Ten-frequency-multiplication millimeter wave signal generation system and method

Abstract

The embodiment of the invention provides a ten-frequency-multiplication millimeter wave signal generation system and method, and belongs to the technical field of photon microwaves. The ten-frequency-multiplication millimeter wave signal generation system is characterized in that the system comprises a continuous wave laser used for inputting an original optical carrier wave; the polarization modulators are arranged in parallel, respectively introduce one path of polarized light of the original optical carrier and one path of radio-frequency signals with different electric phase offsets, and are used for modulating the introduced radio-frequency signals to the corresponding polarized light to obtain corresponding optical signals; the polarization analyzer converges the optical signals output by the polarization modulators and is used for obtaining corresponding coupling optical signals; and the photoelectric detector is connected with the output end of the polarization analyzer and is used for converting the coupling optical signal into a corresponding ten-frequency-multiplication millimeter wave signal. According to the scheme, the problems of inaccurate phase matching and insufficient interference sideband suppression in the existing scheme are solved, and a better solution is provided for 6G communication, radar and other high-frequency applications.

Description

Technical Field

[0001] The present invention relates to the field of photon microwave technology, and in particular to a ten-fold frequency millimeter wave signal generation system and a ten-fold frequency millimeter wave signal generation method. Background Art

[0002] As wireless communications and radar systems develop towards higher frequency bands, the efficient generation of millimeter wave (mmWave) and terahertz (THz) signals has become a research hotspot. Millimeter wave signals are widely used in 6G communications, high-resolution radars, satellite communications and other fields. However, traditional millimeter wave signal generation solutions face many challenges and are difficult to meet the future requirements of high frequency, large bandwidth and high stability.

[0003] At present, the generation of millimeter wave signals mainly relies on two technologies: electronic frequency doubling and photon frequency doubling. Due to the serious loss of high-frequency circuits and low frequency doubling efficiency, the electronic frequency doubling method is difficult to break through the frequency limit above 100GHz, and has gradually failed to meet the needs of high-frequency communications and radar systems. In contrast, the photon frequency doubling method uses optical modulation technology to map low-frequency RF signals to the optical domain, and realizes high-frequency conversion of millimeter wave signals through photodetectors. Due to its ultra-wideband characteristics, low loss and high stability, it has become the focus of current research. Existing photon frequency doubling schemes usually use multiple polarization modulators to modulate optical signals, and enhance the target optical sidebands through phase control, while suppressing other irrelevant sidebands to improve the purity of millimeter wave signals. However, this scheme still has the problem of inaccurate phase matching, resulting in limited suppression of non-target sidebands, causing the millimeter wave signal output by the photodetector to be interfered by additional spectral components, reducing the signal's sideband suppression ratio (OSSR).

[0004] In the photon frequency doubling system, the phase matching of the polarization modulator is a key factor affecting the effect of optical signal synthesis. If the electrical phase offset of different modulators is not optimized and calculated, but is set with a fixed value or empirical value, it may cause phase mismatch of interference sidebands such as ±3rd order and ±7th order, making it impossible to effectively offset them when the final optical signal is synthesized, thereby reducing the signal-to-noise ratio of the millimeter wave signal. In addition, the polarization angle setting of the analyzer, as a key component for the final optical signal to enter the photodetector, directly affects the transmission efficiency of the target optical sideband and the suppression effect of the non-target sideband. Existing schemes are usually based on fixed angles or empirical settings, and do not fully consider the polarization characteristics of the optical signal after coherent synthesis, so that some interference components are still transmitted into the photodetector, affecting the quality of the millimeter wave signal. In view of the problem that the existing scheme cannot generate pure ten-fold frequency millimeter wave signals, it is necessary to propose a new ten-fold frequency millimeter wave signal generation scheme. Summary of the invention

[0005] The purpose of the embodiments of the present invention is to provide a system and method for generating a ten-fold frequency millimeter wave signal, so as to at least solve the problem that the existing solutions cannot generate pure ten-fold frequency millimeter wave signals.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a ten-fold frequency millimeter wave signal generation system, the system comprising: a continuous wave laser, for inputting an original optical carrier; a plurality of polarization modulators arranged in parallel, respectively introducing one polarized light and one radio frequency signal with different electrical phase offsets of the original optical carrier, for modulating the introduced radio frequency signal onto the corresponding polarized light to obtain a corresponding optical signal; wherein the electrical phase offset of each polarization modulator is determined based on a dual-objective optimization algorithm that takes the optimal coherent superposition of ±5-order optical sidebands as the goal and minimizes the interference intensity of non-±5-order optical sidebands; an analyzer, which integrates the optical signals output by each polarization modulator, for performing step-by-step signal coupling of each tube based on the phase difference of each optical signal to obtain a corresponding coupled optical signal; a photodetector, connected to the output end of the analyzer, for converting the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal.

[0007] Optionally, a polarization controller is further arranged between the continuous wave laser and each polarization modulator; the polarization controller is used to perform adaptive polarization direction adjustment of the polarized light based on the working mode of each polarization modulator.

