CN114826426A - Parameter-adaptive high-precision digital laser phase locking system and method - Google Patents
Parameter-adaptive high-precision digital laser phase locking system and method Download PDFInfo
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Abstract
The invention provides a parameter self-adaptive high-precision digital laser phase locking system and method, which comprises two independent lasers, an interference light path, a photoelectric detector module and a control module, wherein the two independent lasers comprise a master laser and a slave laser, the master laser and the slave laser output laser light sources, two drivers of a PZT control module and a TEC control module control the slave laser to follow the phase change of the master laser, the interference light path generates interference light signals of the master laser and the slave laser, the photoelectric detector converts the interference light signals into electric signals, and the control module acquires the electric signals of the photoelectric detector and converts the electric signals into digital signals. The parameter self-adaptive high-precision digital laser phase-locked loop system and the method realize the high-precision digital laser phase-locked loop with the self-optimization of parameters in a complex dynamic environment.
Description
Technical Field
The invention relates to the technical field of laser communication, in particular to a parameter self-adaptive high-precision digital laser phase-locking system and method.
Background
Similar to an electric phase-locked loop system, an optical phase-locked loop is a system for controlling the output signal frequency of a laser through signal phase feedback, so that a slave laser tracks the phase of a master laser, the frequency of the slave laser is controlled through feedback, the phase change of the slave laser and the phase change of the master laser are kept consistent, and for a heterodyne phase-locked system, the phase difference among the slave laser, the master laser and a reference signal is zero.
The optical phase-locked loop is indispensable in the fields of laser interferometry and laser communication. In the application of space gravitational wave detection, the displacement change of pm magnitude can be measured in a range of millions of kilometers by using an extremely high-precision optical phase-locked loop; for quantum communication networks, the information transfer rate can be greatly improved by using a high-precision optical phase-locked loop. The field of gravitational wave detection and quantum communication is more and more concerned and emphasized by international scientific research institutions, and the optical phase-locked loop technology is rapidly developed.
The optical phase-locked loop is a technology for reading phase information of a plurality of light beams and regulating and controlling the phase of the light by an optical voltage-controlled oscillator so that the phases of the plurality of light beams are kept synchronous. In optical communication and interferometry applications, lock-in phase error is a measure of phase stability. The accuracy of this criterion depends on the external environmental noise of the optical phase-locked loop system, the internal device noise, and the ability of the phase-locked control system to suppress the noise.
Compared with the optical phase-locked loop technology applied to the ground, the space application requires a full-automatic unmanned control system to deal with various complex environments, and because relative motion exists between two satellites, laser interference links of the space application are constantly changed, so optical phase-locked interference signals have a plurality of influence factors, and even some potential unknown noises exist in complex dynamic environments.
CN201810652514.3 discloses an adaptive method for suppressing noise in a phase-locked loop by reducing loop bandwidth, which reduces the observed phase noise by reducing the phase noise entering the system, but for a laser phase-locked control system, the loop bandwidth of the phase-locked loop needs to be large enough, and the phase noise of a laser cannot be suppressed by simply reducing the loop bandwidth, so that the whole phase-locked system loses its function, and the environment of the laser phase-locked system is complex, and there are many potential noises.
CN206181084U discloses an instantaneous amplitude spectrum density calculation method, which can use an FPGA to identify frequency components in digital signals, but for a laser phase-locked control system, low-frequency noise is particularly critical, and amplitude spectrum density calculation of long-time data is required, and for noise in an mHz frequency band, data of more than 1 hour needs to be sampled, and amplitude spectrum density calculation is performed on the sampled data.
Firstly, for the measurement of the locking precision, most of the existing technical means only measure the in-loop phase of the phase-locked loop and only reflect the in-loop precision of the phase-locked loop, and the adaptive algorithm also suppresses the in-loop noise of the phase-locked loop, but the locking performance of the phase-locked loop is measured by the out-loop phase-locked precision in practical use. In the second aspect, more and more optical phase-locked loop applications are beginning to be biased towards digital control methods, and although digital circuits have the advantage of flexibility, the existing laser digital phase locking method has the problem of low locking precision in the prior report. In the third aspect, when the system is in a complex dynamic environment, the digital phase-locked system with fixed parameters cannot suppress potential noise, and manual parameter-adjusting optimization is not suitable for an unmanned space application system.
Therefore, how to solve the problem of poor performance of a laser phase-locked control system caused by potential noise in a complex environment, realize a high-precision digital laser phase-locked loop which accurately identifies and inhibits the potential noise in the complex dynamic environment and realizes the autonomous parameter optimization in the complex dynamic environment becomes a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In order to solve the above problems, it is a first object of the present invention to provide a high-precision digital laser phase locking system with autonomous parameter optimization suitable for complex dynamic environments.
Therefore, the above purpose of the invention is realized by the following technical scheme:
a parameter adaptive high-precision digital laser phase-locking system is characterized in that: the laser comprises two independent lasers, an interference light path, a photoelectric detector module and a control module, wherein the two independent lasers comprise a master laser and a slave laser, the master laser and the slave laser output laser light sources, the PZT control module and the TEC control module control the phase change of the slave laser through following the master laser, the interference light path generates interference light signals of the master laser and the slave laser, the photoelectric detector converts the interference light signals into electric signals, the control module collects the electric signals of the photoelectric detector, converts the electric signals into digital signals, digital control signals are formed through digital signal phase locking, the digital control signals are converted into analog control signals, the analog control signals control the signal frequency output from the lasers, the phase of the master laser is tracked and kept consistent with the phase of the master laser, and the control module system comprises a phase high-precision measuring module, The phase high-precision measurement module reads phase information of the interference signal after phase locking, stores continuous phase information and provides data for phase error amplitude spectrum density calculation of the phase amplitude spectrum density calculation module;
the phase amplitude spectrum density calculation module comprises an autocovariance calculation module, a discrete Fourier transform module, a square root module and a maximum value search module, wherein phase information is processed by the autocovariance calculation module to obtain autocovariance, the autocovariance performs discrete Fourier transform on data by the discrete Fourier transform module to obtain a power spectrum density curve, the power spectrum density curve performs square root processing by the square root module to obtain amplitude spectrum density data, the amplitude spectrum density data performs maximum value search processing by the maximum value search module to obtain the frequency position where a maximum value point appears, and the phase amplitude spectrum density calculation module calculates and obtains phase errors of different frequency bands;
the autonomous optimization parameter module comprises an extreme value threshold judgment module, a PID (proportion integration differentiation) progression control module and a PID parameter control module, wherein the extreme value threshold judgment module is used for carrying out threshold judgment on a maximum value point obtained by searching and processing of the maximum value search module, presetting a threshold according to a phase error value after locking of a corresponding frequency band, judging whether the maximum value point is greater than the threshold, recording a frequency position greater than the threshold pole, inputting the recorded frequency position of the pole to the PID progression control module and the PID parameter control module, correspondingly adjusting the progression of a first loop filter locked by phase and a control parameter of each level, and then re-locking the signal phase feedback control system to realize parameter adaptive optimization.
