A broadband microwave-absorbing frequency-selective structure with a hybrid of two-dimensional and three-dimensional structures

Abstract

The present invention discloses a broadband wave-absorbing frequency selection structure that is a mixture of two-dimensional and three-dimensional structures. 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, but the unit structure of the three-dimensional structure is relatively complex. The present invention combines the two-dimensional structure with the three-dimensional structure, taking advantage of each other's strengths and complementing each other's advantages, and not only achieves the high selectivity and broadband wave-absorbing performance of the three-dimensional structure, but also simplifies the overall structural design by using the two-dimensional planar structure, 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 broadband wave-absorbing frequency selection structure with a hybrid two-dimensional and three-dimensional 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] In current military applications, absorbing frequency selection technology is one of the effective means to reduce the cross-section of dual / multi-station radars. By absorbing threatening electromagnetic detection signals, it can effectively improve the stealth performance of our weapon platforms.

[0003] The wave-absorbing frequency selection structure is an improvement on the traditional wave-absorbing frequency selection surface. It is essentially still a spatial filter that can screen electromagnetic waves of specific frequency bands, polarization modes, and incident angles, and transmit the required electromagnetic waves. Outside the working frequency band, the resistor elements or lossy materials loaded on the wave-absorbing frequency selection structure will absorb the incident electromagnetic waves, thereby effectively reducing the reflection of out-of-band electromagnetic waves. This allows the frequency selection structure to have a stealth effect not only for single-station detectors, but also for dual / multi-station radar detection networks, thereby greatly ensuring the safety of our weapons and enhancing our deterrence against combat platforms.

[0004] Most of the absorbing frequency selective structures reported so far have relatively narrow transmission and absorbing bands. Especially the absorbing band, the broadband absorbing characteristics can ensure that the rear antenna is invisible to the ground within a very wide frequency band. In order to expand the absorbing bandwidth of the absorbing frequency selective structure, the three-dimensional absorbing structure is combined with the traditional two-dimensional frequency selective surface, giving full play to the advantages of the two-dimensional and three-dimensional structures, effectively broadening the absorbing band and improving the comprehensive performance of the antenna cover. Summary of the invention

[0005] The purpose of the present invention is to provide a broadband absorbing frequency selective structure with a hybrid of two-dimensional and three-dimensional structures in view of the deficiencies of the prior art. By combining the new three-dimensional absorbing structure with the traditional two-dimensional frequency selective surface, an extremely wide absorbing band is achieved. Compared with the existing two-dimensional absorbing structure, this structure can achieve a wider absorbing band and a wider transmission band. Compared with the existing three-dimensional absorbing structure, this structure is simpler and lighter, with a small number of lumped elements in the unit, low cost, and greatly improved comprehensive performance.

[0006] The invention discloses a broadband wave-absorbing frequency selection structure with a two-dimensional and three-dimensional structure mixture, which comprises a plurality of periodically distributed structural units seamlessly arranged along the x and y axes; each structural unit comprises a three-dimensional lossy structure and a two-dimensional broadband bandpass frequency selection surface.

[0007] The three-dimensional lossy structure is arranged vertically to the two-dimensional broadband bandpass frequency selection surface and is located above the two-dimensional broadband bandpass frequency selection surface; it includes a first dielectric plate, a lossy dipole and a lossy layer; the lossy dipole is printed on the lower surface of the first dielectric plate, and includes a first metal stripline and a first lumped resistor welded at the center of the first metal stripline; the lossy layer includes a second metal stripline equivalent to a series LC circuit printed on the upper surface of the first dielectric plate, two second lumped resistors welded on the second metal stripline, and a third metal stripline printed on the lower surface of the first dielectric plate; the second metal stripline and the third metal stripline are connected through two first metallized vias that penetrate the first dielectric plate;

[0008] The first metal stripline is a C-shaped structure, with its opening facing the two-dimensional broadband bandpass frequency selective surface;

[0009] Preferably, the second metal stripline is arranged in parallel with the two-dimensional broadband bandpass frequency selective surface, and includes a second lumped resistor loaded with an interdigital capacitor and loaded on both sides of the interdigital capacitor;

[0010] Preferably, the third metal strip line does not contact the first metal strip line;

