Digital compensation microwave frequency transmission system based on parameter optimization algorithm

Abstract

The invention discloses a digital compensation microwave frequency transmission system based on a parameter optimization algorithm, which comprises a local end, an optical fiber link and a remote end, and is characterized in that the local end is connected with the remote end through the optical fiber link; a frequency signal f1 generated by a local end is modulated to an optical carrier signal and transmitted to a remote end, a frequency signal f2 is generated after the detected frequency signal f1 is subjected to frequency division at the remote end, and the frequency signal f2 is modulated to another optical carrier signal and transmitted back to the local end. Digital phase discrimination measurement is carried out on a reference frequency signal frep and a returned frequency signal f2 at a local end, introduced phase disturbance is measured, accurate compensation of the phase disturbance is realized through an electrical compensation method based on a digital phase-locked loop technology, and meanwhile, real-time online optimization is carried out on control parameters of a digital phase-locked loop loop through a parameter optimization algorithm. The performance, the stability and the robustness of the optical fiber microwave frequency transmission system can be greatly improved, and the running state of the system can be monitored and analyzed in real time.

Description

Technical Field

[0001] The invention belongs to the field of high-precision optical fiber frequency transmission, and in particular relates to a digital compensation microwave frequency transmission system based on a parameter optimization algorithm. Background Art

[0002] With the continuous expansion of scientific frontiers and the rapid development of engineering technology, the performance requirements of high-precision frequency signals are constantly increasing and their application fields are becoming more and more extensive. Therefore, the use of high-precision frequency transmission technology to achieve long-distance network transmission of standard frequency signals is an important way to meet the needs of high-precision frequency signals in fields such as time and frequency measurement, basic scientific research, and quantum information network construction.

[0003] Compared with traditional frequency transmission methods, optical fiber-based microwave frequency transmission technology has outstanding advantages such as high precision, low loss, low additional noise, and rich channel resources. At present, optical fiber-based microwave transmission systems are based on analog phase-locked loop technology to accurately compensate for phase disturbances (such as temperature, humidity, stress, vibration, etc.) of standard frequency signals during transmission in optical fiber links, thereby achieving high-precision microwave frequency transmission.

[0004] However, the fiber-optic microwave frequency transmission technology based on the analog phase-locked loop can only set fixed loop parameters, which makes it difficult to adapt to various disturbances in the transmission link and changes in environmental conditions. At the same time, the analog system also finds it difficult to record, analyze and upload various system operating parameters. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a digital compensation microwave frequency transmission system based on parameter optimization algorithm. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The embodiment of the present invention provides a digital compensation microwave frequency transmission system based on a parameter optimization algorithm, the system comprising a local end, an optical fiber link and a remote end, the local end and the remote end are connected via an optical fiber link;

[0007] The local end includes a first power divider, a second power divider, a first mixer, a second mixer, a first N frequency divider, a voltage-controlled oscillator, a digital phase detector, an analog-to-digital converter, a processor, a digital-to-analog converter, a first laser, a first modulator and a first optical path detector; wherein,

[0008] The first power divider is used to convert the reference frequency signal f rep The voltage-controlled oscillator is used to generate a frequency signal f1 according to an initially set frequency signal; the second power divider is used to divide the frequency signal f1 into two paths; the first mixer is used to generate a frequency signal f1 according to a reference frequency signal f repand a frequency signal f1 to generate a first mixing signal; the first N frequency divider is used to generate a first frequency division signal according to the first mixing signal; the first laser is used to generate a first optical carrier signal; the first modulator is used to generate a first modulation signal according to the first optical carrier signal and another frequency signal f1, so as to generate a frequency signal f2 at the remote end and return to the local end; wherein the frequency signal f2 is a frequency division signal of the frequency signal f1 detected at the remote end and carries a phase disturbance generated in the optical fiber link transmission; the second mixer is used to generate a first modulation signal according to another reference frequency signal f rep and the frequency signal f2 to generate a second mixing signal; the digital phase detector is used to generate an error voltage signal according to the first frequency division signal and the second mixing signal; the analog-to-digital converter is used to digitize the error voltage signal; the processor is used to use a parameter optimization algorithm to continuously search online for the optimal control parameters and calculate the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal; the digital-to-analog converter is used to analogize the phase-compensated voltage signal; the voltage-controlled oscillator is also used to generate a new frequency signal f1 according to the analog voltage signal.

