Dual-polarization broadband absorbing frequency selective structure based on two-dimensional and three-dimensional interlocking structure

Abstract

The present invention relates to a dual-polarization broadband wave-absorbing frequency selection structure based on a two-dimensional and three-dimensional interlocking structure. In the previous frequency selection structures, the pure two-dimensional structure has the disadvantage that the wave-absorbing frequency band is difficult to be widened, and the filtering selection characteristic is not high, while the three-dimensional structure has a high selection characteristic, and the wave-absorbing band can be effectively widened by setting a resonant structure in the space in the direction of electromagnetic wave propagation. However, the unit structure of the three-dimensional structure is relatively complex, and the complex three-dimensional structure makes it difficult to achieve dual-polarization characteristics. The present invention combines the two-dimensional structure with the three-dimensional structure, adopts the two-dimensional and three-dimensional interlocking structure, takes advantage of each other's strengths and complements each other's advantages, and not only achieves the high selectivity and broadband wave-absorbing performance of the three-dimensional structure, but also uses the two-dimensional planar structure to simplify the overall structural design, and designs the dual-polarization characteristics, making the structure simpler to implement, and greatly expanding its application prospects.

Description

Technical Field

[0001] The present invention belongs to the field of microwave technology and relates to a dual-polarization broadband absorbing frequency selection structure based on a two- and three-dimensional interlocking structure, which can be used as a stealth antenna cover for antennas in the microwave frequency band. Its potential application scenarios include fighter fire control radars, surface ships, etc. Background Art

[0002] Stealth technology is very important in military applications. Applying it to antenna systems can effectively extend the reaction time of enemy systems and reduce their effective range, thereby greatly improving the safety and threat of our weapon platforms.

[0003] The antenna system needs to receive and transmit electromagnetic energy, which will be conducted on the metal structure of the antenna in the form of resonant current. Therefore, some conventional stealth technologies such as coating absorbing coatings and covering absorbing materials cannot be directly applied to the antenna system. Based on the absorbing frequency selection structure, the absorbing antenna cover is designed. By "inserting" the passband structure in the wide absorbing band, electromagnetic waves are allowed to be transmitted losslessly in a specific frequency band, thereby ensuring that electromagnetic waves within the antenna working frequency band can be transmitted losslessly, and electromagnetic waves outside the antenna working frequency band can be effectively absorbed, which not only realizes the stealth of the antenna outside the working frequency band, but also does not affect the normal operation of the antenna within the working frequency band. Summary of the invention

[0004] The purpose of the present invention is to provide a dual-polarization broadband absorbing frequency selection structure based on a two-dimensional and three-dimensional interlocking structure in view of the deficiencies of the prior art, and to adopt a new structural form in which a two-dimensional structure and a three-dimensional structure are interlocked to achieve wider transmission bands, absorbing bands and other performances. The proposed structure retains the advantages of the traditional two-dimensional structure in terms of simplicity and easy processing, and also has the advantages of the three-dimensional structure in terms of high selectivity, broadband and other performances. In general, the comprehensive performance is greatly improved.

[0005] The dual-polarization broadband absorbing frequency selection structure based on a two-dimensional and three-dimensional interlocking structure of the present invention comprises a plurality of periodically distributed units, each of which is seamlessly arranged along the x and y axes; each unit comprises a three-dimensional absorbing structure, a two-dimensional absorbing plane and a bandpass frequency selection surface.

[0006] The three-dimensional wave absorbing structure comprises a cross-shaped first dielectric plate, two metal bent dipoles and two first lumped resistors welded on each metal bent dipole.