[0011] Preferably, the third metal strip line is in a zigzag line shape;

[0012] Preferably, the first metallized via is located between the interdigital capacitor and the second lumped resistor;

[0013] Preferably, the first metal stripline is not in contact with the two-dimensional broadband bandpass frequency selective surface;

[0014] Preferably, two ends of the second metal strip line are connected to the second metal strip line of the adjacent unit;

[0015] The two-dimensional broadband bandpass frequency selective surface includes two dielectric plates and three metal layers, namely a second dielectric plate, a third dielectric plate, a first metal surface printed on the upper layer of the second dielectric plate, a second metal surface printed on the lower layer of the second dielectric plate, and a third metal surface printed on the lower layer of the third dielectric plate.

[0016] Preferably, the length and width of the first metal surface are smaller than the length and width of the second dielectric plate.

[0017] Preferably, the length and width of the third metal surface are smaller than the length and width of the third dielectric plate.

[0018] Preferably, the first metal strip line has a width w along the width of the first dielectric plate. d Smaller than the width of the first dielectric plate and meets 1-w d / b≤0.2;

[0019] Preferably, the resistance value of the first lumped resistor ranges from 100 to 500Ω;

[0020] Preferably, the distance d between the second metal strip line and the second dielectric plate in the lossy layer is m Satisfy 0.4*c / (2*f p )≤d m ≤0.6*c / (2*f p ), where c is the speed of light in free space, f p is the passband frequency;

[0021] Preferably, the second metal strip line, the third metal strip line and the two first metallized vias form a parallel LC resonator, whose resonant frequency is equal to the passband frequency f p ;

[0022] Preferably, a coupling hole is opened at the center of the second metal surface;

[0023] Preferably, the center of the three-dimensional lossy structure is aligned with the center of the two-dimensional broadband bandpass frequency selective surface below;

[0024] The present invention changes the length and width of the structural 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 is 2l s +w d 、Width w s , the resistance of the first lumped resistor is R 1 All structural parameters such as transmission band frequency, transmission band bandwidth, absorption band frequency and absorption band bandwidth are comprehensively controlled.

[0025] Specific working principle: When electromagnetic waves are incident on the surface of the structure, the three-dimensional lossy structure works in an absorbing state at its fundamental mode frequency and third-order mode frequency, while the two-dimensional broadband bandpass frequency selective surface below is equivalent to an ideal metal reflective surface. Therefore, an absorbing band is obtained at its fundamental mode frequency and third-order mode frequency. And because a slot line structure with an open terminal is formed between the first metal strip lines of adjacent structural units, the periodic impedance characteristics of the slot line structure significantly broaden the absorbing frequency band; and at the second-order mode frequency, the slot line structure with an open terminal formed between the first metal strip lines of adjacent structural units works in a transmission mode, which can transmit electromagnetic waves with extremely low loss, and the transmitted electromagnetic waves will still pass through the two-dimensional broadband bandpass frequency selective surface, thereby forming a transmission band. Within the range covered by the entire absorbing band and the transmission band, the reflection coefficient of the structure is very small, thereby achieving a stealth effect for the entire frequency band.

[0026] The broadband wave-absorbing frequency-selective structure with a hybrid of two-dimensional and three-dimensional structures has the following advantages:

[0027] (1) The broadband absorbing frequency selective structure of the hybrid two-dimensional and three-dimensional structure of the present invention adopts a three-dimensional lossy structure to replace the traditional planar absorbing structure. Compared with the previous two-dimensional planar absorbing frequency selective structure, it has a wider absorbing band and transmission band, which greatly improves the stealth characteristics.

[0028] (2) The broadband wave-absorbing frequency-selective structure of the hybrid two-dimensional and three-dimensional structure of the present invention adopts a two-dimensional broadband frequency-selective surface as a reflection surface. Compared with the previous three-dimensional structure, the structure is simpler and easier to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the two-dimensional and three-dimensional mixed unit structure of the present invention;

[0030] Figure 2 It is the parameter annotation of the three-dimensional lossy structure of the present invention;

[0031] Figure 3 is a frequency response characteristic simulation diagram of the present invention;

[0032] Figure 4 It is a simulation diagram of the wave absorption characteristics of the present invention;

[0033] Markings in the figure: first dielectric plate 1, first lumped resistor 2, first metal stripline 3, second lumped resistor 4, second metal stripline 5, third metal stripline 6, first metalized via 7, first metal surface 8, second dielectric plate 9, second metal surface 10, third dielectric plate 11, third metal surface 12. DETAILED DESCRIPTION

[0034] The present invention is further analyzed below in conjunction with specific embodiments.

