Dual-polarization frequency selection wave absorber with adjustable dual-frequency reflection band

Abstract

The invention discloses a dual-polarization frequency selection wave absorber with an adjustable dual-frequency reflection band. The tunable wave-absorbing frequency selection device is composed of a plurality of periodically distributed units, each unit comprises an upper-layer structure and a lower-layer structure, the upper layer is a tunable wave-absorbing frequency selection unit, the lower layer is a tunable frequency selection unit, and an isolation dielectric layer is arranged in the middle. A variable capacitance diode is introduced into a resonant structure, and parameters such as unit size, isolation layer height, resistance value and the like are regulated and controlled, so that tuning and comprehensive control of a reflection band are realized. The wave absorber can generate two independent reflection bands, the two independent reflection bands are combined to achieve broadband reflection, the positions of the reflection bands can be dynamically tuned, the wave absorber has out-of-band stealth performance, and compared with a traditional product, the wave absorber is wider in reflection bandwidth, simple in structure, low in cost and large in potential.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology, and relates to a dual-polarized frequency selective absorber with adjustable dual-frequency reflection bands, which can be applied to related intelligent electromagnetic stealth and protection platforms such as electromagnetic compatibility and intelligent antenna reflector systems with reduced radar cross section outside the band. Background Art

[0002] With the continuous evolution of the electromagnetic battlefield environment and the continuous upgrading of radar technology, the threat of a target being detected by an enemy radar has increased accordingly. At the same time, there is a risk of losing combat effectiveness due to electromagnetic interference. Therefore, it is necessary to accelerate the development of stealth technology to improve the survival ability and anti-interference performance of the target and ensure a competitive advantage in the increasingly complex electromagnetic warfare environment. As an effective method to address these challenges, dual-polarized frequency selective absorbers with tunable reflection bands have received extensive attention. Such structures can generate a tunable reflection band within the original working range of the absorption band, dynamically change the working frequency band, and efficiently absorb incoming wave signals outside the working frequency band, significantly enhancing the communication and stealth capabilities of the communication system.

[0003] In the face of a complex electromagnetic environment, traditional passive absorbing frequency selective absorbers with a single reflection band can only respond to a single electromagnetic environment. Once fabricated, their performance cannot be changed. To solve this problem, by introducing active devices into the structure, the tuning function of the absorber for the reflection band can be constructed, enabling it to have the ability to dynamically tune the reflection band frequency according to the working state of the intelligent antenna reflector system, while ensuring the stealth performance outside the working band and significantly enhancing the stealth ability of the antenna system.

[0004] Currently, there is relatively little work on dual-polarized frequency selective absorbers with tunable reflection bands. In the reported work, the reflection bandwidth of most work only refers to a single frequency point, which has great limitations for its application scenarios. The related research work on dual-polarized frequency selective absorbers with tunable reflection bands is almost blank. Summary of the Invention

[0005] The purpose of the present invention is to provide a dual-polarized frequency selective absorber with adjustable dual-frequency reflection bands in view of the deficiencies of the prior art. Based on the existing advanced design technology of passive frequency selective absorbers with reflection bands, varactor diodes are introduced into the resonant structure to obtain a frequency selective absorber with adjustable dual-frequency reflection bands. This structure can achieve a tunable wide reflection band, with an adjustable reflection bandwidth, and has a simple structure, clear principle, is easy to process, has a low design cost, and has great application potential.

[0006] The present invention provides a dual-polarized frequency selective absorber with an adjustable dual-frequency reflection band, which includes a plurality of periodically distributed frequency selective absorber units. Each frequency selective absorber unit includes a tunable absorber frequency selective unit located in the upper layer and a tunable frequency selective unit located in the lower layer; there is an isolation dielectric layer between the tunable absorber frequency selective unit and the tunable frequency selective unit; The tunable absorber frequency selective unit includes a first dielectric plate, and a first metal surface and a second metal surface printed on the upper side and the lower side of the first dielectric plate respectively, wherein the first metal surface and the second metal surface are connected through a first metallized via; The first metal surface includes a cross-shaped cross strip line and a cross-shaped DC bias line; wherein the sides of the cross-shaped cross strip line form a 45° angle with the sides of the cross-shaped DC bias line, and the centers of the cross-shaped cross strip line and the cross-shaped DC bias line coincide; The tunable frequency selective unit includes a second dielectric plate, and a third metal surface and a fourth metal surface printed on the upper side and the lower side of the second dielectric plate respectively; wherein the third metal surface and the fourth metal surface are connected through a second metallized via; The third metal surface includes a metal ring and a metal patch located inside the metal ring; a second varactor diode is connected in series between the metal ring and the metal patch; The fourth metal surface serves as a metal reflector.

