance of the FMCW radar. The specific implementation principle will be described in detail in the following embodiments.

[0070] It should be noted that before this application, there have been studies on FMCW radars that do not require a nonlinear correction process, that is, by connecting an acousto-optic modulator or an optoelectronic modulator to a laser and modulating it using a high-speed swept-frequency electrical signal, thereby achieving a linear frequency modulation output. At this time, the laser can obtain a higher frequency modulation linearity without a complex nonlinear correction process (Note: the higher the frequency modulation linearity, the lower the frequency modulation nonlinearity), but its cost is relatively high and expensive.

[0071] It should also be noted that, in the present application, a frequency modulated continuous wave laser, that is, an FMCW laser, may also be referred to as an FMCW radar transmitter.

[0072] In a first aspect, the present application provides a nonlinear correction method for a frequency modulated continuous wave laser.

[0073] See also Figure 1 , is a schematic diagram of a nonlinear correction method for a frequency modulated continuous wave laser in an embodiment of the present application, the method is applied to a nonlinear correction system for a frequency modulated continuous wave laser, the method comprising:

[0074] Step 110: Based on the nth voltage signal, a phase curve of the beat frequency signal to be corrected is obtained.

[0075] The nth voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system. When n is 1, the nth voltage signal is a preset original voltage signal.

[0076] In some embodiments, the nth voltage signal is input to the frequency modulated continuous wave laser through the circuit module in the system. The nth voltage signal can modulate the driving current of the frequency modulated continuous wave laser. The modulated driving current generates an optical signal which is input to the optical path module in the system. At this time, the beat frequency signal to be corrected can be obtained.

[0077] It should be noted that, after research and derivation, the present application has concluded that the phase curve of the beat frequency signal to be corrected is proportional to the frequency modulation curve of the frequency modulated continuous wave laser. Therefore, the phase curve of the beat frequency signal to be corrected can be used to represent the nonlinearity of the frequency modulation curve of the frequency modulated continuous wave laser. By improving the nonlinearity of the phase curve, the nonlinearity of the frequency modulation curve of the frequency modulated continuous wave laser can be changed, thereby realizing a nonlinear correction system for the frequency modulated continuous wave laser.

[0078] Step 120: Determine the frequency modulation nonlinearity according to the phase curve.

[0079] In some embodiments, the frequency modulation nonlinearity may be determined by the maximum offset of the phase curve and the distance between its two end points in the y-axis direction.

[0080] In the present application, by determining the frequency modulation nonlinearity, it can be used to judge whether the nonlinear correction of the frequency modulated continuous wave laser has achieved the expected effect. If the expected effect is achieved, there is no need to continue the nonlinear correction. Otherwise, nonlinear correction is still required.

[0081] Step 130: Sampling multiple phase points in the phase curve to obtain multiple target phase points.

[0082] In some embodiments, a plurality of phase points in the phase curve may be downsampled to obtain a plurality of reduced phase points, and then the plurality of reduced phase points may be uniformly resampled to obtain a plurality of target phase points.

[0083] Step 140: Determine the (n+1)th voltage signal according to the multiple target phase points and the (n)th voltage signal, where the (n+1)th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system.

[0084] In some embodiments, the nth voltage signal may be interpolated according to a plurality of target phase points to obtain the (n+1)th voltage signal.

[0085] It should be noted that the n+1th voltage signal is used for the nonlinear correction process of the frequency modulated continuous wave laser in the system, which is similar to the nth voltage signal in step 110 of the above embodiment for the nonlinear correction process of the frequency modulated continuous wave laser in the system, and will not be repeated here.

[0086] Wherein, n successively takes integers greater than 0, and steps 110 to 140 are repeated until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold.

[0087] In the present application, the frequency modulation nonlinearity threshold value can be obtained by the operator based on a large amount of experience, statistics or experiments. Of course, it can also be set by the operator according to actual needs, which is not limited here.

[0088] It should be noted that the nonlinear correction of the frequency modulated continuous wave laser in the present application is a process of continuous iterative correction, which needs to be iterated until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold, at which point the iteration ends.

[0089] It can be understood that when the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold, the nonlinear correction of the frequency modulated continuous wave laser has achieved the expected effect. At this time, the frequency modulated continuous wave laser can be used for tasks such as distance measurement and speed measurement to avoid damage to its distance measurement and speed measurement accuracy.