[0009] In one embodiment of the present invention, the remote end includes a first photodetector, a second laser, a second modulator, a third power divider, a second N frequency divider and a frequency synthesizer; wherein,

[0010] The first photodetector is used to detect the frequency signal f1 from the first modulation signal; the third power divider is used to divide the frequency signal f1 into two paths; the second N frequency divider is used to generate a frequency signal f2 according to one path of the frequency signal f1; the second laser is used to generate a second optical carrier signal; the second modulator is used to generate a second modulation signal according to the second optical carrier signal and the frequency signal f2; the frequency synthesizer is used to generate the reference frequency signal f according to the other path of the frequency signal f1 rep .

[0011] In one embodiment of the present invention, the local end further includes a first optical circulator and a second photodetector; wherein,

[0012] The first optical circulator is used to control the second modulated signal to flow to the second photodetector; the second photodetector is used to detect the frequency signal f2 from the second modulated signal.

[0013] In one embodiment of the present invention, the remote end further includes a second optical circulator; the second optical circulator is used to control the first modulated signal to flow to the first photodetector.

[0014] In one embodiment of the present invention, the frequency signal initially set in the voltage controlled oscillator is a reference frequency signal f rep (N+1) / 2 times, where N represents the division coefficient of the first N frequency divider.

[0015] In one embodiment of the present invention, the processor uses a parameter optimization algorithm to continuously search online for optimal control parameters and calculates the phase-compensated voltage signal based on the control parameters and the digitized error voltage signal. The formula is expressed as:

[0016]

[0017] Where k represents the number of sampling times, V f (k) represents the voltage signal after phase compensation output by the processor at the kth sampling moment, V e (k) represents the digitized error voltage signal at the kth sampling moment, V e (k-1) represents the digitized error voltage signal at the k-1th sampling moment, K p represents the proportional control parameter, K i represents the integral control parameter, K d represents the differential control parameter, K p , K i , K d It is necessary to continuously search online for optimal control parameters through parameter optimization algorithms.

[0018] In one embodiment of the present invention, the parameter optimization algorithm in the processor includes Fibonacci method, golden section method, directional acceleration method, and simplex acceleration method.

[0019] In one embodiment of the present invention, if the parameter optimization algorithm in the processor is a simplex acceleration method, the process of using the parameter optimization algorithm to continuously search online for optimal control parameters and calculating the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal includes:

[0020] constructing a target optimization function controlled by the control parameter according to the digitized error voltage signal;

[0021] Initialize three sets of control parameters;

[0022] According to the three groups of control parameters, the corresponding objective function values ​​are calculated according to the objective optimization function and compared, and the point where the control parameter with the minimum objective function value is located is taken as the starting point X L , take the point where the control parameter with the larger objective function value is located as the starting point X G , take the point where the control parameter with the largest objective function value is located as the starting point X H ;

[0023] Based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M}Continuously search online for the control parameters that minimize the objective function value of the objective optimization function as the optimal control parameters, and calculate the voltage signal after phase compensation based on the optimal control parameters.

[0024] In one embodiment of the present invention, the objective optimization function constructed is expressed as follows:

[0025]

[0026] Where X represents the control parameter, f(X) represents the objective function value corresponding to the control parameter X, and V e (j) represents the digitized error voltage signal at the jth sampling moment, and k represents the sampling number.

[0027] In one embodiment of the present invention, based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M}Continuously search online for the control parameters that minimize the objective function value of the objective optimization function as the optimal control parameters, including:

[0028] Take the starting point X L and the starting point X G The midpoint of the line is X F , connect the midpoint X F and the starting point X H and from the midpoint X F Extend to reflection point X R , and according to the reflection point X R The corresponding control parameter calculates the corresponding objective function value; wherein the extended length is the midpoint X F and the starting point X H The length of the connection;

[0029] If f(X R ) <f(X L ), then from the reflection point X R Continue to extend to expansion point X E Points such that X E -X F =α(X F -X H), α represents the expansion factor; if f(X E ) <f(X R ), then the expansion point X E Replace the starting point X H Construct a new simplex {X G , X L , X E}, return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function according to the three sets of control parameters; if f(X E )>f(X R ), then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R}, the starting point X G , starting point X L , reflection point X R As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters;

[0030] If f(X L ) <f(X R ) <f(X G ), then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R}, the starting point X G , starting point X L , reflection point X R As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters;

[0031] If f(X G ) <f(X R ) <f(X H ), then from the midpoint X F Extend to compression point X S , so that X S -X F =β(X F -X H ), β represents the compression factor, and the compression point X S Replace the starting point X H Construct a new simplex {X G , X L , X S}, the starting point X G , starting point X L , compression point X S As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters;