While adopting the technical scheme, the invention can also adopt or combine the following technical scheme:
as a preferred technical scheme of the invention: the control module is an electronic circuit board and comprises an A/D acquisition circuit, an FPGA circuit and D/A conversion circuits, wherein one A/D acquisition circuit acquires an electric signal of a photoelectric detector and converts the electric signal into a digital signal, the FPGA circuit is loaded with a digital phase automatic locking system to form a digital control signal, and the two D/A conversion circuits are used for converting the digital control signal into an analog control signal;
the digital phase automatic locking system comprises a frequency capturing loop and a phase locking loop, wherein the frequency capturing loop scans and controls the frequency of the slave laser, and the phase locking loop controls the slave laser to track the frequency of the master laser, so that the automatic phase locking of the master laser and the slave laser is realized.
As a preferred technical scheme of the invention: the frequency capturing loop comprises a frequency automatic scanning module, a peak signal identification module, a second D/A conversion circuit and a TEC control module; the frequency automatic scanning module outputs a digital signal which is continuously increased along with the time; the peak signal identification module can receive a target frequency and a target peak value set by external input, automatically judge whether a peak signal enters a target threshold value, stop frequency scanning at the moment of entering the target threshold value and open the phase locking loop; the second D/A conversion circuit converts the digital signal output by the frequency automatic scanning module into a voltage signal and outputs the voltage signal to the TEC control module; the TEC control module changes the frequency of the slave laser to reach the target threshold of the peak signal identification module;
the frequency automatic scanning module comprises a peak signal identification module for identifying the frequency and amplitude of a peak signal in the frequency spectrum of the electric signal; the external input method can be realized by using an upper computer and a serial port, wherein the upper computer comprises a display, a host, a keyboard and the like, is connected with the FPGA through communication, an operator inputs a control signal and communicates the control signal to the FPGA, and the FPGA board card comprises a serial port chip, converts upper computer data into a serial port communication protocol and inputs the serial port communication protocol into the FPGA so as to provide a signal for a phase-locked control system;
as a preferred technical scheme of the invention: the phase locking loop comprises a first phase discriminator, a first numerical control oscillator, a first loop filter, a first D/A conversion circuit, a high-voltage amplification module and a PZT control module, wherein the first numerical control oscillator outputs a sine wave signal with fixed frequency as a digital reference source; the first phase detector receives the digital signals from the A/D acquisition circuit and the digital signals of the first numerically-controlled oscillator, resolves the phase difference of the two paths of signals, and outputs the phase difference of the two paths of signals to the first loop filter; the first loop filter performs digital amplification filtering processing on the phase error signal output by the first phase detector and outputs the phase error signal to the first D/A conversion circuit; the first D/A conversion circuit inputs voltage to the high-voltage amplification module so as to adapt to the voltage control of the PZT control module; the PZT control module directly changes the frequency of the slave laser, and the phase change rate is changed by adjusting the frequency to complete a phase locking loop.
As a preferred technical scheme of the invention: the high-voltage amplification module adopts an OPA552 chip, the amplification factor is set to be 1-30 times and adjustable through a sliding rheostat, and the bandwidth of the high-voltage amplification module is consistent with the bandwidth design of a PZT control module so as to reduce the interference of high-frequency noise of a circuit and improve the phase locking precision;
the parameters of the first loop filter in the phase locking loop are open and adjustable at will, including the stages of the PI and the PD and the parameters in each stage, and are used for the purpose of modifying the transfer function of the first loop filter.
As a preferred technical scheme of the invention: the phase high-precision measurement module comprises a second numerical control oscillator, a second phase discriminator, a second loop filter, a third numerical control oscillator, a phase demodulation module and a phase information acquisition module, wherein the second numerical control oscillator outputs a digital sine signal and a digital cosine signal, the two signals have the same frequency and have the phase difference of 90 degrees; the second phase discriminator receives one path of digital sinusoidal signal of the second numerically controlled oscillator, performs phase discrimination processing on the digital sinusoidal signal and the digital signal of the A/D acquisition circuit, and outputs a phase error signal to a second loop filter; the second loop filter amplifies and filters the phase error signal, outputs the phase error signal to a frequency control word register of the second numerically controlled oscillator, and can change the frequency value of a sinusoidal signal by modifying the frequency control word register of the second numerically controlled oscillator so as to keep the phase of the digital sinusoidal signal output by the second numerically controlled oscillator consistent with the phase of the digital signal of the A/D acquisition circuit; the frequency of the third numerically controlled oscillator is open and adjustable, the frequency is the same as the set frequency of the first numerically controlled oscillator, and the phase value output by the phase accumulator of the third numerically controlled oscillator is used as a reference phase; the phase demodulation module receives phase values output by the phase accumulators and output by the second and third numerically controlled oscillators, performs subtraction operation, and obtains the phase information which is the phase information of the measured signal of the A/D acquisition circuit, wherein the initial frequency of the second numerically controlled oscillator is adjustable to be suitable for interference signals with different frequencies;
the phase information acquisition module samples the phase information calculated by the phase demodulation module, and the sampling time and the sampling rate are referred to the concerned frequency band.
As a preferred technical scheme of the invention: the second loop filter selects a high-order loop filter to suppress noise of a frequency band which is not concerned in the interference signal;
the initial frequency of the second numerically controlled oscillator is arbitrarily modified by an external input to be suitable for interference signals of different frequencies.
As a preferred technical scheme of the invention: the phase amplitude spectral density calculation module comprises a first memory module, an autocovariance calculation module, a second memory module, a discrete Fourier transform module, a third memory module, a square root module, a fourth memory module and a maximum value search module; the first memory module stores the phase information obtained by the phase demodulation module and is used for calculating and obtaining phase errors of different frequency bands, and the storage time and the sampling frequency are required by the frequency band concerned by the phase amplitude spectral density; the autocovariance calculation module performs autocovariance processing on the data in the first memory module and stores the calculated autocovariance into the second memory module; the discrete Fourier transform module performs discrete Fourier transform on the data in the second memory module, stores the power spectral density value of the discrete Fourier transform in a third memory module, stores a power spectral density curve in the third memory, performs square root processing on the data in the third memory by the square root module to obtain the amplitude spectral density of the signal, and stores the amplitude spectral density in the fourth memory module.