[0090] In an embodiment of the present application, a phase curve of a beat frequency signal to be corrected is obtained based on an nth voltage signal, and then the frequency modulation nonlinearity is determined according to the phase curve, and a plurality of phase points in the phase curve are sampled and processed to obtain a plurality of target phase points, and finally an n+1th voltage signal is determined according to the plurality of target phase points and the nth voltage signal, and the n+1th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system, wherein n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to a frequency modulation nonlinearity threshold; that is, the nonlinear correction of the frequency modulated continuous wave laser in the system is realized, and the nonlinear correction of the frequency modulated continuous wave laser in the nonlinear correction system is realized, so that the range and speed measurement accuracy thereof can be prevented from being damaged, and the performance of the FMCW radar can be significantly improved.

[0091] In addition, the nonlinear correction method of the frequency modulated continuous wave laser proposed in this application realizes the effective correction of the nonlinearity of the frequency modulated continuous wave laser by iteratively optimizing the voltage signal, significantly improving the ranging and speed measurement accuracy of the FMCW radar, and has the characteristics of high correction accuracy, high flexibility, high cost-effectiveness and strong adaptability.

[0092] It can be understood that the correction accuracy is high: by directly analyzing the phase curve of the beat frequency signal and sampling and linearizing it, the nonlinear problem of the frequency modulated continuous wave laser can be corrected more accurately, significantly improving the accuracy of ranging and speed measurement; high flexibility: this method does not require changing the hardware structure of the laser, and nonlinear correction can be achieved only by adjusting the input voltage signal, which has high flexibility and practicality; high cost-effectiveness: compared with the method of achieving linear frequency modulation output through an external modulator studied before this application, this method does not require additional high-cost equipment, and can be achieved only through software algorithms, which has higher cost-effectiveness; strong adaptability: this method can be applied to different types of FMCW radar systems, and has wide applicability and scalability.

[0093] In a feasible implementation, step 110 in the above embodiment, obtaining the phase curve of the beat frequency signal to be corrected based on the nth voltage signal, includes: obtaining the beat frequency signal to be corrected based on the nth voltage signal; performing Hilbert transform processing on the beat frequency signal to be corrected to obtain the phase curve.

[0094] In an embodiment of the present application, by obtaining a beat frequency signal to be corrected based on the nth voltage signal, and then performing Hilbert transform processing on the beat frequency signal to be corrected to obtain a phase curve, it is possible to accurately characterize the frequency modulation nonlinearity, improve the correction accuracy, enhance the system stability, and improve the data processing efficiency.

[0095] It can be understood that the frequency modulation nonlinearity is accurately characterized: by processing the beat frequency signal to be corrected through Hilbert transform, its phase information can be accurately extracted, and then the phase curve can be drawn. The phase curve can intuitively reflect the nonlinearity of the frequency modulated continuous wave laser in the frequency modulation process, and provide an accurate data basis for subsequent correction work; improve the correction accuracy: the accurate acquisition of the phase curve makes the subsequent nonlinearity determination more accurate, which in turn affects the accuracy of the iterative correction of the voltage signal, that is, by continuously optimizing the voltage signal, the frequency modulation nonlinearity can be gradually reduced, and the accuracy of ranging and speed measurement can be improved; enhance the system stability: the real-time acquisition and dynamic adjustment of the phase curve makes the nonlinear correction process a closed-loop feedback. This closed-loop feedback can dynamically adjust the voltage signal according to the real-time frequency modulation nonlinearity, thereby enhancing the stability and reliability of the entire FMCW radar system; improve data processing efficiency: Hilbert transform is an efficient signal processing method that can quickly and accurately extract phase information from complex signals, which enables the phase curve to be quickly acquired and subsequently processed in real-time applications, improving data processing efficiency and real-time performance.

[0096] In a feasible implementation, the Hilbert transform processing is performed on the beat frequency signal to be corrected to obtain the phase curve in the above embodiment, including: performing bandpass filtering processing on the beat frequency signal to be corrected to obtain the target beat frequency signal; performing Hilbert transform processing on the target beat frequency signal to obtain the phase curve.

[0097] Regarding the method for determining the target beat frequency signal, in some embodiments, the fir1() function of the MATLAB digital signal processing toolbox can be used to design an FIR bandpass filter, and then the FIR bandpass filter is used to perform bandpass filtering on the beat frequency signal to be corrected to obtain the target beat frequency signal.

