A low-profile, low-incident-angle-sensitivity absorbing surface and its manufacturing process

Abstract

The present invention discloses a low-profile, low-incident-angle-sensitivity absorbing surface, comprising a dielectric substrate, a two-dimensional planar periodic array composed of lossy frequency selection units printed on the front of the dielectric substrate, and a metal backplane; the lossy frequency selection unit is formed by nesting edge-interdigitated resistive square ring patches and metal square patches. The present invention can achieve an absorption rate of more than 90% within the operating frequency band, and at the same time maintain good performance stability for TE and TM polarizations, incident electromagnetic waves with a pitch incident angle in the range of 0 to 40°, and any azimuth incident angle. Compared with the prior art, the advantages of the present invention are extremely low profile, light weight, convenient processing, high absorption rate within the operating frequency band, good polarization stability and angular stability, and good engineering application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave and millimeter wave antennas, and relates to a wave-absorbing surface with low profile and low incident angle sensitivity and a manufacturing process thereof. Background Art

[0002] Absorbing materials refer to electromagnetic materials and electromagnetic structures that can attenuate, lose, and absorb electromagnetic waves. Through the loss of materials, the energy of electromagnetic waves in the microwave frequency band is converted into heat energy or other forms of energy. They are widely used in radar stealth, electromagnetic compatibility / shielding, antenna design and other fields. According to the working principle of the absorber, the resonant frequency of the absorber can be reduced by increasing the capacitance between adjacent patches. If the resonant frequency of the absorber is to be corrected to the original position, the thickness of the dielectric substrate needs to be reduced, thereby reducing the profile height of the absorber. According to the working principle of the absorber, the polarization stability and angle stability of the absorber are closely related to its unit structure. Therefore, high-performance absorbers with light structures and low profiles have always been one of the key research directions of absorbing materials.

[0003] The circuit simulation absorber was first proposed based on the Salisbury screen, which is one of the earliest materials used for radar absorbing materials. In the early stage of design, it was used to shield hostile radar from detecting military aircraft and military ships, that is, to reduce the radar cross-section value of the aircraft or ship surface. However, the Salisbury screen has a narrow absorbing bandwidth. As an improvement, the Jaumann absorber was designed, which increases the absorbing bandwidth, but the absorber profile height also increases.

[0004] Filippo Costa, Agostino Monorchio and others disclosed a frequency selective radome with broadband absorption properties (Filippo Costa and Agostino Monorchio, "A Frequency Selective Radome With Wideband Absorbing Properties," in IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION vol.60, no.6, pp.2740-2747). The frequency selective surface of the square ring resistor film structure uniformly arranged on a 5 mm thick dielectric substrate is helpful to solve the problem of the narrow working bandwidth of the radome to a certain extent. However, the unit period of this design is large and the cross-section is high, and the polarization stability and angular stability are poor, which cannot meet the needs of high-performance engineering applications.

[0005] It can be seen that the profile height of the traditional circuit simulation absorbing surface is relatively high, which greatly limits the use scenarios of the absorber. In addition, various application scenarios also require the absorbing surface to maintain good absorbing performance at different incident angles. Therefore, it is of great significance to design an absorbing surface with low profile and low incident angle sensitivity. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a low-profile and low-incident angle-sensitivity absorbing surface and its manufacturing process, which can solve the problems of the absorbing material having a high profile and being sensitive to the incident angle while ensuring the working performance of the absorbing body.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A low-profile, low-incident-angle-sensitivity wave-absorbing surface comprises a dielectric substrate, a two-dimensional planar periodic array printed on the front surface of the dielectric substrate, and a metal floor printed on the back surface of the dielectric substrate. The overall structure is, from top to bottom, the two-dimensional planar periodic array, the dielectric substrate, and the metal floor.

[0009] Furthermore, the two-dimensional planar periodic array is formed by periodically arranging lossy frequency selection units along the x-axis and y-axis directions.

[0010] Furthermore, the lossy frequency selection unit of the two-dimensional planar periodic array is a nested structure consisting of an edge-interdigitated resistive square ring patch and a metal square patch, and the metal square patch is embedded in the lower left area of ​​the resistive square ring patch.

