An accurate electromagnetic interference method based on spatial power synthesis

Abstract

The present application belongs to the technical field of electronic countermeasure, and particularly relates to a precise electromagnetic interference method based on spatial power synthesis, which comprises seven stages of city low-altitude safety demand analysis, parameter configuration construction, amplitude and phase regulation, frequency offset optimization iteration, beamforming, time domain energy residence control and effect evaluation. The technical scheme provided by the present application comprehensively considers the problems of free space propagation loss and time domain beam drift, reduces the beam width and improves the interference resolution, can implement precise and controllable electromagnetic interference on the target at a specified distance and angle in the city low-altitude, reduces the incidental interference on the legal communication and navigation equipment in the non-target area, and is suitable for scenes such as city low-altitude security, illegal unmanned aerial vehicle rapid management and control, and electromagnetic protection of important public facilities.

Description

Technical Field

[0001] This invention relates to the field of electronic countermeasures technology, and in particular to a precise electromagnetic interference method based on spatial power synthesis. Background Technology

[0002] With the accelerated opening of urban low-altitude airspace, the application of drones, low-altitude aircraft, and integrated air-ground communication and navigation equipment is becoming increasingly widespread. Urban low-altitude airspace has become a core area for public safety, characterized by dense populations, dense equipment, and a highly complex electromagnetic environment. Frequent safety issues such as illegal drone intrusions, low-altitude communication interference, navigation signal deception, and violations of flight control regulations pose serious threats to airport airspace, protection of important locations, and urban public safety. Achieving precise, controllable, and low-collateral electromagnetic control of low-altitude targets has become a key technological requirement for urban low-altitude safety governance.

[0003] Traditional low-altitude airspace control relies on electromagnetic interference methods that employ broadband and omnidirectional suppression, which suffer from low energy efficiency, uncontrollable interference range, and the potential to cause collateral interference to legitimate communications, navigation, and public electronic equipment in the surrounding area. These methods are insufficient to meet the precise control requirements in the complex electromagnetic environment of cities.

[0004] Frequency-controlled arrays, due to the simultaneous angle and distance dependence of their beams, theoretically possess two-dimensional distance-angle resolution, providing a new technical path for precise electromagnetic control at low altitudes. However, existing frequency-controlled array technologies still have the following three shortcomings in practical applications:

[0005] First, existing frequency-controlled array beam analysis and optimization generally neglect the path loss that electromagnetic waves experience as distance increases during free-space propagation. This simplification leads to a discrepancy between the theoretically optimized beam performance and the actual interference effect after deployment, especially in low-altitude urban scenarios at the one-kilometer level, where the impact of path loss on the interference power budget is not negligible.

[0006] Secondly, the frequency offset differences among the elements of the frequency-controlled array cause the beam peak to continuously drift over time, which is an inherent physical characteristic of the frequency-controlled array. Existing research mainly focuses on optimizing the radiation pattern shape at a single moment, lacking effective control methods for this time-varying drift characteristic. In continuous wave transmission mode, the beam peak gradually deviates from the target point over time, and after a long period of time, the interference energy cannot be effectively concentrated in the designated area, making the frequency-controlled array difficult to use in actual jamming missions.

[0007] Third, existing beam optimization evaluations of frequency-controlled arrays typically use sidelobe levels and main lobe widths of the single-moment radiation pattern as indicators, without considering the actual energy distribution under time accumulation effects. For practical applications requiring continuous interference, single-moment snapshots cannot accurately reflect the interference energy level received in the target area and the degree of collateral interference to non-target areas.

[0008] To overcome the limitations of the existing technologies, this invention proposes a precise electromagnetic interference method based on spatial power synthesis. It introduces the free-space path loss factor into the frequency-controlled array signal propagation model, suppresses energy dissipation caused by time-varying beam drift through time-domain energy retention control, periodically compensates for the inherent time-varying beam drift of the frequency-controlled array, and uses time-integrated energy distribution as the evaluation criterion. This significantly improves the directional accuracy and engineering applicability of electromagnetic interference, meeting the needs of precise interference for urban low-altitude safety management. Summary of the Invention

[0009] The purpose of this invention is to provide a precise electromagnetic interference method based on spatial power synthesis, which aims to improve the directional accuracy of electromagnetic interference and meet the needs for precise electromagnetic control in complex low-altitude electromagnetic environments in cities.

[0010] To achieve the above objectives, the present invention provides a precise electromagnetic interference method based on spatial power synthesis, comprising the following steps:

[0011] S1. By analyzing the safety control requirements under the complex electromagnetic environment of urban low-altitude environment, the target interference area range and the interference threshold are defined; the interference threshold is: the peak electromagnetic energy of the target interference area is attenuated by no less than 10dB compared with the energy at a representative detection point in the non-interference area.

[0012] S2. Based on the target interference area range and interference threshold, determine the core system parameters of the frequency control array, including array arrangement, reference carrier frequency, array element spacing, number of array elements, and basic frequency offset. Construct a frequency control array model with symmetrical subarray structure and positive and negative logarithmic frequency offset scheme, determine the transmission frequency of each array element, and construct a signal propagation model that incorporates free space path loss factor.

[0013] S3. Based on the signal propagation model, extract the distance and angle difference phase terms from each array element to the target point, design the corresponding amplitude weighting and phase compensation coefficients, and construct the amplitude weighting and phase compensation signal propagation model.

[0014] S4. Construct a fitness function with the constraints of the lowest electromagnetic energy at non-interference points and the narrowest main lobe of the beam at interference points. Use a genetic algorithm to iteratively optimize the frequency offset of each array element to obtain the optimal combination of array element frequency offsets.

[0015] S5. Input the optimal array element frequency offset combination into the amplitude-weighted and phase-compensated signal propagation model to generate a low-sidelobe point-shaped interference static beam and verify whether the static beam meets the interference threshold.