[0007] Preferably, a first lumped resistor and a first varactor diode are respectively welded to the four sides of the cross-shaped cross strip line.

[0008] Preferably, metal meander lines are introduced at the outer ends of the four sides of the cross-shaped cross strip line.

[0009] Preferably, a second lumped resistor is respectively welded to the four sides of the DC bias line.

[0010] Preferably, the second metal surface adopts a spiral resonator.

[0011] Preferably, the spiral resonator of the second metal surface is composed of four spiral metal strips, and the four spiral metal strips are respectively connected to the four sides of the cross-shaped cross strip line through the first metallized vias.

[0012] Preferably, there is a gap between the metal ring and the metal patch.

[0013] Preferably, a first varactor diode is welded at the center of the cross-shaped intersecting strip line, and the first varactor diode is connected to the spiral resonator of the second metal surface through the first metallized via hole to realize the tuning of the reflection band. By changing the length and width dimensions of the frequency selective absorber unit, tuning the height of the isolation dielectric layer between the absorber frequency selective unit and the tunable frequency selective unit, and the resistance value of the first lumped resistor, the starting frequency of the reflection band and the bandwidth of the absorption band are comprehensively regulated.

[0014] Preferably, when electromagnetic waves are incident on the surface of the tunable absorbing frequency selective unit, the tunable absorbing frequency selective unit absorbs the incident electromagnetic waves that are not in the resonant frequency range, while for the incident electromagnetic waves in the resonant frequency range, they can efficiently pass through the tunable absorbing frequency selective unit and be reflected by the fourth metal surface of the tunable frequency selective unit, thus forming the first reflection point; by welding a first varactor diode at the center of the cross-shaped intersecting strip line of the tunable absorbing frequency selective unit, and connecting the first varactor diode to the spiral resonator of the second metal surface through the first metallized via hole, by changing the capacitance value of the diode, the translation of the first reflection band is realized. The tunable frequency selective unit realizes impedance cancellation with the isolation dielectric layer through reasonable design of its own impedance characteristics, thus generating the second reflection band; by loading a second varactor diode between the metal ring and the metal patch, the impedance characteristics are adjusted to realize the frequency shift of the second reflection band; by independently controlling the positions of the first reflection band and the second reflection band, the tuning of the wide reflection band is realized.

[0015] Preferably, the isolation dielectric layer uses air dielectric.

[0016] The present invention has the following advantages: (1) Based on the original passive frequency selective absorber with a reflection band, the present invention loads varactor diodes to realize the tuning function of the reflection band, enabling the structure to have out-of-band stealth performance while dynamically tuning the position of the reflection band according to the requirements of the working frequency band, greatly improving the security of the system.

[0017] (2) The two structures of the upper and lower layers can generate two independent reflection bands, and the two reflection bands can be combined to realize broadband reflection characteristics.

[0018] (3) Compared with the previous similar works, the present invention can achieve a broadband reflection response instead of a single-point frequency reflection, and the tunable reflection bandwidth demonstrated by the present invention is the widest among the previous similar works. Description of the Drawings

[0019] Figure 1is the three-dimensional structure schematic diagram of the present invention, where t 1 is the thickness of the first dielectric plate, t 2 is the thickness of the second dielectric plate, h 1 is the thickness of the isolation dielectric layer.

[0020] Figure 2 is the top-layer schematic diagram of the tunable absorbing frequency selection unit of the present invention, where P is the period length of the frequency selection absorbing body unit in the x-axis and y-axis directions, w 1 is the line width of the cross-strip line, w 2 is the line width of the metal bias line, w 3 is the distance of the metal meander line from the diagonal boundary, w 4 is the distance of the second lumped resistor from the parallel boundary, l 1 is the inductance line width of the metal meander line, l 2 is the distance between two adjacent transverse bends in the metal meander line, l 3 is the distance between two adjacent longitudinal bends in the metal meander line, R 1 is the resistance value of the first lumped resistor, R 2 is the resistance value of the second lumped resistor, C var1 is the capacitance value of the first varactor diode.