[0011] Furthermore, the edge of each side of the resistive square ring patch in the lossy frequency selection unit of the two-dimensional planar periodic array is provided with a periodic protrusion, i.e., an interdigital finger, and a groove is formed between two adjacent protrusions. The protrusions of adjacent resistive square ring patches are inserted into each other's grooves, and a gap is provided between the protrusion and the groove, i.e., an interdigital gap.

[0012] Furthermore, the edge interdigitated resistive square ring patches of the lossy frequency selection unit of the two-dimensional planar periodic array are made of a uniform resistive material with finite conductivity.

[0013] Furthermore, the metal square patches of the lossy frequency selection unit of the two-dimensional planar periodic array are made of metal material.

[0014] Furthermore, the arrangement period of the lossy frequency selection units of the two-dimensional planar periodic array is 8.25 mm along both the x and y directions.

[0015] Furthermore, the edge interdigitated resistive square ring patch of the lossy frequency selection unit of the two-dimensional planar periodic array has a side length of 6.4 mm, the number of interdigitations of each edge is 8, the width is 0.2 mm, the length is 1.6 mm, and the interdigitation gap is 0.2 mm; the square resistance value of the resistive square ring patch is 8Ω / sq; the side length of the metal square patch of the lossy frequency selection unit of the two-dimensional planar periodic array is 6 mm, and the metal thickness is 0.035 mm.

[0016] Furthermore, the dielectric substrate is made of FR4 material and has a thickness of 1.5 mm.

[0017] The present invention also provides a process for manufacturing a wave absorbing surface with a low profile and low incident angle sensitivity, comprising the following steps:

[0018] (1) The dielectric core layer of the copper clad laminate is selected as the dielectric substrate, and the lower metal layer is used as the metal floor;

[0019] (2) using PCB technology or engraving technology to periodically etch metal square patches on the upper metal layer of the obtained copper-clad board along the x-axis and y-axis directions;

[0020] (3) The designed edge-interdigitated resistive square ring patches are periodically applied to the upper surface of the dielectric substrate along the x-axis and y-axis directions according to the interdigitation production standard by using screen printing or laser engraving technology. In this step, each edge-interdigitated resistive square ring patch should seamlessly surround a metal square patch produced in the previous step, that is, the metal square patch should be seamlessly embedded in the hollow area of ​​the resistive square ring patch.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) The present invention uses edge-interdigitated resistive square ring patches to form the lossy frequency selection unit necessary for the absorber, which makes the present invention have the advantages of low profile, light weight, and simple processing and installation compared with traditional absorbers;

[0023] (2) The two-dimensional planar array used in the present invention has a certain rotational symmetry, so the wave absorbing performance of the present invention is insensitive to the polarization mode and has good polarization stability;

[0024] (3) The unit arrangement period of the two-dimensional planar periodic array adopted by the present invention is relatively small, so the stability of the wave absorbing performance of the present invention with different incident angles is relatively good.

[0025] The objects, features and advantages of the present invention will be further described below with reference to the accompanying drawings in conjunction with examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a schematic diagram of the overall structure decomposition of the low-profile and low-incident-angle-sensitivity absorbing surface of the present invention;

[0027] Figure 2 It is an exploded schematic diagram of the lossy frequency selection unit and its backing dielectric substrate and metal floor of the present invention;

[0028] Figure 3 is a top view of a lossy frequency selection unit of the present invention;

[0029] Figure 4 It is a structural side view of the lossy frequency selection unit and its backing dielectric substrate and metal floor of the present invention;

[0030] Figure 5 It is a reflection coefficient amplitude frequency response simulation curve of the present invention under TE polarization wave excitation at 0° azimuth incident angle and different pitch incident angles;

[0031] Figure 6 It is a reflection coefficient amplitude frequency response simulation curve of the present invention under the excitation of TE polarized waves at an azimuth incident angle of 45° and different pitch incident angles;

[0032] Figure 7 It is a reflection coefficient amplitude frequency response simulation curve of the present invention under the excitation of TM polarized waves at 0° azimuth incident angle and different pitch incident angles;

[0033] Figure 8 It is a reflection coefficient amplitude frequency response simulation curve of the present invention under the excitation of TM polarized waves at an azimuth incident angle of 45° and different pitch incident angles. DETAILED DESCRIPTION

[0034] like Figure 1-4 As shown, the low-profile and low-incident-angle-sensitivity absorbing surface of the present invention comprises a dielectric substrate 1, a two-dimensional planar periodic array 2 printed on the front surface of the dielectric substrate 1, and a metal floor 3 printed on the back surface of the dielectric substrate 1. The overall structure is the two-dimensional planar periodic array 2, the dielectric substrate 1, and the metal floor 3 from top to bottom.