[0035] The present invention adopts a cascaded form of a three-dimensional lossy structure and a two-dimensional broadband bandpass frequency selective surface, and realizes a two- and three-dimensional structure hybrid absorbing frequency selective structure with broadband wave absorbing and wave transmitting characteristics by combining the frequency response characteristics of the two in different frequency bands.

[0036] like Figure 1 , 2 As shown, the broadband absorbing frequency selective structure of the hybrid of two and three-dimensional structures is a periodic structure, and each structural unit includes a three-dimensional lossy structure and a two-dimensional broadband bandpass frequency selective surface.

[0037] The three-dimensional lossy structure includes a first dielectric plate 1, a lossy dipole and a lossy layer printed on the first dielectric plate 1. The lossy dipole includes a C-shaped first metal stripline 3 printed on the lower surface of the first dielectric plate 1 and a first lumped resistor 2 loaded at the center of the C-shaped first metal stripline 3; the lossy layer includes a second metal stripline 5 printed on the upper surface of the first dielectric plate 1 and two second lumped resistors 4 welded on the second metal stripline, a third metal stripline 6 printed on the lower surface of the first dielectric plate and two first metallized vias 7 penetrating the first dielectric plate 1.

[0038] The C-shaped structure opening of the first metal strip line faces the two-dimensional broadband bandpass frequency selection surface; the first metal strip line does not contact the two-dimensional broadband bandpass frequency selection surface;

[0039] The second metal stripline is arranged in parallel with the two-dimensional broadband bandpass frequency selective surface, and includes a second lumped resistor loaded with an interdigital capacitor and loaded on both sides of the interdigital capacitor; two ends of the second metal stripline are connected to the second metal stripline of the adjacent unit;

[0040] The third metal strip line does not contact the first metal strip line; the third metal strip line is in a zigzag shape;

[0041] The first metallized via is located between the interdigital capacitor and the second lumped resistor;

[0042] The two-dimensional broadband bandpass frequency selective surface includes two dielectric plates and three metal layers, namely a second dielectric plate 9, a third dielectric plate 11, a first metal surface 8 printed on the upper layer of the second dielectric plate 9, a second metal surface 10 printed on the lower layer of the second dielectric plate 9, and a third metal surface 12 printed on the lower layer of the third dielectric plate 11.

[0043] A coupling hole is provided at the center of the second metal surface;

[0044] Centers of the first to third dielectric plates are located on the same straight line.

[0045] The second metal strip line 5 printed on the upper surface of the first dielectric plate 1, the third metal strip line 6 printed on the lower surface of the first dielectric plate 1 and the two first metallized vias 7 penetrating the first dielectric plate 1 form a parallel LC resonator.

[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]

[0049]

[0050] Where b is the period length of the unit structure in the x-axis and y-axis directions; t 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 first metal stripline along the y-axis, w s is the line width of the first metal stripline, l s is the length of the first metal stripline along the z-axis, R 1 is the resistance of the first lumped resistor; w m is the line width of the second metal strip line, l c 、w c and c are the length, finger width and distance between fingers of the interdigital part in the second metal strip line, d m is the distance between the second metal stripline and the two-dimensional broadband bandpass frequency selective surface, l l 、w l and l are the length, line width and gap width of the meandering portion in the third metal strip line, D is the diameter of the first metallized via hole, a 1 is the side length of the first metal surface, a 2 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 and third dielectric plates are ε r .