[0021] Figure 3 is the bottom-layer schematic diagram of the tunable absorbing frequency selection unit of the present invention, where a 1 is the outermost line length of the spiral resonator, a 2 is the line width at the center of the spiral resonator, a 3 is the inner line length of the spiral resonator, a 4 is the meander line width of the spiral resonator.

[0022] Figure 4 is the top-layer schematic diagram of the tunable frequency selection unit of the present invention, where b 1 is the line width of the metal ring, b 2 is the width of the gap between the metal ring and the metal patch, b 3 is the line width of the metal patch; C var2 is the capacitance value of the second varactor diode.

[0023] Figure 5 is the bottom-layer schematic diagram of the tunable frequency selection unit of the present invention.

[0024] Figure 6 is the frequency response characteristic curve diagram of the present invention under different capacitance values.

[0025] Markings in the figure: Tunable wave-absorbing frequency selection unit 1, first dielectric plate 11, first metal surface 12, second metal surface 13, first metallized via 14, cross-strip line 121, metal meander line 122, first lumped resistor 123, first varactor diode 124, DC bias line 125, second lumped resistor 126, tunable frequency selection unit 2, second dielectric plate 21, third metal surface 22, fourth metal surface 23, second metallized via 24, metal ring 221, metal patch 222. Detailed implementation mode

[0026] The following further analyzes the present invention in combination with specific embodiments.

[0027] The dual-polarization frequency-selective absorber designed in this embodiment adopts a periodic multi-layer structure in a vertically stacked form. Multiple frequency-selective absorber units are periodically distributed to form the entire absorber. As Figure 1 shown, each frequency-selective absorber unit is arranged vertically in two layers, which are the tunable wave-absorbing frequency selection unit 1 and the tunable frequency selection unit 2 from top to bottom in sequence, and the two are separated by an isolation dielectric layer. In actual application scenarios, the design of this multi-layer structure has significant advantages. For example, in the field of military stealth equipment, such as on the fuselage surface or radome of a fighter plane, the multi-layer structure can flexibly adjust the wave-absorbing and reflection characteristics according to the incident conditions of electromagnetic waves in different directions and frequencies, effectively reducing the probability of being detected by the enemy's radar.

[0028] The isolation dielectric layer plays a key role in the present invention, and air dielectric can be selected. Air dielectric has the characteristics of low dielectric constant and low loss tangent, which can effectively reduce the energy loss of electromagnetic waves during propagation, and at the same time provide a suitable electromagnetic coupling environment for the upper and lower layer units, ensuring that the electromagnetic interaction between the units meets the expected design and guaranteeing the stability and high efficiency of the overall performance of the absorber.

[0029] As Figure 2 、 3 shown, the tunable wave-absorbing frequency selection unit 1 includes a first dielectric plate 11, a first metal surface 12 printed on the upper surface of the first dielectric plate 11, and a second metal surface 13 printed on the lower surface of the first dielectric plate 11, and the two metal surfaces are electrically connected through a first metallized via 14; The first dielectric plate 11, as a load-bearing structure, needs to have a certain mechanical strength and stable dielectric properties. In terms of material selection, materials with moderate dielectric constant and small loss are usually selected, such as common high-performance engineering plastics or ceramic matrix composites, etc.

[0030] The first metal surface 12 includes a cross-shaped strip line 121 and a DC bias line 125. Both of them have a cross-shaped structure and their centers coincide. The sides of the cross-shaped strip line 121 and the sides of the DC bias line 125 are arranged staggeredly at a 45° angle.

[0031] The second metal surface 13 adopts a spiral resonator structure and is composed of four spiral metal strips. This spiral resonator structure has unique resonance characteristics. It can generate strong resonance within a specific frequency range, enabling the electromagnetic waves within this frequency range to pass through this surface without loss and be reflected by the fourth metal surface 23 of the tunable frequency selection unit 2, thereby forming the first reflection point.

[0032] In one implementation, to further optimize the performance, metal zigzag lines 122 are connected in series at the positions near the outer ends of each side of the cross-shaped strip line 121. The introduction of the metal zigzag lines 122 can effectively increase the equivalent inductance of the cross-shaped strip line 121 and broaden the effective working frequency band of the absorber.

