A variable capacitance diode controlled amplitude adjustable wave absorbing structure

Abstract

The application discloses an amplitude-adjustable wave-absorbing structure based on a varactor control. The amplitude-adjustable wave-absorbing structure utilizes a varactor, and by changing an external bias voltage, the wave-absorbing amplitude in a working frequency band can be dynamically adjusted, and the dynamic regulation and control of the absorption efficiency can be realized. The metal layer of the wave-absorbing structure comprises a main resonant microstrip stub, a parallel resonant microstrip stub, a bias feed line, a varactor, a thin-film resistor, a patch inductor and a patch capacitor. By adjusting the capacitance of the varactor in the parallel resonant microstrip stub, the resonant frequency of the parallel resonant microstrip stub can be changed, the load resistance value in the main resonant microstrip stub can be effectively adjusted, the impedance matching of the wave-absorbing structure can be changed, and the effective adjustment of the wave-absorbing amplitude can be realized. Compared with a conventional wave-absorbing device, the application has the advantages of stable operation and control, convenient adjustment, no influence on out-of-band performance and the like. The application has many potential applications in electromagnetic protection, electromagnetic camouflage and a new generation of radar intelligent stealth systems.

Description

Technical Field

[0001] This invention relates to an amplitude-adjustable absorbing structure controlled by a varactor diode, belonging to the field of novel artificial electromagnetic devices. Background Technology

[0002] A radar-absorbing structure is an electromagnetic structure capable of absorbing and dissipating electromagnetic wave energy projected onto its surface. It effectively reduces the radar cross-section of a target, significantly improving the survivability of our equipment. It plays a crucial role in stealth technology, electromagnetic compatibility, security protection, and electromagnetic shielding. In recent years, to cope with complex and ever-changing electromagnetic environments, radar-absorbing structures have shown a trend towards intelligent development, meaning they can adjust their functional states in real time for different electromagnetic environments to achieve intelligent stealth. This invention relates to a varactor diode-controlled amplitude-adjustable radar-absorbing structure, which can dynamically and in real-time tune the absorption amplitude of electromagnetic waves within its operating frequency band. Compared with other structures based on PIN diodes and graphene, this design method is stable in operation, highly controllable, and does not affect electromagnetic performance outside the operating frequency band, showing promising engineering application prospects. Summary of the Invention

[0003] The purpose of this invention is to realize an amplitude-adjustable absorption structure controlled by a varactor diode, which can effectively adjust the absorption amplitude (i.e., the amplitude of the reflection coefficient) under irradiation by linearly polarized electromagnetic waves.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: an amplitude-adjustable absorbing structure controlled by a varactor diode, wherein the metal layer of its basic structural unit includes a main resonant microstrip stub, a parallel resonant microstrip stub, a bias feed line, a varactor diode, a thin-film resistor, a chip inductor, and a chip capacitor; the parallel resonant microstrip stub is connected in parallel with the thin-film resistor loaded in the main resonant microstrip stub, and the chip inductor, varactor diode, and thin-film resistor are welded in the parallel resonant microstrip stub; the resonant frequency of the parallel resonant microstrip stub is jointly determined by the parasitic inductance, the chip inductor, and the varactor diode, and the resonant frequency of the parallel resonant microstrip stub is adjusted by adjusting the capacitance value of the varactor diode, thereby adjusting the impedance load of the main resonant microstrip stub.

[0005] Preferably, the amplitude-adjustable absorbing structure controlled by the varactor diode includes a structural layer, an air layer, and a metal ground plane; the structural layer consists of a dielectric layer and two metal layers with the same structure placed orthogonally to each other, and the metal layers are printed on the upper and lower surfaces of the dielectric layer respectively by PCB process.

[0006] Preferably, the amplitude-adjustable absorbing structure controlled by the varactor diode has a thin-film resistance (R) in the parallel resonant microstrip stub. P The resistance value (R) is less than that of the thin film resistance in the main resonant microstrip stub. M), R M With R P The relationship between the values ​​is R. M :R P ≥5:1; At the resonant frequency of the parallel resonant microstrip stub, the load resistance of the absorbing structure is equivalent to the parallel value of two thin-film resistors (R). P ||R M As the resonant frequency of the parallel resonant microstrip stub moves away from the parallel value (R), the load resistance of the absorbing structure gradually decreases from the parallel value (R). P ||R M Increase the thin film resistance (R) in the main resonant microstrip stub. M The frequency dependence is observed; when the resonant frequency of the parallel resonant microstrip stub changes, within the operating frequency of the main resonant microstrip stub, the load resistance of the absorbing structure varies with R. P ||R M ~R M The amplitude of wave absorption can be effectively adjusted within a certain range.