[0032] If f(X H ) <f(X R ), then from the starting point X H Extend to compression point X M , so that X F -X M =β(X F -X H ); if f(X M ) <f(X H ), then the compression point X M Replace the starting point X H Construct a new simplex {X G , X L , X M}, the starting point X G , starting point X L , compression point X M As three new sets of control parameters, return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function according to the three sets of control parameters; if f(X H ) <f(X M ), then take the starting point X H , the starting point X L The midpoint X N , the midpoint X F , the midpoint X N Replace the starting point X H , the starting point X G Construct a new simplex {X F , X L , X N}, the midpoint X F , starting point X L , midpoint X N As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters;

[0033] Determine whether the search times have reached the maximum search times and whether the optimization result meets the optimization accuracy condition. If the search times have not reached the maximum search times and the optimization result does not meet the optimization accuracy condition, then return the result based on the starting point X. G , starting point X L , starting point X HThe simplex {X G , X L , X M The step of continuously searching online to minimize the objective function value of the objective optimization function and taking the control parameter corresponding to the minimum as the optimal control parameter; if the number of searches has not reached the maximum number of searches and the optimization result has satisfied the optimization accuracy condition, it indicates that the optimization search is successful, and the control parameter that minimizes the objective function value of the objective optimization function is selected from the current simplex as the optimal control parameter; if the number of searches has reached the maximum number of searches and the optimization result has not satisfied the optimization accuracy condition, it indicates that the optimization search has failed, and the optimal control parameter outputted from the last search is maintained.

[0034] Beneficial effects of the present invention:

[0035] The digital compensation microwave frequency transmission system based on parameter optimization algorithm proposed by the present invention modulates the frequency signal f1 generated at the local end onto the optical carrier signal of one channel and transmits it to the remote end through the optical fiber link. At the remote end, the frequency signal f1 detected is divided into two frequency signals to generate the frequency signal f2. The frequency signal f2 carries the phase disturbance generated in the optical fiber link transmission. The frequency signal f2 is modulated onto the optical carrier signal of another channel and transmitted back to the local end. At the local end, the reference frequency signal f rep The digital phase detection measurement is performed with the frequency signal f2 detected by the return transmission, and the phase disturbance introduced by the optical fiber link due to the change of the external environment (such as temperature, humidity, stress, vibration, etc.) is measured. Based on the digital phase-locked loop technology, the phase disturbance is accurately compensated by the electrical compensation method, and the control parameters of the digital phase-locked loop are optimized online in real time through the parameter optimization algorithm to adapt to the change of environmental conditions and system disturbances. It can be seen that by utilizing the inherent advantages of the digital phase-locked loop technology and combining the parameter optimization algorithm to optimize the control parameters of the digital phase-locked loop in real time, compared with the traditional analog phase-locked loop technology, the performance, stability and robustness of the optical fiber microwave frequency transmission system can be greatly improved. At the same time, the digital phase-locked loop technology provides favorable conditions for the quantization, analysis, storage and upload of parameters such as phase detection signals and control signals, which is convenient for real-time monitoring and analysis of the system operation status, and can be better applied to the field of optical fiber frequency transmission.

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a structural schematic diagram of a digital compensation microwave frequency transmission system based on a parameter optimization algorithm provided by an embodiment of the present invention;

[0038] Figure 2 is a schematic diagram of searching on a PI two-dimensional plane provided by an embodiment of the present invention;

[0039] Figure 3 It is a flow chart of continuously searching online for optimal control parameters using a parameter optimization algorithm provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0041] See also Figure 1 , an embodiment of the present invention provides a digital compensation microwave frequency transmission system based on a parameter optimization algorithm, the system includes a local end, an optical fiber link and a remote end, the local end and the remote end are connected through an optical fiber link;

[0042] The local end includes a first power divider, a second power divider, a first mixer, a second mixer, a first N frequency divider, a voltage-controlled oscillator, a digital phase detector, an analog-to-digital converter, a processor, a digital-to-analog converter, a first laser, a first modulator and a first optical path detector; wherein,

[0043] The first power divider is used to divide the reference frequency signal f rep The voltage-controlled oscillator is used to generate a frequency signal f1 according to the initially set frequency signal; the second power divider is used to divide the frequency signal f1 into two paths; the first mixer is used to generate a frequency signal f1 according to a reference frequency signal f rep and a frequency signal f1 to generate a first mixing signal; a first N frequency divider to generate a first frequency division signal according to the first mixing signal; a first laser to generate a first optical carrier signal; a first modulator to generate a first modulation signal according to the first optical carrier signal and another frequency signal f1, so as to generate a frequency signal f2 at the remote end and return to the local end; wherein the frequency signal f2 is a frequency division signal of the frequency signal f1 detected at the remote end and carries the phase disturbance generated in the optical fiber link transmission; a second mixer to generate a first modulation signal according to another reference frequency signal f rep and frequency signal f2 to generate a second mixing signal; a digital phase detector, used to generate an error voltage signal according to the first frequency division signal and the second mixing signal; an analog-to-digital converter, used to digitize the error voltage signal; a processor, used to use a parameter optimization algorithm to continuously search online for optimal control parameters and calculate the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal; a digital-to-analog converter, used to analogize the phase-compensated voltage signal; a voltage-controlled oscillator, also used to generate a new frequency signal f1 according to the analog voltage signal.