[0008] Optionally, the electrical phase offset of each polarization modulator is determined based on the total number of polarization modulators, and the corresponding determination rule is: perform uniform distribution of phase changes based on the total number of polarization modulators, and determine the electrical phase offset of each polarization modulator based on the uniform distribution result as the initial electrical phase offset of each polarization modulator; construct a dual-objective optimization algorithm with the goal of optimizing the coherent superposition of ±5-order optical sidebands while minimizing the interference intensity of non-±5-order optical sidebands; solve the dual-objective optimization algorithm based on the initial electrical phase offset of each polarization modulator to obtain the electrical phase offset of each polarization modulator.

[0009] Optionally, the polarization modulator is configured to modulate the incoming radio frequency signal onto corresponding polarized light to obtain a corresponding optical signal; wherein the rule for modulating the incoming radio frequency signal onto corresponding polarized light is:

[0010] in, and are the polarization components of the output optical signal in the x direction and the y direction respectively; is the amplitude of the introduced polarized light; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the modulation depth; j is the imaginary unit; t is the time; is the electrical phase offset of the introduced RF signal.

[0011] Optionally, the polarizer is configured to: select two optical signals in sequence for coupling according to the principle of minimum phase difference to form multiple first-level coupled optical signals; among the first-level coupled optical signals, continue to select the signal with the smallest phase difference for further coupling to form a second-level coupled optical signal; and repeat this recursively until all optical signals complete coherent synthesis to obtain a coupled optical signal.

[0012] Optionally, the polarizer is further configured to: set a corresponding polarization angle with the goal of maximizing the transmission of ±5th order optical sidebands; and perform selective transmission on the coupled optical signal based on the set polarization angle to obtain a target optical signal.

[0013] Optionally, the target light signal is expressed as:

[0014] in, is the target light signal; A is the amplitude factor; and is the Bessel coefficient representing the modulation intensity of the ±5th order optical sideband; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the set polarization angle; is the modulation depth; j is the imaginary unit; t is the time.

[0015] Optionally, the photodetector is configured to: perform square-law detection on the target light signal to obtain a corresponding ten-fold frequency millimeter wave signal; wherein the square-law detection rule for the target light signal is:

[0016] in, is the output signal of the photodetector; represents taking the real part; is the target light signal; is the normalized optical signal amplitude; is the modulation efficiency of ±5th order optical sideband; is the angular frequency of the introduced RF signal; t is the time.

[0017] The second aspect of the present invention provides a method for generating a ten-fold frequency millimeter wave signal, which is implemented based on the above-mentioned ten-fold frequency millimeter wave signal generation system, and the method includes: dividing the original optical carrier into multiple polarized lights, and introducing each polarized light into the corresponding polarization modulator respectively; introducing a radio frequency signal with a different electrical phase offset to each polarization modulator, so as to modulate the introduced radio frequency signal to the corresponding polarized light based on each polarization modulator to obtain a corresponding optical signal; based on the phase difference of each optical signal, performing step-by-step signal coupling of each tube to obtain a corresponding coupled optical signal; and converting the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal based on a photodetector.

[0018] Optionally, the method further includes: performing adaptive polarization direction adjustment of the polarized light based on the polarization controller, so that each polarized light matches the working mode of the corresponding polarization modulator.

[0019] Through the above technical scheme, the scheme of the present invention realizes efficient generation of ten-fold frequency millimeter wave signals by optimizing the phase matching of the polarization modulator and the polarization angle setting of the analyzer. Multiple polarization modulators perform radio frequency modulation on the original optical carrier respectively, and introduce different electrical phase offsets, so that the target optical sidebands (±5 orders) are coherently superimposed during the final synthesis, while suppressing the interference sidebands (±3 orders, ±7 orders), thereby improving the purity of the optical signal. The role of the analyzer is not only to merge the optical signals output by each polarization modulator, but also to further optimize the transmission characteristics of the target optical sidebands through step-by-step coherent coupling, and reduce the impact of non-target sidebands on millimeter wave signals. Finally, the photodetector receives the optimized optical signal and outputs a high-quality ten-fold frequency millimeter wave signal through the beat frequency effect. This system solves the problems of inaccurate phase matching and insufficient suppression of interference sidebands in the existing scheme, improves the sideband suppression ratio (OSSR) of the millimeter wave signal, and improves the output power and signal purity, providing a better solution for high-frequency applications such as 6G communications and radars.

[0020] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings: Figure 1 is a system structure diagram of a ten-fold frequency millimeter wave signal generation system provided by an embodiment of the present invention; Figure 2 It is a schematic diagram of a first-type Bessel function expansion image provided by an embodiment of the present invention; Figure 3This is a spectrum diagram of 4 optical signals after being injected into the polarization analyzer provided by an embodiment of the present invention; Figure 4 is an electrical spectrum of a photodetector output signal provided by one embodiment of the present invention; Figure 5 It is a flowchart of the steps of a method for generating a ten-fold frequency millimeter wave signal provided by an embodiment of the present invention.