[0016] S6. Add a switch to the transmission link of each array element, and control the periodic on and off of the transmitted signal of each array element through the switch, so that the beam peak returns to the target interference point at the beginning of each switching cycle, compensates for the time-varying drift of the frequency control array beam, and calculates the global time integral energy distribution.

[0017] S7. Using the time-integrated energy distribution pattern as the evaluation basis, determine whether the addition of the switch meets the requirements for accuracy and low accidental injury in urban low-altitude safety control based on the interference radiation effect.

[0018] More preferably, in step S1, the target interference airspace is a square area with a side length of 150 meters centered on a specified coordinate point. This area is set in the low-altitude space within 1 kilometer of the interference source. The representative detection point in the non-interference area is selected at a position 75 meters before and after the target center point along the distance dimension.

[0019] More preferably, in step S2, the symmetrical subarray structure is to divide all uniformly linearly arranged array elements into two groups of subarrays; the positive and negative logarithmic frequency offset scheme is that the frequency offset of the array elements in the first half of the subarray decreases logarithmically as the array element number increases, and the frequency offset of the array elements in the second half of the subarray increases logarithmically as the array element number increases. The frequency offset distribution of the positive and negative logarithmic frequency offset scheme is used to achieve decoupling of the two dimensions of beam distance focusing and angle pointing.

[0020] More preferably, the frequency control array core system parameters in step S2 include the array element arrangement, reference carrier frequency, array element spacing, total number of array elements, basic frequency offset, target point spatial coordinates, and spatial observation point coordinates.

[0021] More preferably, the genetic algorithm execution process in step S4 includes: encoding each array element frequency offset combination into an independent individual, randomly generating an initial population; using a fitness function to quantify and score each frequency offset individual; sequentially performing selection, crossover, and mutation operations to iteratively update the population; and outputting the frequency offset combination with the best fitness within the population; wherein the fitness function calculation logic is the target point energy value minus the total penalty caused by insufficient energy decay of non-target region sidelobes and detection points.

[0022] More preferably, the method for determining the switching period in step S6 is as follows: under the optimal frequency offset parameter condition, simulate the attenuation curve of the normalized interference energy of the target point with the transmission duration, and select the duration corresponding to the attenuation of the peak energy of the target point by 1dB as the single switching period; after the switch is turned on for a single period, it is turned off, and then when it is turned on again, the initial phase of all array element carriers is reset so that the beam peak is re-aligned with the target point.

[0023] More preferably, the comprehensive judgment logic in step S7 is as follows: extract the energy values ​​of the target center point and the detection points 75 meters before and after in the time integral energy distribution map. When the energy attenuation values ​​of both detection points and the target point exceed 10dB, it is determined that the positive and negative logarithmic frequency deviation scheme combined with the switching timing scheme meets the usage standards of precise electromagnetic control and low collateral damage in urban low-altitude areas.

[0024] Compared with the prior art, the advantages of the present invention are as follows: 1. The present invention introduces the free space path loss factor into the frequency control array signal propagation model, corrects the deviation between simulation and actual effect caused by the traditional theory ignoring propagation attenuation, improves the authenticity of the model calculation results, and is more in line with the actual engineering scenario of urban low-altitude one-kilometer level.

[0025] 2. By adopting a symmetrical subarray and a positive and negative logarithmic frequency offset structure, the beam distance and angle dimensions are decoupled. Combined with amplitude-weighted phase compensation, the array element signals are superimposed in phase at the target point to form a point-like interference beam, which compresses the beam width and improves the interference resolution.

[0026] 3. By using a genetic algorithm to iteratively optimize the frequency offset of pairs, the fitness function takes into account both the energy of the target point and the attenuation constraints of the non-interference region, effectively reducing the sidelobe level and ensuring that the energy attenuation of the non-target region reaches the 10dB threshold, thereby reducing the incidental interference.

[0027] 4. By periodically switching the array element link on and off and resetting the initial phase of the carrier, the inherent time-varying beam drift problem of the frequency control array is periodically compensated, the interference energy dissipation under long-term operation is suppressed, and the inherent defect of beam offset failure during continuous transmission is solved.

[0028] 5. Abandoning the single-moment snapshot orientation map evaluation method, the time integral energy distribution is used as the evaluation basis to restore the real energy distribution of the entire domain under actual continuous interference, and the evaluation results are more in line with the actual operating conditions. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the logarithmic frequency offset array frequency control array structure mentioned in this invention;

[0030] Figure 2 This is a comparison diagram of the frequency control array partial sequences optimized by the genetic algorithm mentioned in this invention;

[0031] Figure 3 This is the energy distribution diagram of the logarithmic frequency offset array in this invention;

[0032] Figure 4 This is the distance-dimensional energy map based on a logarithmic frequency bias array in this invention;

[0033] Figure 5 This is the angular dimension energy diagram based on the logarithmic frequency polarizer array in this invention;

[0034] Figure 6 This is the energy distribution diagram of the frequency control array optimized by the genetic algorithm in this invention;

[0035] Figure 7 This is the energy map of the range dimension of the frequency control array optimized by the genetic algorithm according to the present invention;

[0036] Figure 8This is the frequency control array angle dimension energy map optimized by a genetic algorithm according to the present invention;

[0037] Figure 9 This is a time-energy curve of the interference target location in this invention;

[0038] Figure 10 This is a distance-dimensional energy curve diagram at different times according to the present invention;

[0039] Figure 11 This is the energy distribution diagram of the frequency-controlled array after time-domain integration according to the present invention;