As a preferred technical scheme of the invention: the PID series control module and the PID parameter control module automatically adjust the PID series and parameters of the first loop filter, the automatic adjustment is based on the magnitude of amplitude spectrum density data, when a maximum value larger than a noise threshold value appears in the amplitude spectrum density data, the phase noise of the optical phase-locked loop is automatically considered to be further suppressed, a first-stage PID controller is added when each maximum value point is larger than the noise threshold value, and the PID controller enables the gain of a baud chart of the first loop filter at the frequency of the noise maximum value point to be increased, so that the phase noise suppression capability at the frequency point is enhanced; especially, when the potential noise is introduced into the parameter adaptive high-precision digital laser phase-locked system, the system can automatically identify the occurrence of the noise from the amplitude spectrum density data, because the occurrence of the potential noise can enable the amplitude spectrum density data to have a maximum value point which is larger than a noise threshold, the PID series control module can automatically increase a first-level PID controller, and the PID parameter control module is utilized to increase control gain for the frequency of the potential noise, enhance the noise suppression capability at the frequency until the potential noise is suppressed to be below the noise threshold, so that the optical phase-locked system can autonomously suppress the potential noise, autonomously adapt to a complex dynamic environment, and always keep high-precision phase locking.
The second purpose of the present invention is to provide a high-precision digital phase locking method suitable for the parameter autonomous optimization of complex dynamic environment.
Therefore, the above purpose of the invention is realized by the following technical scheme:
a high-precision digital phase locking method suitable for parameter autonomous optimization of a complex dynamic environment comprises the following steps:
s1, the digital phase automatic locking system automatically locks the phases of the master laser and the slave laser;
s2, the phase high-precision measuring module reads the high-precision measurement of the phase of the laser interference signal and records the locking phase value;
s3, calculating the locked phase value by the phase amplitude spectrum density calculation module to obtain the amplitude spectrum density of the phase error, and analyzing the frequency band of the locked noise;
s4, analyzing the noise frequency band autonomous optimization algorithm parameters through the amplitude spectral density curve obtained in S3 by the autonomous optimization parameter module algorithm, automatically identifying the frequency points which do not meet the target phase precision, automatically modifying the stage number of the loop filter and the control parameters of each stage, and controlling the frequency of the signal output from the laser to be consistent with the frequency change of the main laser; the autonomous optimization algorithm of the autonomous optimization parameter module comprises the following steps:
the system starts to operate after the first phase locking function is completed until the system is shut down, the iteration number J is recorded, the initial iteration number J is set to be 1, and a maximum value searching module is waited to complete the processing of one frame of data;
then, an extreme value threshold judging module is used for processing a maximum value searching module, when a maximum value larger than a noise threshold does not exist, the system meets the high-precision phase locking requirement, otherwise, the system does not meet the high-precision phase locking requirement, and the phase noise needs to be further inhibited; firstly, storing N maximum value points which are greater than a noise threshold, wherein N is greater than or equal to 1, and a maximum value point set is marked as A i,j I represents the ith maximum point, j represents the corresponding frequency value of the jth iteration maximum point and is marked as f i.j ；
If the system is iterated for the first time, all maximum value points are considered to be processed for the first time, namely, each maximum value point needs to be added with a PID controller, N PID controllers are added in total, and the PID controllers are controlled to be in f i,j The gain at (d) is set to 4dB, where PI is 2dB, PD is 2dB, set to 4 dB;
if the iteration is not the first iteration, the system is shown to be possible to process certain maximum value points in the previous iteration, a new PID controller is not required to be added, and only the gain of the previous controller is required to be increased; firstly, searching the maximum value point set A of the iteration i,j Whether there is a maximum point set P from the previous J-1 iterations i,j There is intersection, and the intersection is embodied as A i,j Frequency f of i,j And P i,j Frequency f of i`,j` The values are equal, if the same frequency does not exist, the A found at this time is considered to be i,j All are never processed, and are the same as the processing of the first iteration; if the same frequency is present, A i,j And P i,j There is an intersection and the same frequency f i,j Or f i`.j` The noise suppression capability is not enough, and the gain needs to be further increased to improve the noise suppression capability; a. the i,j And P i,j Is denoted as B i,j Let B be i,j Containing M elements, M<N，B i,j The maximum points of (a) are all processed in the previous J-1 iterations;set A i,j Exclusion of B i,j Set of postremainders as C i,j ，C i,j N-M maximum points exist, which are unprocessed maximum points in J-1 iterations; for B i,j Only gain increase for the previous PID controller is required, for C i,j N-M PID controllers are needed to be added, and initial gain is set; after the iteration is finally completed, the counting of J is increased by one; the state of the current first loop filter is kept until the output of the extreme value threshold judging module is that no maximum value larger than the noise threshold exists; if the potential noise occurs in the system, the method automatically enters the program flow of the autonomous optimization parameter algorithm, and the potential noise is suppressed in a targeted manner.
The invention relates to a parameter self-adaptive high-precision digital laser phase-locking system and a parameter self-adaptive high-precision digital laser phase-locking method, which are characterized in that two independent free-running lasers and other optical elements form an interferometer, an analog-to-digital conversion is carried out on interference signals by using a high-speed ADC (analog-to-digital converter), the core part uses an FPGA (field programmable gate array) to realize parameter self-adaptive high-precision phase-locking control, two basic functions are read out based on automatic phase locking and high-precision phase, the phase-locking noise frequency band is automatically identified, and parameters are automatically optimized according to the frequency band where noise is located. Finally, the system still has the capability of autonomously suppressing noise even though potential noise interference occurs in a complex dynamic environment, so that the system keeps high-precision optical phase locking for a long time, and the laser phase locking system can leave a stable environment of a laboratory.