[0098] In the embodiment of the present application, by first performing bandpass filtering on the signal and then performing Hilbert transform on the filtered target beat frequency signal, it is possible to improve signal quality, accurately extract phase information, optimize the accuracy of the phase curve, enhance system stability and reliability, etc.

[0099] It can be understood that the signal quality is improved: by bandpass filtering, the noise and interference components in the beat frequency signal to be corrected can be effectively removed, especially those signal components that are not within the target frequency range (i.e., DC components and high-frequency signals), which helps to improve the signal-to-noise ratio and purity of the signal, and provide a more accurate input signal for the subsequent Hilbert transform; accurately extract phase information: by performing a Hilbert transform on the filtered target beat frequency signal, the phase information of the signal can be accurately extracted, which is crucial for analyzing the frequency characteristics and nonlinear characteristics of the signal; optimize the accuracy of the phase curve: the target beat frequency signal after bandpass filtering is closer to the real frequency-modulated signal, so the phase curve obtained by performing a Hilbert transform based on the signal is also more accurate, which helps to more accurately reflect the nonlinearity of the frequency-modulated continuous wave laser during the frequency modulation process, and provide reliable data support for subsequent nonlinear correction; enhance system stability and reliability: through the processing flow of filtering first and then transforming, the phase extraction error caused by signal noise and interference can be effectively avoided, thereby enhancing the stability and reliability of the entire system, which is particularly important for application scenarios that require high-precision phase information, such as ranging and speed measurement mentioned in this application.

[0100] In a feasible implementation, step 120 in the above embodiment, determining the frequency modulation nonlinearity according to the phase curve, includes: determining the maximum offset of the phase curve, and determining the endpoint distance between the two endpoints of the phase curve in the y-axis direction; determining the frequency modulation nonlinearity according to the maximum offset and the endpoint distance.

[0101] Regarding the method for determining the maximum offset, in some embodiments, the straight lines at the two end points of the phase curve can be determined, and then the distance between each phase point on the phase curve and the straight line can be determined to obtain multiple distances. Finally, among all the distances, the maximum distance is used as the maximum offset of the phase curve.

[0102] In the embodiment of the present application, by determining the maximum offset of the phase curve and the endpoint distance between the two endpoints in the y-axis direction, and calculating the frequency modulation nonlinearity based on this, it is possible to quantify the nonlinear characteristics, provide a correction basis, and optimize system performance.

[0103] It can be understood that quantifying nonlinear characteristics: by determining the maximum offset and endpoint distance of the phase curve, the nonlinear characteristics of the frequency modulated continuous wave laser during the frequency modulation process can be quantitatively described. This quantification makes the evaluation of nonlinearity more objective and accurate, avoiding errors in subjective judgment; providing a basis for correction: the obtained frequency modulation nonlinearity is an important basis for subsequent nonlinear correction; optimizing system performance: by continuously determining the frequency modulation nonlinearity according to the phase curve and correcting it, the performance of the frequency modulated continuous wave laser can be gradually optimized, thereby improving the overall accuracy and stability of the system.

[0104] In a feasible implementation, step 130 in the above embodiment, sampling multiple phase points in the phase curve to obtain multiple target phase points, includes: downsampling multiple phase points in the phase curve to obtain multiple downsampled phase points; uniformly resampling the multiple downsampled phase points to obtain multiple target phase points.

[0105] Regarding the method for determining multiple phase reduction points, in some embodiments, the resample() function of the MATLAB digital signal processing toolbox is used to downsample multiple phase points in the phase curve to obtain multiple phase reduction points; wherein the total number of the multiple phase reduction points needs to be the same as the number of triangular wave points of the triangular wave signal in the circuit module. For example, the number of triangular wave points of the triangular wave signal in the circuit module is 1000, and at this time, the total number of the multiple phase reduction points must also be 1000.

[0106] It should be noted that since the multiple phase reduction points are not equally spaced, it is necessary to use the first point of the multiple phase reduction points as the starting point and the last point as the end point, and uniformly resample the multiple phase reduction points to obtain multiple target phase points.

[0107] In an embodiment of the present application, by sequentially downsampling and uniformly resampling multiple phase points in the phase curve, the amount of data can be reduced, redundant information can be removed, data consistency can be ensured, and analysis accuracy can be improved, thereby improving processing efficiency and data quality.