[0033] In one implementation, a first lumped resistor 123 and a first varactor diode 124 are welded to each side of the cross-shaped strip line 121. The first lumped resistor 123 is close to the metal zigzag line 122, the first varactor diode 124 is close to the center position, and there is a cross-shaped strip line 121 between the first lumped resistor 123 and the first varactor diode 124. The cross-shaped strip line 121 welded with the first lumped resistor 123 can be equivalent to a combined network of resistance, inductance, and capacitance. It exhibits different impedance characteristics under the action of electromagnetic waves of different frequencies and guides the induced current of the incident electromagnetic wave to flow through the first lumped resistor 123, enabling the absorption of electromagnetic waves within this unit. The first varactor diode 124 is one of the key devices for realizing the tuning of the reflection band. By changing its capacitance value, the resonance frequency of the resonant circuit connected to it can be changed, thereby realizing the translational control of the reflection band.

[0034] The DC bias line 125 is mainly used to provide a stable DC bias voltage for the subsequent connected active devices to ensure their normal operation. In one implementation, to eliminate the influence of the feeder on the structural performance, a second lumped resistor 126 with a relatively large resistance value is welded to the DC bias line 125; the second lumped resistor 126 is close to the outer end position of the DC bias line 125.

[0035] As Figure 4 、 5 shown, the tunable frequency selection unit 2 includes a second dielectric plate 21, a third metal surface 22 printed on the upper side of the second dielectric plate 21, and a fourth metal surface 23 printed on the lower side of the second dielectric plate 21. The two metal surfaces are electrically connected through the second metallized vias 24; The second dielectric plate 21 is similar to the first dielectric plate 11 and needs to have good mechanical properties and stable dielectric properties. Its thickness t 2 is also an important parameter affecting the electromagnetic performance of the unit. In different application scenarios, according to the required frequency response characteristics and overall structural design requirements, appropriate materials and thickness t 2 will be selected to ensure that the unit can play the expected role in the entire absorber.

[0036] The third metal surface 22 includes a metal ring 221 and a metal patch 222 located inside the metal ring 221. In this embodiment, both the metal ring 221 and the metal patch 222 are octagonal. This shape design can provide a relatively unique electromagnetic field distribution pattern while ensuring a certain structural symmetry. There is a gap between the metal ring 221 and the metal patch 222, and they are connected by four second varactor diodes 223. The metal ring 221 and the metal patch 222 form a structure similar to a capacitance-inductance coupling, and its own resonance characteristics will have an important impact on the electromagnetic waves passing through this unit. The second varactor diode 223 provides a means to adjust the impedance characteristics of this unit. By changing its capacitance value, the coupling degree and resonance frequency between the metal ring 221 and the metal patch 222 can be changed, thereby realizing the frequency shift control of the second reflection band and working in cooperation with the tunable absorbing frequency selection unit 1 to achieve the tuning function of the wide reflection band.

[0037] The fourth metal surface 23 is a pure metal reflection surface, and its main function is to reflect the electromagnetic waves passing through the tunable absorbing frequency selection unit 1. During the actual working process, when electromagnetic waves are incident on the surface of the tunable absorbing frequency selection unit 1, for the electromagnetic waves within the resonance frequency range, they will efficiently pass through this unit and be reflected by the fourth metal surface 23, thus forming the first reflection point. The material of the fourth metal surface 23 is usually selected as a metal with good conductivity, such as copper or aluminum, etc.

[0038] The above structure realizes the tuning function of the first reflection band by welding a first varactor diode Varactor124 at the center of the cross-shaped cross-strip line 121 and connecting the first varactor diode Varactor 124 to the spiral resonator of the second metal surface 13 through the first metallized via 14. When the capacitance value of the first varactor diode 124 is changed, the resonance frequency of the spiral resonator will change accordingly, thereby causing the first reflection band to shift along the frequency axis.

[0039] The tunable frequency selection unit 2 achieves impedance cancellation with the isolation dielectric layer by reasonably designing its own impedance characteristics, thereby generating a second reflection point. This process involves the comprehensive application of complex electromagnetic field theory and circuit theory. From the perspective of the electromagnetic field, by adjusting the structural parameters of the metal ring 221 and the metal patch 222 and the capacitance value of the second varactor diode 223, the electromagnetic field distribution and propagation characteristics inside the unit can be changed, so that the electromagnetic field of the unit interacts with that of the isolation dielectric layer at a specific frequency to achieve the effect of impedance cancellation. From the circuit perspective, it is equivalent to constructing a specific resonant circuit that generates a reflection phenomenon under certain impedance matching conditions. By loading the second varactor diode 223 between the metal ring 221 and the metal patch 222, the impedance characteristics of the unit can be flexibly adjusted to achieve the frequency shift of the second reflection band.

