Decade-Frequency Millimeter-Wave Signal Generation System and Method

Abstract

An embodiment of the present invention provides a ten-fold frequency millimeter-wave signal generation system and method, belonging to the field of photon microwave technology. The ten-fold frequency millimeter-wave signal generation system is characterized in that the system includes: a continuous-wave laser for inputting an original optical carrier; a plurality of polarization modulators arranged in parallel, each introducing a path of polarized light of the original optical carrier and a radio frequency signal with different electrical phase offsets, for modulating the introduced radio frequency signal onto the corresponding polarized light to obtain a corresponding optical signal; a polarization analyzer for combining the optical signals output by each polarization modulator to obtain a corresponding coupled optical signal; and a photodetector connected to the output end of the polarization analyzer for converting the coupled optical signal into a corresponding ten-fold frequency millimeter-wave signal. The solution of the present invention solves the problems of inaccurate phase matching and insufficient interference sideband suppression in the existing solutions, and provides a better solution for high-frequency applications such as 6G communication and radar.

Description

Technical Field

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

[0002] With the development of wireless communication and radar systems towards higher frequency bands, the efficient generation of millimeter wave (mmWave) and terahertz (THz) signals has become a research hotspot. Millimeter wave signals have wide applications in fields such as 6G communication, high-resolution radar, and satellite communication. However, traditional millimeter wave signal generation schemes face many challenges and are difficult to meet the future requirements of high frequency, large bandwidth, and high stability.

[0003] Currently, the generation of millimeter wave signals mainly relies on two technologies: electronic frequency multiplication and photon frequency multiplication. Due to severe losses in high-frequency circuits and low frequency multiplication efficiency, the electronic frequency multiplication method is difficult to break through the frequency limit above 100 GHz and has gradually become difficult to meet the requirements of high-frequency communication and radar systems. In contrast, the photon frequency multiplication method uses optical modulation technology to map low-frequency radio frequency signals into the optical domain and realizes high-fold frequency conversion of millimeter wave signals through photodetectors. Because of its ultra-wideband characteristics, low loss, and high stability, it has become the key research direction currently. Existing photon frequency multiplication 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 ability of non-target sidebands, interfering with the millimeter wave signals output by photodetectors with additional spectral components, and reducing the optical sideband suppression ratio (OSSR) of the signals.

[0004] In a photon frequency multiplication system, the phase matching of polarization modulators is a key factor affecting the synthesis effect of optical signals. If the electrical phase offset amounts of different modulators are not optimized and calculated, but set with fixed values or empirical values, it may lead to phase mismatches of interference sidebands such as ±3rd order and ±7th order, making them unable to be effectively canceled during the final optical signal synthesis, thereby reducing the signal-to-noise ratio of millimeter wave signals. In addition, as a key device for the final optical signal to enter the photodetector, the setting of the polarization angle of the polarization analyzer directly affects the transmission efficiency of the target optical sidebands and the suppression effect of non-target sidebands. Existing schemes are usually set based on fixed angles or experience, without fully considering the polarization characteristics after coherent synthesis of optical signals, allowing some interference components to still transmit into the photodetector and affecting the quality of millimeter wave signals. Aiming at the problem that the existing schemes cannot generate pure ten-fold frequency millimeter wave signals, a new ten-fold frequency millimeter wave signal generation scheme needs to be proposed. Summary of the Invention

[0005] The objective of the embodiment of the present invention is to provide a ten - times - frequency millimeter - wave signal generation system and method, so as to at least solve the problem that the existing solutions cannot generate a pure ten - times - frequency millimeter - wave signal.

[0006] To achieve the above objective, the first aspect of the present invention provides a ten - times - frequency millimeter - wave signal generation system, which includes: a continuous - wave laser for inputting an original optical carrier; a plurality of polarization modulators arranged in parallel, each introducing a path of polarized light of the original optical carrier and a radio - frequency signal with different electrical phase offsets, 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 by optimizing a dual - objective optimization algorithm aiming at the optimal coherent superposition of ±5 - order optical sidebands and minimizing the interference intensity of non - ±5 - order optical sidebands; a polarization analyzer for combining the optical signals output by each polarization modulator, and for performing step - by - step coupling of each tube signal 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 polarization analyzer for converting the coupled optical signal into a corresponding ten - times - 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 adjustment of the polarization direction 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 respectively 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 aiming at the optimal 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 to obtain the electrical phase offset of each polarization modulator.