[0007] Preferably, the amplitude-adjustable absorption structure controlled by the varactor diode has the positive and negative terminals of the bias feed line connected to the two ends of the parallel resonant microstrip stub, respectively; the capacitance of the varactor diode is adjusted by changing the voltage difference between the positive and negative terminals of the bias feed line, thereby adjusting the absorption amplitude.

[0008] Preferably, the amplitude-adjustable absorbing structure controlled by the varactor diode has three surface-mount inductors soldered in each bias feed line to suppress the induced current in the bias feed line and reduce the impact of the bias feed line on the absorbing structure.

[0009] Preferably, in the amplitude-adjustable absorbing structure controlled by the varactor diode, the main resonant microstrip stub is a straight microstrip line running through the center of the unit, the parallel resonant microstrip stub is parallel to the main resonant microstrip stub, and the two bias feed lines are located at both ends of the parallel resonant microstrip stub and are perpendicular to the main resonant microstrip stub.

[0010] Preferably, the amplitude-adjustable absorbing structure controlled by the varactor diode can adjust the operating frequency band of the absorbing structure by adjusting the geometric parameters of the main resonant microstrip stub and the capacitance value of the patch capacitor.

[0011] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0012] 1. Wide amplitude adjustment range and strong amplitude adjustment capability: The amplitude-adjustable absorbing structure controlled by the varactor diode described in this invention can dynamically adjust the absorption depth for single / dual-polarized (TE polarization and TM polarization) incident electromagnetic waves, with a wide amplitude adjustment range and strong amplitude adjustment capability. For example, in a specific embodiment, under TE polarization incident waves, the amplitude-adjustable absorbing structure achieves adjustable absorption amplitude in the range of 0 to 0.85 at 1.96 GHz; under TM polarization, the amplitude-adjustable absorber achieves adjustable absorption amplitude in the range of 0.03 to 0.85 at 1.915 GHz.

[0013] 2. Effective adjustment of absorption amplitude within a certain bandwidth range: The amplitude-adjustable absorption structure controlled by the varactor diode described in this invention can effectively adjust the absorption amplitude within a certain bandwidth range. For example, in the specific embodiment, under TE polarization, the amplitude-adjustable absorption structure can effectively adjust the amplitude range from <0.2 to >0.8 within the frequency range of 1.83 to 2.03 GHz, and can effectively adjust the amplitude range from <0.2 to >0.7 within the frequency range of 1.83 to 2.12 GHz; under TM polarization, the amplitude-adjustable absorption structure can effectively adjust the amplitude range from <0.2 to >0.8 within the frequency range of 1.79 to 2.05 GHz, and can effectively adjust the amplitude range from <0.2 to >0.7 within the frequency range of 1.79 to 2.09 GHz.

[0014] 3. More stable and controllable, enhancing practical application capabilities: The amplitude-adjustable absorbing structure controlled by the varactor diode described in this invention can adjust the absorption amplitude by adjusting the reverse bias voltage in actual operation. Compared with the existing amplitude-adjustable absorbing structure design based on graphene and PIN diode, it is more stable and controllable, easier to adjust, and has more stable performance, effectively improving the application capabilities in practical environments.

[0015] 4. Does not affect electromagnetic performance outside the operating frequency band and has frequency reuse potential: The varactor diode-controlled amplitude-adjustable absorbing structure described in this invention only adjusts the absorption amplitude within the operating frequency band. Unlike existing designs that use varactor diodes to adjust the position of the absorption frequency point to adjust the absorption amplitude at a specific frequency point, this solution does not affect the electromagnetic characteristics outside the operating frequency band. It can design more functions for other frequency bands outside the operating frequency band and has the potential for frequency reuse.

[0016] 5. Polarization insensitive: The amplitude-adjustable absorption structure controlled by the varactor diode described in this invention can effectively adjust the absorption amplitude of incident electromagnetic waves with dual-polarization (TE polarization and TM polarization);

[0017] 6. Flexible design with frequency band mobility: The varactor diode-controlled amplitude-adjustable absorbing structure described in this invention has good frequency band mobility. The operating frequency band can be flexibly designed by designing the main resonant microstrip stub; the range of amplitude adjustment can also be flexibly designed by reasonably designing the parallel resonant microstrip stub. Attached Figure Description

[0018] Figure 1 This is a structural design diagram of an embodiment of the present invention; lumped elements are not shown.