[0022] Description of Reference Numerals 10-continuous wave laser; 20-polarization modulator; 30-polarization analyzer; 40-photodetector; 50-polarization controller. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0024] Figure 1 1 is a system structure diagram of a ten-fold frequency millimeter wave signal generation system provided by an embodiment of the present invention. Figure 1 As shown, an embodiment of the present invention provides a ten-fold frequency millimeter wave signal generation system, the system comprising: a continuous wave laser 10, for inputting an original optical carrier; a plurality of polarization modulators 20 arranged in parallel, for respectively introducing one polarized light and one radio frequency signal with different electrical phase offsets of the original optical carrier, for modulating the introduced radio frequency signal onto the corresponding polarized light to obtain a corresponding optical signal; an analyzer 30, for collecting the optical signals output by each polarization modulator 20, for performing step-by-step signal coupling of each tube based on the phase difference of each optical signal to obtain a corresponding coupled optical signal; a photodetector 40, connected to the output end of the analyzer 30, for converting the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal.

[0025] Preferably, a polarization controller 50 is further provided between the continuous wave laser 10 and each polarization modulator 20 ; the polarization controller 50 is used to perform adaptive polarization direction adjustment of the polarized light based on the working mode of each polarization modulator 20 .

[0026] In the embodiment of the present invention, in the ten-fold frequency millimeter wave signal generation system, the continuous wave laser 10 is used as a light source to provide a stable optical carrier. However, since the polarization state of the optical signal directly affects the modulation effect of the polarization modulator 20 (PolM), a polarization controller 50 (PC) is introduced between the continuous wave laser 10 and each polarization modulator 20 to dynamically adjust the polarization direction of the optical signal to ensure that each polarization modulator 20 can work under the optimal polarization condition, thereby improving the modulation efficiency and the coherent superposition effect of the target sideband.

[0027] Specifically, the core function of the polarization controller 50 is to adapt the working mode of the polarization modulator 20, that is, to adjust the polarization direction of the input light so that it is aligned with the working polarization axis of each polarization modulator 20. The modulation efficiency of the polarization modulator 20 depends on the polarization state of the input light. If the polarization direction of the incident light does not match, the polarization component of the modulated signal may be reduced, resulting in a decrease in the light modulation depth and affecting the output power of the target frequency-doubled sideband (±5th order). Through the adjustment of the polarization controller 50, it can be ensured that each optical signal entering the polarization modulator 20 is in the optimal polarization direction, so that the RF modulation effect fully acts on the orthogonal polarization components of the optical signal, thereby improving the polarization modulation efficiency, enhancing the energy of the target optical sideband, and reducing the generation of interference sideband (such as ±3rd order, ±7th order) components.

[0028] Based on the scheme of the present invention, by introducing the polarization controller 50, the system can dynamically adjust the polarization direction of the incident light according to the working mode of each polarization modulator 20, ensuring that all modulators are in the best working state. This not only improves the stability of optical signal modulation, but also enhances the coherent superposition effect of the target frequency-multiplied sidebands, reduces the interference of non-target sidebands, thereby improving the sideband suppression ratio (OSSR) of the millimeter wave signal, optimizing the system performance, and is particularly suitable for high-frequency millimeter wave and terahertz wave communication systems.

[0029] Preferably, the electrical phase offset of each polarization modulator 20 is determined based on the total number of polarization modulators 20, and the corresponding determination rule is: perform uniform distribution of phase changes based on the total number of polarization modulators 20, and determine the electrical phase offset of each polarization modulator 20 based on the uniform distribution result as the initial electrical phase offset of each polarization modulator 20; construct a dual-objective optimization algorithm with the goal of optimizing the coherent superposition of ±5-order optical sidebands and minimizing the interference intensity of non-±5-order optical sidebands; solve the dual-objective optimization algorithm based on the initial electrical phase offset of each polarization modulator 20 to obtain the electrical phase offset of each polarization modulator 20.

[0030] In the embodiment of the present invention, in the ten-fold frequency millimeter wave signal generation system, the electrical phase offset of each polarization modulator 20 (PolM) plays a decisive role in the coherent superposition effect of the target optical sideband (±5 order). In order to ensure that the final synthesized optical signal can maximize the enhancement of the ±5 order optical sidebands while suppressing non-target optical sidebands (such as ±3 order and ±7 order), the system needs to reasonably allocate the electrical phase offset based on the total number of polarization modulators 20. The allocation process involves key steps such as uniform phase distribution, dual-objective optimization algorithm, and optimal solution to achieve the optimal optical signal synthesis effect.

[0031] Specifically, the electrical phase offset of each modulator is preliminarily determined according to the total number N of polarization modulators 20 in the system. The most basic method is to adopt a uniform distribution strategy, that is, according to:

[0032] in, is the electrical phase offset of each polarization modulator 20. In this way, the electrical phase offset of each polarization modulator 20 is evenly distributed in the range [0,π], ensuring that all modulators have a relatively uniform effect on the optical signal. However, this uniform distribution does not necessarily guarantee the optimal coherent superposition of the ±5-order optical sidebands. Therefore, it is necessary to further optimize the phase offset to achieve the effect of enhancing the target sideband and suppressing the interference sideband. To this end, the system constructs a dual-objective optimization algorithm, in which: 1) Objective 1: Maximize the coherent superposition effect of ±5-order optical sidebands, expressed as:

[0033] Among them, among them, Represents the modulation contribution of the nth polarization modulator 20 on the ±5th order optical sidebands.

[0034] 2) Objective 2: Minimize the intensity of non-±5th order optical sidebands (±3rd order, ±7th order, etc.).

