Dual-polarization band-pass wave-absorbing frequency selective surface with low profile and wide wave-absorbing band

Abstract

The invention discloses a dual-polarized band-pass wave-absorbing frequency selective surface with a low profile and a wide wave-absorbing band, which comprises a plurality of periodically distributed band-pass wave-absorbing frequency selection units, and each band-pass wave-absorbing frequency selection unit comprises a lossy layer, an air spacing layer and a band-pass frequency selection layer; wherein the lossy layer is composed of a first dielectric substrate and first lossy metal faces printed on the two sides of the first dielectric substrate, each metal face comprises a bent line resonator and a strip line, and a radio frequency resistor is arranged on each strip line; the air spacing layer is located between the lossy layer and the band-pass frequency selection layer; the band-pass frequency selection layer is composed of a second dielectric substrate, a third dielectric substrate and a metal structure printed on the second dielectric substrate and the third dielectric substrate. The filter circuit is constructed based on induction current and an electric field excited by electromagnetic waves on a metal structure, electromagnetic wave transparency in a passband and electromagnetic wave energy loss outside the passband are realized, the profile thickness and the unit size are reduced, the angle stability is improved, and 45 degrees can be easily reached.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic stealth and protection, and relates to a dual-polarized band-pass type absorbing frequency selective surface with a low profile and a wide absorbing band. Background Art

[0002] A frequency selective surface is a surface formed by periodically arranging unit structures. Through the special design of the unit structure, the regulation of electromagnetic waves irradiated on its surface can be realized. The band-pass absorbing frequency selective surface is based on the equivalent circuit principle, and a band-pass filtering characteristic can be designed. Within the designed passband, electromagnetic waves can pass through, and outside the passband, electromagnetic waves can be absorbed or reflected. The band-pass absorbing frequency selective surface can be incorporated into equipment such as stealth antennas to play an electromagnetic protection role, and has a very broad application prospect.

[0003] Currently, most of the methods for realizing the absorbing band of the band-pass absorbing frequency selective structure are based on the stacked structure of a lossy layer and a frequency selective surface. The frequency selective surface is equivalent to a metal ground outside the passband, and the impedance matching structure is realized by combining with the lossy layer to achieve electromagnetic wave absorption. For a wide absorbing band, it has been reported that multiple stacked lossy layers are mostly used to achieve it. Although the absorbing band is broadened, the profile thickness and unit size are sacrificed, which limits the practical applicability. Summary of the Invention

[0004] The purpose of the present invention is to provide a dual-polarized band-pass type absorbing frequency selective surface with a low profile and a wide absorbing band in view of the deficiencies of the prior art. This structure innovatively loads a lumped resistor (radio frequency resistor) into the second-order band-pass frequency selective surface in accordance with the structural form of a single-layer lossy layer, an air gap, and a second-order band-pass frequency selective surface, so as to broaden the absorbing band without increasing the profile thickness and unit size.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A dual-polarized band-pass type absorbing frequency selective surface with a low profile and a wide absorbing band is composed of a two-dimensional planar array structure formed by regularly and vertically stacking a plurality of PCB boards. The two-dimensional planar array structure is composed of a plurality of band-pass absorbing frequency selective units arranged periodically along the x-axis and the y-axis. The band-pass absorbing frequency selective unit is composed of a lossy layer, an air gap layer, and a band-pass frequency selective unit stacked according to regulations.

[0007] The lossy layer is composed of a first dielectric substrate and first lossy metal surfaces printed on both sides of the first dielectric substrate; each first lossy metal surface includes a meander line resonator and first strip lines connected to both sides of the meander resonator; two first radio frequency resistors are arranged on the first strip line.

[0008] The air gap layer is located between the lossy layer unit and the band-pass frequency selective unit.

[0009] The described band-pass frequency selection is composed of a dielectric substrate and a metal structure printed on the dielectric substrate; wherein, the dielectric substrate includes a second dielectric substrate and a third dielectric substrate, and the metal structure includes a first square patch printed on the top surface of the second dielectric substrate, a second lossy metal surface printed on the top surface of the third dielectric substrate, and a second square patch and a first metal ring printed on the bottom surface of the third dielectric substrate.

[0010] The four sides of the described second dielectric substrate are provided with the same dielectric grooves.

[0011] The described second lossy metal surface is composed of a second metal ring and second strip lines connected to the four sides; a second RF resistor is arranged at the end of the second strip line.

[0012] Preferably, the first lossy metal surfaces printed on the upper and lower surfaces of the lossy layer are symmetrically rotated 90 degrees in the vertical direction.

[0013] Preferably, the first square metal patch and the second square metal patch have the same size.

[0014] Preferably, the outer boundary length sl of the second metal ring is greater than the side length pw of the first square patch.

[0015] Preferably, the inner boundary length s of the second metal ring w is less than the side length pw of the second square patch.

[0016] Preferably, the thickness h of the air spacer layer should be slightly less than one quarter of the wavelength corresponding to the passband frequency.