[0108] It can be understood that reducing the amount of data: through downsampling, the number of phase points in the phase curve can be significantly reduced, thereby reducing the computational burden of subsequent processing and improving the processing speed; removing redundant information: in high-frequency or high-resolution phase curves, there are often a lot of redundant or repeated information, and downsampling can effectively remove this redundant information; ensuring data consistency: after downsampling, the distribution of phase points may become uneven. Through uniform resampling, it can be ensured that the phase points are evenly distributed at the new sampling rate, which is convenient for subsequent analysis and processing; improving analysis accuracy: uniform resampling helps to improve the accuracy of data analysis while maintaining data integrity; improving processing efficiency: through downsampling and uniform resampling, the processing efficiency of the phase curve can be significantly improved, reducing computing time and resource consumption; improving data quality: removing redundant information, suppressing noise and ensuring data consistency can all help improve the data quality of the phase curve and provide a more accurate and reliable basis for subsequent analysis.

[0109] In a feasible implementation, step 140 in the above embodiment, determining the n+1th voltage signal according to multiple target phase points and the nth voltage signal, includes: interpolating the nth voltage signal according to the multiple target phase points to obtain the n+1th voltage signal.

[0110] In the embodiment of the present application, by interpolating the nth voltage signal according to multiple target phase points to determine the n+1th voltage signal, the accuracy and performance of the FMCW radar can be improved.

[0111] It can be understood that improving accuracy: the interpolation method can more accurately estimate the exact position of the target phase point by considering the relationship between adjacent sampling points, thereby improving the accuracy of the voltage signal; improving the performance of FMCW radar: accurate voltage signals can achieve better nonlinear correction, which is crucial to improving the overall performance of FMCW radar.

[0112] In a second aspect, the present application provides a nonlinear correction system for a frequency modulated continuous wave laser.

[0113] See also Figure 2 , is a schematic diagram of a nonlinear correction system for a frequency modulated continuous wave laser in an embodiment of the present application, the system comprising a frequency modulated continuous wave laser 210, an optical path module 220, a circuit module 230 and a processor 240.

[0114] The frequency modulated continuous wave laser 210 is connected to the optical path module 220 and the circuit module 230 respectively, and the optical path module 220 and the circuit module 230 are both connected to the processor 240 .

[0115] In a feasible implementation, the circuit module 230 is used to generate a triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser 210; the frequency modulated continuous wave laser 210 is used to modulate the driving current of the frequency modulated continuous wave laser 210 according to the triangular wave signal to generate an optical signal, and transmit the optical signal to the optical path module 220; the optical path module 220 is used to generate a beat frequency signal according to the optical signal, and transmit the beat frequency signal to the circuit module 230; the circuit module 230 is used to convert the beat frequency signal into a beat frequency signal to be corrected, and transmit the beat frequency signal to be corrected to the processor 240; the processor 240 is used to execute a nonlinear correction method for a frequency modulated continuous wave laser in the above method embodiment.

[0116] In the embodiment of the present application, by integrating multiple components such as the frequency modulated continuous wave laser 210, the optical path module 220, the circuit module 230 and the processor 240, the nonlinear correction of the optical signal output by the frequency modulated continuous wave laser 210 is achieved, which can improve the measurement accuracy, enhance the system stability and optimize the signal processing process.

[0117] It can be understood that the measurement accuracy is improved: the nonlinear correction system generates a more linear optical signal by accurately controlling the driving current of the frequency modulated continuous wave laser 210, which helps to reduce the measurement error caused by the nonlinear effect of laser frequency modulation, thereby improving the accuracy of applications such as distance measurement and speed measurement; enhance system stability: the nonlinear correction system can timely detect and correct the nonlinear changes of the frequency modulated continuous wave laser 210 during the frequency modulation process by real-time monitoring and processing of the beat frequency signal. This real-time feedback mechanism helps to maintain the stability of the system and reduce performance fluctuations; optimize the signal processing process: the nonlinear correction system uses advanced signal processing algorithms, such as Hilbert transform, linear interpolation, etc., to accurately process and analyze the beat frequency signal. These algorithms can efficiently extract phase information and determine the frequency modulation nonlinearity based on this, providing reliable data support for subsequent correction operations. At the same time, by optimizing the signal processing process, the nonlinear correction system can respond to measurement needs more quickly and improve overall processing efficiency;

[0118] In addition, since this method adopts the circuit module 230, the cost is greatly reduced compared with the method previously studied in this application.