[0040] Therefore, by independently controlling the positions of the first and second reflection bands, the tuning function of the wide reflection band is achieved. This collaborative working mechanism enables the absorber to adapt to complex and changeable electromagnetic environments. For example, in the face of multi-band electromagnetic interference, the positions and bandwidths of the two reflection bands can be precisely adjusted according to the frequency distribution of different interference sources to achieve efficient suppression of interference signals, while ensuring normal communication and stealth performance within the working frequency band.

[0041] In summary, in this embodiment, the starting frequency of the reflection band and the bandwidth of the absorption band can be comprehensively regulated in various ways. In addition to the above-mentioned translation and frequency shift of the reflection band achieved by changing the capacitance value of the varactor diode, the length and width dimensions of the frequency selective absorber unit can also be adjusted, as well as the height of the isolation dielectric layer between the tuning absorption frequency selection unit 1 and the tunable frequency selection unit 2, and the resistance value of the first lumped resistor 123 and other parameters.

[0042] Changing the length and width dimensions of the frequency selective absorber unit will affect the resonant frequency and electromagnetic field distribution mode of the unit. From the perspective of the resonant cavity model of electromagnetic theory, changing the unit dimensions is equivalent to changing the boundary conditions of the resonant cavity, thereby causing the resonant frequency to change. For example, increasing the length or width of the unit may lower the resonant frequency, thereby affecting the starting frequency and bandwidth of the reflection band.

[0043] Adjusting the height h of the isolation dielectric layer 1 will change the electromagnetic coupling strength between the upper and lower layer units. When h 1 increases, the electromagnetic coupling weakens, which may cause the bandwidth of the reflection band to narrow, but at the same time may also cause the center frequency of the reflection band to shift. Conversely, decreasing h1 will enhance the electromagnetic coupling, having the opposite effect on the bandwidth and frequency of the reflection band.

[0044] The resistance change of the first lumped resistor 123 mainly affects the impedance characteristics and energy loss of the circuit. Increasing the resistance will increase the impedance of the circuit, increase the energy loss of the electromagnetic wave in the unit, and may cause the bandwidth of the wave-absorbing band to become narrower.

[0045] Through the comprehensive regulation of these parameters, the fine adjustment of the performance of the wave absorber can be achieved to meet the requirements in different application scenarios. For example, in military stealth applications, according to the detection frequency range and power intensity of the enemy radar, the parameters of the wave absorber can be accurately adjusted to minimize the impact on its own communication and electronic devices while ensuring the stealth effect.

[0046] Figure 6 This is the frequency response characteristic curve graph of this embodiment when the first varactor diode and the second varactor diode have different capacitance values. It can be seen that when the capacitance continuously increases, its reflection band will shift accordingly, and the maximum reflection range that satisfies double-sideband absorption (|S 11 | < -10dB) is 6.65 - 3.09 GHz. As the reflection band tunes to lower frequencies, the wave-absorbing range also extends to lower frequencies accordingly. Specifically, when the capacitance values are adjusted from C var1 = 0.265 pF and C var2 = 0.23 pF to C var1 = 1.31 pF and C var2 = 1.46 pF, the wave-absorbing range extends from 3.87 - 9.46 GHz to 3.02 - 9.15 GHz. This fully demonstrates the advantages of the present invention in wide reflection band tuning and wave-absorbing performance, laying a solid foundation for its wide application in fields such as electromagnetic compatibility and intelligent antenna reflector systems.

[0047] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements are also regarded as the protection scope of the present invention.