[0019] Figure 2 This is a basic unit structure design diagram of an embodiment of the present invention. (a) is a plan view of the first layer metal structure, and (b) is a plan view of the second layer metal structure; the metal floor is not shown.

[0020] Figure 3 This is a schematic diagram showing the variation of the reflection coefficient amplitude under TE polarization state when the varactor diode has different capacitance values. The dark shaded area represents the frequency band where the absorption amplitude varies from <0.2 to >0.8, and the light shaded area represents the frequency band where the absorption amplitude varies from <0.2 to >0.7.

[0021] Figure 4 This is a schematic diagram showing the variation of the reflection coefficient amplitude under different capacitance values ​​of the varactor diode in the TM polarization state according to an embodiment of the present invention. The dark shaded area represents the frequency band in which the absorption amplitude varies from <0.2 to >0.8, and the light shaded area represents the frequency band in which the absorption amplitude varies from <0.2 to >0.7.

[0022] Figure 2 In the diagram, 1-Bias feed line; 2-Surface mount inductor; 3-Thin film resistor; 4-Varactor diode; 5-Main resonant microstrip line; 6-Surface mount capacitor; 7-Surface mount inductor; 8-Thin film resistor. Detailed Implementation

[0023] The present invention will be further described below with reference to specific embodiments and the accompanying drawings.

[0024] This invention discloses a varactor diode-controlled amplitude-adjustable absorbing structure that can effectively adjust the absorption amplitude under single / dual-line polarized (TE polarization and TM polarization) electromagnetic wave irradiation. Through a reasonable bias feeder design, the performance of the absorbing structure is not affected before or after the introduction of the bias feeder. Using an external DC voltage source, a reverse bias voltage is applied to the varactor diode through the bias feeder network, allowing for dynamic adjustment of the absorption amplitude. This structural design has many potential applications in intelligent radar stealth systems. The amplitude-adjustable absorbing structure includes a structural layer, an air layer, and a metal ground plane; the structural layer includes a dielectric layer and metal layers printed on both sides of the dielectric using PCB manufacturing processes, such as... Figure 1 As shown. Specifically, each metal layer includes a main resonant microstrip stub, a parallel resonant microstrip stub, a bias feed line, a varactor diode, a thin-film resistor, a chip inductor, and a chip capacitor. To more clearly observe the composition of each metal layer structure, Figure 2 The planar structural diagrams of the first and second metal layers are given respectively; the first and second metal layers are identical and are placed orthogonally to each other to achieve a polarization-insensitive design.

[0025] In each layer of the metal structure, the basic structure of the main resonant microstrip stub is a section of main resonant microstrip line 5. To better excite resonance in the structure, a 0.1pF chip capacitor 6 is loaded on the main resonant microstrip line 5. To achieve electromagnetic wave loss, a 100-ohm thin-film resistor 8 is also loaded on the main resonant microstrip line 5. The parallel resonant microstrip stub is a section of metal microstrip line connected in parallel with the 100-ohm thin-film resistor 8. To achieve effective adjustment of the load resistance of the main resonant structure, a 4.7nH chip inductor 2, a 10-ohm thin-film resistor 3, and a varactor diode 4 are soldered onto the parallel resonant stub. The resonant frequency of the parallel resonant microstrip stub is determined by the parasitic inductance of the microstrip stub itself, the chip inductor 2, and the varactor diode 4. When the capacitance of the varactor diode 4 changes, the resonant frequency of the parallel resonant microstrip stub changes accordingly. By adjusting the resonant frequency of the parallel resonant microstrip stub, the impedance load of the main resonant microstrip stub can be adjusted.

[0026] An externally adjustable DC reverse bias voltage can be applied to the varactor diode 4 through the bias feeder network. By changing the reverse bias voltage difference between the positive and negative terminals of the varactor diode 4, the capacitance of the varactor diode 4 can be adjusted, thereby adjusting the absorption amplitude.

[0027] Since the 0.1pF surface-mount capacitor 6 is soldered as a resonant element in the main resonant microstrip line 5, its presence will block DC voltage. Therefore, the bias feed line 1 cannot be connected to either end of the main resonant microstrip line 5. The positive and negative terminals of the bias feed line 1 are connected to the two ends of the parallel resonant stub, respectively. Because the bias feed line 1 crosses the absorbing structure, the induced current on the bias feed line will affect the performance of the absorbing structure. To reduce the impact of the bias feed line 1 on the performance of the absorbing structure, three 1uH surface-mount inductors 7 are loaded on each bias feed line to reduce the induced current in the bias feed line 1. Through the bias feed line 1, a DC voltage source can be used to apply a reverse bias voltage to the varactor diode to achieve adjustment of the absorption amplitude.