[0040] Figure 12 This is a flowchart of the method of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used in this invention mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0042] This invention proposes a precise electromagnetic interference method based on spatial power synthesis. The overall process includes seven stages: First, determining the target interference airspace range and interference threshold based on urban low-altitude safety control requirements; second, configuring the core system parameters of the frequency control array according to the interference requirements, constructing a frequency control array model with a symmetrical subarray structure and positive and negative logarithmic frequency offsets, and introducing the free space path loss factor into the signal propagation model so that the signal amplitude of each array element propagating to any point in space attenuates with the propagation distance according to actual physical laws; third, performing amplitude weighting and phase modulation on the output signals of each array element so that the phases of the signals of each array element are superimposed in phase at the target point to form point energy. Fourth, with the optimization objectives of minimizing the energy at non-interference points and narrowing the main lobe at interference points, a genetic algorithm is used for iterative optimization to obtain the optimal array element frequency offset combination; fifth, the optimized frequency offset parameters are input into the frequency-controlled array model to generate a low-sidelobe, directional, and precise point-like interference beam; sixth, considering the inherent time-varying drift characteristics of the frequency-controlled array beam peak, periodic on / off control of the transmitted signals of each array element is implemented through switching to periodically compensate for the beam drift, ensuring that the interference energy continuously converges within the target area; seventh, the time-integrated energy distribution pattern is used as the evaluation basis to compare the interference radiation effects before and after optimization to determine whether the accuracy and low false alarm requirements are met. The complete method flow of this invention implementation case is shown in [link to implementation details]. Figure 12 .

[0043] This implementation case presents a precise electromagnetic interference method based on spatial power synthesis, including the following steps;

[0044] Step 1: Define the target interference area, determine the quantification interference threshold, and identify the non-interference area and detection point locations.

[0045] This case study focuses on precise electromagnetic control of low-altitude targets such as illegal drones in urban low-altitude environments. The electromagnetic environment in urban low-altitude zones is highly complex, containing numerous legal communication base stations, satellite navigation receivers, civil aviation radio navigation equipment, and other sensitive electronic facilities. Therefore, electromagnetic interference must be precisely limited to its effective range to avoid collateral damage to non-target areas.

[0046] 1.1 Define the interference area clearly; determine the effective range of the target interference area based on the actual control requirements. In this implementation case, the target interference area is set as a square area with a side length of 150 meters centered on a specified coordinate point. The center point of this area is the target point where electromagnetic interference is expected to be implemented. This square area is located at any position within one kilometer of the interference source, covering the typical effective range for controlling illegal low-altitude drones in urban areas.

[0047] 1.2. Define the non-interference region: The non-interference region refers to all spatial areas outside the target interference region. In this method, the focus is on the transition regions immediately adjacent to the target interference region on both sides of the distance dimension. That is, along the direction of the target point, the spatial locations adjacent to the target region before and after it. These locations are closest to the target point and are most easily affected by the side lobes or tails of the interference energy. In this implementation case, 75 meters before and after the center of the target interference region along the distance dimension are used as representative detection points in the non-interference region to measure the degree of attenuation of interference energy from the target region to the non-target region.

[0048] 1.3 Determine the interference threshold; the interference threshold means that the electromagnetic energy level within the target interference area must be higher than the electromagnetic energy level at the representative detection point in the non-interference area by a preset decibel value. In this implementation case, the preset decibel value is set to 10 dB, meaning that the peak interference energy within the target interference area must be at least 10 dB higher than the interference energy at the representative detection point in the non-interference area. This threshold meets the technical requirements for precise, controllable, and low-damage electromagnetic control in urban low-altitude airspace.

[0049] The above-mentioned definition of the target interference spatial range, non-interference area, and interference threshold serves as the basis for subsequent array parameter design, frequency offset optimization, and effect evaluation, and is applied throughout the entire methodology.

[0050] Step 2: Determine the core parameters of the array, construct a symmetric subarray and a positive and negative logarithmic frequency offset array model, and introduce the free space path loss factor into the signal propagation model.

[0051] Based on the target interference area and interference threshold defined in Step 1, this step determines all the core system parameters of the frequency control array, constructs a frequency control array model with a symmetrical subarray structure and positive and negative logarithmic frequency offset scheme, completes the mathematical modeling of the entire link signal propagation from the transmitted signal to the target energy distribution, and constructs a signal propagation model that incorporates the free space path loss factor.

[0052] 2.1 Array Geometry and Parameter Definition; This implementation uses a logarithmic frequency offset array frequency-controlled array, which consists of... Each array element ( (Values ​​are even numbers) along The elements are arranged at equal intervals along the axes to form a uniform linear array, with the leftmost element of the array serving as the reference element (element number). The signal transmission frequency of the reference array element is the reference carrier frequency. Its corresponding reference wavelength and array element spacing They are defined as follows: ; ;in, The speed of light, which is also the speed at which electromagnetic waves propagate in free space, and the spacing between array elements. Taking half of the reference wavelength is the standard engineering value for suppressing grating lobes in a uniform linear array.

[0053] To achieve a symmetrical subarray distribution, the entire array is divided into two subarrays in sequence: element index... to For subarray 1, the element number is... to For subarray 2; using positive and negative logarithmic frequency offsets as the initial frequency offset reference, the frequency offset of the first half of the array elements... Follow-up element sequence number The increase of shows a logarithmic decreasing trend, which is _____. Multiplying by the fundamental frequency offset The frequency offset of the second half of the array element follows The increase of shows a logarithmic increasing trend, which is... Multiplying by the fundamental frequency offset This positive and negative logarithmic frequency offset structure is key to achieving decoupling between the distance and angle dimensions. The relationship between the two is as follows: Figure 1 As shown.

[0054] No. The actual transmit carrier frequency of each element From the reference carrier frequency The frequency offset of the superimposed array element get;

[0055] The first in the array Spatial position of each array element (with the reference element as the origin, along) (Positive axis direction) is the array element number m multiplied by the array element spacing. ;

[0056] Define the coordinates of any point in space as ,in This represents the distance from any point in space to the reference array element. Represents any point in space and The angle between axes (i.e., the angle at which the target deviates from the front of the array).

[0057] In this implementation case, the typical values ​​for each core parameter are: the array elements are arranged in a uniform linear pattern, and the reference carrier frequency is... Array element spacing Meter, fundamental frequency offset Number of array elements Reference wavelength Meters, the target interference point position is set to That is, the target is located 500 meters directly in front of the reference array element. The logarithmic frequency offset distribution of the 32 array elements calculated based on the above parameters is as follows: Figure 2 As shown. The derivation and analysis of the signal model below are all based on the above parameter configuration.