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

[0010]

[0011] wherein, and are the polarization components of the output optical signal in the x - direction and 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 radio - frequency signal; is the modulation depth; j is the imaginary unit; t is the time; is the electrical phase offset of the introduced radio frequency signal.

[0012] Optionally, the polarizer is configured to: sequentially select two optical signals for coupling according to the principle of the minimum phase difference to form a plurality of first-level coupled optical signals; among the first-level coupled optical signals, continue to select the signal with the minimum phase difference for further coupling to form second-level coupled optical signals; and so on recursively until all optical signals complete coherent synthesis to obtain the coupled optical signal.

[0013] Optionally, the polarizer is further configured to: set the corresponding polarization angle with the goal of maximizing the transmission of the ±5th order optical sidebands; perform selective transmission on the coupled optical signal based on the set polarization angle to obtain the target optical signal.

[0014] Optionally, the target optical signal is expressed as:

[0015]

[0016] where is the target optical signal; A is the amplitude factor; and are the Bessel coefficients representing the modulation intensity of the ±5th order optical sidebands; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced radio frequency signal; is the set polarization angle; is the modulation depth; j is the imaginary unit; t is the time.

[0017] Optionally, the photodetector is configured to: perform square-law detection on the target optical signal to obtain the corresponding ten-fold frequency millimeter-wave signal; where the rule for performing square-law detection on the target optical signal is:

[0018]

[0019] where is the output signal of the photodetector; represents taking the real part; is the target optical signal; is the normalized optical signal amplitude; is the modulation efficiency of the ±5th order optical sidebands; is the angular frequency of the introduced radio frequency signal; t is the time.

[0020] In a second aspect of the present invention, a method for generating a ten - times - frequency millimeter - wave signal is provided. The method is implemented based on the above - mentioned ten - times - frequency millimeter - wave signal generation system, and the method includes: dividing an original optical carrier into multiple polarized lights, and respectively introducing each polarized light into a corresponding polarization modulator; introducing radio - frequency signals with different electrical phase offsets into each polarization modulator, so as to modulate the introduced radio - frequency signals onto the corresponding polarized lights based on each polarization modulator to obtain corresponding optical signals; performing coupling of each tube signal step by step based on the phase difference of each optical signal to obtain corresponding coupled optical signals; converting the coupled optical signals into corresponding ten - times - frequency millimeter - wave signals based on a photodetector.

[0021] Optionally, the method further includes: performing adaptive adjustment of the polarization direction of the polarized light based on a polarization controller, so that each polarized light matches the working mode of the corresponding polarization modulator.

[0022] Through the above technical solutions, the present invention realizes efficient generation of ten - times - frequency millimeter - wave signals by optimizing the phase matching of the polarization modulator and the polarization angle setting of the analyzer. Multiple polarization modulators respectively perform radio - frequency modulation on the original optical carrier and introduce different electrical phase offsets, enabling the target optical sidebands (±5th order) to coherently superpose during final synthesis, while suppressing interference sidebands (±3rd order, ±7th order) and improving the purity of the optical signal. The role of the analyzer is not only to combine 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, reducing the influence of non - target sidebands on the millimeter - wave signal. Finally, the photodetector receives the optimized optical signal and outputs a high - quality ten - times - 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 solutions, improves the optical sideband suppression ratio (OSSR) of the millimeter - wave signal, enhances the output power and signal purity, and provides a better solution for high - frequency applications such as 6G communication and radar.

[0023] Other features and advantages of the embodiments of the present invention will be described in detail in the subsequent detailed description part. Brief Description of the Drawings

[0024] The 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 detailed description, they are used to explain the embodiments of the present invention, but do not constitute a limitation to the embodiments of the present invention. In the drawings:

[0025] Figure 1 is a system structure diagram of a ten - times - frequency millimeter - wave signal generation system provided by an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of the expansion image of the first - kind Bessel function provided by an embodiment of the present invention;

[0027] Figure 3 It is the spectrogram after the 4-channel optical signal injection polarization analyzer provided by an embodiment of the present invention;

[0028] Figure 4 It is the electrical spectrogram of the output signal of the photodetector provided by an embodiment of the present invention;

[0029] Figure 5 It is the step flow chart of the ten-fold frequency millimeter wave signal generation method provided by an embodiment of the present invention.