[0028] The amplitude-tunable absorbing structure controlled by the varactor diode in this embodiment consists of a main resonant microstrip stub composed of a main resonant microstrip line 5, a 0.1pF chip capacitor 6, and a 100-ohm thin-film resistor 8 loaded on the main resonant microstrip line 5. The operating frequency band of the amplitude-tunable absorbing structure is determined by the parasitic inductance of the 0.1pF chip capacitor 6 and the main resonant microstrip line 5. By adjusting the geometric parameters of the main resonant microstrip line 5 and the capacitance value of the chip capacitor, the operating frequency band of the amplitude-tunable absorbing structure can be flexibly designed. The parallel resonant microstrip stub is connected in parallel with the 100-ohm thin-film resistor 8. On top, a 4.7nH surface mount inductor 2, a 10-ohm thin-film resistor 3, and a varactor diode 4 are soldered respectively. The resonant frequency of the parallel resonant microstrip stub is determined by the parasitic inductance in the parallel resonant microstrip stub, the 4.7nH surface mount inductor 2, and the varactor diode 4. The resonant frequency of the parallel resonant stub can be adjusted by adjusting the capacitance of the varactor diode 4. At the resonant frequency of the parallel resonant stub, the load resistance of the overall absorbing structure is the parallel resistance of the 10-ohm thin-film resistor 3 and the 100-ohm thin-film resistor 8. In the frequency range outside the resonant frequency, the resistance of the load resistance is from the parallel resistance value. Gradually changing to 100 ohms, exhibiting frequency-dependent characteristics; by changing the resonant frequency of the parallel resonant stub, the load resistor value can be effectively adjusted within the operating frequency range of the main resonant microstrip stub; in order to effectively adjust the absorption amplitude, the 10-ohm thin-film resistor 3 and the thin-film resistor 8 have values ​​much smaller than the 100-ohm resistor; therefore, in actual operation, through the bias feeder 1, the voltage across the varactor diode 4 is controlled by an external DC voltage source. By changing the output voltage of the DC voltage source, the capacitance value of the varactor diode 4 can be tuned. Within the ohm range, the load resistance of the absorbing structure can be effectively adjusted, thereby achieving effective adjustment of the absorption amplitude.

[0029] Based on the above unit design, we used the commercial full-wave simulation software CSTMicrowaveStudio (CST-MWS) to simulate the unit structure. Periodic boundary conditions were set around the unit structure, while the longitudinal direction was set as an open boundary. The electrically adjustable varactor diode described in this invention is model SMV2020-079LF. When the reverse bias voltage across the varactor diode varies within the range of 0 to 20V, the capacitance value of the varactor diode continuously varies within the range of 0.35 to 3.2pF. For convenience, during the simulation, the varactor diode is equivalent to a series-connected lumped element. The varactor diode model SMV2020-079LF used in this invention can be equivalent to a series-connected 2.5-ohm resistor, a 0.7nH inductor, and a capacitor whose capacitance value can continuously vary within the range of 0.35 to 3.2pF. Specifically, Figure 2The basic parameters of the unit cell model shown are as follows: unit cell period p = 10 mm, air layer thickness h = 10 mm, t = 0.5 mm, w1 = 0.5 mm, w2 = 0.4 mm, w3 = 0.3 mm. The metal microstrip line structure uses a conductivity of 5.8 × 10⁻⁶ mm. 7 The copper has a dielectric constant of 4.3 and a loss tangent of 0.025. The dielectric layer is FR-4.