[0051] Figure 3 The simulation results of the scattering parameters of the broadband wave-absorbing frequency-selective structure of the two-dimensional and three-dimensional 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 1.72GHz~12.27GHz, and the relative bandwidth of the stealth band reaches 150.8%. 11 |≤-10dB,|S 21 |≤-10dB) covers the frequency band from 1.72GHz to 5.95GHz, with a relative bandwidth of 110.3%, and the high-frequency absorption band covers the frequency band from 8.15GHz to 12.27GHz, with a relative bandwidth of 40.4%. And between the two absorption bands, a wide transmission band is realized near 7.1GHz, with a transmission band insertion loss of only 0.56dB and a 3dB bandwidth of 19.2%. Figure 2The absorption rate simulation results of the broadband absorption frequency selection structure of the two- and three-dimensional hybrid structure are as follows. As can be seen from the figure, the absorption efficiency in the frequency bands of 1.71GHz to 5.81GHz and 8.63GHz to 12.28GHz reaches more than 90%, and the absorption effect is very good.

[0052] 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 broadband wave-absorbing frequency-selective structure with a hybrid two-dimensional and three-dimensional structure, comprising a plurality of periodically distributed structural units; characterized in that Each structural unit includes a three-dimensional lossy structure and a two-dimensional broadband bandpass frequency selective surface; The three-dimensional lossy structure is arranged vertically with the two-dimensional broadband bandpass frequency selection surface and is located above the two-dimensional broadband bandpass frequency selection surface; it includes a first dielectric plate, a lossy dipole and a lossy layer; the lossy dipole is printed on the lower surface of the first dielectric plate, and includes a first metal stripline and a first lumped resistor welded at the center of the first metal stripline; the lossy layer includes a second metal stripline equivalent to a series LC circuit printed on the upper surface of the first dielectric plate, two second lumped resistors welded on the second metal stripline, and a third metal stripline printed on the lower surface of the first dielectric plate; the second metal stripline and the third metal stripline are connected through two first metallized vias penetrating the first dielectric plate; the second metal stripline is arranged parallel to the two-dimensional broadband bandpass frequency selection surface, and includes a second lumped resistor loaded with an interdigital capacitor and loaded on both sides of the interdigital capacitor; the third metal stripline does not contact the first metal stripline; the first metal stripline does not contact the two-dimensional broadband bandpass frequency selection surface; both ends of the second metal stripline are connected to the second metal striplines of adjacent units; The first metal stripline is a C-shaped structure, with its opening facing the two-dimensional broadband bandpass frequency selective surface; The two-dimensional broadband bandpass frequency selective surface comprises two dielectric plates and three metal layers, namely a second dielectric plate, a third dielectric plate, a first metal surface printed on the upper layer of the second dielectric plate, a second metal surface printed on the lower layer of the second dielectric plate, and a third metal surface printed on the lower layer of the third dielectric plate; A coupling hole is formed at the center of the second metal surface.

2. The broadband wave-absorbing frequency selective structure of the two-dimensional and three-dimensional structure hybrid according to claim 1, characterized in that The third metal strip line is in a zigzag line shape.

3. The broadband wave-absorbing frequency-selective structure of the hybrid two-dimensional and three-dimensional structure according to claim 1, characterized in that The first metallized via hole is located between the interdigital capacitor and the second lumped resistor.

4. The broadband wave-absorbing frequency-selective structure of the hybrid two-dimensional and three-dimensional structure according to claim 1, characterized in that The length and width of the first metal surface are smaller than those of the second dielectric plate; the length and width of the third metal surface are smaller than those of the third dielectric plate.

5. The broadband wave-absorbing frequency-selective structure of the hybrid two-dimensional and three-dimensional structure according to claim 1, characterized in that The first metal strip line has a width w along the width of the first dielectric plate. d Smaller than the width of the first dielectric plate and meets 1-w d / b≤0.2, where b is the period length of the structural unit.

6. The broadband wave-absorbing frequency-selective structure of a two-dimensional and three-dimensional hybrid structure according to claim 1, characterized in that The distance d between the second metal strip line and the second dielectric plate in the lossy layer m Satisfy 0.4*c / (2*f p )≤d m ≤0.6*c / (2*f p ), where c is the speed of light in free space, f p is the passband frequency.

7. The broadband wave-absorbing frequency-selective structure of a two-dimensional and three-dimensional hybrid structure according to claim 1, characterized in that The second metal strip line, the third metal strip line and the two first metallized vias form a parallel LC resonator, whose resonant frequency is equal to the passband frequency f p .

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