[0017] Specific working principle: When incident electromagnetic waves irradiate on the periodically arranged metal structure, induced currents and induced electric fields will be excited on the metal structure, thereby generating corresponding electromagnetic responses. According to the induced currents and electric fields, the distributed metal structure can be equivalent to lumped elements and a filter circuit can be constructed. Within the passband of the band-pass absorbing frequency selective surface, the metal structure generates resonance, so that the electromagnetic waves are transparent; outside the passband, the current can be guided through the RF resistor through circuit design to dissipate the energy of the electromagnetic waves.

[0018] The meander line resonator in the first lossy metal surface provides a low insertion loss wide passband, and the first strip line and the first RF resistor provide a frequency response for transmitting electromagnetic waves with loss outside the passband.

[0019] The air spacer layer can be equivalent to a quarter-wavelength lossless transmission line, which plays a role in impedance transformation.

[0020] The first square metal patch, the second square metal patch, and the second metal ring with band-pass frequency selection form a strong resonance structure for reception-coupling-transmission, which can be regarded as a band-pass transmission channel. In the frequency band below the passband, this resonance structure does not work, and the current is partially consumed on the RF resistor loaded at the end of the stripline. In the frequency band above the passband, the electromagnetic wave is reflected. The frequency response of the band-pass frequency selection is "wave absorption - wave transmission - reflection". Combined with the lossy layer, it has the effect of broadening the low-frequency wave absorption band.

[0021] The band-pass frequency selection can be regarded as a resistive surface at low frequencies and a metal ground at high frequencies. Through the impedance change of the air spacer layer and being connected in parallel with the lossy layer, it is the input impedance of this band-pass frequency selection; when the input impedance matches the air impedance, the reflected wave is absorbed, and a lower reflection coefficient is obtained.

[0022] When the meander line resonator resonates in the same frequency band as the band-pass frequency selection, the electromagnetic wave can pass through the band-pass frequency selection with low insertion loss.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) Based on the typical second-order band-pass frequency selective surface, the present invention innovatively loads lumped resistors into the structure. Without affecting the normal performance of the passband, it partially absorbs low-frequency electromagnetic waves and further broadens the bandwidth of the low-frequency wave absorption band.

[0025] (2) Based on the impedance characteristics of the proposed resistor-loaded band-pass frequency selective surface, through the structural design of the lossy layer, it is easy to realize a band-pass wave absorption frequency selective surface with a wide absorption band, a wide passband, and a low profile. The thickness and unit size of the present invention are both less than one-tenth of the lowest operating wavelength.

[0026] (3) Based on the proposed resistor-loaded band-pass frequency selective surface and the miniaturized lossy layer design, while ensuring the bandwidth, it reduces the profile thickness and unit size, further improves the angular stability, and is easy to reach 45°. Description of the Drawings

[0027] Figure 1 It is a schematic diagram of the array structure of the present invention.

[0028] Figure 2 It is a diagram of the band-pass wave absorption frequency selection unit of the present invention.

[0029] Figure 3 It is a diagram of the lossy layer unit of the present invention.

[0030] Figure 4 It is a diagram of the resistor-loaded band-pass frequency selective surface unit of the present invention.

[0031] Figure 5It is the upper layer structure diagram of the resistively loaded band-pass frequency selective surface of the present invention.

[0032] Figure 6 It is the lower layer structure diagram of the resistively loaded band-pass frequency selective surface of the present invention.

[0033] Figure 7 It is the simulated S-parameter diagram of the band-pass absorbing frequency selective structure of the present invention under normal incidence.

[0034] Figure 8 It is the simulated S-parameter diagram of the band-pass absorbing frequency selective structure of the present invention under the incidence of electromagnetic waves at 45°.

[0035] Markings in the figure: band-pass absorbing frequency selective array 1, band-pass absorbing frequency selective unit 2, lossy layer 3, first dielectric substrate 31, first lossy metal surface 32, meandered line resonator 33, first strip line 34, first RF resistor 35, air spacer layer 4, band-pass frequency selection 5, second dielectric substrate 51, first square patch 511, dielectric slot 512, third dielectric substrate 52, second lossy metal surface 521, second square patch 522, first metal ring 523, second RF resistor 524, second metal ring 525, second strip line 526. Detailed implementation manners

[0036] The following further analyzes the present invention in combination with specific embodiments.

[0037] As Figure 1 、 2 shown, the present invention provides a dual-polarized band-pass type absorbing frequency selective surface with a low-profile wide absorbing band, specifically a band-pass absorbing frequency selective array 1, which includes a plurality of identical band-pass absorbing frequency selective units 2 distributed periodically and arranged at intervals along the x and y axes;

[0038] As Figure 2 shown, each band-pass absorbing frequency selective unit 2 includes three layers of PCB boards, which are, from top to bottom, a lossy layer 3, an air spacer layer 4, and a band-pass frequency selection 5.

[0039] As Figure 3 shown, the lossy layer 3 includes a first dielectric substrate 31 and first lossy metal surfaces 32 printed on the upper and lower surfaces; two meandered line resonators 33, a first strip line 34, and a first RF resistor 35 are included in the unit; the first lossy metal surface structures on the upper and lower surfaces are the same and rotationally symmetric in the vertical direction.