[0030] The full-wave simulation results of the amplitude-tunable absorbing structure under TE and TM polarization states are respectively in Figure 3 and Figure 4 The information is provided in the text. In TE polarization, as the capacitance of the varactor diode gradually increases from 0.35pF to 3.2pF, the amplitude-adjustable absorbing structure can effectively adjust the amplitude from <0.2 to >0.8 within the frequency range of 1.83–2.03 GHz, and from <0.2 to >0.7 within the frequency range of 1.83–2.12 GHz. Specifically, at 1.96 GHz, the absorption amplitude can be adjusted within the range of 0–0.85. In TM polarization, as the capacitance of the varactor diode gradually increases from 0.35pF to 3.2pF, the amplitude-adjustable absorbing structure can effectively adjust the amplitude from <0.2 to >0.8 within the frequency range of 1.79–2.05 GHz, and from <0.2 to >0.7 within the frequency range of 1.79–2.09 GHz. Specifically, at 1.915 GHz, the absorption amplitude can be adjusted within the range of 0.03–0.85. It should be noted that, under the same capacitance condition, the amplitude-adjustable absorber exhibits a slight deviation in its electromagnetic wave response to TE polarization and TM polarization. This is because the first and second metal structures are distributed on the upper and lower surfaces of the dielectric layer, respectively. Due to the thickness of the dielectric layer, the metal structures operating in the two polarization states are not located in the same plane, which leads to a slight deviation in the resonant frequency and absorption amplitude of the two polarization states. This deviation can be improved by fine-tuning the dimensions of the metal structures.

[0031] The above embodiments are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several improvements and equivalent substitutions without departing from the principle of the present invention. For example, the design of amplitude-adjustable absorption by varactor diode control when migrating to other frequency bands in single-polarization or dual-polarization states, or obtaining different amplitude tuning ranges by changing the type of varactor diode and the values ​​of surface-mount components, etc., these technical solutions after improvements and equivalent substitutions to the claims of the present invention all fall within the protection scope of the present invention.

Claims

1. An amplitude-adjustable absorbing structure controlled by a varactor diode, characterized in that, The basic structural unit includes a structural layer, an air layer, and a metal ground plane. The structural layer consists of a dielectric layer and two identical, orthogonally placed metal layers, which are printed on the upper and lower surfaces of the dielectric layer using PCB technology. The metal layers include a main resonant microstrip stub, a parallel resonant microstrip stub, a bias feed line, a varactor diode, a thin-film resistor, a surface mount inductor, and a surface mount capacitor. The parallel resonant microstrip stub is connected in parallel with the thin-film resistor loaded in the main resonant microstrip stub. The surface mount inductor, varactor diode, and thin-film resistor are soldered into the parallel resonant microstrip stub. The resonant frequency of the parallel resonant microstrip stub is determined by the parasitic inductance, the surface mount inductor, and the varactor diode. By adjusting the capacitance of the varactor diode, the resonant frequency of the parallel resonant microstrip stub is adjusted, thereby adjusting the impedance load of the main resonant microstrip stub.

2. The amplitude-adjustable absorbing structure controlled by a varactor diode according to claim 1, characterized in that, Thin-film resistance value in parallel resonant microstrip stub R P Less than the thin film resistance value in the main resonant microstrip stub R M , R M and R P The value relationship between them is R M : R P ≥5:1; When at the resonant frequency of the parallel resonant microstrip stub, the load resistance of the absorbing structure is equivalent to the parallel value of two thin-film resistors. R P || R M As the resonant frequency of the parallel resonant microstrip stub moves away from the parallel value, the load resistance of the absorbing structure gradually decreases from the parallel value. R P || R M Increase the thin film resistance value in the microstrip stub of the main resonant microstrip R M It exhibits frequency dependence; when the resonant frequency of the parallel resonant microstrip stub changes, within the operating frequency of the main resonant microstrip stub, the load resistance of the absorbing structure is... R P || R M ~ R M The amplitude of wave absorption can be effectively adjusted within a certain range.

3. The amplitude-adjustable absorbing structure controlled by a varactor diode according to claim 1, characterized in that, The positive and negative terminals of the bias feed line are connected to the two ends of the parallel resonant microstrip stub, respectively. The capacitance of the varactor diode is adjusted by changing the voltage difference between the positive and negative terminals of the bias feed line, thereby adjusting the absorption amplitude.

4. The amplitude-adjustable absorbing structure controlled by a varactor diode according to claim 3, characterized in that, Three surface-mount inductors are soldered into each bias feed line to suppress the induced current in the bias feed line and reduce the impact of the bias feed line on the absorbing structure.

5. The amplitude-adjustable absorbing structure controlled by a varactor diode according to claim 1, characterized in that, The main resonant microstrip stub is a straight microstrip line that runs through the center of the unit. The parallel resonant microstrip stub is parallel to the main resonant microstrip stub. Two bias feed lines are located at both ends of the parallel resonant microstrip stub and are perpendicular to the main resonant microstrip stub.

6. The amplitude-adjustable absorbing structure controlled by a varactor diode according to claim 1, characterized in that, The operating frequency band of the absorbing structure can be adjusted by modifying the geometric parameters of the main resonant microstrip stub and the capacitance of the patch capacitor.

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