[0044] In the embodiment of the present invention, the remote end includes a first photodetector, a second laser, a second modulator, a third power divider, a second N frequency divider and a frequency synthesizer; wherein,

[0045] The first photodetector is used to detect the frequency signal f1 from the first modulation signal; the third power divider is used to divide the frequency signal f1 into two paths; the second N frequency divider is used to generate the frequency signal f2 according to one path of the frequency signal f1; the second laser is used to generate the second optical carrier signal; the second modulator is used to generate the second modulation signal according to the second optical carrier signal and the frequency signal f2; the frequency synthesizer is used to generate the reference frequency signal f according to the other path of the frequency signal f1 rep Among them, the signals divided into two paths by the first power divider, the third power divider, and the second power divider have the same frequency, and the power can be the same or different, which is selected according to the actual situation.

[0046] In the embodiment of the present invention, the local end further includes a first optical circulator and a second photoelectric detector; wherein,

[0047] The first optical circulator is used to control the second modulated signal to flow to the second photodetector; the second photodetector is used to detect the frequency signal f2 from the second modulated signal.

[0048] In the embodiment of the present invention, the remote end further includes a second optical circulator; the second optical circulator is used to control the first modulated signal to flow to the first photodetector.

[0049] In the embodiment of the present invention, the frequency signal initially set in the voltage controlled oscillator is the reference frequency signal f rep (N+1) / 2 times, N represents the frequency division coefficient of the first N frequency divider. The frequency division coefficient of the first N frequency divider is the same as the frequency division coefficient of the second N frequency divider. The specific frequency division coefficient is selected according to the actual situation. For example, a frequency divider of 2 can be selected. The signal power after frequency division is the same, but the frequency can be the same or different.

[0050] It can be seen that at the local end, the voltage-controlled oscillator generates a frequency signal f1, whose frequency is set to the reference signal f rep The frequency signal f1 is divided into two paths by the second power divider: one path of the frequency signal f1 is modulated by the first modulator onto the optical carrier signal generated by the first laser, and transmitted to the remote end through the optical fiber link, and then detected by the first photodetector at the remote end, and then respectively passed through the second N frequency divider to generate a frequency signal f2 = f1 / N and transmitted back to the local end and detected by the second photodetector. At this time, the frequency signal f2 transmitted back to the local end carries the phase disturbance Δθ caused by the optical fiber link. The frequency signal f2 and the reference frequency signal f rep The second mixer generates a second mixing signal (f rep -f2-Δθ); another frequency signal f1 and the reference frequency signal f rep The first mixer generates a first mixing signal (f2-f rep), and then the first N frequency divider generates the first frequency division signal (f2-f rep ) / N. The first frequency division signal (f2-f rep ) / N and the second mixing signal (f rep -f2-Δθ) is sent to the digital phase detector, where the phase disturbance Δθ is converted into an error voltage signal V e (t), the error voltage signal V e (t) After being digitized by the analog-to-digital converter, the processor collects the data and generates the phase-compensated voltage signal V through the parameter optimization algorithm. f (k), the voltage signal V f (k) After being converted into analog signals by a digital-to-analog converter, the signals are input to the voltage-controlled end of the voltage-controlled oscillator to achieve accurate compensation for the phase disturbance Δθ of the optical fiber link.

[0051] At the remote end, the frequency signal f1 transmitted from the local end is detected by the first photodetector and then divided into two paths by the third power divider: one path of the frequency signal f1 is directly divided by the second N-frequency divider to generate a frequency signal f2, which is modulated by the second modulator to the optical carrier signal generated by the second laser and transmitted back to the local end via the same optical fiber link. The signal carries the phase disturbance Δθ caused in the optical fiber link, providing a reference for the local end to achieve accurate compensation; the other path of the frequency signal f1 is generated by the frequency synthesizer to generate a reference frequency signal f rep Since the frequency signal f1 at the local end has been phase compensated, the reference frequency signal f recovered from the frequency signal f1 at the remote end is rep The phase of the reference frequency signal at the local end is almost completely consistent, so that the reference frequency signal f rep It is transmitted from the local end to the remote end via the optical fiber link.