[0035]

[0036] This ensures that the ±3rd-order and ±7th-order optical sidebands can cancel each other out during the final synthesis process, thereby reducing interference to the millimeter-wave signal.

[0037] In a possible implementation, taking a genetic algorithm (GA) as an example, the entire solution process is as follows: 1) Initialize the population: Use the phase offset obtained from a uniform distribution as the initial solution, and randomly introduce a small amount of disturbance to form multiple initial individuals.

[0038] 2) Fitness calculation: Based on the above dual objective function, the synthesis effect of the ±5-order optical sidebands and the interference degree of the ±3-order and ±7-order optical sidebands under each phase offset configuration are calculated to comprehensively evaluate their advantages and disadvantages.

[0039] 3) Selection and mutation: Through the selection, crossover and mutation operations of the genetic algorithm, the phase offset configuration is continuously optimized iteratively, so that the intensity of the ±5-order optical sidebands is gradually enhanced, while the intensity of the non-target optical sidebands is gradually reduced.

[0040] 4) Convergence judgment: When the optimization algorithm reaches a certain number of rounds or the change of the objective function tends to be stable, the optimal phase offset configuration is output as the final electrical phase offset of each polarization modulator 20.

[0041] In traditional photon frequency doubling systems, if not optimized, the phase offset may lead to low coherent superposition efficiency of the target optical sidebands (±5th order), thus affecting the power output of the millimeter wave signal. At the same time, if the phase offset is not selected properly, the interference sidebands such as ±3rd order and ±7th order may not be effectively offset, thereby reducing the sideband suppression ratio (OSSR) of the millimeter wave signal and reducing the purity of the system output signal. The above dual-objective optimization algorithm can ensure that the power of the ±5th order optical sidebands is maximized, while suppressing non-target sidebands, improving the signal quality of the millimeter wave signal and the overall performance of the system.

[0042] In a possible implementation, the light wave output by the laser is first injected into the polarization controller 50, at which time the azimuth angle of the polarization controller 50 is 45°, and then passes through a 1×4 optical beam splitter, where the light wave is divided into four polarized lights, which are respectively injected into four polarization modulators 20PolM1-PolM4 for modulation. The azimuth angle of the polarization controller 50 is adjusted to , and adjust the electrical phase shifter loaded on the polarization modulator 20 (PolM) from the 1st to the 4th path to be 0, , , .

[0043] Preferably, the polarization modulator 20 is configured to modulate the incoming radio frequency signal onto the corresponding polarized light to obtain the corresponding optical signal; wherein, The rule for modulating the incoming RF signal onto the corresponding polarized light is:

[0044] in, and are the polarization components of the output optical signal in the x direction and the y direction respectively; is the amplitude of the introduced polarized light; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the modulation depth; j is the imaginary unit; t is the time; is the electrical phase offset of the introduced RF signal.

[0045] Specifically, the input polarized light has a certain amplitude and angular frequency, and is modulated by the polarization modulator 20. The modulated optical signal is output in two orthogonal polarization directions, and the optical signal in each direction is affected by the modulation of the RF signal. In this process, the modulation depth of the RF signal determines the intensity of the modulation, and the angular frequency of the RF signal affects the time variation characteristics of the modulated signal. In addition, the electrical phase offset of the RF signal is used to adjust the modulation phase of different paths, so that the optical signals output by each polarization modulator 20 have a controllable phase relationship, providing optimization conditions for subsequent coherent superposition. Finally, the modulated optical signal contains the phase modulation information of the RF signal in two orthogonal polarization directions. This modulation method is used to generate high-frequency millimeter-wave signals in the photonic frequency doubling system.

[0046] In a possible implementation, taking the above-mentioned 4-channel polarization modulator 20 as an example, the output of the first channel PolM is: .

[0047] The output of PolM 2 is: .

[0048] The output of the third PolM is: .

[0049] The output of the 4th PolM is: .

[0050] The signal output from PolM is injected into the polarization analyzer 30 (pol), and the output signal is: .

[0051] It should be noted that the specific embodiment of the scheme of the present invention takes four-way polarization modulator 20 as an example, but this modulation method is not limited to four-way polarization modulator 20, but can be extended to any number of polarization modulators 20. The number of polarization modulators 20 in the system depends on the frequency multiples of the target millimeter wave signal, the complexity of the system, and the optimization requirements for the coherent synthesis effect of the optical signal.

[0052] In a multi-channel polarization modulation system, each polarization modulator 20 receives polarized light from a continuous wave laser 10 and modulates it with a radio frequency signal with a different phase offset, thereby forming an optical signal with a specific phase relationship in two orthogonal polarization directions. After appropriate phase control, these optical signals enter the polarizer 30 for final coherent superposition. Whether it is a four-channel, six-channel or more polarization modulator 20, the system needs to preliminarily set the electrical phase offset based on the principle of uniform distribution, and solve it through an optimization algorithm so that the target optical sideband is optimally coherently superimposed during the final synthesis, while suppressing the influence of non-target sidebands. As the number of channels increases, the system can achieve higher-order frequency doubling effects, such as ten-fold, twelve-fold or even higher frequency millimeter wave signal generation. Therefore, this method is applicable to a variety of photonic frequency doubling architectures, and provides a flexible and efficient signal generation solution for high-frequency applications such as millimeter wave and terahertz wave communications, radars, etc.