Drawings
FIG. 1 is a schematic diagram of a high precision digital laser phase-locked system with autonomous parameter optimization for complex dynamic environments according to the present invention;
FIG. 2 is a schematic diagram of the digital phase lock system of the present invention;
FIG. 3 is a schematic diagram of a first loop filter structure according to the present invention;
FIG. 4 is a block diagram of a phase high accuracy measurement module of the present invention;
FIG. 5 is a schematic diagram of a phase magnitude spectral density calculation module according to the present invention;
FIG. 6 is a schematic diagram of the autonomic optimization parameter algorithm of the present invention;
FIG. 7 is a schematic flow chart of an autonomic optimization parameter algorithm routine of the present invention;
FIG. 8 is a block diagram of an autonomous optimization process of the present invention;
in the drawing, a master laser 1, a slave laser 2, a PZT control module 2.1, a TEC control module 2.2, an interference optical path 3, an electronic circuit board 4, an a/D acquisition circuit 4.1, a first D/a conversion circuit 4.2, a second D/a conversion circuit 4.3, an FPGA circuit 4.4, a high-voltage amplification module 5, a first phase discriminator 6.2, a first digitally controlled oscillator 6.1, a first loop filter 6.3, a peak signal identification module 7.1, a frequency auto-scan module 7.2, a second digitally controlled oscillator 8.1, a second phase discriminator 8.2, a second loop filter 8.3, a phase adjustment module 8.4, a phase acquisition module 8.5, a first memory module 9.1, an auto-covariance calculation module 9.2, a second memory module 9.3, a square root discrete transformation module 9.4, a third memory module 9.5, a fourier transform module 9.6, a fourth memory module 9.7, a maximum search module 9.8, a maximum threshold judgment module 10.1, a threshold judgment module 9.2, a second memory module 9.2, a second phase discriminator module 8, a second phase discriminator module 8.2, a second loop filter, a third memory module, a second loop filter, a third filter, a second loop filter, a second loop filter, a third loop filter, a second filter, a third loop filter, a second loop filter, a third loop filter, a third filter, a second filter, a third loop filter, a third filter, a second loop filter, a third filter, a second loop filter, a third filter, a second loop filter, a third filter, a second loop filter, a fourth memory module, a third filter, a third, A PID series control module 10.2, a PID parameter control module 10.3, an autonomous optimization parameter algorithm program flow 10.4 and a system complete machine autonomous optimization flow 11.
Detailed Description
As shown in fig. 1, the present invention provides a high-precision digital laser phase-locking system with autonomously optimized parameters for complex dynamic environment, and a fully automatic phase-locking device for two independent lasers, wherein the automatic phase-locking device enables the two lasers to automatically complete phase locking under unmanned conditions, and mainly comprises three parts, an interference optical path, an electronic circuit and an automatic phase-locking algorithm.
A parameter self-adaptive high-precision digital laser phase-locked system comprises two independent lasers, an interference light path, a photoelectric detector module and a control module, wherein the two independent lasers comprise a master laser and a slave laser, the master laser and the slave laser output laser light sources, two drivers of a PZT control module and a TEC control module control the slave laser to change by following the phase of the master laser, the interference light path generates interference light signals of the master laser and the slave laser, the photoelectric detector converts the interference light signals into electric signals, the control module collects the electric signals of the photoelectric detector, converts the electric signals into digital signals, digital control signals are formed by digital signal phase locking, the digital control signals are converted into analog control signals, the analog control signals control the signal frequency output by the slave laser, the phase of the master laser is tracked and kept consistent with the analog control signals, the control module system comprises a phase high-precision measurement module, a phase amplitude spectrum density calculation module and an autonomous optimization parameter module, wherein the phase high-precision measurement module reads phase information of the interference signal after phase locking, stores continuous phase information and provides data for phase error amplitude spectrum density calculation of the phase amplitude spectrum density calculation module.
As shown in fig. 1, the parameter adaptive high-precision digital laser phase-locked system of the present invention comprises: the two independent 1064nm lasers comprise a master laser 1 and a slave laser 2, are used for generating laser source signals, do not control the master laser 1, and are controlled by the slave laser 2 through a PZT control module 2.1 and a TEC control module 2.2, and are used for following the phase change of the master laser 1; the interference light path 3 is an optical platform and is used for generating interference light signals of two beams of laser; and the photoelectric detector is used for converting the interference optical signal into an electric signal.
The PZT control module is a piezoelectric ceramic driver, the TEC control module is a temperature control driver, the PZT control module can rapidly change laser frequency, the bandwidth is hundreds of kHz magnitude, the TEC control module can slowly change the laser frequency, and the bandwidth is Hz magnitude.
In the implementation process of the invention, an electronic circuit board is developed as a control module, and the control module comprises: one A/D acquisition circuit 4.1 is used for acquiring the electric signal of the photoelectric detector and converting the electric signal into a digital signal; the first D/A conversion circuit is used for converting the digital control signal into an analog control signal; and the FPGA circuit 4.4 is used for loading a digital phase-locking algorithm.
The digital phase automatic locking system comprises a phase locking loop and a frequency capturing loop, wherein the phase locking loop and the frequency capturing loop are used for realizing automatic locking of a phase, the frequency capturing loop is used for scanning and controlling the frequency of a slave laser in a large range, the phase locking loop 6 is used for tracking the slave laser to a master laser, and the phase locking loop 6 comprises a first phase detector and a first numerical control oscillation first loop filter which are all realized on an FPGA circuit as shown in figure 2, so that the integration level of the system is improved.
The phase locking loop comprises a first phase detector 6.2, a first numerical control oscillator 6.1, a first loop filter 6.3, a first D/A conversion circuit 4.2, a high-voltage amplification module 5 and a PZT control module 2.1; a first phase detector 6.2 in the phase locking loop receives the digital signal from the A/D acquisition circuit 4.1 and the digital signal of a first numerical control oscillator 6.1, calculates the phase difference of the two paths of signals and finally outputs the phase difference to a first loop filter 6.3; the first numerically controlled oscillator 6.1 outputs a sine wave signal with fixed frequency as a digital reference source; the first loop filter 6.3 performs digital amplification filtering processing on the phase error signal output by the first phase detector 6.2, and outputs the phase error signal to the first D/a conversion circuit 4.2; the first D/A conversion circuit 4.2 inputs the voltage to the high-voltage amplification module 5, so that the voltage is amplified to a certain degree and can be suitable for the voltage control range of the PZT control module 2.1; the PZT control module 2.1 will directly change the frequency of the slave laser, and finally complete the phase-locked loop by adjusting the frequency to change the phase change rate.
The frequency acquisition loop comprises a frequency automatic scanning module 7.2, a peak signal identification module 7.1, a second D/A conversion circuit 4.3 and a TEC control module 2.2; the frequency automatic scanning module 7.2 in the frequency capture loop module outputs a digital signal which is continuously increased along with the time; the frequency automatic scanning module 7.2 receives the signal from the peak signal identification module 7.1, and is used for identifying the frequency and amplitude of the peak signal in the frequency spectrum of the electric signal; the peak signal identification module 7.1 can receive a target frequency and a target peak value input from the outside, judge whether a peak signal enters a target threshold value, stop frequency scanning at the moment of entering the target threshold value, and open the phase locking loop; the second D/a conversion circuit 4.3 can convert the digital signal output by the frequency automatic scanning module 7.2 into a voltage signal, and output the voltage signal to the TEC control module 2.2; the TEC control module 2.2 will vary the frequency of the slave laser 2 over a wide range to reach the target threshold of the peak signal identification module.