[0052] Furthermore, the embodiment of the present invention adopts digital phase-locked loop technology, because digital phase-locked loops are naturally easier to record, analyze and upload various operating parameters of the system, which is conducive to strengthening data analysis and real-time monitoring of system operation, and digital phase-locked loop technology is easy to combine with various algorithms to achieve the optimal loop parameters for various link disturbances and environmental conditions, thereby improving system performance, stability and robustness. As is known to all, the loop gain, damping coefficient, loop bandwidth and other loop parameters of the phase-locked loop are determined by the transfer function of each device in the loop and K p , K i , K d Theoretically, when the other parameters of the phase-locked loop are determined, the appropriate control parameter K is selected. p , K i , K d In practical engineering applications, the control parameter K p, K i , K d The adaptability to changes in system characteristics is limited, and the fixed control parameter K p , K i , K d It is difficult to adapt to changes in environmental conditions and system disturbances, so the control parameter K p , K i , K d It is very necessary to conduct online adaptive optimization search.

[0053] In view of the above requirements, the embodiment of the present invention proposes to use a parameter optimization algorithm in a processor to continuously search online for optimal control parameters and calculate the voltage signal after phase compensation according to the control parameters and the digitized error voltage signal. The formula is expressed as:

[0054]

[0055] Where k represents the number of sampling times, V f (k) represents the voltage signal after phase compensation output by the processor at the kth sampling moment, V e (k) represents the digitized error voltage signal at the kth sampling moment, V e (k-1) represents the digitized error voltage signal at the k-1th sampling moment, K p The proportional control parameter is recorded as P parameter, K i The integral control parameter is recorded as I parameter, K d The differential control parameter is recorded as D parameter, K p , K i , K d It is the control parameter that needs to be continuously searched online through the parameter optimization algorithm. From formula (1), it can be seen that the control parameter K obtained by online search optimization is p , K i , K d Phase compensation can be better achieved.

[0056] The parameter optimization algorithm in the processor of the embodiment of the present invention includes the Fibonacci method, the golden section method, the directional acceleration method, and the simplex acceleration method. Taking the simplex acceleration method as an example, the control parameter K is described in detail. p , K i , K d The search and optimization process. Specifically:

[0057] In the embodiment of the present invention, when the parameter optimization algorithm in the processor is the simplex acceleration method, the process of using the parameter optimization algorithm to continuously search online for the optimal control parameters and calculating the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal includes:

[0058] According to the digitized error voltage signal, a target optimization function controlled by the control parameters is constructed; three sets of control parameters are initialized; according to the three sets of control parameters, the corresponding target function values ​​are calculated and compared according to the target optimization function, and the point where the control parameter with the smallest target function value is located is taken as the starting point X L , take the point where the control parameter with the larger objective function value is located as the starting point X G , take the point where the control parameter with the largest objective function value is located as the starting point X H ; Based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M}Continuously search online to minimize the objective function value of the target optimization function and the corresponding control parameter as the optimal control parameter, and calculate the voltage signal after phase compensation according to the optimal control parameter.

[0059] The embodiment of the present invention determines the performance of the group of control parameters by the output error voltage signal, and adopts the control parameter with the smallest ISTE (Integral Square Time Square Error) to adapt to changes in environmental conditions and system disturbances. Therefore, the target optimization function constructed is expressed as follows:

[0060]

[0061] Where X represents the control parameter, f(X) represents the objective function value corresponding to the control parameter X, and V e (j) represents the digitized error voltage signal at the jth sampling moment, and k represents the number of sampling times. The smaller the objective function value f(X) of the objective optimization function shown in formula (2), the better the control effect of the corresponding control parameter X.

[0062] For better understanding, assume that the P parameter and the I parameter together form a two-dimensional simplex such as Figure 2 As shown, each set of PI parameters constitutes a point on the two-dimensional plane, and three sets of control parameters X are initialized according to experience. H , X G , X L , as three vertices forming a triangle on the two-dimensional plane formed by the P parameters and the I parameters. See Figure 3In the process of continuously searching for optimal control parameters online, the embodiment of the present invention first gives α, β, ε, K=0, α represents the expansion factor, and the value range of α is any number greater than 1, β represents the compression factor, and the value range of β is 0-1, K represents the number of searches, ε represents the optimization accuracy, and the value range of ε is 0-1, and the maximum number of searches is K. max , specifically α, β, ε, K max Set according to actual situation;

[0063] According to formula (2), calculate the starting point X G , starting point X L , starting point X H The objective function value f(X H )、f(X G )、f(X L ), and compare their sizes. Assuming that f(X H )>f(X G )>f(X L ), indicating the starting point X H The performance is the worst, starting point X G The performance is second, starting point X L The performance is optimal.