[0007] The cross-shaped first dielectric plate is formed by dielectric plate A and dielectric plate B intersecting vertically to form a cross-shaped cross-section; a metal bent dipole is provided on each of dielectric plate A and dielectric plate B; the metal bent dipole is a C-shaped structure, and its opening faces the bandpass frequency selection surface;

[0008] Preferably, the center of the metal bent dipole is the intersection of the dielectric plate A and the dielectric plate B, and the two first lumped resistors located on the same metal bent dipole are distributed on both sides of the center of the metal bent dipole;

[0009] The two-dimensional absorbing plane is arranged vertically to the three-dimensional absorbing structure and is located in the middle of the cross-shaped first dielectric plate; it includes a second dielectric plate, a first metal surface equivalent to an LC circuit printed on the upper surface of the second dielectric plate, eight second lumped resistors welded on the first metal surface, eight first metallized vias penetrating the second dielectric plate, and a second metal surface printed on the lower surface of the second dielectric plate; the first metal surface and the second metal surface are connected through the first metallized vias;

[0010] Preferably, the center of the second dielectric plate coincides with the center of the cross-shaped first dielectric plate;

[0011] Preferably, the first metal surface comprises a cross-shaped metal strip; each of the four arms of the cross-shaped metal strip is provided with an interdigital capacitor, and a second lumped resistor loaded on both sides of the interdigital capacitor;

[0012] Preferably, the eight second lumped resistors have the same resistance value;

[0013] Preferably, the second metal surface includes four first metal strip lines that are independent of each other and do not contact each other.

[0014] Preferably, the first metal strip line is a zigzag microstrip line.

[0015] Preferably, the metal bent dipole does not contact the first metal surface and the second metal surface;

[0016] Preferably, the first metallized via is located between the interdigital capacitor and the second lumped resistor;

[0017] Preferably, the metal bent dipole does not contact the bandpass frequency selective surface;

[0018] Preferably, the ends of the four arms of the cross-shaped metal strip are connected to the cross-shaped metal strips of the adjacent units;

[0019] The bandpass frequency selective surface comprises two dielectric plates and three metal layers, namely a third dielectric plate, a fourth dielectric plate, a third metal surface printed on the upper layer of the third dielectric plate, a fourth metal surface printed on the lower layer of the third dielectric plate, and a fifth metal surface printed on the lower layer of the fourth dielectric plate; a coupling port is opened at the center of the fourth metal surface;

[0020] Preferably, the width w of the metal bent dipole along the width direction of the dielectric plate is d must be smaller than the width b of the medium plate on which it is located and satisfy (bwd ) / b≤1 / 5;

[0021] Preferably, the resistance range of the first lumped resistor is 50 to 250Ω;

[0022] Preferably, the lower center of the cross-shaped first dielectric plate in the three-dimensional absorbing structure is hollowed out to facilitate embedding of the two-dimensional absorbing plane;

[0023] Preferably, the length and width of the third metal surface are smaller than the length and width of the second dielectric plate;

[0024] Preferably, the length and width of the fifth metal surface are smaller than the length and width of the third dielectric plate;

[0025] Preferably, the height d between the two-dimensional absorbing plane and the bandpass frequency selective surface is m Satisfies the relationship d m ∈[0.2*c / f p ,0.3*c / f p ], where c is the speed of light in free space, f p is the operating frequency of the transmission belt;

[0026] Preferably, the first metal surface, the second metal surface and the first metallized via hole form four identical but independent parallel LC resonators, whose resonant frequency is the same as the operating frequency f of the passband. p same;

[0027] The centers of the three-dimensional absorbing structure, the two-dimensional absorbing plane, and the bandpass frequency selective surface are located on the same straight line;

[0028] The present invention changes the length and width of the unit, the thickness t of the first dielectric plate a And the dielectric constant ε r , the total length of the first metal strip line l s +w d , width w s All structural parameters such as the resistance value R1 of the first lumped resistor comprehensively regulate the performance such as the transmission band frequency, the transmission band bandwidth, the absorption band frequency and the absorption band bandwidth.