[0035] The two-dimensional planar periodic array (2) is formed by periodically arranging lossy frequency selection units along the x-axis and y-axis directions.

[0036] The lossy frequency selection unit of the two-dimensional planar periodic array 2 is a nested structure consisting of an edge-interdigitated resistive square ring patch and a metal square patch, and the metal square patch is embedded in the lower left area of ​​the resistive square ring patch.

[0037] The edge of each side of the resistive square ring patch in the lossy frequency selection unit of the two-dimensional planar periodic array 2 is provided with a periodic protrusion (i.e., interdigitation), and a groove is formed between two adjacent protrusions. The protrusions of adjacent resistive square ring patches are inserted into each other's grooves, and a gap is provided between the protrusion and the groove, i.e., the interdigitation gap.

[0038] The edge interdigitated resistive square ring patches of the lossy frequency selection unit of the two-dimensional planar periodic array 2 are made of a uniform resistive material with finite conductivity.

[0039] The metal square patches of the lossy frequency selection unit of the two-dimensional planar periodic array 2 are made of metal material.

[0040] The arrangement period of the lossy frequency selection units of the two-dimensional planar periodic array 2 is 8.25 mm along both the x and y directions.

[0041] The edge interdigitated resistive square ring patch of the lossy frequency selection unit of the two-dimensional planar periodic array 2 has a side length of 6.4 mm, the number of interdigitated fingers 20 on each edge is 8, the width is 0.2 mm, the length is 1.6 mm, and the interdigitated gap is 0.2 mm; the square resistance value of the resistive square ring patch is 8Ω / sq; the side length of the metal square patch 21 of the lossy frequency selection unit of the two-dimensional planar periodic array 2 is 6 mm, and the metal thickness is 0.035 mm.

[0042] The dielectric substrate 1 is made of FR4 material and has a thickness of 1.5 mm.

[0043] The manufacturing process of the low-profile and low-incident-angle-sensitivity absorbing surface of the present invention is as follows: first, a double-sided epoxy resin (FR4) dielectric substrate with a dielectric core layer thickness of 1.5 mm is selected; the dielectric core layer of the obtained copper-clad laminate is used as a dielectric substrate 1, and the lower metal layer is used as a metal floor 3; then, a PCB process or engraving technology is used to periodically etch metal square patches 21 with a side length of 6 mm along the x-axis and y-axis directions on the upper metal layer of the obtained copper-clad laminate, and the period is 8.25 mm; finally, screen printing or laser engraving is used to The process periodically covers the designed edge-interdigitated resistive square ring patch on the upper surface of the dielectric substrate 1 along the x-axis and y-axis directions according to the manufacturing standards of 0.2mm width, 1.6mm length, 0.2mm interdigitated gap, and 8Ω / sq square resistance, and the arrangement period is also 8.25mm. In this step, each edge-interdigitated resistive square ring patch should seamlessly surround a metal square patch manufactured in the previous step, that is, the metal square patch should be seamlessly embedded in the hollow area of ​​the resistive square ring patch.

[0044] Figure 5 , 6The performance changes of the present invention under the irradiation of TE polarized waves at different angles are as follows: when the incident wave frequency is in the frequency band of 3.55 GHz to 3.65 GHz, for the full range of azimuth incident angles of 0° to 360° and the elevation incident angles of 0° to 40°, the reflection coefficient amplitude is below -10 dB. Figure 7 , 8 The performance changes of the present invention under the irradiation of TM polarized waves at different angles are shown. When the incident wave frequency is in the frequency band of 3.55 GHz to 3.65 GHz, the reflection coefficient amplitude is below -10 dB for the full range of azimuth incident angles of 0° to 360° and the elevation incident angles of 0° to 40°.

[0045] The resulting low-profile, low-incident-angle-sensitive absorbing surface has a small unit period and a certain rotational symmetry. While achieving absorbing waves near the 3.6 GHz operating frequency band, it also ensures that the absorbing performance within the absorbing frequency band has good polarization stability and angular stability.