[0058] 2.2 Derivation of the frequency-controlled array signal propagation model: Based on the above array geometry and frequency offset definition, a mathematical model of the entire process of electromagnetic waves being emitted from each array element, propagating through free space, and superimposed at any point in space is realized, and a complete signal equation for calculating the beam energy at any spatial location is derived.

[0059] 2.2.1 Derivation of the single-element transmitted signal model; The baseband waveform shared by all elements is derived. Modulated to the carrier frequency unique to this array element Above, and the complex carrier signal multiplied by the transmitted carrier frequency. Receive array element transmission signal ;in, The imaginary unit, The baseband waveforms of each array element are continuous-time variables. The same, only in the transmit carrier frequency There are some differences.

[0060] 2.2.2 Derivation of the Propagation Signal Model and Introduction of the Free Space Path Loss Factor; The signal is radiated into space from each array element in the form of electromagnetic waves. When any point in space... Satisfying the far-field condition (i.e.) ), then the first Distance from each element to any point in space It can be simplified to the first-order Taylor approximation as minus The physical meaning of this approximation is: since the distance *r* from any point in space to the reference array element satisfies the far-field condition, the difference in distance from each array element to the target is mainly reflected in the path difference. superior.

[0061] The signal is radiated into space from each array element in the form of electromagnetic waves, and its propagation speed is the speed of light. Then the signal is generated by the array elements. There is a time delay in propagation to any point in space. for Divide by Meanwhile, when electromagnetic waves propagate in free space, their power density decreases with the square of the distance according to the spherical diffusion law. This is reflected in the signal amplitude as a free space path loss factor that is inversely proportional to the propagation distance. for Divide by Propagation distance of each array element under far-field conditions All are approximately equal to the distance from any point in space to the reference array element. ,but The elements of each array are approximately equal. Divide by The introduction of this factor enables the beam energy calculation results of this model to reflect the actual physical propagation attenuation, rather than relying solely on the simplified analysis of the normalized radiation pattern. This is one of the important differences between this invention and existing frequency control array theory analysis.

[0062] Combining the time delay and path loss mentioned above, at any point in space The received by the first The signal emitted by each element Free space path loss factor Multiplied by the baseband waveform after propagation delay and the delayed complex carrier signal This formula reflects the physical law that the transmitted signal of a single array element propagates through free space to reach any point in space.

[0063] 2.2.3 Approximate simplification of envelope delay; Under narrowband signal conditions, when the signal envelope bandwidth... satisfy The signal envelope at the maximum time delay It remains almost unchanged over the time scale, in this implementation case. , rice, , Under these conditions, the signal envelope is The time scale changes extremely slowly, and the difference in envelope delay between the paths of each array element has a negligible impact on the signal amplitude. Therefore, the time delay of the envelope term for all array elements is negligible. The time delay of the reference array element can be used uniformly. Instead, the baseband waveform after propagation delay becomes Under this approximation, the first... The propagation signal of each array element Simplified to free space path loss factor Multiplied by the baseband waveform after propagation delay and the delayed complex carrier signal ;in The expression is ;

[0064] because (In this implementation case, the maximum frequency offset is approximately 3MHz, and the reference carrier frequency is...) =2.4GHz, the two differ by nearly three orders of magnitude), cross term Its contribution to the overall phase is much smaller than that of the same position. If this is negligible in engineering practice, then the phase offset term introduced by the frequency and spatial position differences of each array element becomes... This is the core of subsequent beamforming and pattern analysis.

[0065] 2.2.4 Derivation of target location and signal and beam energy distribution; [The rest of the text appears to be incomplete and requires further context.] By coherently superimposing the signals propagated from each array element to any point in space, the actual sum and signal at any point in space can be obtained. ;

[0066] The magnitude of this summation directly reflects the coherent superposition intensity of electromagnetic waves at any point in space. By calculating the magnitude of the summation signal, the magnitude of the frequency-controlled array at any given time can be obtained. any location in spacetime Beam energy distribution:

[0067] ;

[0068] in, The array factor amplitude describes the energy distribution of the frequency-controlled array in the space-time two dimensions; This represents the magnitude of the free space path loss factor.

[0069] When the frequency deviation of each array element When the positive and negative logarithmic frequency offset distributions defined in step 2.1 are taken, the above array factor summation formula exhibits decoupling characteristics in the range-angle dimensions: beam focusing in the range dimension is controlled by the frequency offset distribution, while beam pointing in the angle dimension is achieved by phase modulation. The independence of the two is the physical basis for this method to achieve precise spatial point-like interference.

[0070] In summary, the complete structure of the frequency-controlled array signal propagation model with free-space path loss constructed in this embodiment is as follows: First, the transmission frequency of each array element is determined based on the array geometric parameters and positive and negative logarithmic frequency offset rules set in 2.1; starting from the original transmission signal of a single array element, the electromagnetic wave spatial propagation delay and free-space path loss are introduced to establish a signal propagation model; the expression is simplified under narrowband signal conditions; then, the arrival of all array elements at the spatial observation point is considered. The signals are coherently superimposed to obtain the total superimposed signal at any location and time in space. By calculating the magnitude of the superimposed signal, the expression for the array amplitude factor carrying the propagation attenuation term is obtained. This refers to a signal propagation model for a frequency-controlled array with free-space path loss. The model's input parameters include array configuration, frequency offset parameters, and spatial coordinates. With time t, the output is the array factor amplitude at the corresponding position, which can quantify the magnitude of the interference energy in the target interference area and the adjacent transition area. This model provides a computational basis for evaluating the attenuation characteristics of interference energy to non-target areas in step 3.

[0071] Step 3: Design the array element weighting coefficients to compensate for the phase difference between the distance and angle dimensions, and achieve in-phase superposition at the target point.

[0072] Based on the frequency-controlled array signal propagation model with free-space path loss established in step two, this step performs amplitude weighting and phase modulation on the transmitted signals of each array element to ensure that the signals of all array elements are aligned with the target interference point. At that point, the electromagnetic interference energy is maximized by superimposing in phase.