[0029] Specific working principle: When electromagnetic waves are incident on the surface of the structure, the three-dimensional absorbing structure works in the absorbing state at its fundamental mode frequency and the third-order mode frequency. At the same time, the two-dimensional absorbing plane will produce partial absorbing effects on both sides of the passband. At this time, the two-dimensional broadband bandpass frequency selection surface below is equivalent to an ideal metal reflective surface. And because the two metal bent dipoles located in the same plane in adjacent units form a slot line structure with an open terminal, the naturally existing periodic zero point of the slot line structure makes the absorbing frequency band significantly widened. Therefore, the dual-polarization broadband absorbing frequency selection structure based on the two-dimensional interlocking structure will obtain broadband absorbing bands at its fundamental mode frequency and the third-order mode frequency. At the second-order mode frequency, the terminal open slot line structure of the three-dimensional absorbing structure can provide infinite impedance, so that the electromagnetic wave can pass through with low loss. At the same time, the parallel LC resonator in the two-dimensional absorbing plane also allows the electromagnetic wave to pass through with low loss, and then pass through the lowest bandpass frequency selection surface, thereby forming a transmission band. Within the entire range of the absorption band and transmission band, the reflection coefficient of the structure is very small, thus achieving a stealth effect in the entire frequency band.

[0030] The dual-polarization broadband absorbing frequency selective structure based on the two-dimensional and three-dimensional interlocking structure has the following advantages:

[0031] (1) The dual-polarization broadband absorbing frequency selective structure based on the two-dimensional and three-dimensional interlocking structure of the present invention utilizes the three-dimensional transmission line to broaden the absorbing band. Compared with the previous pure two-dimensional absorbing frequency selective structure, it has a wider absorbing band and transmission band, greatly improving the stealth characteristics.

[0032] (2) The dual-polarization broadband absorbing frequency selective structure based on the two-dimensional and three-dimensional interlocking structure of the present invention adopts a two-dimensional broadband frequency selective surface as a reflecting surface. Compared with a pure three-dimensional structure, the structure is simpler, easier to implement and convenient to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a three-dimensional perspective view of the unit structure of the present invention;

[0034] Figure 2 is a side view of the unit structure of the present invention;

[0035] Figure 3 is a structural diagram of the first wave absorbing plane of the present invention;

[0036] Figure 4 is a simulation diagram of the frequency response characteristics of the present invention;

[0037] Markings in the figure: cross-shaped first dielectric plate 1, metal bent dipole 2, first lumped resistor 3, second dielectric plate 4, first metal surface 5, second lumped resistor 6, first metalized via 7, second metal surface 8, third metal surface 9, third dielectric plate 10, fourth metal surface 11, fourth dielectric plate 12, fifth metal surface 13. DETAILED DESCRIPTION

[0038] The present invention is further analyzed below in conjunction with specific embodiments.

[0039] The present invention adopts a structural form in which a two-dimensional structure and a three-dimensional structure are embedded in each other, and is cascaded with a bandpass frequency selective surface. Through the combination of the frequency response characteristics of the three in different frequency bands, a dual-polarization broadband wave absorbing frequency selective structure based on a two-dimensional and three-dimensional embedded structure with broadband wave absorbing and wave transmitting characteristics is realized.

[0040] like Figure 1 , 2 As shown in FIG. 3 , the dual-polarization broadband absorbing frequency selective structure based on the two- and three-dimensional interlocking structure is a periodic structure, and each structural unit is composed of a three-dimensional absorbing structure, a two-dimensional absorbing plane and a bandpass frequency selective surface.

[0041] The three-dimensional wave absorbing structure is a centrosymmetric structure, which includes a cross-shaped first dielectric plate 1, a metal bent dipole 2 printed on the first dielectric plate 1 and a first lumped resistor 3 above it; the cross-shaped first dielectric plate is formed by a dielectric plate A and a dielectric plate B intersecting and perpendicularly forming a cross-shaped structure in cross section; a metal bent dipole is provided on each of the dielectric plates A and B; the metal bent dipole is a C-shaped structure, and its opening faces the bandpass frequency selective surface; the center of the metal bent dipole is the intersection of the dielectric plate A and the dielectric plate B, and the two first lumped resistors located on the same metal bent dipole are distributed on both sides of the center of the metal bent dipole;