[0064] The embodiment of the present invention is based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M}Continuously search online to minimize the objective function value of the target optimization function and the corresponding control parameters as the optimal control parameters, including:

[0065] Take the starting point X L and starting point X G The midpoint of the line is X F , connect the midpoint X F and starting point X H and from the midpoint X F Extend to reflection point X R , and according to the reflection point X R Calculate the corresponding objective function value f(X R ), where the extended length is the midpoint X F and the starting point X H The length of the line; that is, from the starting point with the worst performance X H Start your search.

[0066] For calculating f(X R ), the following situations may occur:

[0067] If f(X R ) <f(X L ), indicating that the search direction is correct, and we can further search along the starting point X H , reflection point X R Direction expansion search, then from the reflection point X R Continue to extend to expansion point X E , so that X E -X F =α(X F -X H ), and calculate the expansion point X E The corresponding objective function value f(X E ); if f(X E ) <f(X R ), indicating that expansion is beneficial, then the expansion point X E Replace the starting point X H Construct a new simplex {X G , X L , X E} to search for the next time, that is, return to the step of calculating the corresponding objective function values ​​according to the objective optimization function according to the three sets of control parameters and comparing them; if f(X E )>f(X R ), indicating that the expansion is unfavorable, then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R}, the starting point X G , starting point X L , reflection point X R Use the three new control parameter groups for the next search, i.e., return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function based on the three control parameter groups;

[0068] If f(X L ) <f(X R ) <f(X G ), indicating that the search direction is correct and no expansion is needed, then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R}, the starting point X G , starting point X L , reflection point X R Use the three new control parameter groups for the next search, i.e., return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function based on the three control parameter groups;

[0069] If f(X G ) <f(X R ) <f(X H ), indicating that at the starting point X H The search step length in the direction of the reflection point is too long. The search step length should be reduced. F Extend to compression point X S , so that X S -X F =β(X F -X H ), and the compression point X S Replace the starting point X H Construct a new simplex {X G , X L , X S}, the starting point X G , starting point X L , compression point X S Use the three new control parameter groups for the next search, i.e., return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function based on the three control parameter groups;

[0070] If f(X H ) <f(X R ), indicating that at the starting point X H The search compensation in the direction of the reflection point should be further compressed, so from the starting point X H Extend to compression point X M , so that X F -X M =β(X F -X H ), and calculate the compression point X M The corresponding objective function value f(X M ); if f(X M ) <f(X H ), then the compression point X M Replace the starting point X H Construct a new simplex {X G , X L , X M}, the starting point X G , starting point X L , compression point X M As the new three sets of control parameters for the next search, that is, return to the steps of calculating the corresponding objective function values ​​according to the objective optimization function and comparing them according to the three sets of control parameters; if f(X H ) <f(X M ), indicating that at the starting point X H All control parameter combinations in the direction of the reflection point are inferior to those at the starting point X H, so we cannot search along this direction, we should start from the starting point X L The simplex {X H , X G , X L} to shrink and take the starting point X H , starting point X L The midpoint X N , midpoint X F , midpoint X N Replace the starting point X H , starting point X G Construct a new simplex {X F , X L , X N}, the midpoint X F , starting point X L , midpoint X N Use the three new control parameter groups for the next search, i.e., return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function based on the three control parameter groups;

[0071] Determine whether the number of searches has reached the maximum number of searches K max And judge whether the optimization result meets the optimization accuracy condition, where the optimization accuracy condition is defined as f(X H )-f(X L )<εf(X L ), if the search times do not reach the maximum search times and the optimization result does not meet the optimization accuracy condition, then return to the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M}Continuously search online to minimize the objective function value of the target optimization function and use the control parameters corresponding to the minimum as the optimal control parameters. If the number of searches has not reached the maximum number of searches and the optimization result has met the optimization accuracy condition, it indicates that the optimization search is successful. Select the control parameters that minimize the objective function value of the target optimization function from the current simplex as the optimal control parameters. If the number of searches has reached the maximum number of searches and the optimization result has not met the optimization accuracy condition, it indicates that the optimization search has failed and the optimal control parameters output by the last search are maintained.