[0119] based on Figure 2 , see Figure 3 , is another schematic diagram of a nonlinear correction system for a frequency modulated continuous wave laser in an embodiment of the present application, wherein the optical path module 220 includes an isolator ISO, a variable optical attenuator VOA, a Mach-Zehnder interferometer MZI and a balanced detector BPD connected in sequence.

[0120] The frequency modulated continuous wave laser 210 is connected to the isolator ISO, and the balanced detector BPD is connected to the circuit module 230 .

[0121] In a feasible implementation, the frequency modulated continuous wave laser 210 is used to transmit the optical signal to the adjustable optical attenuator VOA through the isolator ISO; the adjustable optical attenuator VOA is used to adjust the signal strength of the optical signal to obtain an adjusted optical signal, and transmit the adjusted optical signal to the Mach-Zehnder interferometer MZI; the Mach-Zehnder interferometer MZI is used to generate an initial beat signal according to the adjusted optical signal, and transmit the initial beat signal to the balanced detector BPD; the balanced detector BPD is used to detect the initial beat signal, obtain the beat signal, and transmit the beat signal to the circuit module 230.

[0122] In some embodiments, Figure 3 As shown, the frequency modulated continuous wave laser 210 may be a distributed feedback laser (DFB).

[0123] Among them, ISO is Isolator, VOA is Variable Optical Attenuator, MZI is Mach-Zehnder Interferometer, and BPD is Balanced Photodetector.

[0124] In the embodiment of the present application, the design of the optical path module 220 in the nonlinear correction system of the frequency modulated continuous wave laser 210 includes key components such as the isolator ISO, the variable optical attenuator VOA, the Mach-Zehnder interferometer MZI and the balanced detector BPD, which can improve the system stability and anti-interference ability, enhance the signal processing capability and optimize the nonlinear correction effect.

[0125] It can be understood that the stability and anti-interference ability of the system are improved: the isolator ISO can prevent the reverse optical signal from interfering with the frequency modulated continuous wave laser 210, which helps to protect the normal operation of the laser and avoid performance degradation or damage caused by feedback light. The variable optical attenuator VOA can accurately control the intensity of the optical signal, and the system can better match the sensitivity of the Mach-Zehnder interferometer MZI, thereby optimizing the generation and detection of the beat frequency signal; enhance the signal processing capability: the Mach-Zehnder interferometer MZI is used to generate the initial beat frequency signal according to the adjusted optical signal, and its high precision and stability help to ensure the accuracy and reliability of the beat frequency signal, which can be received and detected by the balanced detector BPD. The initial beat frequency signal is used to more effectively extract the phase information in the optical signal, thereby improving the measurement accuracy and anti-interference ability of the system; optimizing the nonlinear correction effect: the various components in the optical path module 220 work together to jointly optimize the effect of nonlinear correction, that is, the isolator ISO ensures the unidirectional transmission and stability of the laser signal, the variable optical attenuator VOA accurately controls the intensity of the optical signal, the Mach-Zehnder interferometer MZI generates the initial beat frequency signal with high precision, and the balanced detector BPD accurately detects and extracts the phase information, so that the system can more accurately identify and correct the nonlinear changes of the frequency modulated continuous wave laser 210 during the frequency modulation process, which helps to reduce measurement errors and improve the overall performance and measurement accuracy of the system.

[0126] based on Figure 2 Please continue reading Figure 3 The circuit module 230 includes a programmable gate array signal processing circuit FPGA and a digital-to-analog converter DAC connected in sequence.

[0127] The frequency modulated continuous wave laser 210 is connected to the digital-to-analog converter DAC, and the programmable gate array signal processing circuit FPGA is connected to the processor 240 .

[0128] In a feasible implementation, the programmable gate array signal processing circuit FPGA is used to drive the digital-to-analog converter DAC to generate a triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser 210 .

[0129] Among them, FPGA stands for Field Programmable Gate Array and DAC stands for Digital to Analog Converter.

[0130] In the embodiment of the present application, by designing a circuit module 230 in the nonlinear correction system of the frequency modulated continuous wave laser 210, which includes the combined use of a programmable gate array signal processing circuit FPGA and a digital-to-analog converter DAC, the frequency modulated continuous wave laser 210 can be accurately controlled.