[0042] The center position of the lower end of the cross-shaped first dielectric plate in the three-dimensional wave absorbing structure is hollowed out to facilitate the embedding of the two-dimensional wave absorbing plane;

[0043] The two-dimensional wave absorbing plane is composed of a first metal surface 5 printed on the upper surface of the second dielectric plate 4, eight second lumped resistors 6 welded on the first metal surface 5, eight first metallized vias 7 penetrating the second dielectric plate 4, and a second metal surface 8 printed on the lower surface of the second dielectric plate. The center of the second dielectric plate coincides with the center of the cross-shaped first dielectric plate; the second metal surface includes a cross-shaped metal strip; the four arms of the cross-shaped metal strip are each provided with an interdigital capacitor and a second lumped resistor loaded on both sides of the interdigital capacitor; the second metal surface includes four first metal strip lines that are independent of each other and do not contact each other. The first metal strip line is a zigzag microstrip line. The metal bent dipole does not contact the first metal surface and the second metal surface; the first metallized via is located between the interdigital capacitor and the second lumped resistor; the metal bent dipole does not contact the bandpass frequency selection surface; the four arm ends of the cross-shaped metal strip are connected to the cross-shaped metal strip of the adjacent unit.

[0044] The bandpass frequency selective surface is composed of two dielectric plates and three metal layers, namely a third dielectric plate 10, a fourth dielectric plate 12, a third metal surface 9 printed on the upper surface of the third dielectric plate 10, a fourth metal surface 11 printed on the lower surface of the third dielectric plate 10 (or the upper surface of the fourth dielectric plate 12), and a fifth metal surface 13 printed on the lower surface of the fourth dielectric plate 12.

[0045] The first metal surface 5 printed on the upper surface of the second dielectric plate 4, the second metal surface 8 printed on the lower surface of the second dielectric plate 4 and the two first metallized vias 7 penetrating the second dielectric plate 4 form four parallel LC resonators separated from each other.

[0046] The results of optimizing the structural set parameters of the broadband wave-absorbing frequency-selective structure of the two- and three-dimensional hybrid structure of the present invention are shown in Table 1.

[0047] Table 1

[0048] b(mm) 12 <![CDATA[l a (mm)]]> 20 <![CDATA[t a (mm)]]> 0.762 <![CDATA[t b (mm)]]> 1.016 <![CDATA[l s (mm)]]> 12 <![CDATA[d m (mm)]]> 10 <![CDATA[w s (mm)]]> 0.3 <![CDATA[w d (mm)]]> 11 D(mm) 0.3 <![CDATA[l c (mm)]]> 1.95 <![CDATA[w c (mm)]]> 0.15 <![CDATA[s c (mm)]]> 0.15 <![CDATA[l l (mm)]]> 0.8 <![CDATA[w l (mm)]]> 0.2 <![CDATA[s l (mm)]]> 0.2 <![CDATA[a1(mm)]]> 9.4 <![CDATA[a2(mm)]]> 3.7 <![CDATA[R1(Ω)]]> 150 <![CDATA[R2(Ω)]]> 150 ε 3.66

[0049] Where b is the period length of the unit structure in the x-axis and y-axis directions. a is the thickness of the first dielectric plate, l a is the length of the first dielectric plate, ε r is the relative dielectric constant of the first dielectric plate, w d is the length of the metal bending dipole along the y-axis, w s is the line width of the first metal stripline, l s is the length of the metal bent dipole along the z-axis, and R1 is the resistance of the first lumped resistor. m is the line width on the second metal surface, l c 、w c and c are the length, width and distance between the interdigital parts in the second metal surface, respectively, m is the distance between the first two-dimensional absorbing plane and the bandpass frequency selection surface, l l 、w l and l are the length, line width and gap width of the meandering part in the third metal surface, D is the diameter of the first metalized via, R2 is the resistance of the first lumped resistor. a1 is the side length of the first metal surface, a2 is the side length of the square hole in the second metal surface, t b is the thickness of the second dielectric plate and the third dielectric plate. The relative dielectric constants of the first, second, third and fourth dielectric plates are all ε r .