[0073] From the simplified expression of the propagation signal in step two, we can see that the first... The signal of each element propagates to any spatial location At that time, its phase offset term for: This phase also depends on the target's angle. and distance and array element number and frequency offset Without any adjustment, the phases of each array element cannot be coherently superimposed at any point in space, making it difficult to achieve the desired energy focusing effect.

[0074] The core idea of ​​this step is to apply preset amplitude weighting and phase compensation to each array element at the transmitting end, so that the signal of each array element propagates in space to the preset target point. Furthermore, when the transmission start time is 0, all differential phase terms are precisely canceled out, and the phase of each signal component at that point is... Multiples of , thus achieving in-phase superposition. Specifically, let the . Amplitude weighting coefficients of each array element for: ;in, This is the basic amplitude coefficient. In this formula, the first exponential term... Used to compensate for frequency offset of each array element Distance to target The introduced distance-dimensional phase difference, the second exponential term Used to compensate for the spatial position and target angle of each array element. An angular phase difference is introduced. After the two terms are superimposed, the initial phase of the transmitted signal of each array element is pre-biased, so that when the signal propagates to... At this point, the phase delay introduced by the path cancels out the preset phase at the transmitting end, meaning that the phase offset of each array element signal at the target point is zero, satisfying the in-phase superposition condition.

[0075] After applying the above amplitude weighting and phase modulation, the frequency control array at any spatial position The expression for the beam energy distribution at a certain point is:

[0076] ;

[0077] The physical meanings of each term in the formula are as follows: For the angular phase difference, when When this term is zero, there is no phase difference between the array elements in the target angular direction. and For the phase difference in the distance dimension, when When this term is zero, there is no distance-dimensional phase difference between each array element at the target distance. and It is a time-varying phase term, unlike the previous two terms, it... The time is zero, and it increases with time. It gradually increases as it increases.

[0078] After amplitude weighting and phase modulation, at the launch start time At that time, all array elements All are zero. If the signals of each array element are precisely in phase and superimposed at the target point, then the beam energy at the target point location... Reaching the global maximum value is Modulus multiplication ;

[0079] When the spatial coordinates deviate from the target point, that is or The phases of each array element differ, causing the summation modulus to decay. However, The term was not eliminated by the weighting coefficient. Over time... Starting from zero, the elements of each array... The elements accumulate at different rates according to their respective frequency offset values, resulting in phase deviations between array elements that vary over time. This is an inherent physical characteristic of frequency-controlled arrays caused by the different transmission frequencies of each array element, and cannot be eliminated by any static amplitude-phase weighting scheme.

[0080] In summary, the complete implementation logic of the array element amplitude and phase modulation designed in this embodiment is as follows: First, based on the frequency-controlled array signal propagation model with free space path loss established in step two, the differential phase terms in the distance and angle dimensions of each array element signal propagating to the target point are extracted; corresponding amplitude weighting and phase compensation coefficients are designed for the two types of phase deviations; the compensation weighting coefficients are superimposed on the transmitting end of each array element to cancel all inherent phase differences introduced during propagation; so that all array element signals at the target interference point... The phase difference at the initial time t=0 is Integer multiples are used to achieve coherent superposition of in-phase signals; combined with the signal propagation model, the beam energy expression for the entire spatial domain after applying weighted compensation is derived. This is a frequency-controlled array signal propagation model with free-space path loss after amplitude weighting and phase compensation, which realizes point-like convergence of electromagnetic energy at the target point. The input parameters of this control scheme include array configuration, array element frequency offset sequence, and target interference point coordinates. The output is the full-time-domain spatial beam energy distribution of each array element after amplitude weighting and phase compensation. It can maximize the interference energy gain at the target point, and at the same time provide an amplitude-weighted and phase-compensated frequency-controlled array signal propagation model with free-space path loss after amplitude weighting and phase compensation for the genetic algorithm in step four to construct the fitness function and quantitatively evaluate the merits of the frequency offset scheme.

[0081] In this implementation case, The amplitude-weighted beam energy distribution diagram calculated at each time step is shown below. Figure 3 This allows for a direct observation of the point-like energy convergence effect at the target point (500 meters, 0°) and the spatial distribution of the side lobes. Along... The distance-dimensional energy curve intercepted in the direction is shown in the figure. Figure 4 ,along The angular energy curve taken at the meter position is shown below. Figure 5 .

[0082] Step 4: Use a genetic algorithm to iteratively optimize the combination of array elements with frequency offset, and use the fitness function to balance the energy of the target point and the attenuation constraint of the non-interference region.

[0083] After amplitude weighting and phase modulation in step three, the frequency-controlled array can form a point-like beam convergence at the target point. However, the positive and negative logarithmic frequency offset scheme in step two cannot meet the interference threshold requirement described in step one. The main lobe of the beam is not narrow enough and the side lobes are too high, resulting in the energy attenuation in the non-interference area not reaching the 10dB target. Therefore, this step introduces a genetic algorithm to iteratively optimize the frequency offset parameters. Without changing the array geometry and amplitude weighting scheme, it searches for the optimal array element frequency offset combination that meets the interference threshold requirement described in step one.

[0084] The core search algorithm of the genetic algorithm has the following steps:

[0085] 4.1 Frequency Offset Coding and Initial Population Construction; The frequency offset values ​​of each array element are arranged in the order of the array elements into a single array. The vector is a real number vector representing a frequency offset scheme (i.e., a genetic individual in the genetic algorithm). The value range of each frequency offset component is bounded by upper and lower limits based on the numerical range of the logarithmic frequency offset in step two, ensuring that the search space covers the region where the potential optimal solution is located. First, a certain number of frequency offset schemes are randomly generated within the space to form an initial population (the population size is 30 in this implementation case), providing a diverse set of basic solutions for subsequent iterative evolution.