The parameters of the first loop filter 6.3 in the phase locking loop are opened and randomly adjusted, including the stage numbers of PI and PD, 10 stages of PI and PD are designed, the stage numbers of PI and PD and the parameters in each stage can be freely modified, the purpose of modifying the transmission function of the first loop filter 6.3 is finally realized, and an interface is opened for an autonomous optimization parameter algorithm. And the phase locking loop opening enabling interface receives an enabling signal of the frequency acquisition loop.
The high-voltage amplification module 5 adopts an OPA552 chip, the amplification factor is set to be 1-30 times and adjustable through a sliding rheostat, the bandwidth of the high-voltage amplification module 5 is designed to be consistent with the bandwidth of the PZT control module 2.1, the high-frequency noise interference of a circuit can be reduced, and the phase locking precision is improved.
In the present invention, the frequency of the first digitally controlled oscillator 6.1 is open and adjustable, and is used to arbitrarily adjust the frequency difference between the master laser and the slave laser.
The phase high-precision measurement module and the phase locking loop are realized on the same FPGA circuit 4.4, and are used for reading phase information of interference signals after full-automatic phase locking of a laser and storing long-term phase information for calculating phase error amplitude spectral density. The phase high-precision measurement module comprises a second numerically controlled oscillator 8.1, a second phase discriminator 8.2, a second loop filter 8.3, a third numerically controlled oscillator 8.6, a phase demodulation module 8.4 and a phase acquisition module 8.5, wherein the second numerically controlled oscillator 8.1 outputs a digital sine signal and a digital cosine signal, the two signals have the same frequency and have the phase difference of 90 degrees; the second phase discriminator 8.2 receives one path of digital sinusoidal signal of the second numerically controlled oscillator 8.1, performs phase discrimination processing on the digital sinusoidal signal and the digital signal of the a/D acquisition circuit 4.1, and outputs a phase error signal to enter a second loop filter 8.3; the second loop filter 8.3 amplifies and filters the phase error signal, and outputs the amplified and filtered phase error signal to the frequency control word register of the second digital controlled oscillator 8.1, and the frequency value of the sinusoidal signal can be changed by modifying the frequency control word register of the second digital controlled oscillator 8.1, so that the phase of the digital sinusoidal signal output by the second digital controlled oscillator 8.1 is consistent with the phase of the digital signal of the a/D acquisition circuit 4.1; the frequency of the third numerically controlled oscillator 8.6 is open and adjustable, is the same as the set frequency of the first numerically controlled oscillator 6.1, and the phase value output by the phase accumulator of the third numerically controlled oscillator 8.6 is used as a reference phase; the phase demodulation module 8.4 receives the phase values output by the phase accumulators and output by the second and third numerically controlled oscillators 8.1 and 8.3, performs subtraction operation, and obtains the phase information, which is the phase information of the measured signal of the a/D acquisition circuit 4.1, where the initial frequency of the second numerically controlled oscillator 8.1 is adjustable to be suitable for interference signals of different frequencies.
The third numerically controlled oscillator 9.5 is used as a phase reference, and the traditional method is to use the data in the frequency control word register of the second numerically controlled oscillator 8.1 to carry out accumulation calculation, so that the phase of the improved scheme is more intuitive, and the data post-processing is reduced.
The resolved high precision phase data is stored in the first memory module 9.1 as an initial input to the phase magnitude spectral density calculation module. The phase information acquisition module 8.5 samples the resolved phase information, and the sampling time and the sampling rate are based on the concerned frequency band, for example, the frequency band of 1mHz to 10Hz is concerned, so that the sampling time corresponds to the low frequency band, which needs to be greater than twice of the period of the low frequency band, and is at least 2000 s; the sampling rate corresponds to the high band and needs to be more than twice the frequency of the high band, at least 20 Hz.
The second loop filter 8.3 is changed from a conventional low-order loop filter into a high-order loop filter, and in the invention, the second loop filter 8.3 uses a third-order filter to better compress noise in a frequency band which is not concerned in an interference signal.
The initial frequency of the second numerically controlled oscillator 8.1 can be modified arbitrarily by an external input to adapt to interference signals of different frequencies.
The phase amplitude spectrum density calculation module can be used for calculating an amplitude spectrum density curve of locking phase information which can be recorded on the basis of completing a phase locking function, the curve shows phase errors of the system in different frequency bands, and the curve can be used as a parameter optimization direction.
The phase amplitude spectral density calculation module comprises a first memory module 9.1, an autocovariance calculation module 9.2, a second memory module 9.3, a discrete fourier transform module 9.4, a third memory module 9.5, a square root module 9.6, a fourth memory module 9.7 and a maximum value search module 9.8, wherein the first memory module 9.1 stores high-precision phase data calculated by the phase demodulation module 8.4, and the storage time and the sampling frequency are required by a frequency band concerned by power spectral density, for example, the frequency band concerned by 1mHz to 100Hz needs to be concerned, the storage time needs to exceed 2000 seconds, and the sampling rate needs to exceed 200 Hz. The autocovariance calculating module 9.2 performs autocovariance processing on the data in the memory module, and stores the calculated autocovariance in the second memory module 9.3. The discrete fourier transform module 9.4 performs discrete fourier transform on the data in the second memory module 9.3, and stores the result of the discrete fourier transform in a third memory module 9.5, where the third memory module 9.5 stores a power spectral density curve. The square root module 9.6 square root processes the data in the third memory 9.5 and stores the result in the fourth memory module 9.7, and the data in the fourth memory module 9.7 is the amplitude spectral density. The maximum search module 9.8 performs maximum search processing on the data in the fourth memory 9.7, and obtains the frequency position where the maximum point appears.
The first memory module 9.1, the second memory module 9.3, the third memory module 9.5 and the fourth memory module 9.7 multiplex the same memory module, thus saving memory hardware resources.
The square root module 9.6 uses cordic IP core provided by xilinx to perform square root processing on the power spectral density data by using cordic algorithm in sequence to obtain phase amplitude spectral density data.
And carrying out extremum search on the phase amplitude spectrum density data, calculating to obtain a phase amplitude spectrum density maximum value and a corresponding frequency point, and inputting as an autonomous optimization parameter module.
The main optimization parameter module in the invention is specifically an autonomous optimization parameter module based on noise band analysis, and is used for carrying out extremum search on the phase amplitude spectral density data, calculating to obtain a phase amplitude spectral density maximum and a frequency point corresponding to the phase amplitude spectral density maximum, carrying out autonomous optimization on the transmission function of the first loop filter 6.3, and realizing autonomous optimization by modifying the number of stages of the first loop filter 6.3 and the control parameter of each stage.