[0030] Description of reference numerals

[0031] 10 - Continuous wave laser; 20 - Polarization modulator; 30 - Polarization analyzer; 40 - Photodetector; 50 - Polarization controller. Specific embodiments

[0032] The following will describe in detail the specific embodiments of the present invention with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for the purpose of illustrating and explaining the present invention, and are not intended to limit the present invention.

[0033] Figure 1 It is the system structure diagram of the ten-fold frequency millimeter wave signal generation system provided by an embodiment of the present invention. As Figure 1 shown, an embodiment of the present invention provides a ten-fold frequency millimeter wave signal generation system, the system includes: a continuous wave laser 10 for inputting an original optical carrier; a plurality of juxtaposed polarization modulators 20, each introducing a path of polarized light of the original optical carrier and a radio frequency signal with different electrical phase offsets, for modulating the introduced radio frequency signal onto the corresponding polarized light to obtain the corresponding optical signal; a polarization analyzer 30 for collecting the optical signals output by each polarization modulator 20, and for performing stage-by-stage coupling of each tube signal based on the phase difference of each optical signal to obtain the corresponding coupled optical signal; a photodetector 40 connected to the output end of the polarization analyzer 30 for converting the coupled optical signal into the corresponding ten-fold frequency millimeter wave signal.

[0034] 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 for performing adaptive adjustment of the polarization direction of the polarized light based on the working mode of each polarization modulator 20.

[0035] In an embodiment of the present invention, in a ten - fold frequency millimeter - wave signal generation system, a continuous - wave laser 10 serves 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, so as to ensure that each polarization modulator 20 can work under the optimal polarization conditions, thereby improving the modulation efficiency and the coherent superposition effect of the target sidebands.

[0036] Specifically, the core function of the polarization controller 50 is to adapt to 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 modulation signal may decrease, resulting in a decrease in the optical modulation depth and affecting the output power of the target frequency - doubled sidebands (±5th order). Through the adjustment of the polarization controller 50, it can be ensured that the optical signal entering each polarization modulator 20 is in the optimal polarization direction, enabling the radio - frequency modulation to fully act on the orthogonal polarization components of the optical signal, thereby improving the polarization modulation efficiency, enhancing the energy of the target optical sidebands, and at the same time reducing the generation of interfering sidebands (such as ±3rd order, ±7th order) components.

[0037] Based on the solution 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 optimal working state. This not only improves the stability of the optical signal modulation but also enhances the coherent superposition effect of the target frequency - doubled sidebands, reduces the interference of non - target sidebands, thereby improving the optical sideband suppression ratio (OSSR) of the millimeter - wave signal and optimizing the system performance, which is particularly suitable for high - frequency millimeter - wave and terahertz wave communication systems.

[0038] Preferably, the electrical phase offset of each polarization modulator 20 is determined based on the total number of paths of the polarization modulator 20. The corresponding determination rule is as follows: perform a uniform distribution of phase changes based on the total number of paths of the polarization modulator 20, and respectively determine the electrical phase offset of each polarization modulator 20 based on the uniform distribution result as the initial electrical phase offset of the corresponding polarization modulator 20; construct a two - objective optimization algorithm with the optimal coherent superposition of the ±5th order optical sidebands as the goal and simultaneously minimizing the interference intensity of non - ±5th order optical sidebands; solve the two - 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.

[0039] In the embodiments of the present invention, in a 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 sidebands (±5th order). To ensure that the finally synthesized optical signal can maximize the enhancement of the ±5th order optical sidebands and suppress non - target optical sidebands (such as ±3rd order, ±7th order) at the same time, the system needs to reasonably allocate the electrical phase offset based on the total number of paths of the polarization modulator 20. This allocation process involves key steps such as uniform phase distribution, dual - objective optimization algorithm, and optimization solution to achieve the optimal optical signal synthesis effect.