[0086] 4.2 Fitness Function Design; The fitness function is the quantitative standard for evaluating each frequency offset scheme using the genetic algorithm. Based on the interference requirements analyzed in Step 1, the fitness function design follows two principles: First, the beam energy at the target interference point should be as high as possible (i.e., the main lobe of the interference point beam should be the narrowest); Second, the energy in the non-interference area (outside the target interference area, especially the representative detection point at a distance of ±75 meters) should be as low as possible compared to the energy at the target point, and the difference must meet the attenuation requirement of 10 dB.

[0087] Based on the above principles, the steps for calculating the fitness function are as follows:

[0088] 4.2.1 Substitute the current frequency offset scheme into the signal propagation model established in step three, and calculate the frequency control array at the target point. The beam energy value at that location is denoted as ;

[0089] 4.2.2 Calculate along the target direction 75 meters above the target point ( The beam energy value (in meters) is denoted as ;

[0090] 4.2.3 Calculate the energy difference between the detection point and the target point. for reduce If a certain individual If the value is higher than -10 dB (i.e., the attenuation is less than 10 dB), then the value generated for this individual is... Add 10 to the penalty amount If a certain individual Below -10dB (i.e., attenuation greater than 10dB), the penalty amount =0;

[0091] 4.2.4 Simultaneously consider the sidelobe energy of all sampling points within the range of 10 meters to 425 meters along the target direction to measure the collateral influence range of the sidelobes on the nearby non-interference area. For this range, a sampling distance is set (in this case, the range is 10 meters to 425 meters, with a total of 415 sampling points), and the energy difference between the points within the range and the target point is calculated. for reduce ;in, The value range is [10, 425]. The energy value at a point within the interval; its total sidelobe penalty within the interval. The sum of penalty values ​​for all sampled points; total penalty amount. for and Add;

[0092] 4.2.5 Final fitness value Energy at the target point Subtract the total penalty A higher fitness level indicates better interference accuracy of the frequency offset scheme.

[0093] 4.3 Genetic Operations and Population Evolution; Based on fitness values, high-fitness, high-quality frequency-biased schemes are selected from the current population as parent individuals. A crossover operation is performed on the selected parent individuals according to a preset crossover probability (0.7 in this implementation): the frequency-biased vectors of the two parent individuals are exchanged at random positions to generate new offspring frequency-biased schemes that inherit the characteristics of their parents. Simultaneously, a mutation operation is performed on the new individuals according to a preset mutation probability (0.2 in this implementation): a small random perturbation is applied to some components of the frequency-biased vector, introducing a solution space region not yet covered by the current population, preventing the algorithm from getting trapped in local optima.

[0094] 4.4 Convergence Judgment and Optimal Frequency Offset Output; Repeat the above population evaluation and genetic operation steps, with the new generation replacing the previous generation to complete one iteration. When the number of iterations reaches the preset threshold of 60 rounds, the average fitness value of the population tends to stabilize and no longer increases, or the fitness value of the current best individual meets the preset optimization accuracy (…), the process continues. and When all values ​​are less than -10 dB, the algorithm is considered converged. At this point, the individual with the highest fitness in the population is the optimal frequency offset distribution scheme, and its corresponding frequency offset sequence is the optimal array element frequency offset combination that satisfies the optimization objective of the frequency control array point beam convergence.

[0095] In this implementation case, a 32-element logarithmic frequency offset subarray is used as the initial solution, and the fitness function is designed according to the aforementioned 10dB decay constraint. After 60 rounds of genetic iterative optimization with a crossover probability of 0.7 and a mutation probability of 0.2, the optimal frequency offset distribution is obtained as follows: Figure 2 The solid curve in the middle is shown ( Figure 2 The dashed line represents the logarithmic frequency offset distribution before optimization, i.e., the original frequency offset, used for comparison. The solid curve represents the GA-optimized frequency offset, i.e., the frequency offset optimized by the genetic algorithm. While maintaining the overall trend of the symmetrical logarithmic structure, the frequency offset values ​​of each array element are automatically adjusted through the search space, resulting in a final beam pattern performance that is significantly better than the initial preset scheme.

[0096] Step 5: Substitute the optimal frequency offset to generate a static low sidelobe point interference beam and verify the static performance.

[0097] The optimal array element frequency offset combination obtained through iterative optimization using a genetic algorithm in step four. Substituting the amplitude-weighted and phase-modulated frequency control array signal propagation model from step three, the propagation time at the start of transmission is calculated. The frequency-controlled array exhibits static low sidelobes and precise point-like interference beam pattern.

[0098] The core objective of this step is to verify whether the frequency offset parameter optimized by the genetic algorithm is within acceptable limits. The instantaneous snapshot meets the 10dB interference threshold requirement defined in step one, that is, the energy at the target point reaches the maximum value, and the energy at the representative detection point in the non-interference area (at a distance of ±75 meters) is at least 10dB lower than that at the target point.

[0099] Optimal frequency offset Substitute the weighted beam energy expression from step three, and take... At time 1, the optimized static radiation pattern is obtained. ;

[0100] In this implementation, the optimal frequency offset distribution obtained using a 32-element array and 60 rounds of genetic algorithm iterations (crossover probability 0.7, mutation probability 0.2) is as follows: Figure 2 The solid line curve is shown in the figure, while the dashed line represents the preset logarithmic frequency offset before optimization, used for comparison.

[0101] The above optimal frequency offset The static beam energy distribution obtained by substituting into the model is shown in the figure. Figure 6 And compared with only amplitude weighting without frequency offset optimization Figure 3 In comparison, the optimized pattern has a narrower main lobe and lower side lobe levels, with energy more concentrated at the target point (500 meters, 0°).

[0102] Along the target direction The intercepted distance-dimensional energy curve is shown below. Figure 7 From this, it can be seen that the energy at the target point (500 meters) is the global peak, and the energy values ​​at 425 meters and 575 meters both meet the threshold requirement of attenuation of more than 10 dB compared to the target point. The angular energy curve taken at a distance of 500 meters from the target is shown below. Figure 8 Compared to before the genetic algorithm optimization Figure 5 The main lobe is narrower and the side lobes have lower energy.

