Energy selection surface rapid design method based on equivalent circuit

Abstract

The invention relates to a rapid design method for an energy selective surface based on an equivalent circuit, and belongs to the field of electromagnetic protection design. The method comprises the following steps: establishing an energy selective surface equivalent circuit according to actual requirements, calculating whether the transmission characteristics of the equivalent circuit meet requirements or not, determining an energy selective surface unit structure according to an equivalent circuit element connection mode, selecting energy selective surface optimization parameters, and initializing the parameters and a target function; and calling Bayesian optimization to update the structural parameters of the energy selection surface, carrying out multiple iterations, and finally finding the structural parameters of the energy selection surface meeting the design requirements to complete the design of the energy selection surface. The method has the advantages that the energy selective surface structure is constructed based on the equivalent circuit model, the Bayesian optimization algorithm is combined with energy selective surface design electromagnetic simulation, information obtained by full-wave simulation of each energy selective surface structure parameter change is fully utilized, and the energy selective surface design efficiency is greatly improved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic protection design and relates to a rapid design method of energy selective surface based on equivalent circuit. Background Art

[0002] The rapid development of electronics technology in recent years has, on the one hand, led to the increasing intelligence and integration of communications equipment used in modern warfare, significantly improving its performance. However, this has also significantly increased the sensitivity of these devices to electromagnetic attacks, making them susceptible to irreversible damage. Furthermore, as electromagnetic pulse weapons develop features such as high mobility, adjustable pulse waveforms, wide bandwidth, and high power, the threat posed to communications equipment by these weapons is becoming increasingly severe. Therefore, to minimize the damage to communications equipment during military warfare, effective strong electromagnetic pulse protection measures are necessary.

[0003] An energy selective surface (ESS) allows electromagnetic waves with energies below a safety threshold to pass through, while attenuating strong electromagnetic pulses with energies above the safety threshold. Based on the FSS, the ESS consists of a periodic structure and PIN diodes mounted on it. Its operating principle is to leverage the strong electric field effect of high-power microwaves and the voltage-controlled conductivity of semiconductors. When irradiated by high-energy electromagnetic waves, the high voltage induced on the ESS causes it to rapidly change from a high-resistance state to a low-resistance state, thereby attenuating high-energy electromagnetic waves and providing a shielding effect. However, when low-energy electromagnetic waves irradiate the ESS, the voltage induced on the ESS is too small to cause the surface to change from a high-resistance state to a low-resistance state, allowing low-energy electromagnetic waves to pass through. The ESS utilizes the switching of the PIN diodes to change the surface impedance of the structure, thereby altering the ESS's transmission characteristics for electromagnetic waves, thereby protecting electronic equipment from damage caused by high-power microwaves.

[0004] The design of energy selective surface structures cannot use conventional experience or formulas, and must rely on high-precision electromagnetic simulation, but its computational analysis cost is expensive. With the development of computer technology, intelligent optimization algorithms have been widely used in energy selective surface design, including genetic algorithms, particle swarm algorithms, etc. The Chinese invention patent application with application number 202210734562.3 discloses a method for designing and optimizing ultra-wideband energy selective surfaces. The invention analyzes the structural parameters that affect the performance of ultra-wideband energy selective surfaces and obtains the optimal solution through genetic algorithms. However, these intelligent algorithms usually require hundreds of iterations to find the optimal parameters, and each iteration requires the use of full-wave analysis methods to calculate the frequency response corresponding to each set of structural parameters, which is too computationally intensive. The cycle of designing energy selective surface structures using this method is too long, and computing resources are wasted. Therefore, it is necessary to find a fast method for designing energy selective surfaces. Summary of the Invention

[0005] The present invention provides an energy selective surface rapid design method based on an equivalent circuit, which can find energy selective surface structural parameters that meet the requirements while calling a small number of full-wave simulations, thereby realizing rapid design of the energy selective surface.

[0006] The technical solution adopted by the present invention comprises the following steps:

[0007] 1) Build an energy selective surface equivalent circuit based on actual needs;

[0008] 2) Calculate whether the transmission characteristics of the equivalent circuit meet the requirements;

[0009] 3) Determine the energy selective surface unit structure based on the connection method of equivalent circuit elements;

[0010] 4) Select energy selective surface optimization parameters and initialize the parameters and objective function;

[0011] 5) Call Bayesian optimization to update energy selection surface structure parameters;

[0012] 6) Perform multiple iterations to finally find the energy selective surface structural parameters that meet the design requirements and complete the design of the energy selective surface.