[0040] Specifically, according to the total number of paths N of the polarization modulator 20 in the system, the electrical phase offset of each modulator is initially determined. The most basic method is to adopt a uniform distribution strategy, that is, according to:

[0041]

[0042] where, is the electrical phase offset of each polarization modulator 20. In this way, the electrical phase offset of each polarization modulator 20 is uniformly distributed within the range of [0, π], ensuring that the effects of all modulators on the optical signal are relatively uniform. However, this uniform distribution does not necessarily guarantee the optimal coherent superposition of the ±5th order optical sidebands. Therefore, it is necessary to further optimize the phase offset to achieve the effect of enhancing the target sidebands and suppressing the interfering sidebands. For this purpose, the system constructs a dual - objective optimization algorithm, where:

[0043] 1) Objective 1: Maximize the coherent superposition effect of the ±5th order optical sidebands, expressed as:

[0044]

[0045] where, where, represents the modulation contribution of the nth polarization modulator 20 on the ±5th order optical sidebands.

[0046] 2) Objective 2: Minimize the intensity of non - ±5th order optical sidebands (±3rd order, ±7th order, etc.).

[0047]

[0048] This ensures that the ±3rd order and ±7th order optical sidebands can be cancelled out with each other during the final synthesis process, thereby reducing the interference to the millimeter - wave signal.

[0049] In a possible implementation manner, taking the genetic algorithm (Genetic Algorithm, GA) as an example, the entire solution process is as follows:

[0050] 1) Initialize the population: Use the phase offset obtained by uniform distribution as the initial solution, and randomly introduce a small amount of perturbation to form multiple initial individuals.

[0051] 2) Fitness calculation: According to the above double-objective function, calculate the synthesis effect of the ±5th-order optical sidebands under each set of phase offset configurations, as well as the interference levels of the ±3rd-order and ±7th-order optical sidebands, and comprehensively evaluate their advantages and disadvantages.

[0052] 3) Selection and mutation: Through the selection, crossover, and mutation operations of the genetic algorithm, continuously iterate and optimize the phase offset configuration to gradually increase the intensity of the ±5th-order optical sidebands and gradually decrease the intensity of the non-target optical sidebands.

[0053] 4) Convergence judgment: When the optimization algorithm reaches a certain number of rounds or the change of the objective function tends to be stable, output the optimal phase offset configuration as the final electrical phase offset of each polarization modulator 20.

[0054] In a traditional photon frequency doubling system, without optimization, the phase offset may lead to low coherent superposition efficiency of the target optical sidebands (±5th order), thereby affecting the power output of the millimeter-wave signal. At the same time, if the phase offset is not properly selected, it may cause the interference sidebands such as ±3rd order and ±7th order to be unable to be effectively canceled, thus reducing the optical sideband suppression ratio (OSSR) of the millimeter-wave signal and decreasing the purity of the system output signal. Through the above double-objective optimization algorithm, it is possible to ensure the maximization of the power of the ±5th-order optical sidebands, while suppressing the non-target sidebands, improving the signal quality of the millimeter-wave signal and the overall performance of the system.

[0055] In a possible implementation manner, the light wave output by the laser is first injected into the polarization controller 50. At this time, the azimuth angle of the polarization controller 50 is 45°, and then passes through a 1×4 optical splitter. The light wave is divided into 4 linearly polarized lights, which are respectively injected into the 4 polarization modulators 20 PolM1 - PolM4 for modulation. Adjust the azimuth angle of the polarization controller 50 to and adjust the electrical phase offsets loaded on the polarization modulators 20 (PolM) from the first path to the fourth path to be 0, , , .

[0056] Preferably, the polarization modulator 20 is configured to modulate the introduced radio frequency signal onto the corresponding polarized light to obtain the corresponding optical signal; wherein,

[0057] The rule for modulating the introduced radio frequency signal onto the corresponding polarized light is:

[0058]

[0059] wherein, and are respectively the polarization components of the output optical signal in the x direction and the y direction; is the amplitude of the introduced polarized light; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced radio frequency signal; is the modulation depth; j is the imaginary unit; t is time; is the electrical phase offset of the introduced radio frequency signal.

[0060] 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 respectively, and the optical signal in each direction is affected by the modulation of the radio frequency signal. In this process, the modulation depth of the radio frequency signal determines the intensity of the modulation, and the angular frequency of the radio frequency signal affects the time variation characteristics of the modulation signal. In addition, the electrical phase offset of the radio frequency 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 optimized conditions for subsequent coherent superposition. Finally, the modulated optical signal contains the phase modulation information of the radio frequency signal in two orthogonal polarization directions respectively. This modulation method is used to generate high-frequency millimeter-wave signals in the photon frequency doubling system.