[0053] Preferably, the polarizer 30 is configured as follows: according to the principle of minimum phase difference, two optical signals are selected in sequence for coupling to form multiple first-level coupled optical signals; among the first-level coupled optical signals, the signal with the smallest phase difference is further selected for further coupling to form a second-level coupled optical signal; and this process is repeated recursively until all optical signals are coherently synthesized to obtain a coupled optical signal.

[0054] In the embodiment of the present invention, in the photon frequency doubling system of the ten-fold frequency millimeter wave signal, the role of the polarizer 30 is not only to transmit the optical signal of a specific polarization direction, but also to undertake the core task of coherent superposition of the optical signal. In order to ensure that the final synthesized optical signal has the best coherent characteristics, the polarizer 30 adopts a step-by-step coupling strategy based on the minimum phase difference principle to gradually optimize the coherent synthesis process of the optical signal, thereby enhancing the target optical sideband (such as ±5 order) and suppressing the non-target optical sideband (such as ±3 order, ±7 order).

[0055] Specifically, the analyzer 30, in accordance with the principle of optimal phase matching, first selects two optical signals with the smallest phase difference from the input multiple polarization modulator 20 output optical signals for preliminary coupling to form multiple first-level coupled optical signals. The goal of this stage is to ensure that the optical signals with close phases are first coherently synthesized to reduce interference loss and optimize the enhancement effect of the target sideband. Subsequently, in the first-level coupled optical signal, the signal pair with the smallest phase difference is continuously selected for secondary coherent synthesis to generate a second-level coupled optical signal. This process is repeated recursively until all optical signals complete the final coherent synthesis to obtain an optimized coupled optical signal, ensuring that the superposition of the target optical sidebands reaches the optimal state.

[0056] Based on the scheme of the present invention, in a traditional photon frequency doubling system, if a fixed optical signal synthesis method is used without considering the phase matching of the input optical signal, the coherence efficiency of the target optical sideband may be reduced, or even interference may be weakened, thereby affecting the output power of the millimeter wave signal. In addition, if the coupling order of the optical signal is not reasonably arranged during the synthesis process, the non-target optical sideband (such as ±3rd order, ±7th order) may be coherently enhanced, while the target optical sideband (±5th order) cannot be effectively enhanced, resulting in a decrease in the sideband suppression ratio (OSSR), affecting the purity of the millimeter wave signal. Therefore, by introducing a step-by-step coupling strategy based on the minimum phase difference, the synthesis process of the optical signal can be effectively optimized, the coherent superposition of the target optical sideband can be maximized, and the interference of the non-target sideband can be suppressed, thereby improving the output power and spectrum quality of the millimeter wave signal. The scheme of the present invention optimizes the optical signal coupling process step by step to ensure the optimal phase matching, thereby effectively improving the purity and output power of the millimeter wave signal. Ultimately, this strategy enables the optical signal received by the photodetector 40 to reach the optimal coherence state, thereby achieving higher quality millimeter-wave signal output and providing an efficient and reliable photon frequency doubling solution for high-frequency applications such as 6G communications and radar.

[0057] In a possible implementation manner, the polarization angle of the polarizer 30 is controlled to be When , the optical signal output by the polarization modulator 20 can be described as: .

[0058] Furthermore, taking four polarized lights as an example, the optical signals output by the third and fourth parallel polarization modulators 20 are firstly transmitted through After the phase shift, the optical signal is coupled with the output of the polarization modulator 20 in parallel with the first and second paths, and then injected into the polarization angle The output light wave signal can be described as follows:

[0059] Preferably, the Jacobi-Anger formula is applied to expand the above formula to obtain:

[0060] because, , , at this time, the third-order optical sideband and the seventh-order optical sideband tend to 0, and the output light wave can be expressed as: .

[0061] Preferably, the polarizer 30 is further configured to: set a corresponding polarization angle with the goal of maximizing the transmission of ±5-order optical sidebands; and perform selective transmission on the coupled optical signal based on the set polarization angle to obtain a target optical signal.

[0062] In the embodiment of the present invention, in the ten-fold frequency millimeter wave signal generation system, the analyzer 30 is not only responsible for the coherent synthesis of the optical signal, but also selectively transmits the final optical signal by reasonably setting the polarization angle to maximize the energy of the target optical sideband (±5 order) while suppressing the interference of non-target sidebands (such as ±3 order and ±7 order). In order to achieve this goal, the polarization angle of the analyzer 30 needs to be accurately set according to the characteristics of the input coupled optical signal to ensure that the polarization direction of the target optical sideband is optimally matched with the transmission direction of the analyzer 30.

[0063] Specifically, after completing the coherent coupling of the optical signal, the optical signal input to the analyzer 30 still contains multiple optical sidebands of different orders, among which the ±5-order optical sidebands are the target components for millimeter wave signal generation, while other sidebands such as ±3-order and ±7-order are interference signals. Since optical sidebands of different orders may have different polarization directions after passing through the polarization modulator 20, if not controlled, the interfering optical sidebands may be partially transmitted into the photodetector 40, reducing the purity of the millimeter wave signal. Therefore, the polarization angle of the analyzer 30 needs to be optimized to maximize the transmittance of the ±5-order optical sidebands while suppressing the transmission of other sidebands.

