CN108270085A - Inhale integrated frequency-selective surfaces structure thoroughly - Google Patents

Abstract

The invention discloses an absorption-through-integrated frequency selection surface structure, which has two absorption frequency bands, and is composed of a curved strip-shaped metal patch, a first type of square dielectric substrate, a patch resistor, an air layer, a second type of square dielectric substrate, a square Composed of metal patches and square ring metal patches. The frequency-selective surface structure of the present invention with integrated absorbing and penetrating characteristics not only ensures the low insertion loss wave-transmission of the broadband in the C-band, but also makes the upper and lower parts of the wave-transmitting frequency band have wave-absorbing frequency bands, and realizes a wide frequency band with a very small size. The electromagnetic wave transmission control is very suitable for combining with most of the thickness of the skin, shell, protective cover and other structures to exert its unique electrical performance; at the same time, when the incident angle is 0-30 degrees, the electromagnetic wave transmission characteristics remain stable.

Description

Absorbing and penetrating integrated frequency selective surface structure

technical field

The invention belongs to the technical field of electromagnetic fields and microwaves, and in particular relates to an absorbing and penetrating integrated frequency selective surface structure.

Background technique

In modern warfare, the radar antenna system on the aircraft is an important source of scattering. It has a high radar cross section (RCS) in certain frequency and viewing angle ranges. Reducing the RCS of the antenna system is an important issue for the aircraft to achieve stealth. Frequency Selective Surface (FSS) is a two-dimensional structure composed of a large number of periodically arranged metal patch units with specific shapes or gaps between metal planes. When the incident electromagnetic wave frequency is at the resonant frequency of the unit, FSS It shows total reflection (patch type) or total transmission (aperture type), and electromagnetic waves of other frequencies can pass through FSS (patch type) or be totally reflected (aperture type), so FSS can effectively control the transmission characteristics of electromagnetic waves. It is widely used in radome.

When the operating frequency bands of the radars of the enemy and the enemy are different, the FSS-based hybrid radome technology can realize the stealth of the antenna system in the frequency domain. Adding band-pass FSS to the radome can make a frequency-selective wave-transparent radome with in-band wave transmission and out-of-band total reflection, which can make the antenna system exhibit different RCS characteristics inside and outside the wave-transmission frequency band. The in-band RCS is determined by the antenna rather than the radome; outside the operating frequency band, the RCS will be determined by the structure and shape of the radome; at the transition frequency band, the RCS will be determined by both the FSS radome and the antenna. The FSS radome has good wave-transmitting performance in the working frequency band of the antenna system, and does not affect the normal operation of the antenna; outside the frequency band, the stealth shape design can be used to reflect the out-of-band radar wave to the direction away from the incoming wave, reducing the band Outer single station RCS. This kind of FSS radome can effectively realize the stealth of the antenna system in the face of single base station radar detection by reflecting incoming radar waves from the main threat direction to other directions.

However, this means of stealth cannot achieve omnidirectional stealth and may yield a large RCS increase from certain viewing angles. The anti-stealth technology aimed at the defects of this stealth technology is also gradually developed. Among them, the dual (multi) base station radar or space-based radar system using radar networking technology can use the system with separate transceivers to receive radar wave signals scattered from stealth targets to other directions, and detect and identify them. Anti-stealth potential. In the face of these anti-stealth technologies, the FSS stealth radome has the danger of losing its stealth ability. To meet this new requirement, a frequency selective surface (Frequency Selective Radome, FSR) with in-band wave-transmitting/out-of-band wave-absorbing characteristics is proposed.