[0061] In a possible implementation manner, taking the 4-channel polarization modulator 20 exemplified above as an example, the output of the first PolM is:

[0062] .

[0063] The output of the second PolM is:

[0064] .

[0065] The output of the third PolM is:

[0066] .

[0067] The output of the fourth PolM is:

[0068] .

[0069] The signal output from the PolM is injected into the polarization analyzer 30 (pol), and the output signal is:

[0070] .

[0071] It should be noted that, in the specific embodiments of the solution of the present invention, a four-channel polarization modulator 20 is taken as an example, but this modulation method is not limited to the four-channel polarization modulator 20, but can be extended to configurations of any number of polarization modulators 20. The number of polarization modulators 20 in the system depends on the frequency multiple of the target millimeter-wave signal, the complexity of the system, and the optimization requirements for the coherent combination effect of the optical signals.

[0072] In a multi-channel polarization modulation system, each polarization modulator 20 receives polarized light from a continuous-wave laser 10 and modulates it with radio-frequency signals with different phase offsets, so as to form optical signals with a specific phase relationship in two orthogonal polarization directions. After appropriate phase control, these optical signals enter an analyzer 30 for final coherent superposition. Whether it is a four-channel, six-channel or more-channel polarization modulator 20, the system needs to initially set the electrical phase offset based on the principle of uniform distribution and solve it through an optimization algorithm, so that the target optical sidebands are optimally coherently superposed during 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 frequency doubling, twelve-fold frequency doubling or even generation of millimeter-wave signals with higher frequencies. Therefore, this method is applicable to various photon frequency doubling architectures, providing a flexible and efficient signal generation solution for high-frequency applications such as millimeter-wave and terahertz-wave communication and radar.

[0073] Preferably, the analyzer 30 is configured to: sequentially select two optical signals for coupling according to the principle of the smallest phase difference to form a plurality of 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 second-level coupled optical signals; and so on recursively until all optical signals are coherently combined to obtain coupled optical signals.

[0074] In the embodiment of the present invention, in the photon frequency doubling system of a ten-fold frequency millimeter-wave signal, the function of the analyzer 30 is not only to transmit optical signals in a specific polarization direction, but also to undertake the core task of coherent superposition of optical signals. In order to ensure that the finally synthesized optical signal has the best coherent characteristics, the analyzer 30 adopts a step-by-step coupling strategy based on the principle of the smallest phase difference to gradually optimize the coherent synthesis process of the optical signals, thereby enhancing the target optical sidebands (such as ±5th order) and suppressing the non-target optical sidebands (such as ±3rd order, ±7th order).

[0075] Specifically, according to the principle of optimal phase matching, the analyzer 30 first selects two optical signals with the smallest phase difference from the optical signals output by multiple input polarization modulators 20 for preliminary coupling to form multiple first-level coupled optical signals. The goal of this stage is to ensure that optical signals with close phases are first coherently combined to reduce interference loss and optimize the enhancement effect of the target sideband. Subsequently, among the first-level coupled optical signals, signal pairs with the smallest phase difference are continuously selected for secondary coherent synthesis to generate second-level coupled optical signals. This process is recursively repeated until all optical signals complete the final coherent synthesis to obtain optimized coupled optical signals, ensuring that the superposition of the target optical sideband reaches the optimal state.

[0076] Based on the solution of the present invention, in a traditional photon frequency doubling system, if a fixed optical signal synthesis method is adopted without considering the phase matching of the input optical signals, it may lead to a reduction in the coherence efficiency of the target optical sideband, and even cause interference weakening, thereby affecting the output power of the millimeter-wave signal. In addition, if the coupling order of the optical signals is not reasonably arranged during the synthesis process, non-target optical sidebands (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 optical sideband suppression ratio (OSSR) and 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 signals can be effectively optimized, maximizing the coherent superposition of the target optical sideband and suppressing the interference of non-target sidebands, thereby improving the output power and spectral quality of the millimeter-wave signal. The solution of the present invention effectively improves the purity and output power of the millimeter-wave signal by gradually optimizing the optical signal coupling process to ensure optimal phase matching. Finally, this strategy enables the optical signal received by the photodetector 40 to reach the optimal coherent 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 communication and radar.