The autonomous optimization parameter module comprises an extreme value threshold value judging module 10.1, a PID series control module 10.2 and a PID parameter control module 10.3. At the beginning of the autonomous optimization parameter module, the first loop filter 6.3 is firstly set to be a structure of two stages of PI and one stage of PD, so as to complete the full-automatic phase locking of the master laser 1 and the slave laser 2. The extremum threshold value determining module 10.1 is configured to perform threshold value determination on an extremum, for example, if the phase error is lower than 1mrad after the system requires locking in a certain frequency band, the threshold value is set to 1mrad, and it is determined whether each maximum value point obtained by performing maximum value search processing on data in the fourth memory 9.7 by the maximum value searching module 9.8 is greater than 1mrad, if so, the position of each maximum value point is recorded, otherwise, no recording is performed, and the frequency position where the maximum value point greater than 1mrad appears, which is obtained by the maximum value searching module 9.8, is input to the PID stage control module and the PID parameter control module. The PID stage number control module 10.2 increases the first stage PI and the first stage PD for every pole number greater than the threshold pole number. The PID parameter control module 10.3 modifies the parameters of each stage of PI and PD added by the PID stage control module 10.2, including the corner frequency and the gain, by default, limits the gain saturation to infinity, sets the extreme frequency position to the corner frequency of each stage of PI and PD, and sets the initial gain of each stage to 2 dB.
As shown in fig. 6, the autonomous optimization parameter module, the PID parameter control module 10.3 and the PID series control module 10.2 read data from the extremum threshold determination module 10.1, and input the data into the program flow of the autonomous optimization parameter algorithm, so as to obtain the phase noise suppression for the optical phase-locked loop system, and implement high-precision phase locking.
As shown in fig. 7, the autonomous parameter optimization algorithm starts to operate after the system completes the first phase locking function until the system is shut down, records the iteration number J after starting, sets the initial iteration number J to 1, waits for the maximum value search module 9.8 to complete one frame of data processing, processes the maximum value search module by using the extremum threshold determination module, and when there is no maximum value greater than the noise threshold, it indicates that the system meets the high-precision phase locking requirement, otherwise, the system does not meet the high-precision phase locking requirement, and needs to further suppress the phase noise. Firstly, storing N maximum value points which are greater than a noise threshold, wherein N is greater than or equal to 1, and a maximum value point set is marked as A i,j The corresponding frequency value of the maximum value point is denoted as f i.j . If the system is the first iteration, all the maximum value points are considered to be processed for the first time, namely, each maximum value point needs to be added with a stage of PID controller, N PID controllers are added in total, and the PID controllers are controlled to be in f i,j The gain at (4 dB) is set to be 4dB (2 dB for PI and 2dB for PD). If the iteration is not the first iteration, the system is shown to be possible to process some maximum value points in the previous iteration, and a new PID controller is not required to be added, and only the gain is required to be increased for the previous controller. Firstly, searching the maximum value point set A of the iteration i,j Whether there is a maximum point set P from the previous J-1 iterations i,j There is intersection, and the intersection is embodied as A i,j Frequency f of i,j And P i,j Frequency f of i`,j` The values are equal, if the same frequency does not exist, the A found at this time is considered to be i,j All are never processed, the same as the first iteration; if the same frequency is present, A i,j And P i,j There is an intersection and the same frequency f i,j (or f) i`.j` ) The noise suppression capability is still insufficient, and further gain increase and noise suppression capability improvement are required. A. the i,j And P i,j Is denoted as B i,j Let B be i,j Containing M elements (M)<N)，B i,j The maximum points of (a) were processed in the previous J-1 iterations. Set A i,j Exclusion of B i,j Set of postremainders as C i,j ，C i,j There are N-M maxima, which are the maxima that were not processed in J-1 iterations. For B i,j Only gain increase for the previous PID controller is required, for C i,j N-M PID controllers need to be added and an initial gain set. And finally, after the iteration is completed, the counting of J is increased by one. And keeping the state of the current first loop filter until the output of the extreme value threshold judging module is that the maximum value larger than the noise threshold does not exist. If the potential noise occurs in the system, the process automatically enters an autonomous optimization parameter algorithm program flow, and the potential noise is suppressed in a targeted manner.
The overall system autonomous optimization process is as shown in fig. 8, and is used as a cyclic control process of the whole parameter adaptive high-precision digital laser phase locking method, and the process is started and runs until the system is shut down. The automatic phase locking system is used for locking two lasers, the high-precision phase measuring module is used for measuring the locked phase, the storage time is T seconds, and sampling is performed every second
Point, co-existence storage
Point; using the phase amplitude spectrum density calculation module to calculate the amplitude spectrum of the stored N points, wherein the calculation result is
Curve of which
Is a discrete frequency of the phase amplitude spectral density,
the amplitude corresponding to the discrete frequency; for is to
Performing extreme value operation and curve existence
An extreme value, storing the calculated extreme value as
. Will be provided with
One by one with the phase amplitude threshold
Making a comparison of
Is greater than
Is stored to
Wherein
To exceed a phase amplitude threshold
The frequency value of (2). Each one of which is provided with
Then add a stage PI and a stage PD, and set the corner frequency
Consistently, its initial gain was set to 4dB, with PI and PD each at 2 dB. From this, the first iteration of the autonomous optimization parameter algorithm is completed. In the second iteration, if still
If the PI and PD orders exist, the same PI and PD order increase is carried out, and if the PI and PD orders exist
From the last iteration
The same, 2dB increase for the last increased PI and PD gains. In a certain iteration
Are all less than
The system state is maintained until there is a new one
Exceedance
And (4) a threshold value. After the autonomous optimization parameter algorithm is executed, the system can be automatically locked again by the overall autonomous optimization process of the system, the second task and the third task are performed again, if the previous pole still exceeds the threshold in the fourth task, the corresponding PI and PD are sequentially increased by 2dB until all the poles are below the threshold, if a new pole exceeding the threshold appears, the PID series is increased, if the new pole exceeding the threshold does not appear, the system keeps the locking state unchanged, the overall autonomous optimization enables the system to automatically complete the locking function after parameter modification is completed every time, the noise state of the system is monitored in real time, noise is suppressed autonomously, and the high-precision digital phase-locked loop for autonomous parameter optimization is realized.
The parameter self-adaptive high-precision digital laser phase locking system is particularly suitable for complex dynamic environments applied in space or ground, when potential noise occurs, the control algorithm can automatically identify the frequency band of the system noise, automatically optimize control parameters and follow the dynamic change of the environment where the phase locking system is located, so that the system stably works in the optimal state, namely the state with the minimum phase error after locking.