[0013] The equivalent circuit described in step 1) is composed of an LC parallel resonant parallel diode circuit and an LC series resonant circuit connected in series.

[0014] The transmission characteristics described in step 2) specifically include the transmission coefficient S when the diode is cut off in the equivalent circuit 21 The transmission coefficient S when the diode is conducting in the equivalent circuit 21 value.

[0015] In step 3), the method for determining the unit structure of the energy selective surface is that the inductor in the equivalent circuit corresponds to a metal wire segment in the equivalent circuit, and the capacitor in the equivalent circuit corresponds to two adjacent metal wire segments. The energy selective surface optimization parameters designed through the equivalent circuit model should correspond to the parameters of the equivalent circuit model components.

[0016] In step 4), the objective function is to accumulate and solve the objective function in the diode conduction state and the objective function in the diode cutoff state according to the weights, thereby converting the solution of the multi-objective parameter optimization problem into a single-objective optimization solution, where the accumulated objective function is: ,in and are the weight coefficients corresponding to the target indicators, , where n is the number of sampling points, is the equivalent circuit transmission coefficient S when the diode is turned off 21 Transfer curve sampling value, is the full-wave simulation transmission coefficient S 21 Transfer curve sampling value. , where n is the number of sampling points, is the equivalent circuit transmission coefficient S when the diode is turned on 21 Transfer curve sampling value, is the full-wave simulation transmission coefficient S 21 Transfer curve sampling value.

[0017] In step 5), a data transmission channel is established between the full-wave simulation tool and the optimization tool. The full-wave simulation tool is used as a tool to calculate the objective function. The transmission coefficient data of the energy selective surface in the diode off-state and diode on-state are obtained using the full-wave simulation tool. This data is then combined with the transmission coefficient data obtained from the equivalent circuit calculation to calculate the objective function. A Bayesian optimization program is executed in the optimization tool. By inputting the structural parameters and fitness function values ​​obtained from each iteration into the proxy model of the Bayesian optimization, the algorithm is guided to select the structural parameters for the next iteration and find the parameter values ​​of the energy selective surface structure that minimize the objective function.

[0018] The advantages of the present invention are:

[0019] 1. Using the equivalent circuit model to guide the construction of the energy selective surface unit structure can intuitively reflect the working principle of the energy selective surface and more quickly determine the parameters to be optimized.

[0020] 2. The transmission coefficient of the diode in the on and off states of the equivalent circuit model is used to calculate the objective function to guide the optimization of the energy selective surface structure parameters. The energy selective surface structure parameters can be automatically adjusted to avoid tedious manual updates.

[0021] 3. The use of the Bayesian optimization algorithm avoids a large number of iterative processes. The proxy model in the Bayesian optimization can combine the information obtained from the previous iteration to guide the selection of the next structural parameters, which can reduce the number of times full-wave simulation is called during the design process, significantly shorten the design cycle, and greatly improve the efficiency of energy selective surface design. The optimized energy selective surface has a clear electromagnetic wave modulation mechanism, and the transmission coefficient fits well with the equivalent circuit model, which can be used for strong electromagnetic pulse protection of communication equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the equivalent circuit diagram of the energy selective surface;

[0023] Figure 2 It is the equivalent circuit diagram of the PIN diode when it is cut off and turned on;

[0024] Figure 3 This is a transmission line model diagram of an electromagnetic periodic structure with metal loaded on one side of a dielectric substrate;

[0025] Figure 4 is the transmission coefficient S of the equivalent circuit model when the diode is turned on and off 21 picture;

[0026] Figure 5 It is a unit structure diagram of the energy selection surface constructed based on the equivalent circuit model;

[0027] Figure 6 It is the Matlab and CST joint simulation flow chart;

[0028] Figure 7 This is a comparison chart of the transmission coefficients of the CST full-wave simulation and the equivalent circuit model of the energy selective surface structure under optimal parameters when the diode is cut off.