[0077] In a possible implementation, when the polarization angle of the analyzer 30 is the optical signals output by the polarization modulator 20 can be described as:

[0078] .

[0079] Further, taking four-way polarized light as an example, the optical signals output by the 3rd and 4th parallel polarization modulators 20 first pass through phase shift and then are coupled with the optical signals output by the 1st and 2nd parallel polarization modulators 20, and then injected into the analyzer 30 with a polarization angle of The output optical wave signal can be described as:

[0080]

[0081] Preferably, applying the Jacobi-Anger formula and expanding the above formula, we get:

[0082]

[0083] Since, , , at this time, the 3rd-order optical sideband and the 7th-order optical sideband tend to 0, and the output optical wave can be expressed as:

[0084] .

[0085] Preferably, the polarizer 30 is further configured to: set the corresponding polarization angle with the goal of maximizing the transmission of the ±5th-order optical sidebands; perform selective transmission on the coupled optical signal based on the set polarization angle to obtain the target optical signal.

[0086] In the embodiment of the present invention, in the ten-fold frequency millimeter-wave signal generation system, the polarizer 30 is not only responsible for the coherent synthesis of the optical signal, but also performs selective transmission on the final optical signal by reasonably setting the polarization angle to maximize the energy of the target optical sidebands (±5th order) and suppress the interference of non-target sidebands (such as ±3rd order, ±7th order). To achieve this goal, the polarization angle of the polarizer 30 needs to be accurately set according to the characteristics of the input coupled optical signal to ensure the optimal matching between the polarization direction of the target optical sidebands and the transmission direction of the polarizer 30.

[0087] Specifically, after the coherent coupling of the optical signal is completed, the optical signal input to the polarizer 30 still contains multiple optical sidebands of different orders. Among them, the ±5th-order optical sidebands are the target components for millimeter-wave signal generation, while other sidebands such as ±3rd order and ±7th order belong to interference signals. Since the 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 partially transmit into the photodetector 40, reducing the purity of the millimeter-wave signal. Therefore, the polarization angle of the polarizer 30 needs to be optimized so that the transmittance of the ±5th-order optical sidebands reaches the maximum while suppressing the transmission of other sidebands.

[0088] To achieve this optimization goal, the system adopts a dual-objective optimization strategy:

[0089] Objective 1: Maximize the transmission power of the ±5th-order optical sidebands: Set the polarization angle of the polarizer 30 so that the polarization direction of the ±5th-order optical sidebands is completely matched with its transmission direction to ensure the maximum transmission of the optical signal. Determine the optimal polarization angle through experiments or simulation calculations to make the transmittance of the ±5th-order sidebands reach the highest.

[0090] Objective 2: Minimize the transmission of non-±5 order optical sidebands (±3 order, ±7 order, etc.): Since the polarization directions of ±3 order and ±7 order optical sidebands are different from that of ±5 order, the polarizer 30 can reduce the projection transmittance of these interfering light components by setting an appropriate polarization angle, ultimately reducing the power of non-target optical sidebands. This process can calculate the polarization directions of optical sidebands of each order based on Bessel functions and use an optimization algorithm to solve for the optimal polarization angle to enhance the target optical signal while attenuating the interfering optical signal.

[0091] Based on the solution of the present invention, the polarizer 30 realizes the 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 interfering optical sidebands such as ±3 order and ±7 order. This method significantly improves the quality of the optical signal input to the photodetector 40, resulting in a higher output power of the millimeter-wave signal and better signal purity, making it suitable for high-frequency applications such as 6G communication and radar.

[0092] Preferably, the target optical signal is expressed as:

[0093]

[0094] where is the target optical signal; A is the amplitude factor; and are the Bessel coefficients representing the modulation intensity of the ±5 order optical sidebands; is the angular frequency of the introduced polarized light; is the angular frequency of the introduced radio frequency signal; is the set polarization angle; is the modulation depth; j is the imaginary unit; t is time.