[0131] It can be understood that the frequency modulated continuous wave laser 210 is precisely controlled: the programmable gate array signal processing circuit FPGA can precisely control the driving current and the frequency of the output optical signal of the frequency modulated continuous wave laser 210 by driving the triangular wave signal generated by the digital-to-analog converter DAC, which helps to reduce the measurement error caused by the nonlinear effect of frequency modulation and improve the measurement accuracy and reliability of the system.

[0132] In addition, since this method uses a programmable gate array signal processing circuit FPGA, its cost is greatly reduced compared to the methods previously studied in this application.

[0133] based on Figure 2 Please continue reading Figure 3 , the circuit module 230 includes an analog-to-digital converter ADC.

[0134] The analog-to-digital converter ADC is connected to the optical path module 220 and the processor 240 respectively.

[0135] In a feasible implementation, the optical path module 220 is used to transmit the beat frequency signal to the analog-to-digital converter ADC; the analog-to-digital converter ADC is used to convert the beat frequency signal into a beat frequency signal to be corrected, and transmit the beat frequency signal to be corrected to the processor 240 .

[0136] Among them, ADC stands for Analog to Digital Converter.

[0137] In the embodiment of the present application, the circuit module 230 in the nonlinear correction system of the frequency modulated continuous wave laser 210 is designed to also include an analog-to-digital converter ADC, which can improve the signal conversion accuracy and speed.

[0138] It can be understood that the signal conversion accuracy and speed are improved: high-precision conversion: the analog-to-digital converter ADC can accurately convert the beat frequency signal transmitted by the optical path module 220 into a digital signal, that is, the beat frequency signal to be corrected. The high-performance analog-to-digital converter ADC has high resolution and low noise characteristics, which can ensure that the converted digital signal accurately reflects the frequency and phase information of the original beat frequency signal; high-speed conversion: the nonlinear correction system of the frequency-modulated continuous wave laser 210 needs to process a large number of beat frequency signals in real time to achieve precise control of the laser. The high-speed conversion capability of the analog-to-digital converter ADC can meet this requirement, ensuring that the system can obtain and process the beat frequency signal in real time, thereby improving the response speed and measurement accuracy of the system.

[0139] In some embodiments, the correction effect of the nonlinear correction of the present application can also be verified through experiments after executing the present application.

[0140] In this experiment, a DFB was used with a wavelength of 1550ns, a driving voltage range from 2V to 5.08V, and a sweep period of 50kHz. The effect of the correction can be verified by comparing the beat signal spectra under different states.

[0141] Take the down sweep of the beat frequency signal before and after correction as an example, see Figure 4 and Figure 5 , Figure 4 Schematic diagram of the down-sweep frequency spectrum of the beat frequency signal before correction in an embodiment of the present application, Figure 5 Schematic diagram of the downward sweep frequency spectrum of the corrected beat frequency signal in the embodiment of the present application; Figure 4 and Figure 5 By comparing the calibration results, we can see the difference before and after calibration. The signal frequency after calibration is basically stable and can achieve the expected effect.

[0142] For further information, see Figures 6 to 9 , Figure 6 is a schematic diagram of the instantaneous frequency of the beat signal before correction in an embodiment of the present application, Figure 7 is a schematic diagram of the instantaneous frequency of the corrected beat signal in an embodiment of the present application, Figure 8 Schematic diagram of the phase of the down-sweep frequency of the beat frequency signal before correction in an embodiment of the present application, Fig. 9 Schematic diagram of the phase of the downward sweep frequency of the corrected beat frequency signal in the embodiment of the present application; Figure 8 and Fig. 9 By comparing the phase curve of the MZI beat signal before correction, it is easy to see that the curvature of the phase curve is relatively large, and the nonlinearity is 10.29%. The corrected phase curve is similar to a straight line, and the nonlinearity is reduced to 0.83%. Then, by taking the derivative of the corresponding phase, the instantaneous frequency corresponding to the beat signal can be obtained, as shown in Figure 6 and Figure 7As shown, through Figure 6 and Figure 7 By comparing the calibration results, it can be seen that after calibration, except for the inflection point where the up-sweep and down-sweep meet, the frequency of the middle part of the signal is basically stable. The difference before and after calibration can also be seen, and the expected effect can be achieved.

[0143] In a third aspect, the present application provides a nonlinear correction device for a frequency modulated continuous wave laser.