[0072] In summary, the digital compensation microwave frequency transmission system based on parameter optimization algorithm proposed in the embodiment of the present invention modulates the frequency signal f1 generated at the local end onto an optical carrier signal of one channel, and transmits it to the remote end through an optical fiber link. At the remote end, the detected frequency signal f1 is divided into two frequencies to generate a frequency signal f2, and the frequency signal f2 carries the phase disturbance generated in the optical fiber link transmission. The frequency signal f2 is modulated onto an optical carrier signal of another channel and transmitted back to the local end. At the local end, the reference frequency signal f rep The digital phase detection measurement is performed with the frequency signal f2 detected by the return transmission, and the phase disturbance introduced by the optical fiber link due to the change of the external environment (such as temperature, humidity, stress, vibration, etc.) is measured. Based on the digital phase-locked loop technology, the phase disturbance is accurately compensated by the electrical compensation method, and the control parameters of the digital phase-locked loop are optimized online in real time through the parameter optimization algorithm to adapt to the change of environmental conditions and system disturbances. It can be seen that by utilizing the inherent advantages of the digital phase-locked loop technology and combining the parameter optimization algorithm to optimize the control parameters of the digital phase-locked loop in real time, compared with the traditional analog phase-locked loop technology, the performance, stability and robustness of the optical fiber microwave frequency transmission system can be greatly improved. At the same time, the digital phase-locked loop technology provides favorable conditions for the quantization, analysis, storage and upload of parameters such as phase detection signals and control signals, which is convenient for real-time monitoring and analysis of the system operation status, and can be better applied to the field of optical fiber frequency transmission.

[0073] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0074] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the specification and its drawings. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude multiple situations. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0075] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A digital compensation microwave frequency transmission system based on parameter optimization algorithm, characterized in that: The system comprises a local end, an optical fiber link and a remote end, wherein the local end and the remote end are connected via the optical fiber link; The local end includes a first power divider, a second power divider, a first mixer, a second mixer, a first N frequency divider, a voltage-controlled oscillator, a digital phase detector, an analog-to-digital converter, a processor, a digital-to-analog converter, a first laser, a first modulator and a first optical path detector; wherein, The first power divider is used to convert the reference frequency signal f rep The voltage-controlled oscillator is used to generate a frequency signal f1 according to an initially set frequency signal; the second power divider is used to divide the frequency signal f1 into two paths; the first mixer is used to generate a frequency signal f1 according to a reference frequency signal f rep and a frequency signal f1 to generate a first mixing signal; the first N frequency divider is used to generate a first frequency division signal according to the first mixing signal; the first laser is used to generate a first optical carrier signal; the first modulator is used to generate a first modulation signal according to the first optical carrier signal and another frequency signal f1, so as to generate a frequency signal f2 at the remote end and return to the local end; wherein the frequency signal f2 is a frequency division signal of the frequency signal f1 detected at the remote end and carries a phase disturbance generated in the optical fiber link transmission; the second mixer is used to generate a first modulation signal according to another reference frequency signal f rep and the frequency signal f2 to generate a second mixing signal; the digital phase detector is used to generate an error voltage signal according to the first frequency division signal and the second mixing signal; the analog-to-digital converter is used to digitize the error voltage signal; the processor is used to use a parameter optimization algorithm to continuously search online for the optimal control parameters and calculate the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal; the digital-to-analog converter is used to analogize the phase-compensated voltage signal; the voltage-controlled oscillator is also used to generate a new frequency signal f1 according to the analog voltage signal.

2. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 1 is characterized in that: The remote end includes a first photodetector, a second laser, a second modulator, a third power divider, a second N frequency divider and a frequency synthesizer; wherein, The first photodetector is used to detect the frequency signal f1 from the first modulation signal; the third power divider is used to divide the frequency signal f1 into two paths; the second N frequency divider is used to generate a frequency signal f2 according to one path of the frequency signal f1; the second laser is used to generate a second optical carrier signal; the second modulator is used to generate a second modulation signal according to the second optical carrier signal and the frequency signal f2; the frequency synthesizer is used to generate the reference frequency signal f according to the other path of the frequency signal f1 rep .

3. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 2 is characterized in that: The local end also includes a first optical circulator and a second photodetector; wherein, The first optical circulator is used to control the second modulated signal to flow to the second photodetector; the second photodetector is used to detect the frequency signal f2 from the second modulated signal.

4. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 2 is characterized in that: The remote end also includes a second optical circulator; the second optical circulator is used to control the first modulated signal to flow to the first photodetector.

5. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 1 is characterized in that: The frequency signal initially set in the voltage-controlled oscillator is the reference frequency signal f rep (N+1) / 2 times; wherein N represents the division coefficient of the first N divider.

6. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 1 is characterized in that: The processor uses a parameter optimization algorithm to continuously search online for optimal control parameters and calculates the voltage signal after phase compensation based on the control parameters and the digitized error voltage signal. The formula is expressed as: Where k represents the number of sampling times, V f (k) represents the voltage signal after phase compensation output by the processor at the kth sampling moment, V e (k) represents the digitized error voltage signal at the kth sampling moment, V e (k-1) represents the digitized error voltage signal at the k-1th sampling moment, K p represents the proportional control parameter, K i represents the integral control parameter, K d represents the differential control parameter, K p , K i , K d It is necessary to continuously search online for optimal control parameters through parameter optimization algorithms.

7. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 1 is characterized in that: The parameter optimization algorithms in the processor include Fibonacci method, golden section method, directional acceleration method and simplex acceleration method.

8. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 7 is characterized in that: If the parameter optimization algorithm in the processor is a simplex acceleration method, the process of using the parameter optimization algorithm to continuously search online for optimal control parameters and calculating the phase-compensated voltage signal according to the control parameters and the digitized error voltage signal includes: constructing a target optimization function controlled by the control parameter according to the digitized error voltage signal; Initialize three sets of control parameters; According to the three groups of control parameters, the corresponding objective function values ​​are calculated according to the objective optimization function and compared, and the point where the control parameter with the minimum objective function value is located is taken as the starting point X L , take the point where the control parameter with the larger objective function value is located as the starting point X G , take the point where the control parameter with the largest objective function value is located as the starting point X H ; Based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M }Continuously search online for the control parameters that minimize the objective function value of the objective optimization function as the optimal control parameters, and calculate the voltage signal after phase compensation based on the optimal control parameters.

9. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 8 is characterized in that: The constructed objective optimization function is expressed as follows: Where X represents the control parameter, f(X) represents the objective function value corresponding to the control parameter X, and V e (j) represents the digitized error voltage signal at the jth sampling moment, and k represents the sampling number.

10. The digital compensation microwave frequency transmission system based on parameter optimization algorithm according to claim 9 is characterized in that: Based on the starting point X G , starting point X L , starting point X H The simplex {X G , X L , X M }Continuously search online for the control parameters that minimize the objective function value of the objective optimization function as the optimal control parameters, including: Take the starting point X L and the starting point X G The midpoint of the line is X F , connect the midpoint X F and the starting point X H and from the midpoint X F Extend to reflection point X R , and according to the reflection point X R The corresponding control parameter calculates the corresponding objective function value; wherein the extended length is the midpoint X F and the starting point X H The length of the connection; If f(X R ) <f(X L ), then from the reflection point X R Continue to extend to expansion point X E Points such that X E -X F =α(X F -X H ), α represents the expansion factor; if f(X E ) <f(X R ), then the expansion point X E Replace the starting point X H Construct a new simplex {X G , X L , X E }, return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function according to the three sets of control parameters; if f(X E )>f(X R ), then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R }, the starting point X G , starting point X L , reflection point X R As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters; If f(X L ) <f(X R ) <f(X G ), then the reflection point X R Replace the starting point X H Construct a new simplex {X G , X L , X R }, the starting point X G , starting point X L , reflection point X R As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters; If f(X G ) <f(X R ) <f(X H ), then from the midpoint X F Extend to compression point X S , so that X S -X F =β(X F -X H ), β represents the compression factor, and the compression point X S Replace the starting point X H Construct a new simplex {X G , X L , X S }, the starting point X G , starting point X L , compression point X S As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters; If f(X H ) <f(X R ), then from the starting point X H Extend to compression point X M , so that X F -X M =β(X F -X H ); if f(X M ) <f(X H ), then the compression point X M Replace the starting point X H Construct a new simplex {X G , X L , X M }, the starting point X G , starting point X L , compression point X M As three new sets of control parameters, return to the step of calculating and comparing the corresponding objective function values ​​according to the objective optimization function according to the three sets of control parameters; if f(X H ) <f(X M ), then take the starting point X H , the starting point X L The midpoint X N , the midpoint X F , the midpoint X N Replace the starting point X H , the starting point X G Construct a new simplex {X F , X L , X N }, the midpoint X F , starting point X L , midpoint X N As three new groups of control parameters, returning to the step of calculating and comparing corresponding objective function values ​​according to the objective optimization function respectively according to the three groups of control parameters; Determine whether the search times have reached the maximum search times and whether the optimization result meets the optimization accuracy condition. If the search times have not reached the maximum search times and the optimization result does not meet the optimization accuracy condition, then return the result based on the starting point X. G , starting point X L , starting point X H The simplex {X G , X L , X M The step of continuously searching online to minimize the objective function value of the objective optimization function and taking the control parameter corresponding to the minimum as the optimal control parameter; if the number of searches has not reached the maximum number of searches and the optimization result has satisfied the optimization accuracy condition, it indicates that the optimization search is successful, and the control parameter that minimizes the objective function value of the objective optimization function is selected from the current simplex as the optimal control parameter; if the number of searches has reached the maximum number of searches and the optimization result has not satisfied the optimization accuracy condition, it indicates that the optimization search has failed, and the optimal control parameter outputted from the last search is maintained.

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