[0095] In a possible implementation, the optical wave output by the polarizer 30 is subjected to a Bessel function expansion of the first kind to obtain the corresponding expansion function, such as Figure 2 . As can be seen from the figure, when the modulation coefficient is 3.83, the first-order function approaches zero. Thus, by adjusting the amplitude voltage of the radio frequency drive signal to control the modulation coefficient such that the modulation coefficient , at this time the first-order optical sideband . At this time, the output optical wave only contains the 5th order optical sideband, and the finally output optical wave signal can be written as:

[0096]

[0097] Based on this, the target optical signal is expressed as:

[0098]

[0099] 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 part is the original optical carrier frequency of the polarized light, and the other part 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 sidebands, while the low-order and high-order interference sidebands have been effectively suppressed. This means that through coherent superposition and the selective transmission of the polarization analyzer 30, the optimized system enhances the target optical sidebands while minimizing the intensity of the non-target optical sidebands. 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.

[0100] Preferably, the photodetector 40 is configured to: perform square-law detection on the target optical signal to obtain the corresponding ten-fold frequency millimeter-wave signal; wherein, the rule for performing square-law detection on the target optical signal is:

[0101]

[0102] Wherein, is the output signal of the photodetector 40; represents taking the real part; is the target optical signal; is the normalized optical signal amplitude; is the modulation efficiency of the ±5th order optical sidebands; is the angular frequency of the introduced radio frequency signal; t is time.

[0103] In the embodiment of the present invention, after the target optical signal undergoes polarization modulation, coherent superposition, and the selective transmission of the polarization analyzer 30, it mainly contains the components of the positive and negative fifth-order optical sidebands. The photodetector 40 uses the photoelectric conversion effect to convert the input optical signal into an electrical signal and extracts the frequency information of the millimeter-wave signal through square-law detection.

[0104] 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 the positive and negative fifth-order optical sidebands, after the photodetector 40 performs the square operation, a low-frequency DC component and an AC component with a frequency ten times that of the radio frequency signal as the main frequency will be obtained. Among them, the component with a frequency ten times that 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 sidebands, 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 retains the ten-fold frequency radio frequency component, thus realizing the generation of high-frequency millimeter-wave signals.

[0105] Based on the solution of the present invention, by optimizing the coherent superposition and the polarization angle setting of the polarization analyzer 30, the transmittance of the positive and negative fifth-order optical sidebands can be effectively improved, while suppressing the non-target optical sidebands, making the signal input to the photodetector 40 purer, thereby enhancing the sideband suppression ratio of the millimeter-wave signal. In addition, the process of square-law detection ensures that the system can stably output a millimeter-wave signal with a ten-fold frequency, which is suitable for applications such as high-frequency communication and radar. Overall, this method realizes an efficient and low-loss millimeter-wave signal generation solution through the combination of optical modulation and optoelectronic conversion.

[0106] Embodiment:

[0107] To verify the accuracy of the millimeter-wave generation solution result of the present invention, based on the principle of the 4-channel polarization modulator 20, a simulation model was constructed using a simulation experimental platform. Among them, the frequency of the continuous-wave laser is 193.1 THz, the power is 20 dBm, the frequency of the RF drive signal is 10 GHz, the RF amplitude is 1.22 V, the azimuth angle of the polarization controller 50 is 45 degrees, and the angle of the polarization analyzer 30 is -45°. The responsivity of the photodetector 40 is 1 A / W. After the optical wave signals output by the 4-channel PolM are injected into the polarization analyzer 30, only the positive and negative fifth-order optical sidebands are included, and the optical carrier suppression ratio reaches 60.04 dB. The simulation diagram is as Figure 3 shown. Finally, the optical wave signal output by the polarization analyzer 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 that of the RF drive signal. As Figure 4 shown, at this time, the RF sideband suppression ratio reaches 56.9 dB.

[0108] Figure 5 is the flowchart of the method for generating a ten-fold frequency millimeter-wave signal provided by an embodiment of the present invention. As Figure 5 shown, an embodiment of the present invention provides a method for generating a ten-fold frequency millimeter-wave signal, and the method includes:

[0109] Step S10: Divide the original optical carrier into multiple polarized lights, and introduce each polarized light into the corresponding polarization modulator 20 respectively.

[0110] Specifically, the continuous-wave laser 10 generates a stable optical carrier signal, usually linearly polarized light, to ensure good polarization consistency in the subsequent modulation process. The original optical carrier is divided into multiple optical signals through an optical splitter, and the polarization state of each optical signal is adjusted by the polarization controller 50 to adapt to the working modes 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. Then, the adjusted multiple optical signals are respectively introduced into the corresponding polarization modulators 20, laying a foundation for subsequent RF modulation and coherent synthesis.