[0029] Figure 8 This is a comparison chart of the transmission coefficients of the CST full-wave simulation and the equivalent circuit model of the energy selective surface structure under optimal parameters when the diode is turned on. DETAILED DESCRIPTION

[0030] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. That is, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0031] The following steps are involved:

[0032] Step 1: In a strong electromagnetic pulse environment, the satellite navigation system antenna will couple the electromagnetic energy in the antenna operating frequency band and transmit it to the subsequent circuits, causing irreversible damage to sensitive components in the subsequent circuits, such as low-noise amplifiers. By installing an energy selective surface at the front end of the antenna, the antenna can be adaptively protected against strong electromagnetic pulses. The design indicators of the energy selective surface are: 2.046MHz) and GPS L1 (1575.42 1.023MHz) frequency band, low energy wave is incident, the diode is closed, and the transmission coefficient , high energy wave is incident, the diode is turned on, and its transmission coefficient ;

[0033] According to the actual needs of L-band satellite navigation strong electromagnetic pulse protection, an energy selective surface equivalent circuit is built. Figure 1 As shown, L1 and L2 are inductors, C1 and C2 are capacitors, and D1 is a PIN diode. The equivalent circuit is composed of an LC parallel resonant parallel diode circuit and an LC series resonant circuit in series.

[0034] The equivalent circuit of the PIN diode in the cut-off and conduction states is as follows Figure 2 As shown in Figure 2, when the power of the incident wave is low, the induced voltage across the PIN diode is less than the conduction threshold, the diode is cut off, and the working signal can pass normally. At this time, the PIN diode can be equivalent to a capacitor C off , at this time the impedance expression of the diode cutoff equivalent circuit is:

[0035]

[0036] In the formula represents the angular frequency;

[0037] When high-power microwave radiation energy selects the surface, the induced voltage on both sides of the PIN diode exceeds the threshold, causing the diode to turn on, and a metal grid or grid structure is formed on the surface to shield the electromagnetic wave. At this time, the PIN diode can be equivalent to an inductor L on and a resistor R on The series circuit is equivalent to the PIN diode short-circuited parallel resonance. At this time, the impedance expression of the equivalent circuit of the diode conduction is:

[0038]

[0039] Step 2: Calculate whether the transmission characteristics of the equivalent circuit meet the requirements: The PIN diode model NSR201 is used in this example. Other semiconductor diodes with switching characteristics can also be used instead. The substrate is FR-4 with a relative dielectric constant of 4.3 and a loss tangent of 0.025. The transmission line model of the electromagnetic periodic structure with metal loaded on one side of the dielectric substrate is as follows: Figure 3 As shown, is the impedance of the equivalent circuit. The dielectric substrate is equivalent to a transmission line. Its impedance , is the relative dielectric constant of the dielectric substrate, Z0 (Z0 = 377) represents the wave impedance in free space;

[0040] The transmission coefficient calculated from the transmission line model shown in Figure 3 is:

[0041]

[0042] Where S 21 represents the transmission coefficient, A, B, C, and D are the elements of the normalized transmission matrix, and the calculation formula is:

[0043]

[0044] In the formula , c is the speed of light in vacuum, h is the thickness of the dielectric substrate, and f represents the frequency;

[0045] After calculation, the transmission coefficient S of the equivalent circuit model when the diode is turned on and off 21 like Figure 4 As shown, from Figure 4 It can be seen that when the diode is turned on and when the diode is turned off, the S of the equivalent circuit is 21 All meet the design indicators;

[0046] Step 3: According to the electromagnetic equivalent circuit principle, the current distribution and field distribution in each periodic unit structure are the same. If the distribution of the near field is ignored, the propagation of electromagnetic waves in space can be equated to the transmission of voltage and current on a lossless transmission line. When an electric field is applied to the periodic unit, due to the induced potential difference between adjacent metal zigzag lines, it can store electrical energy like a capacitor, and its effect is equivalent to a capacitor; the current generated by the movement of charges on the metal zigzag lines can form a magnetic field, so it can store magnetic energy like an inductor, and its effect is equivalent to an inductor. Therefore, according to Figure 1 The energy selective surface unit structure model was established by connecting the equivalent circuit elements. Figure 5As shown in the figure, the bottom dielectric substrate is a square structure. The energy selective surface unit is structured such that the inductor in the equivalent circuit corresponds to a metal line segment in the equivalent circuit, and the capacitor in the equivalent circuit corresponds to two adjacent metal lines. The optimized parameters of the energy selective surface designed using the equivalent circuit model should correspond to the parameters of the equivalent circuit model components. The meandering structure of the metal strips on the bottom side can increase the inductive inductance while maintaining the substrate size.