[0050] Figure 4The scattering parameter simulation results of the dual-polarization broadband absorbing frequency selective structure based on the two-dimensional and three-dimensional interlocking structure are shown in Figure 2. The simulation results show that the structure has good stealth characteristics in the designed frequency band (|S 11 |≤-10dB), the frequency range is 1.71GHz~12.34GHz, and the relative bandwidth of the stealth band reaches 151.3%. 11 |≤-10dB,|S 21 |≤-10dB) covers the frequency band of 1.71GHz to 6.25GHz, with a relative bandwidth of 114.1%, and the high-frequency absorption band covers the frequency band of 7.88GHz to 12.34GHz, with a relative bandwidth of 44.1%. And between the two absorption bands, a wide transmission band is realized near 7GHz, with a transmission band insertion loss of only 1.05dB, a 3dB bandwidth of 15.7%, and a frequency of 6.5GHz to 7.61GHz. It can also be seen from the figure that the performance of the structure under the irradiation of TE and TM polarized electromagnetic waves is basically consistent, indicating that the structure realizes dual-polarization characteristics.

[0051] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure, comprising a plurality of periodically distributed units, characterized in that Each unit includes a three-dimensional absorbing structure, a two-dimensional absorbing plane and a bandpass frequency selective surface; The three-dimensional wave absorbing structure comprises a cross-shaped first dielectric plate, two metal bent dipoles and two first lumped resistors welded on each metal bent dipole; The cross-shaped first dielectric plate is formed by dielectric plate A and dielectric plate B intersecting vertically to form a cross-shaped cross-section; a metal bent dipole is provided on each of dielectric plate A and dielectric plate B; the metal bent dipole is a C-shaped structure, and its opening faces the bandpass frequency selection surface; The two-dimensional absorbing plane is arranged vertically with the three-dimensional absorbing structure and is located in the middle of the cross-shaped first dielectric plate; it includes a second dielectric plate, a first metal surface equivalent to an LC circuit printed on the upper surface of the second dielectric plate, eight second lumped resistors welded on the first metal surface, eight first metallized vias penetrating the second dielectric plate, and a second metal surface printed on the lower surface of the second dielectric plate; the first metal surface and the second metal surface are connected through the first metallized vias; the first metal surface includes a cross-shaped metal strip; the four arms of the cross-shaped metal strip are each provided with an interdigital capacitor and second lumped resistors loaded on both sides of the interdigital capacitor; the second metal surface includes four first metal strip lines that are independent of each other and do not contact each other; the metal bent dipole does not contact the first metal surface and the second metal surface; the metal bent dipole does not contact the bandpass frequency selection surface; The bandpass frequency selective surface includes two dielectric plates and three metal layers, namely a third dielectric plate, a fourth dielectric plate, a third metal surface printed on the upper layer of the third dielectric plate, a fourth metal surface printed on the lower layer of the third dielectric plate, and a fifth metal surface printed on the lower layer of the fourth dielectric plate; a coupling port is opened in the center of the fourth metal surface.

2. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The first metal surface, the second metal surface and the first metallized via hole form four identical but independent parallel LC resonators, whose resonant frequency is the same as the operating frequency f of the passband. p same.

3. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The center of the second dielectric plate coincides with the center of the cross-shaped first dielectric plate.

4. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The first metal strip line is a zigzag microstrip line.

5. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The ends of the four arms of the cross-shaped metal strip are connected to the cross-shaped metal strips of the adjacent units.

6. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The width w of the metal bent dipole along the width direction of the dielectric plate is d is smaller than the width b of the dielectric plate on which it is located and satisfies (bw d ) / b≤1 / 5.

7. The dual-polarization broadband absorbing frequency selective structure based on a two-dimensional and three-dimensional interlocking structure according to claim 1 is characterized in that The height d between the two-dimensional absorbing plane and the bandpass frequency selective surface m Satisfy m ∈[0.2*c / f p ,0.3*c / f p ], where c is the speed of light in free space, f p is the operating frequency of the transmission belt.

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