[0111] Step S20: Introduce radio frequency signals with different electrical phase offsets to each polarization modulator 20, so as to modulate the introduced radio frequency signals onto the corresponding polarized light based on each polarization modulator 20 to obtain corresponding optical signals.

[0112] Specifically, each polarization modulator 20 not only receives the optical signal after beam splitting and polarization adjustment, but also needs to input radio frequency signals with different electrical phase offsets. The frequency of the radio frequency signal determines the position of the optical sidebands 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 radio frequency signal is applied to the polarization modulator 20, so that the input polarized light is respectively loaded with radio frequency modulation signals in two orthogonal polarization directions, thereby forming a series of optical sidebands in the spectrum. Finally, the optical signals output by each path of the polarization modulator 20 all contain positive and negative multiple-order optical sidebands, and the output phase of each polarization modulator 20 is affected by the electrical phase offset of its input radio frequency signal, providing a control means for subsequent coherent superposition.

[0113] Step S30: Based on the phase differences of the optical signals, perform tube signal coupling step by step to obtain corresponding coupled optical signals.

[0114] Specifically, the optical signals output by each polarization modulator 20 may be different in polarization direction and phase. Therefore, before entering the photodetector 40, coherent coupling of the optical signals is required. First, according to the principle of the smallest phase difference, select two signals with the closest phases from all the optical signals for preliminary coupling to form a first-level coupled optical signal. Then, on the basis of the first-level coupled optical signal, continue to select the signal with the closest phase for second-level coupling, and so on, until all the optical signals complete the final coherent synthesis. In this process, the role of the analyzer 30 is crucial. It not only transmits the optical signals in a specific polarization direction, but also maximizes the transmittance of the target optical sidebands and suppresses the interference of non-target sidebands by optimizing the polarization angle setting, so that the final coupled optical signal has better spectral purity.

[0115] Step S40: Based on the photodetector 40, convert the coupled optical signal into a corresponding ten-fold frequency millimeter wave signal.

[0116] Specifically, after the coherently coupled optical signal enters the photodetector 40, it is converted into an electrical signal through the optoelectronic 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. During this process, beat frequency effects occur between the positive and negative fifth-order optical sidebands in the optical signal, and their frequency difference is equal to ten times the frequency of the input radio frequency signal. Therefore, the frequency of the finally output millimeter-wave signal is equal to ten times the frequency of the radio frequency signal. To ensure the high purity of the millimeter-wave signal, this step relies on the optimized control of the optical signal phase and polarization in the previous step. Finally, after the conversion by the photodetector 40, the system successfully outputs a ten-fold frequency millimeter-wave signal with high frequency and high stability, which can be widely applied to high-frequency technical fields such as 6G communication, radar detection, and terahertz imaging.

[0117] Preferably, the method further includes: performing an adaptive adjustment of the polarization direction of the polarized light based on the polarization controller 50 so that each path of polarized light matches the working mode of the corresponding polarization modulator 20.

[0118] Those skilled in the art can understand that all or part of the steps in the method for implementing the above embodiments can be completed by instructing relevant hardware through a program. This program is stored in a storage medium and includes several instructions to enable a single-chip microcomputer, a chip, or a processor to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical disks, etc., which can store program codes.

[0119] The optional embodiments of the present invention have been 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 scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. Additionally, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any suitable manner without conflict. To avoid unnecessary repetition, the embodiments of the present invention do not separately describe various possible combination methods.

[0120] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the embodiments of the present invention, and it should also be regarded as the content disclosed by 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 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. Solving 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; The polarizer 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; wherein, 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; and this process is repeated recursively until all optical signals are coherently combined to obtain a 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 2, 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.

4. The system according to claim 1, 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.

5. The system according to claim 4, 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 modulation depth; j is the imaginary unit; t is time.

6. The system according to claim 4, 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 amplitude factor; It is the square of the Bessel coefficient of the modulation intensity of the ±5th order optical sideband, which is used to reflect the change of the optical signal intensity; is the angular frequency of the introduced RF signal; t is time.

7. 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 6, 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.

8. The method according to claim 7, 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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