[0103] Step 6: Periodically switch on and off to compensate for the inherent time-varying beam drift of the frequency control array and calculate the time integral energy distribution.

[0104] Step five verified The beam performance meets the requirements in real time, but step three points out that the phase of each array element at the target point after weighting retains a time-dependent relationship. Proportional terms As time goes by, phase deviations that vary with time appear between the array elements, causing the beam peak to deviate from the target point. If this time-varying drift phenomenon is not controlled, the interference energy will dissipate over time, and the actual interference effectiveness will be greatly reduced.

[0105] This step uses a time-domain energy dwell control mechanism to periodically switch the signals transmitted by each array element on and off, thereby periodically compensating for the inherent time-varying beam drift of the frequency-controlled array.

[0106] 6.1 Physical mechanism of beam drift; under the condition that each array element emits continuously, i.e. At that time, in the beam energy expression in step three The term is not zero, and the target point position is... The beam energy is:

[0107] ;

[0108] Frequency offset of each array element They are different, therefore at the same launch time Within the array, the element with the larger frequency offset will experience more phase changes in the same amount of time; All array elements at time All terms are zero, all complex exponential components point in the same direction, and the vector sum reaches its maximum value. ; The complex exponential components of each array element point in different directions due to the additional phase difference, and disperse from each other. The vector and magnitude decrease accordingly. The coherent superposition energy at the target point is attenuated. This is an inherent physical phenomenon caused by the different frequencies of each array element in the frequency-controlled array, and cannot be eliminated by static amplitude and phase weighting.

[0109] 6.2 Configuration and Working Principle of the Switch Array; To suppress energy dissipation caused by drift, a switch is connected in series at the front end of the RF transmission link of each array element. All switches are driven by a unified clock signal and synchronously perform periodic on / off operations. A single switching cycle... The steps inside are as follows:

[0110] 6.2.1 Cycle Start: The switch is closed, and each array element begins to transmit signals. At this time... The carrier phase of each array element is restored to the initial phase state set in step three, and the beam peak is precisely aligned with the target point. Then the maximum energy at the target point is obtained as Modulus multiplication .

[0111] 6.2.2 During the cycle: The switch remains closed, and each array element transmits continuously. The time phase of each array element... As the changes gradually occur, the differences between them increase, the coherence superposition decreases, and the energy at the target point decays from its peak.

[0112] 6.2.3 Cycle termination (disconnection): When At that time, the clock signal drives all switches to open simultaneously, interrupting transmission. Indicates the switching cycle.

[0113] 6.2.4 Start of the next cycle: The switch closes again. The carrier phase of each element is reset to its initial state, and the beam peak jumps back to the target point. This marks the beginning of a new cycle of launch and decay.

[0114] 6.3 Determination of the switching cycle; Switching cycle The value of is a key design parameter for time-domain energy dwell control. Its design objective is to maintain the energy at the target point at an effective disturbance level throughout a single switching cycle. Take the time required for the peak energy to decay by 1 dB.

[0115] Due to the frequency offset of each array element under the logarithmic frequency offset distribution With array element number The relationship is nonlinear, and the drift trajectory of the beam peak in space does not have a simple analytical expression. Therefore, this method does not rely on the analytical derivation of the spatial drift amount to constrain it. Instead, it uses the time-domain decay characteristics of energy at the target point as the criterion. In this implementation case, simulation results show that... It is 0.083 μs, such as Figure 9 As shown. Specifically: Under the selected optimal frequency offset distribution, the target point is calculated through simulation. The normalized received energy decay curve over time at the location for: ;in Let be the energy at the target location at any given time. for Energy at the target location at any given time.

[0116] 6.4 Time-integrated energy distribution; after The accumulation of a complete switching cycle, at any spatial location The time-integral energy is the sum of the instantaneous energies within each cycle. Since the transmitted signal waveform and switching timing are completely identical in each cycle, the time-integral energy can be expressed as the average time energy per cycle multiplied by the number of cycles: ;

[0117] Substituting the weighted beam energy expression given in step three into the integrand, and expanding it, we get: ;

[0118] The value range is a single period. , To evaluate the number of complete switching cycles contained within a time period.

[0119] Step 7: Interference effectiveness assessment, using time integral energy distribution to determine whether the interference threshold requirements are met.

[0120] After completing all the aforementioned steps, this step provides a comprehensive evaluation of the interference effectiveness of the entire method. Unlike traditional FDA studies that use only a single-moment static radiation pattern as the evaluation basis, the evaluation in this invention uses the time integral energy distribution radiation pattern calculated in step six as the benchmark, which truly reflects the actual electromagnetic interference energy levels received by the target and non-target areas over a continuous period of time.

[0121] The evaluation process is as follows:

[0122] 7.1 Calculate the static effect before optimization for comparison: Substitute the preset positive and negative logarithmic frequency offsets from step two into the frequency control array model to obtain the results. Calculate the static radiation pattern at any time, such as Figure 3 As shown, the calculation is performed along the target direction. The distance-dimensional energy curve is as follows Figure 4 As shown, this baseline reflects the single-moment interference performance without the optimization scheme of this invention.

[0123] 7.2 Calculate the optimized time integral effect as the final output of the present invention: the optimal frequency offset obtained by the genetic algorithm in step four. Substituting into the model and combining it with the periodic reset mechanism of the switch in step six, the time integral energy formula in section 6.4 of step six is ​​used to calculate... The energy distribution diagram of the frequency-controlled array after time-domain integration is shown below. Figure 11 As shown, and calculate The distance-dimensional energy curve is as follows Figure 10 As shown.