[0064] In order to achieve this optimization goal, the system adopts a dual-objective optimization strategy: Objective 1: Maximize the transmission power of the ±5th order optical sidebands: Set the polarization angle of the analyzer 30 so that the polarization direction of the ±5th order optical sidebands completely matches their transmission direction to ensure maximum transmission of the optical signal. Determine the optimal polarization angle through experiments or simulation calculations to maximize the transmittance of the ±5th order sidebands.

[0065] Objective 2: Minimize the transmission of non-±5th order optical sidebands (±3rd order, ±7th order, etc.): Since the polarization directions of ±3rd order and ±7th order optical sidebands are different from ±5th order, the analyzer 30 can reduce the projection transmittance of these interfering light components by setting a suitable polarization angle, and finally reduce the power of non-target optical sidebands. This process can calculate the polarization direction of each order optical sideband based on the Bessel function, and use the optimization algorithm to solve the optimal polarization angle, so that the target optical signal is enhanced and the interfering optical signal is attenuated.

[0066] Based on the scheme of the present invention, the analyzer 30 achieves selective transmission of the coupled optical signal by optimizing the polarization angle setting, ensuring the maximum transmission of the ±5-order optical sidebands, while suppressing the interference optical sidebands such as the ±3-order and ±7-order. This method significantly improves the quality of the optical signal input to the photodetector 40, making the output power of the millimeter wave signal higher and the signal purity better, which is suitable for high-frequency applications such as 6G communication and radar.

[0067] Preferably, the target light signal is expressed as:

[0068] in, is the target light signal; A is the amplitude factor; and is the Bessel coefficient representing the modulation intensity of the ±5th order optical sideband; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the set polarization angle; is the modulation depth; j is the imaginary unit; t is the time.

[0069] In a possible implementation manner, the light wave output by the polarizer 30 is subjected to a first-order Bessel function expansion to obtain a corresponding expansion function, such as Figure 2 It can be seen from the figure that when the modulation coefficient is 3.83, the first-order function tends to zero. In this way, the modulation coefficient can be controlled by adjusting the amplitude voltage of the RF drive signal. , at this time the first-order optical sideband , at this time the output light wave only contains the 5th order optical sideband, then the final output light wave signal can be written as:

[0070] Based on this, the target light signal is expressed as:

[0071] The output of the target optical signal consists of two main parts, corresponding to the positive and negative fifth-order optical sidebands respectively. The modulation intensity of each optical sideband is determined by the Bessel coefficient, which depends on the modulation depth. The phase of the target optical signal contains two parts, one is the original optical carrier frequency of the polarized light, and the other is the five-fold frequency component generated by the modulation of the radio frequency signal. Under ideal conditions, the target optical signal only retains the components of the fifth-order optical sideband, while the low-order and high-order interference sidebands have been effectively suppressed. This means that the optimized system enhances the target optical sideband through coherent superposition and selective transmission of the analyzer 30, while minimizing the intensity of the non-target optical sideband. Finally, after the target optical signal enters the photodetector 40, a ten-fold frequency millimeter-wave signal can be generated through the beat frequency effect.

[0072] Preferably, the photodetector 40 is configured to: perform square-law detection on the target optical signal to obtain a corresponding ten-fold frequency millimeter wave signal; wherein the square-law detection rule for the target optical signal is:

[0073] in, is the output signal of the photodetector 40; represents taking the real part; is the target light signal; is the normalized optical signal amplitude; is the modulation efficiency of ±5th order optical sideband; is the angular frequency of the introduced RF signal; t is the time.

[0074] In the embodiment of the present invention, the target optical signal mainly includes components of positive and negative fifth-order optical sidebands after polarization modulation, coherent superposition, and selective transmission of the polarizer 30. The photodetector 40 converts the input optical signal into an electrical signal by using the photoelectric conversion effect, and extracts the frequency information of the millimeter wave signal by square law detection.

[0075] Furthermore, the basic principle of square-law detection is to calculate the intensity of the target optical signal, that is, the square of the amplitude of the optical signal. Since the target optical signal only contains positive and negative fifth-order optical sidebands, the photodetector 40 will obtain a low-frequency DC component and an AC component with a main frequency of ten times the frequency of the radio frequency signal after performing the square operation. Among them, the component with ten times the frequency of the radio frequency signal is the final required millimeter wave signal. The intensity of this part of the signal is determined by the modulation efficiency of the target optical sideband, and the modulation efficiency is affected by the modulation depth. During the detection process, the output signal of the photodetector 40 is proportional to the intensity of the target optical signal, and only the ten-fold frequency radio frequency component is retained, thereby realizing the generation of high-frequency millimeter wave signals.

[0076] Based on the scheme of the present invention, by optimizing the coherent superposition and polarization angle setting of the analyzer 30, the transmittance of the positive and negative fifth-order optical sidebands can be effectively improved, while suppressing non-target optical sidebands, making the signal input by the photodetector 40 purer, thereby improving the sideband suppression ratio of the millimeter-wave signal. In addition, the square-law detection process ensures that the system can stably output ten-fold frequency millimeter-wave signals, which are suitable for applications such as high-frequency communications and radar. Overall, this method realizes an efficient and low-loss millimeter-wave signal generation scheme through the combination of optical modulation and photoelectric conversion.