[0047] Step 4: Select the energy selective surface optimization parameters and initialize the parameters and objective function: the two metal strips with a length of l1 in the energy selective surface unit structure correspond to the capacitor C1 in the equivalent circuit model, the metal strip with a length of l3 corresponds to the inductor L1 in the equivalent circuit model, the metal strip with a length of l2 is connected in series with the metal strip with a length of l3, and is adjacent to the metal strip with a length of l4 in the next unit structure of the energy selective surface. Therefore, the metal strip with a length of l2 has a corresponding relationship with the inductor L1 and the capacitor C2 in the equivalent circuit. The zigzag metal strip with a length of l4 has a corresponding relationship with the inductor L2 in the equivalent circuit. At the same time, the zigzag metal strips are adjacent to each other and also have a corresponding relationship with C2 in the equivalent circuit.

[0048] The objective function is to accumulate and solve the objective function in the diode conduction state and the objective function in the diode cutoff state according to the weight, thereby converting the solution of the multi-objective parameter optimization problem into a single-objective optimization solution, where the accumulated objective function is:

[0049]

[0050] in and are the weight coefficients corresponding to the target indicators,

[0051]

[0052] Where n is the number of sampling points, is the equivalent circuit transmission coefficient S when the diode is turned off 21 Transfer curve sampling value, is the CST full-wave simulation transmission coefficient S 21 Transfer curve sampling value,

[0053]

[0054] Where n is the number of sampling points, is the sampling value of the transmission curve of the equivalent circuit transmission coefficient S21 when the diode is turned on, For CST full-wave simulation S 21 Transfer curve sampling value.

[0055] Step 5: Call Bayesian optimization to update the energy selective surface structure parameters: Since the PIN diode needs to be welded to the energy selective surface unit structure, the PIN diode welding position must be reserved on the unit structure, and the parameters d1=0.4mm, w2=1mm are fixed. At the same time, the trace width w1=0.2mm on the energy selective structure dielectric substrate is fixed. The energy selective surface unit structure parameters l1, l2, l3, l4 are optimized to minimize the objective function so that the transmission coefficient S of the energy selective surface is 21 And the equivalent circuit S 21 The difference between them is the smallest. Using Matlab combined with CST simulation for Bayesian optimization, the CST full-wave simulation is regarded as a tool for calculating the objective function. The flowchart of Matlab combined with CST simulation is as follows: Figure 6 As shown. Build a data transmission channel between Matlab and CST, and find the optimal structural parameters of the energy selective surface by executing the Bayesian optimization function in Matlab. Bayesian optimization is a global optimization strategy that can help us find the black box objective function in relatively few evaluations. The optimization process of this algorithm is as follows: First, the objective function Consider it as a random function and select a suitable prior model (also called a surrogate model). There are several possible choices for the surrogate model. In this example, we use the most widely used Gaussian distribution process. Then, the objective function Observe and collect The observation value is updated through the likelihood function to form the posterior distribution. Finally, an auxiliary function is constructed using the posterior distribution, and the objective function is calculated by the auxiliary function. The next point to be evaluated is observed again. Repeat this process, continuously observe and update the model, and finally find the objective function The minimum value of .

[0056] Step 6: After 30 iterations, the ESS structural parameters, l1 = 6.52 mm, l2 = 9.92 mm, l3 = 7.52 mm, and l4 = 8.45 mm, were finally found, completing the ESS design. Compared to swarm intelligence algorithms, which require full-wave simulation to calculate the objective function for each individual in each iteration, Bayesian optimization combined with a proxy model can find the ESS structural parameters that meet the design requirements in just a few dozen iterations, accelerating the ESS design process.