[0040] As Figure 4As shown, the band-pass frequency selective structure is composed of the same back-to-back second dielectric substrate 51 and third dielectric substrate 52. The upper layer of the second dielectric substrate 51 is printed with a first square patch 511, and the upper layer of the third dielectric substrate 52 is printed with a second lossy metal surface 521. The second lossy metal surface is composed of a first metal ring 525, a second strip line 526, and a second RF resistor 524. The lower layer of the third dielectric substrate 52 is printed with a second square patch 522 and a second metal ring 523. The second dielectric substrate 51 is provided with dielectric slots 512 around it.

[0041] In the structure, p is the length and width of the band-pass absorbing frequency selective unit 2 in the x and y axis directions, t1 is the thickness of the first dielectric substrate 31, and t2 is the thickness of the second dielectric substrate 51 and the third dielectric substrate 52; h is the thickness of the air spacer layer 4; R w is the width of the bent line in the bent line resonator 33, g w is the interval of the bent line in the bent line resonator 33, L w is the width of the first strip line 34, L l is the length of the first strip line 34; p w is the side length of the first square patch 511 and the second square patch 522, d l is the length of the dielectric slot 512, d w is the width of the dielectric slot 512, s l is the outer boundary length of the second metal ring 525, s w is the inner boundary length of the second metal ring 525, w r is the width of the second strip line 526; w d is the width of the first metal ring 523.

[0042] Figure 7 This is the simulated S-parameter diagram of the band-pass absorbing frequency selective structure of the present invention under normal incidence. The absorption bands of the present invention with an absorption rate greater than 80% under normal incidence are 2.8 GHz - 8.44 GHz and 11.9 GHz - 17.7 GHz, the 3 dB passband is 8.9 GHz - 11.4 GHz, and the minimum insertion loss is 0.57 dB.

[0043] Figure 8This is the simulated S-parameter diagram of the band-pass absorbing frequency selection structure of the present invention under the incidence of 45° electromagnetic waves. It can be seen that under the incidence of 45° TE polarized waves, the absorption bands with an absorption rate greater than 80% achieved by the present invention are 3.25 GHz - 8.68 GHz and 11.81 GHz - 16.25 GHz, the 3 dB passband is 8.9 GHz - 11.59 GHz, and the minimum insertion loss is 1.18 dB; under the incidence of 45° TM polarized waves, the absorption bands with an absorption rate greater than 80% achieved by the present invention are 4.15 GHz - 8.62 GHz and 12.71 GHz - 16.05 GHz, the 3 dB passband is 8.94 GHz - 10.96 GHz, and the minimum insertion loss is 0.46 dB.

[0044] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, the material type / property / size can be replaced, or the structural form / size / layer number of the metamaterial absorber can be changed, as well as several other improvements and refinements. These improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A dual-polarization bandpass absorbing frequency selective surface with a low profile and a wide absorbing band, comprising a plurality of periodically distributed bandpass absorbing frequency selective units (2), characterized in that: The bandpass wave absorbing frequency selection unit (2) comprises, from top to bottom, a lossy layer (3), an air spacing layer (4) and a bandpass frequency selection (5); The lossy layer (3) is composed of a first dielectric substrate (31) and first lossy metal surfaces (32) printed on both sides of the first dielectric substrate (31); each first lossy metal surface (32) comprises a meander line resonator (33) and a first strip line (34) connected to both sides of the meander line resonator (33); two first radio frequency resistors (35) are arranged on the first strip line (34); The bandpass frequency selector (5) is composed of a dielectric plate and a metal structure printed on the dielectric plate; wherein the dielectric plate includes a second dielectric substrate (51) and a third dielectric substrate (52), and the metal structure includes a first square patch (511) printed on the top surface of the second dielectric substrate (51), a second lossy metal surface (521) printed on the top surface of the third dielectric substrate (52), and a second square patch (522) and a first metal ring (523) printed on the bottom surface of the third dielectric substrate (52).

2. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 1, characterized in that: Dielectric grooves (512) with the same structure are provided around the second dielectric substrate (51).

3. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 2, characterized in that: The second lossy metal surface (521) is composed of a second metal ring (525) and a second stripline (526); one end of the second stripline (526) is connected to the second metal ring (525), and the other end is connected to the edge of the second lossy metal surface (521); and a second radio frequency resistor (524) is provided at the end of the second stripline (526).

4. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 1, characterized in that: The first lossy metal surfaces (32) printed on the upper and lower surfaces of the lossy layer (3) are symmetrically rotated 90 degrees in the vertical direction.

5. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 1, characterized in that: The outer boundary length of the second metal ring (525) is greater than the side length of the first square patch (511).

6. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 5, characterized in that: The inner boundary length of the second metal ring (525) is smaller than the side length of the second square patch (522).

7. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 1, characterized in that: The first square metal patch (511) and the second square metal patch (522) have the same size.

8. The dual-polarization bandpass type absorbing frequency selective surface with low profile and wide absorbing band according to claim 1, characterized in that: The thickness of the air spacing layer (4) is less than one quarter of the wavelength corresponding to the passband frequency.

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