The above-described embodiments are intended to illustrate the present invention, but not to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit of the present invention and the scope of the claims fall within the scope of the present invention.
Claims (10)
1. A parameter adaptive high-precision digital laser phase-locking system is characterized in that: the laser tracking system comprises two independent lasers, an interference light path, a photoelectric detector module and a control module, wherein the two independent lasers comprise a master laser and a slave laser, the master laser and the slave laser output laser light sources, the PZT control module and the TEC control module control the phase change of the slave laser following the master laser, the interference light path generates interference light signals of the master laser and the slave laser, the photoelectric detector converts the interference light signals into electric signals, the control module acquires the electric signals of the photoelectric detector, converts the electric signals into digital signals, forms digital control signals through digital signal phase locking, converts the digital control signals into analog control signals, controls the signal frequency output from the lasers through the analog control signals, tracks the phase of the master laser and keeps consistent with the phase of the master laser, and the control module system comprises a phase high-precision measuring module, The phase high-precision measurement module reads phase information of the interference signal after phase locking, stores continuous phase information and provides data for phase error amplitude spectrum density calculation of the phase amplitude spectrum density calculation module;
the phase amplitude spectrum density calculation module comprises an autocovariance calculation module, a discrete Fourier transform module, a square root module and a maximum value search module, wherein phase information is processed by the autocovariance calculation module to obtain autocovariance, the autocovariance performs discrete Fourier transform on data by the discrete Fourier transform module to obtain a power spectrum density curve, the power spectrum density curve performs square root processing by the square root module to obtain amplitude spectrum density data, the amplitude spectrum density data performs maximum value search processing by the maximum value search module to obtain the frequency position where a maximum value point appears, and the phase amplitude spectrum density calculation module calculates and obtains phase errors of different frequency bands;
the autonomous optimization parameter module comprises an extreme value threshold judgment module, a PID (proportion integration differentiation) progression control module and a PID parameter control module, wherein the extreme value threshold judgment module is used for carrying out threshold judgment on a maximum value point obtained by searching and processing of the maximum value search module, presetting a threshold according to a phase error value after locking of a corresponding frequency band, judging whether the maximum value point is greater than the threshold, recording a frequency position greater than the threshold pole, inputting the recorded frequency position of the pole to the PID progression control module and the PID parameter control module, correspondingly adjusting the progression of a first loop filter locked by phase and a control parameter of each level, and then re-locking the signal phase feedback control system to realize parameter adaptive optimization.
2. The parameter adaptive high precision digital laser phase locking system of claim 1, wherein: the control module is an electronic circuit board and comprises an A/D acquisition circuit, an FPGA circuit and D/A conversion circuits, wherein one A/D acquisition circuit acquires an electric signal of a photoelectric detector and converts the electric signal into a digital signal, the FPGA circuit is loaded with a digital phase automatic locking system to form a digital control signal, and the two D/A conversion circuits are used for converting the digital control signal into an analog control signal;
the digital phase automatic locking system comprises a frequency capturing loop and a phase locking loop, wherein the frequency capturing loop scans and controls the frequency of the slave laser, and the phase locking loop controls the slave laser to track the frequency of the master laser, so that the automatic phase locking of the master laser and the slave laser is realized.
3. The parameter adaptive high precision digital laser phase locking system of claim 2, wherein: the frequency capture loop comprises a frequency automatic scanning module, a peak signal identification module, a second D/A conversion circuit and a TEC control module; the frequency automatic scanning module outputs a digital signal which is continuously increased along with the time; the peak signal identification module can receive a target frequency and a target peak value set by external input, judge whether a peak signal enters a target threshold value, stop frequency scanning at the moment of entering the target threshold value and open the phase locking loop; the second D/A conversion circuit converts the digital signal output by the frequency automatic scanning module into a voltage signal and outputs the voltage signal to the TEC control module; the TEC control module changes the frequency of the slave laser to reach the target threshold of the peak signal identification module;
the frequency automatic scanning module comprises a peak signal identification module for identifying the frequency and amplitude of a peak signal in the frequency spectrum of the electric signal.
4. The parameter adaptive high precision digital laser phase locking system of claim 2, wherein: the phase locking loop comprises a first phase discriminator, a first numerical control oscillator, a first loop filter, a first D/A conversion circuit, a high-voltage amplification module and a PZT control module, wherein the first numerical control oscillator outputs a sine wave signal with fixed frequency as a digital reference source; the first phase detector receives the digital signals from the A/D acquisition circuit and the digital signals of the first numerically-controlled oscillator, resolves the phase difference of the two paths of signals, and outputs the phase difference of the two paths of signals to the first loop filter; the first loop filter performs digital amplification filtering processing on the phase error signal output by the first phase detector and outputs the phase error signal to the first D/A conversion circuit; the first D/A conversion circuit inputs voltage to the high-voltage amplification module so as to adapt to the voltage control of the PZT control module; the PZT control module directly changes the frequency of the slave laser, and the phase change rate is changed by adjusting the frequency to complete a phase locking loop.
5. The parameter adaptive high precision digital laser phase locking system of claim 4, wherein: the high-voltage amplification module adopts an OPA552 chip, the amplification factor is set to be 1-30 times and adjustable through a sliding rheostat, and the bandwidth of the high-voltage amplification module is consistent with the bandwidth design of a PZT control module so as to reduce the interference of high-frequency noise of a circuit and improve the phase locking precision;
the parameters of the first loop filter in the phase locking loop are open and adjustable at will, including the stages of the PI and the PD and the parameters in each stage, and are used for the purpose of modifying the transfer function of the first loop filter.
6. The parameter adaptive high precision digital laser phase locking system of claim 1, wherein: the phase high-precision measurement module comprises a second numerical control oscillator, a second phase discriminator, a second loop filter, a third numerical control oscillator, a phase demodulation module and a phase information acquisition module, wherein the second numerical control oscillator outputs a digital sine signal and a digital cosine signal, the two signals have the same frequency and have the phase difference of 90 degrees; the second phase discriminator receives one path of digital sinusoidal signal of the second numerically controlled oscillator, performs phase discrimination processing on the digital sinusoidal signal and the digital signal of the A/D acquisition circuit, and outputs a phase error signal to a second loop filter; the second loop filter amplifies and filters the phase error signal, outputs the phase error signal to a frequency control word register of the second numerically controlled oscillator, and can change the frequency value of a sinusoidal signal by modifying the frequency control word register of the second numerically controlled oscillator so as to keep the phase of the digital sinusoidal signal output by the second numerically controlled oscillator consistent with the phase of the digital signal of the A/D acquisition circuit; the frequency of the third numerically controlled oscillator is open and adjustable, the frequency is the same as the set frequency of the first numerically controlled oscillator, and the phase value output by the phase accumulator of the third numerically controlled oscillator is used as a reference phase; the phase demodulation module receives phase values output by the phase accumulators and output by the second and third numerically controlled oscillators, performs subtraction operation, and obtains the phase information which is the phase information of the measured signal of the A/D acquisition circuit, wherein the initial frequency of the second numerically controlled oscillator is adjustable to be suitable for interference signals with different frequencies;
the phase information acquisition module samples the phase information calculated by the phase demodulation module, and the sampling time and the sampling rate are referred to the concerned frequency band.