[0077] Example: In order to verify the accuracy of the millimeter wave generation solution results of the present invention, a simulation model was constructed using a simulation experiment platform based on the principle of a 4-way polarization modulator 20. The frequency of the connected light wave laser is 193.1THz, the power is 20dBm, the frequency of the RF drive signal is 10GHz, the RF amplitude is 1.22V, the azimuth angle of the polarization controller 50 is 45 degrees, and the angle of the analyzer 30 is -45°. The responsivity of the photodetector 40 is 1A / W. After the light wave signal output by the 4-way PolM is injected into the analyzer 30, it only contains positive and negative 5th order optical sidebands, and the optical carrier suppression ratio reaches 60.04dB. The simulation diagram is as follows Figure 3Finally, the optical wave signal output by the polarizer 30 is injected into the photodetector 40 for square law detection, and a millimeter wave signal with a frequency of 100 GHz is obtained, which is 10 times the RF drive signal. Figure 4 As shown, the RF sideband suppression ratio reaches 56.9dB at this time.

[0078] Figure 5 FIG. 1 is a flow chart of a method for generating a ten-fold frequency millimeter wave signal provided by an embodiment of the present invention. Figure 5 As shown, an embodiment of the present invention provides a method for generating a ten-fold frequency millimeter wave signal, the method comprising: Step S10: Split the original optical carrier into multiple polarized lights, and introduce each polarized light into the corresponding polarization modulator 20 respectively.

[0079] Specifically, the continuous wave laser 10 generates a stable optical carrier signal, which is usually linearly polarized light, to ensure good polarization consistency in the subsequent modulation process. The original optical carrier is divided into multiple optical signals by an optical beam splitter, and each optical signal is adjusted to its polarization state by a polarization controller 50 to adapt to the working mode of different polarization modulators 20. The purpose of this polarization adjustment is to ensure that when each optical signal enters the polarization modulator 20, its polarization direction matches the polarization axis of the modulator to maximize the modulation efficiency. Afterwards, the adjusted multiple optical signals are respectively introduced into the corresponding polarization modulators 20, laying the foundation for subsequent RF modulation and coherent synthesis.

[0080] Step S20: introducing radio frequency signals with different electrical phase offsets into each polarization modulator 20 respectively, so as to modulate the introduced radio frequency signals onto corresponding polarized light based on each polarization modulator 20 to obtain corresponding optical signals.

[0081] Specifically, each polarization modulator 20 not only receives the optical signal after beam splitting and polarization adjustment, but also needs to input the RF signal with different electrical phase offsets. The frequency of the RF signal determines the position of the optical sideband generated after optical modulation, and different phase offsets are used to control the phase relationship of the optical signals output by each polarization modulator 20. During the modulation process, the RF signal is applied to the polarization modulator 20 so that the polarized light input by it is loaded with the RF modulation signal in two orthogonal polarization directions, thereby forming a series of optical sidebands on the spectrum. Ultimately, the optical signal output by each polarization modulator 20 contains multiple positive and negative orders of optical sidebands, and the output phase of each polarization modulator 20 is affected by the electrical phase offset of its input RF signal, providing a control means for subsequent coherent superposition.

[0082] Step S30: Based on the phase difference of each optical signal, perform signal coupling of each tube step by step to obtain a corresponding coupled optical signal.

[0083] Specifically, the optical signals output by each polarization modulator 20 may differ in polarization direction and phase, so coherent coupling of the optical signals is required before entering the photodetector 40. First, according to the principle of minimum phase difference, two signals with the closest phases are selected from all optical signals for preliminary coupling to form a first-level coupled optical signal. Then, based on the first-level coupled optical signal, continue to select the signal with the closest phase for secondary coupling, and so on, until all optical signals complete the final coherent synthesis. In this process, the role of the analyzer 30 is crucial. It not only transmits optical signals in a specific polarization direction, but also maximizes the transmittance of the target optical sideband by optimizing the polarization angle setting, while suppressing the interference of non-target sidebands, so that the final coupled optical signal has better spectral purity.

[0084] Step S40: converting the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal based on the photodetector 40 .

[0085] Specifically, after the coherently coupled optical signal enters the photodetector 40, it is converted into an electrical signal through a photoelectric conversion process. The photodetector 40 uses a square-law detection mechanism to detect the intensity of the input optical signal and generate a current signal. In this process, the positive and negative fifth-order optical sidebands in the optical signal undergo a beat frequency effect, and their frequency difference is equal to ten times the frequency of the input RF signal. Therefore, the frequency of the final output millimeter-wave signal is equal to ten times the frequency of the RF signal. In order to ensure the high purity of the millimeter-wave signal, this step relies on the optimization control of the phase and polarization of the optical signal in the previous step. Finally, after the conversion of the photodetector 40, the system successfully outputs a high-frequency, high-stability ten-fold frequency millimeter-wave signal, which can be widely used in high-frequency technical fields such as 6G communications, radar detection, and terahertz imaging.

[0086] Preferably, the method further comprises: performing adaptive polarization direction adjustment of the polarized light based on the polarization controller 50 , so that each polarized light matches the working mode of the corresponding polarization modulator 20 .