Claims

1. A dual-polarization frequency selective absorber with adjustable dual-frequency reflection bands, comprising a plurality of periodically distributed frequency selective absorber units, each frequency selective absorber unit comprising a tunable absorbing frequency selective unit (1) located at an upper layer and a tunable frequency selective unit (2) located at a lower layer; an isolation dielectric layer is present between the tunable absorbing frequency selective unit (1) and the tunable frequency selective unit (2); The tunable wave absorbing frequency selection unit (1) comprises a first dielectric plate (11), and a first metal surface (12) and a second metal surface (13) respectively printed on the upper side and the lower side of the first dielectric plate (11), wherein the first metal surface (12) and the second metal surface (13) are connected via a first metallized via (14); The first metal surface (12) comprises a cross-shaped cross strip line (121) and a cross-shaped DC bias line (125); wherein the side of the cross-shaped cross strip line (121) and the side of the cross-shaped DC bias line (125) form an angle of 45°, and the centers of the cross-shaped cross strip line (121) and the cross-shaped DC bias line (125) coincide with each other; The tunable frequency selection unit (2) comprises a second dielectric plate (21), and a third metal surface (22) and a fourth metal surface (23) respectively printed on the upper side and the lower side of the second dielectric plate (21); wherein the third metal surface (22) and the fourth metal surface (23) are connected via a second metallized via (24); The third metal surface (22) comprises a metal ring (221) and a metal patch (222) located inside the metal ring (221); a second variable capacitance diode (223) is connected in series between the metal ring (221) and the metal patch (222); The fourth metal surface (23) serves as a metal reflection surface.

2. The dual-polarization frequency selective absorber according to claim 1, characterized in that: The four sides of the cross-shaped cross strip line (121) are respectively welded with a first lumped resistor (123) and a first variable capacitance diode (124).

3. The dual-polarization frequency selective absorber according to claim 1 or 2, characterized in that: Metal meandering lines (122) are also introduced into the four outer ends of the cross-shaped cross strip line (121).

4. The dual-polarization frequency selective absorber according to claim 1, characterized in that: The four sides of the DC bias line (125) are respectively welded with a second lumped resistor (126).

5. The dual-polarization frequency selective absorber according to claim 1, characterized in that: The second metal surface (13) adopts a spiral resonator.

6. The dual-polarization frequency selective absorber according to claim 1, characterized in that: The spiral resonator of the second metal surface (13) is used for four spiral metal strips, and the four spiral metal strips are respectively connected to the four sides of the cross-shaped cross strip line (121) through the first metallized via holes (14).

7. The dual-polarization frequency selective absorber according to claim 1, characterized in that: There is a gap between the metal ring (221) and the metal patch.

8. The dual-polarization frequency selective absorber according to claim 1, characterized in that: A first variable capacitance diode (124) is welded at the center of a cross-shaped cross strip line (121), and the first variable capacitance diode (124) is connected to a spiral resonator of a second metal surface (13) through a first metallized via (14), thereby realizing tuning of a reflection band. By changing the length and width of a frequency selective absorber unit, tuning the height of an isolation dielectric layer between an absorbing frequency selective unit (1) and a tunable frequency selective unit (2), and the resistance value of a first lumped resistor (123), the starting frequency of the reflection band and the bandwidth of the absorbing band are comprehensively regulated.

9. The dual-polarization frequency selective absorber according to claim 1, characterized in that: When an electromagnetic wave is incident on the surface of the tunable wave absorbing frequency selection unit (1), the tunable wave absorbing frequency selection unit (1) absorbs the incident electromagnetic wave that is not within the resonant frequency range, while the incident electromagnetic wave that is within the resonant frequency range can efficiently pass through the tunable wave absorbing frequency selection unit (1) and be reflected by the fourth metal surface (23) of the tunable frequency selection unit (2), thereby forming a first reflection point; by welding a first variable capacitance diode (124) at the center of a cross-shaped cross strip line (121) of the tunable wave absorbing frequency selection unit (1), and connecting the first variable capacitance diode (124) to the spiral resonator of the second metal surface (13) through a first metallized via (14), the capacitance value of the first variable capacitance diode (124) is changed, thereby achieving translation of the first reflection band; The tunable frequency selection unit (2) achieves impedance cancellation with the isolation dielectric layer by reasonably designing its own impedance characteristics, thereby generating a second reflection point; and adjusts the impedance characteristics to achieve frequency shift of the second reflection band by loading a second variable capacitance diode (223) between the metal ring (221) and the metal patch (222); Finally, tuning of a wide reflection band is achieved by independently controlling the positions of the first reflection band and the second reflection band.

10. The dual-polarization frequency selective absorber according to claim 1, characterized in that: The isolation medium layer is air medium.

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