7. The parameter adaptive high precision digital laser phase lock system according to claim 6, wherein: the second loop filter selects a high-order loop filter to suppress noise of a frequency band which is not concerned in the interference signal;
the initial frequency of the second numerically controlled oscillator is arbitrarily modified by an external input to be suitable for interference signals of different frequencies.
8. The parameter adaptive high precision digital laser phase locking system of claim 1, wherein: the phase amplitude spectral density calculation module comprises a first memory module, an autocovariance calculation module, a second memory module, a discrete Fourier transform module, a third memory module, a square root module, a fourth memory module and a maximum value search module; the first memory module stores the phase information obtained by the phase demodulation module and is used for calculating and obtaining phase errors of different frequency bands, and the storage time and the sampling frequency are required by the frequency band concerned by the phase amplitude spectral density; the autocovariance calculation module performs autocovariance processing on the data in the first memory module and stores the calculated autocovariance into the second memory module; the discrete Fourier transform module performs discrete Fourier transform on the data in the second memory module, stores the power spectral density value of the discrete Fourier transform in a third memory module, stores a power spectral density curve in the third memory, performs square root processing on the data in the third memory by the square root module to obtain the amplitude spectral density of the signal, and stores the amplitude spectral density in the fourth memory module.
9. The parameter adaptive high precision digital laser phase locking system of claim 1, wherein: the PID series control module and the PID parameter control module automatically adjust the PID series and parameters of the first loop filter according to the magnitude of amplitude spectrum density data, when a maximum value larger than a noise threshold value appears in the amplitude spectrum density data, the phase noise of the optical phase-locked loop is automatically considered to be further suppressed, and a first-stage PID controller is added every time a maximum value point larger than the noise threshold value is arranged, so that the gain of a baud chart of the first loop filter at the frequency of the noise maximum value point is increased by the first-stage PID controller, and the phase noise suppression capability at the frequency point is enhanced; especially, when the potential noise is introduced into the parameter adaptive high-precision digital laser phase-locked system, the system can automatically identify the occurrence of the noise from the amplitude spectrum density data, because the occurrence of the potential noise can enable the amplitude spectrum density data to have a maximum value point which is larger than a noise threshold, the PID series control module can automatically increase a first-level PID controller, and the PID parameter control module is utilized to increase control gain for the frequency of the potential noise, enhance the noise suppression capability at the frequency until the potential noise is suppressed to be below the noise threshold, so that the optical phase-locked system can autonomously suppress the potential noise, autonomously adapt to a complex dynamic environment, and always keep high-precision phase locking.
10. A parameter adaptive high precision digital laser phase locking method using the system of any one of claims 1 to 9, characterized in that: the method comprises the following steps:
s1, the digital phase automatic locking system automatically locks the phases of the master laser and the slave laser;
s2, the phase high-precision measuring module reads the high-precision measurement of the phase of the laser interference signal and records the locking phase value;
s3, calculating the locked phase value by the phase amplitude spectrum density calculation module to obtain the amplitude spectrum density of the phase error so as to analyze the frequency band of the locked noise;
s4, the autonomous optimization parameter module analyzes the noise frequency band autonomous optimization algorithm parameters through the amplitude spectral density curve obtained in S3, automatically identifies the frequency points which do not meet the target phase noise, automatically modifies the stage number of the loop filter and the control parameters of each stage, and controls the frequency of the signal output from the laser to be consistent with the frequency change of the main laser;
the autonomous optimization algorithm of the autonomous optimization parameter module comprises the following steps:
the system starts to operate after the first phase locking function is completed until the system is shut down, the iteration number J is recorded, the initial iteration number J is set to be 1, and a maximum value searching module is waited to complete the processing of one frame of data;
then, an extreme value threshold judging module is used for processing a maximum value searching module, when a maximum value larger than a noise threshold does not exist, the system meets the high-precision phase locking requirement, otherwise, the system does not meet the high-precision phase locking requirement, and the phase noise needs to be further inhibited; firstly, storing N maximum value points which are greater than a noise threshold, wherein N is greater than or equal to 1, and a maximum value point set is marked as A i,j I represents the ith maximum point, j represents the jth iteration, and the corresponding frequency value of the maximum point is marked as f i.j ；
If the system is the first iteration, all the maximum value points are considered to be processed for the first time, namely, each maximum value point needs to be added with a stage of PID controller, N PID controllers are added in total, and the PID controllers are controlled to be in f i,j The gain at (d) is set to 4dB, where PI is 2dB, PD is 2dB, set to 4 dB;
if the iteration is not the first iteration, the system is shown to be possible to process certain maximum value points in the previous iteration, a new PID controller is not required to be added, and only the gain of the previous controller is required to be increased; firstly, searching the maximum value point set A of the iteration i,j Whether there is a maximum point set P from the previous J-1 iterations i,j There is intersection, and the intersection is embodied as A i,j Frequency f of i,j And P i,j Frequency f of i`,j` The values are equal, if the same frequency does not exist, the A found at this time is considered to be i,j All are never processed, the same as the first iteration; if the same frequency is present, A i,j And P i,j There is an intersection and the same frequency f i,j Or f i`.j` The noise suppression capability is not enough, and the gain needs to be further increased to improve the noise suppression capability; a. the i,j And P i,j Is denoted as B i,j Let B be i,j Contains M elements, and M<N，B i,j The maximum points of (a) are all processed in the previous J-1 iterations; set A i,j Exclusion of B i,j Set of postremainders as C i,j ，C i,j N-M maximum points exist, which are unprocessed maximum points in J-1 iterations; for B i,j Only gain increase for the previous PID controller is required, for C i,j N-M PID controllers are needed to be added, and initial gain is set; after the iteration is finally completed, the counting of J is increased by one; the state of the current first loop filter is kept until the output of the extreme value threshold judging module is that no maximum value larger than the noise threshold exists; if the potential noise occurs in the system, the process automatically enters an autonomous optimization parameter algorithm program flow, and the potential noise is suppressed in a targeted manner.
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