[0124] 7.3 Comparative Evaluation: The energy distribution diagram of the frequency-controlled array after time-domain integration is shown in the figure. Figure 11 See the optimized static beam energy distribution diagram. Figure 6 The main lobe and side lobe levels and energy of the radiation pattern after time-domain integration are almost identical to those of the optimized static radiation pattern at the target point (500 meters, 0°). This indicates that periodically switching the transmitted signals of each array element on and off effectively compensates for the inherent time-varying beam drift of the frequency-controlled array, achieving a square area with a side length of 150 meters centered at the specified coordinate point for the target interference. The target interference point can be read from the distance-dimensional energy curve after optimization based on the time-domain integration. Peak energy at And representative detection points in the non-interference area (at ±75 meters from the target point, i.e.) Mihe Energy value at (meters) and Then the peak energy difference and They are respectively minus and minus ;

[0125] like and If the threshold of quantization interference in step one is met, the peak interference energy in the target interference square area is more than 10 dB higher than the interference energy at the representative detection point in the non-interference area.

[0126] 7.4 Simultaneously compare the static baseline curve before optimization with the time integral curve after optimization: If the static curve before optimization no longer meets the 10dB attenuation requirement at the ±75m detection point, while the time integral curve after optimization does, then the effectiveness of the superposition of the two links of genetic algorithm frequency offset optimization and switching time domain control is verified.

[0127] The evaluation results of this implementation case are as follows: It is 11.4 dB; The values ​​of 10.1dB are all greater than 10dB, meeting the threshold requirements. Compared with the static baseline before optimization, the energy attenuation in the non-interference area after optimization is more significant, and the sidelobe suppression effect is significantly improved. The effective range of the target interference airspace covers a square area with a side length of 150 meters within a kilometer. The interference energy continuously converges within the target area, and the energy in the non-interference area is effectively suppressed, meeting the needs of precise, controllable, and low-damage electromagnetic control in urban low-altitude airspace.

[0128] While the embodiments of the present invention have been described in detail above, this should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A precise electromagnetic interference method based on spatial power synthesis, characterized in that, Includes the following steps: S1. By analyzing the safety control requirements under the complex electromagnetic environment of urban low-altitude environment, the target interference area range and the interference threshold are defined; the interference threshold is: the peak electromagnetic energy of the target interference area is attenuated by no less than 10dB compared with the energy at a representative detection point in the non-interference area. S2. Based on the target interference area range and interference threshold, determine the core system parameters of the frequency control array, including array arrangement, reference carrier frequency, array element spacing, number of array elements, and basic frequency offset. Construct a frequency control array model with symmetrical subarray structure and positive and negative logarithmic frequency offset scheme, determine the transmission frequency of each array element, and construct a signal propagation model that incorporates free space path loss factor. S3. Based on the signal propagation model, extract the distance and angle difference phase terms from each array element to the target point, design the corresponding amplitude weighting and phase compensation coefficients, and construct the amplitude weighting and phase compensation signal propagation model. S4. Construct a fitness function with the constraints of the lowest electromagnetic energy at non-interference points and the narrowest main lobe of the beam at interference points. Use a genetic algorithm to iteratively optimize the frequency offset of each array element to obtain the optimal combination of array element frequency offsets. S5. Input the optimal array element frequency offset combination into the amplitude-weighted and phase-compensated signal propagation model to generate a low-sidelobe point-shaped interference static beam and verify whether the static beam meets the interference threshold. S6. Add a switch to the transmission link of each array element, and control the periodic on and off of the transmitted signal of each array element through the switch, so that the beam peak returns to the target interference point at the beginning of each switching cycle, compensates for the time-varying drift of the frequency control array beam, and calculates the global time integral energy distribution. S7. Using the time-integrated energy distribution pattern as the evaluation basis, determine whether the addition of a switch to achieve periodic on / off transmission meets the requirements for accuracy and low accidental injury in urban low-altitude safety control based on the interference radiation effect.

2. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, In step S1, the target interference airspace is a square area with a side length of 150 meters centered on the specified coordinate point. This area is set in the low-altitude space within 1 kilometer of the interference source. The representative detection point in the non-interference area is selected at a position 75 meters before and after the target center point along the distance dimension.

3. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, In step S2, the symmetrical subarray structure is to divide all uniformly linearly arranged array elements into two groups of subarrays. The positive and negative logarithmic frequency offset scheme is that the frequency offset of the array elements in the first half of the subarray decreases logarithmically as the array element number increases, while the frequency offset of the array elements in the second half of the subarray increases logarithmically as the array element number increases. The frequency offset distribution of the positive and negative logarithmic frequency offset scheme is used to achieve decoupling of the two dimensions of beam distance focusing and angle pointing.

4. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, The frequency control array core system parameters mentioned in step S2 include the array element arrangement, reference carrier frequency, array element spacing, total number of array elements, basic frequency offset, target point spatial coordinates, and spatial observation point coordinates.

5. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, The genetic algorithm execution process in step S4 includes: encoding each array element frequency offset combination into an independent individual, randomly generating an initial population; using the fitness function to quantify and score each frequency offset individual; sequentially performing selection, crossover, and mutation operations to iteratively update the population; and outputting the frequency offset combination with the best fitness within the population. The fitness function calculation logic is the target point energy value minus the total penalty caused by insufficient energy decay of side lobes in non-target regions and detection points.

6. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, The method for determining the switching period in step S6 is as follows: under the optimal frequency offset parameter condition, simulate the attenuation curve of the normalized interference energy of the target point with the transmission time, and select the time corresponding to the attenuation of the peak energy of the target point by 1dB as the single conduction period of the switch. The switch is turned on for one cycle and then turned off. When it is turned on again, the initial phase of all array element carriers is reset so that the beam peak is re-aligned with the target point.

7. The precise electromagnetic interference method based on spatial power synthesis according to claim 1, characterized in that, The comprehensive judgment logic in step S7 is as follows: extract the energy values ​​of the target center point and the detection points 75 meters before and after in the time integral energy distribution map. When the energy attenuation values ​​of both detection points and the target point exceed 10dB, it is determined that the positive and negative logarithmic frequency deviation scheme combined with the switching timing scheme meets the usage standards of precise electromagnetic control and low collateral damage in urban low-altitude areas.

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