[0057] Figure 7 、 Figure 8The transmission coefficients of the energy selective surface structure under the optimal parameters of the CST full-wave simulation and the equivalent circuit model are compared. It can be seen that the energy selective surface transmission coefficient S is 21 With the equivalent circuit S 21 The changing trends of the curves are basically the same. Figure 7 It means that when low energy wave hits the energy selective surface, the diode is cut off and the designed energy selective surface is in the satellite navigation working frequency band. ; Figure 8 It means that when high energy wave hits the energy selective surface, the diode is turned on due to the induced voltage at both ends. The designed energy selective surface is in the satellite navigation working frequency band. The energy selective surface designed in the embodiment meets the design specifications and can be used for strong electromagnetic pulse protection of satellite navigation systems.

[0058] This method constructs an ESS structure based on an equivalent circuit model and combines a Bayesian optimization algorithm with electromagnetic simulation for ESS design. This algorithm leverages the information gained from each full-wave simulation of ESS structural parameter changes, reducing the number of full-wave simulations required and significantly improving ESS design efficiency. The optimized ESS demonstrates a clear electromagnetic wave modulation mechanism, with a transmission coefficient that closely matches the equivalent circuit model, making it suitable for use in communications equipment to protect against strong electromagnetic pulses.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A fast design method for energy selective surfaces based on equivalent circuits, characterized in that: The following steps are involved: 1) Build an energy selective surface equivalent circuit based on actual needs; 2) Calculate whether the transmission characteristics of the equivalent circuit meet the requirements; 3) Determine the energy selective surface unit structure based on the connection method of equivalent circuit elements; 4) Select energy selective surface optimization parameters and initialize the parameters and objective function; 5) Call Bayesian optimization to update energy selection surface structure parameters; 6) Perform multiple iterations to finally find the energy selective surface structural parameters that meet the design requirements and complete the design of the energy selective surface.

2. The method for rapid design of energy selective surfaces based on equivalent circuits according to claim 1, characterized in that: In the step 1), the equivalent circuit is formed by connecting an LC parallel resonant parallel diode circuit and an LC series resonant circuit in series.

3. The method for rapid design of energy selective surfaces based on equivalent circuits according to claim 1, characterized in that: The transmission characteristics in step 2) specifically include the transmission coefficient S when the diode in the equivalent circuit is cut off. 21 The transmission coefficient S when the diode is conducting in the equivalent circuit 21 value.

4. The method for rapid design of energy selective surfaces based on equivalent circuits according to claim 1, characterized in that: In step 3), the method for determining the unit structure of the energy selective surface is that the inductor in the equivalent circuit corresponds to a metal wire segment in the equivalent circuit, and the capacitor in the equivalent circuit corresponds to two adjacent metal wire segments. The energy selective surface optimization parameters designed through the equivalent circuit model should correspond to the component parameters of the equivalent circuit model.

5. The method for rapid design of energy selective surfaces based on equivalent circuits according to claim 1, characterized in that: The objective function in step 4) is to accumulate and solve the objective function in the diode conduction state and the objective function in the diode cutoff state according to the weights, thereby converting the solution of the multi-objective parameter optimization problem into a single-objective optimization solution, wherein the accumulated objective function is: ,in and are the weight coefficients corresponding to the target indicators, , where n is the number of sampling points, is the equivalent circuit transmission coefficient S when the diode is turned off 21 Transfer curve sampling value, is the full-wave simulation transmission coefficient S 21 Transfer curve sampling value, , where n is the number of sampling points, is the equivalent circuit transmission coefficient S when the diode is turned on 21 Transfer curve sampling value, is the full-wave simulation transmission coefficient S 21 Transfer curve sampling value.

6. The method for rapid design of energy selective surfaces based on equivalent circuits according to claim 1, characterized in that: In the step 5), a data transmission channel is established between the full-wave simulation tool and the optimization tool. The full-wave simulation tool is regarded as a tool for calculating the objective function. The full-wave simulation tool is used to obtain the transmission coefficient data of the energy selective surface in the diode cut-off state and the diode conduction state, and the transmission coefficient data obtained by equivalent circuit calculation is calculated to obtain the objective function. The Bayesian optimization program is executed in the optimization tool. By inputting the structural parameters of each iteration and the fitness function values ​​obtained in each iteration into the agent model in the Bayesian optimization, the algorithm is guided to select the structural parameters of the next iteration, and the parameter values ​​of the energy selective surface structure when the objective function is minimized are found.

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