[0144] See also Fig.10 , is a schematic diagram of a nonlinear correction device for a frequency modulated continuous wave laser in an embodiment of the present application, the device is applied to a nonlinear correction system for a frequency modulated continuous wave laser, the device 1010 comprises:

[0145] An acquisition module 1011 is used to acquire a phase curve of the beat frequency signal to be corrected based on the nth voltage signal;

[0146] A first determination module 1012, configured to determine frequency modulation nonlinearity according to the phase curve;

[0147] The processing module 1013 is used to perform sampling processing on multiple phase points in the phase curve to obtain multiple target phase points;

[0148] A second determination module 1014 is used to determine an n+1th voltage signal according to a plurality of target phase points and an nth voltage signal, wherein the n+1th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system;

[0149] Wherein, n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold.

[0150] In the embodiment of the present application, the relevant contents of the acquisition module 1011, the first determination module 1012, the processing module 1013 and the second determination module 1014 can be referred to in Figure 1 The contents in the illustrated embodiment will not be described in detail here.

[0151] It should be noted that the device 1010 of the present application also includes some other modules. It can be understood that the method of the present application and the device 1010 have a one-to-one correspondence. Therefore, some other modules of the device 1010 of the present application are the contents corresponding to the method of the present application in the above-mentioned embodiment.

[0152] In an embodiment of the present application, a phase curve of a beat frequency signal to be corrected is obtained based on an nth voltage signal, and then the frequency modulation nonlinearity is determined according to the phase curve, and a plurality of phase points in the phase curve are sampled and processed to obtain a plurality of target phase points, and finally an n+1th voltage signal is determined according to the plurality of target phase points and the nth voltage signal, and the n+1th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system, wherein n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to a frequency modulation nonlinearity threshold; that is, the nonlinear correction of the frequency modulated continuous wave laser in the system is realized, and the nonlinear correction of the frequency modulated continuous wave laser in the nonlinear correction system is realized, so that the range and speed measurement accuracy thereof can be prevented from being damaged, and the performance of the FMCW radar can be significantly improved.

[0153] In addition, the nonlinear correction method of the frequency modulated continuous wave laser proposed in this application realizes the effective correction of the nonlinearity of the frequency modulated continuous wave laser by iteratively optimizing the voltage signal, significantly improving the ranging and speed measurement accuracy of the FMCW radar, and has the characteristics of high correction accuracy, high flexibility, high cost-effectiveness and strong adaptability.

[0154] It can be understood that the correction accuracy is high: by directly analyzing the phase curve of the beat frequency signal and sampling and linearizing it, the nonlinear problem of the frequency modulated continuous wave laser can be corrected more accurately, significantly improving the accuracy of ranging and speed measurement; high flexibility: this method does not require changing the hardware structure of the laser, and nonlinear correction can be achieved only by adjusting the input voltage signal, which has high flexibility and practicality; high cost-effectiveness: compared with the method of achieving linear frequency modulation output through an external modulator studied before this application, this method does not require additional high-cost equipment, and can be achieved only through software algorithms, which has higher cost-effectiveness; strong adaptability: this method can be applied to different types of FMCW radar systems, and has wide applicability and scalability.

[0155] In a fourth aspect, the present application further provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes a nonlinear correction method for a frequency modulated continuous wave laser in the above method embodiment.

[0156] In a fifth aspect, the present application further provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes a nonlinear correction method for a frequency modulated continuous wave laser in the above method embodiment.

[0157] Fig.11 The internal structure diagram of a computer device in some embodiments is shown. The computer device may be a terminal, a server, or a gateway. Fig.11As shown, the computer device includes a processor, a memory and a network interface connected through a system bus.

[0158] The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor can implement each step in the above method embodiment. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement each step in the above method embodiment. Those skilled in the art can understand that Fig.11 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0159] A person of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing related hardware through a computer program. The program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods.

[0160] Among them, any reference to memory, storage, database or other media used in the embodiments provided in the present application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0161] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0162] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A nonlinear correction method for a frequency modulated continuous wave laser, characterized in that: The method is applied to a nonlinear correction system of a frequency modulated continuous wave laser, and the method comprises: Based on the nth voltage signal, obtaining a phase curve of the beat frequency signal to be corrected; determining frequency modulation nonlinearity according to the phase curve; Sampling a plurality of phase points in the phase curve to obtain a plurality of target phase points; Determine an n+1th voltage signal according to a plurality of target phase points and an nth voltage signal, wherein the n+1th voltage signal is used for nonlinear correction of a frequency modulated continuous wave laser in the system; Among them, n successively takes integers greater than 0 until the frequency modulation nonlinearity is less than or equal to the frequency modulation nonlinearity threshold.