[0087] Those skilled in the art will understand that all or part of the steps in the method for implementing the above-mentioned embodiments can be completed by instructing the relevant hardware through a program, and the program is stored in a storage medium, including several instructions for making a single-chip microcomputer, a chip or a processor (processor) execute all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0088] The optional embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the technical concept of the embodiments of the present invention, the technical scheme of the embodiments of the present invention can be subjected to a variety of simple modifications, and these simple modifications all belong to the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0089] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the embodiments of the present invention, they should also be regarded as the contents disclosed in the embodiments of the present invention.

Claims

1. A ten-fold frequency millimeter wave signal generation system, characterized in that: The system comprises: A continuous wave laser for inputting a raw optical carrier; A plurality of polarization modulators arranged in parallel respectively introduce one polarized light and one radio frequency signal with different electrical phase offset of the original optical carrier, and are used to modulate the introduced radio frequency signal onto the corresponding polarized light to obtain the corresponding optical signal; wherein, The electrical phase offset of each polarization modulator is determined based on a dual-objective optimization algorithm that takes the optimal coherent superposition of the ±5-order optical sidebands as the goal and minimizes the interference intensity of the non-±5-order optical sidebands. The polarization analyzer receives the optical signals output by each polarization modulator and is used to perform the signal coupling of each tube step by step based on the phase difference of each optical signal to obtain the corresponding coupled optical signal; A photoelectric detector is connected to the output end of the polarizer and is used to convert the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal.

2. The system according to claim 1, characterized in that A polarization controller is also provided between the continuous wave laser and each polarization modulator; The polarization controller is used to perform adaptive polarization direction adjustment of polarized light based on the working mode of each polarization modulator.

3. The system according to claim 1, characterized in that The electrical phase offset of each polarization modulator is determined based on the total number of polarization modulators, and the corresponding determination rule is: Performing uniform distribution of phase changes based on the total number of polarization modulators, and determining the electrical phase offset of each polarization modulator based on the uniform distribution result as the initial electrical phase offset corresponding to each polarization modulator; A dual-objective optimization algorithm is constructed with the goal of optimizing the coherent superposition of ±5-order optical sidebands and minimizing the interference intensity of non-±5-order optical sidebands. The dual-objective optimization algorithm is solved based on the initial electrical phase offset of each polarization modulator to obtain the electrical phase offset of each polarization modulator.

4. The system according to claim 3, characterized in that The polarization modulator is configured to modulate the incoming radio frequency signal onto the corresponding polarized light to obtain the corresponding optical signal; wherein, The rule for modulating the incoming RF signal onto the corresponding polarized light is: in, and are the polarization components of the output optical signal in the x direction and the y direction respectively; is the amplitude of the introduced polarized light; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the modulation depth; j is the imaginary unit; t is time; is the electrical phase offset of the introduced RF signal.

5. The system according to claim 1, characterized in that The polarization analyzer is configured as: According to the principle of minimum phase difference, two optical signals are selected in sequence for coupling to form multiple first-level coupled optical signals; Among the first-level coupled optical signals, the signal with the smallest phase difference is further selected for further coupling to form a second-level coupled optical signal; This process is repeated recursively until all optical signals are coherently combined to obtain a coupled optical signal.

6. The system according to claim 5, characterized in that The polarization analyzer is further configured as: The corresponding polarization angle is set with the goal of maximizing the transmission of the ±5th order optical sidebands; The coupled optical signal is selectively transmitted based on the set polarization angle to obtain a target optical signal.

7. The system according to claim 6, characterized in that The target light signal is expressed as: in, is the target light signal; A is the amplitude factor; and is the Bessel coefficient representing the modulation intensity of the ±5th order optical sideband; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced RF signal; is the set polarization angle; is the modulation depth; j is the imaginary unit; t is time.

8. The system according to claim 6, characterized in that The photodetector is configured as: Performing square-law detection on the target optical signal to obtain a corresponding ten-fold frequency millimeter wave signal; wherein, The square law detection rule for the target optical signal is: in, is the output signal of the photodetector; represents taking the real part; is the target light signal; is the normalized optical signal amplitude; is the modulation efficiency of ±5th order optical sideband; is the angular frequency of the introduced RF signal; t is time.

9. A method for generating a ten-fold frequency millimeter wave signal, characterized in that: The method is implemented based on the ten-fold frequency millimeter wave signal generation system according to any one of claims 1 to 8, and the method comprises: The original optical carrier is divided into multiple polarized lights, and each polarized light is introduced into the corresponding polarization modulator respectively; Introducing radio frequency signals with different electrical phase offsets to each polarization modulator, so as to modulate the introduced radio frequency signals onto corresponding polarized light based on each polarization modulator to obtain corresponding optical signals; Based on the phase difference of each optical signal, the signal coupling of each tube is performed step by step to obtain the corresponding coupled optical signal; The coupled optical signal is converted into a corresponding ten-fold frequency millimeter wave signal based on a photodetector.

10. The method according to claim 9, characterized in that The method further comprises: Based on the polarization controller, the polarization direction of the polarized light is adaptively adjusted so that each polarized light matches the working mode of the corresponding polarization modulator.

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