[0046] Compared with the prior art, the present invention has the following advantages:

[0047] 1. The present invention adopts edge-interdigitated resistive square ring patches to form the lossy frequency selection unit necessary for the absorber, which makes the present invention have the advantages of low profile, light weight, simple processing and installation compared with the traditional absorber;

[0048] 2. The two-dimensional planar array used in the present invention has a certain rotational symmetry, so the wave absorbing performance of the present invention is insensitive to the polarization mode and has good polarization stability;

[0049] 3. The unit arrangement period of the two-dimensional planar periodic array adopted by the present invention is relatively small, so the wave absorbing performance of the present invention has good stability with different incident angles.

[0050] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not depart from the present invention based on the technical revelations disclosed in the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims

1. A low profile, low incident angle sensitivity absorbing surface, characterized in that: It comprises a dielectric substrate (1), a two-dimensional plane periodic array (2) printed on the front side of the dielectric substrate (1), and a metal floor (3) printed on the back side of the dielectric substrate (1); the overall structure is, from top to bottom, the two-dimensional plane periodic array (2), the dielectric substrate (1), and the metal floor (3); The edge interdigitated resistive square ring patches of the lossy frequency selection unit of the two-dimensional planar periodic array (2) are made of a uniform resistive material with finite conductivity; The arrangement period of the lossy frequency selection units of the two-dimensional planar periodic array (2) is 8.25 mm in both the x and y directions; The edge interdigitated resistive square ring patch of the lossy frequency selection unit of the two-dimensional planar periodic array (2) has a side length of 6.4 mm, the number of interdigitated fingers (20) on each side is 8, the width is 0.2 mm, the length is 1.6 mm, and the interdigitated gap is 0.2 mm; the square resistance value of the resistive square ring patch is 8Ω / sq; the side length of the metal square patch (21) of the lossy frequency selection unit of the two-dimensional planar periodic array (2) is 6 mm, and the metal thickness is 0.035 mm.

2. The low profile low incident angle sensitivity absorbing surface according to claim 1, characterized in that: The two-dimensional planar periodic array (2) is formed by periodically arranging lossy frequency selection units along the x-axis and y-axis directions.

3. The low profile low incident angle sensitivity absorbing surface according to claim 2, characterized in that: The lossy frequency selection unit of the two-dimensional planar periodic array (2) is a nested structure consisting of an edge-interdigitated resistive square ring patch and a metal square patch, and the metal square patch is embedded in the lower left area of ​​the resistive square ring patch.

4. The low profile low incident angle sensitivity absorbing surface according to claim 3, characterized in that: The edge of each side of the resistive square ring patch in the lossy frequency selection unit of the two-dimensional planar periodic array (2) is provided with a periodic protrusion, i.e., an interdigital finger, a groove is formed between two adjacent protrusions, the protrusions of adjacent resistive square ring patches are inserted into each other's grooves, and a gap is provided between the protrusion and the groove, i.e., an interdigital gap.

5. The low profile low incident angle sensitivity absorbing surface according to claim 1, characterized in that: The metal square patches of the lossy frequency selection units of the two-dimensional planar periodic array (2) are made of metal material.

6. The low profile low incident angle sensitivity absorbing surface according to claim 1, characterized in that: The dielectric substrate (1) is made of FR4 material and has a thickness of 1.5 mm.

7. A process for manufacturing a low-profile, low-incident-angle-sensitivity absorbing surface according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) A dielectric core layer of a copper-clad laminate is selected as a dielectric substrate (1), and a lower metal layer is selected as a metal floor (3); (2) using PCB technology or engraving technology to periodically etch metal square patches (21) on the upper metal layer of the obtained copper-clad board along the x-axis and y-axis directions; (3) Using screen printing or laser engraving technology, the designed edge-interdigitated resistive square ring patches are periodically applied to the upper surface of the dielectric substrate (1) along the x-axis and y-axis directions according to the interdigitation production standard. In this step, each edge-interdigitated resistive square ring patch should seamlessly surround a metal square patch produced in the previous step, that is, the metal square patch should be seamlessly embedded in the hollow area of ​​the resistive square ring patch.

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