2. The method according to claim 1, characterized in that The step of obtaining a phase curve of the beat frequency signal to be corrected based on the nth voltage signal includes: Based on the nth voltage signal, obtaining the beat frequency signal to be corrected; The beat frequency signal to be corrected is subjected to Hilbert transform processing to obtain the phase curve.

3. The method according to claim 2, characterized in that The step of performing Hilbert transform processing on the beat frequency signal to be corrected to obtain the phase curve comprises: Performing bandpass filtering on the beat frequency signal to be corrected to obtain the target beat frequency signal; The target beat frequency signal is subjected to Hilbert transform processing to obtain the phase curve.

4. The method according to claim 1, characterized in that: Determining the frequency modulation nonlinearity according to the phase curve includes: Determining a maximum offset of the phase curve, and determining an endpoint distance between two endpoints of the phase curve in the y-axis direction; The frequency modulation nonlinearity is determined according to the maximum offset and the endpoint distance.

5. The method according to claim 1, characterized in that The sampling process of the multiple phase points in the phase curve to obtain multiple target phase points includes: Downsampling the multiple phase points in the phase curve to obtain multiple downsampled phase points; The multiple phase reduction points are uniformly resampled to obtain multiple target phase points.

6. The method according to claim 1, characterized in that The determining the (n+1)th voltage signal according to the multiple target phase points and the (n)th voltage signal comprises: According to the multiple target phase points, the nth voltage signal is interpolated to obtain the (n+1)th voltage signal.

7. A nonlinear correction system for a frequency modulated continuous wave laser, characterized in that: The system includes a frequency modulated continuous wave laser, an optical path module, a circuit module and a processor; The frequency modulated continuous wave laser is connected to the optical path module and the circuit module respectively, and the optical path module and the circuit module are both connected to the processor; The circuit module is used to generate a triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser; The frequency modulated continuous wave laser is used to modulate the driving current of the frequency modulated continuous wave laser according to the triangular wave signal to generate an optical signal, and transmit the optical signal to the optical path module; The optical path module is used to generate a beat signal according to the optical signal, and transmit the beat signal to the circuit module; The circuit module is used for converting the beat frequency signal into a beat frequency signal to be corrected, and transmitting the beat frequency signal to be corrected to the processor; The processor is configured to execute the method according to any one of claims 1 to 6.

8. The system according to claim 7, characterized in that The optical path module includes an isolator, an adjustable optical attenuator, a Mach-Zehnder interferometer and a balanced detector connected in sequence; The frequency modulated continuous wave laser is connected to the isolator, and the balanced detector is connected to the circuit module; The frequency modulated continuous wave laser is used to transmit the optical signal to the adjustable optical attenuator through the isolator; The adjustable optical attenuator is used to adjust the signal strength of the optical signal to obtain an adjusted optical signal, and transmit the adjusted optical signal to the Mach-Zehnder interferometer; The Mach-Zehnder interferometer is used to generate the initial beat signal according to the adjusted optical signal, and transmit the initial beat signal to the balanced detector; The balanced detector is used to detect the initial beat frequency signal, obtain the beat frequency signal, and transmit the beat frequency signal to the circuit module.

9. The system according to claim 7, characterized in that The circuit module includes a programmable gate array signal processing circuit and a digital-to-analog converter connected in sequence; The frequency modulated continuous wave laser is connected to the digital-to-analog converter, and the programmable gate array signal processing circuit is connected to the processor; The programmable gate array signal processing circuit is used to drive the digital-to-analog converter to generate the triangular wave signal according to the nth voltage signal, and transmit the triangular wave signal to the frequency modulated continuous wave laser.

10. The system according to claim 7, characterized in that The circuit module includes an analog-to-digital converter; The analog-to-digital converter is connected to the optical path module and the processor respectively; The optical path module is used to transmit the beat frequency signal to the analog-to-digital converter; The analog-to-digital converter is used to convert the beat frequency signal into the beat frequency signal to be corrected, and transmit the beat frequency signal to be corrected to the processor.

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