At present, the vast majority of research results on the frequency selection surface of the integrated absorber are low-frequency wave-transparent/high-frequency wave-absorbing and high-frequency wave-transparent/low-frequency wave-absorbing FSR, and the research on FSR with wave-absorbing characteristics both above and below the wave-transmitting frequency band is very important. few. This is because if the FSR wants to have the characteristics of absorbing bands above and below the wave-transmitting frequency band, the absorbing frequency band cannot affect the wave-transmitting performance of the wave-transmitting frequency band, so a sufficiently wide matching frequency band is required. At the same time, it is very difficult to ensure that the constant smaller unit size can satisfy the wave transmission/absorption characteristics in a wide frequency band. Since the frequency selective surface is essentially a spatial filter, in order to provide better out-of-band suppression characteristics, it should have the performance of absorbing waves at both ends of the passband in order to obtain better stealth performance. Absorbing and penetrating integrated frequency selective surfaces have great application prospects in practical applications such as aircraft stealth design and electromagnetic shielding.

Contents of the invention

Purpose of the invention: In view of the above problems, the present invention proposes a frequency-selective surface structure with integrated absorption and penetration.

Technical solution: In order to achieve the purpose of the present invention, the technical solution adopted in the present invention is: a frequency-selective surface structure with absorption and penetration integrated, including an upper lossy layer, an intermediate air layer and a lower lossless layer;

Wherein, the upper lossy layer includes four centrally symmetrical curved strip-shaped metal patches, four chip resistors and a first-type square dielectric substrate; each metal patch can be regarded as a straight strip-shaped The metal patch is formed by bending multiple times. Two adjacent curved strip metal patches are connected by a chip resistor. The four chip resistors are identical. The symmetrical centers of the four curved strip metal patches are connected to the square dielectric substrate. center alignment of

The lower lossless layer consists of two identical square metal patches, two identical second-type square dielectric substrates and a square ring metal patch, according to the square metal patch, dielectric substrate, square ring metal patch, The order of the dielectric substrate and the square metal patch is arranged in sequence; the square ring metal patch is composed of a square patch whose side length is the same as the unit length of the dielectric substrate and cut out another square patch whose center coincides with it and has a smaller side length. , the centers of the square metal patch and the square ring metal patch are aligned with the center of the dielectric substrate;

Between the upper lossy layer and the lower lossless layer is an air layer with a certain thickness, and the symmetry centers of the upper lossy layer and the lower lossless layer are aligned.

Further, the material of the first type square dielectric substrate is Isola FR408.

Further, the material of the second type square dielectric substrate is F4BM220.

Further, the thickness of the intermediate air layer is 5 mm.

Further, the side length of the square metal patch is 9.8 mm.

Further, the model of the chip resistor is 0603, and the resistance value is 62 ohms.

Beneficial effects: the frequency-selective surface structure with integrated absorbing and penetrating characteristics of the present invention ensures low insertion loss wave-transmission in a wide frequency band in the C-band, and at the same time makes the upper and lower wave-transmitting frequency bands have wave-absorbing frequency bands, which are realized in a very small size Broadband electromagnetic wave transmission control is very suitable for combining with skins, shells, protective covers and other structures of most thicknesses to give full play to its unique electrical properties; at the same time, when the incident angle is 0-30 degrees, the electromagnetic wave transmission characteristics remain stable .

Description of drawings

Fig. 1 is a unit structure diagram of the frequency selective surface structure of the present invention;

Figure 2 is an overall view of the frequency selective surface structure of the present invention, (a) is the main view, (b) is the side view;

Fig. 3 is a unit structure diagram of the lower lossless layer of the absorbing and penetrating integrated frequency selective surface structure of the present invention, (a) is an overall split diagram, (b) is a schematic diagram of a square patch, and (c) is a schematic diagram of a square ring patch;

Fig. 4 is a reflection curve, a transmission curve and an absorption curve diagram of the frequency selective surface of the present invention under the condition of normal incidence;

Fig. 5 is a reflection curve and a transmission curve diagram of the absorbing and penetrating integrated frequency selective surface of the present invention under the condition of a certain angle of incidence, (a) is the TE mode, (b) is the TM mode;

Fig. 6 is an absorption curve diagram of the frequency selective surface of the present invention under the condition of a certain angle of incidence.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, Figure 2 and Figure 3, the absorbing and permeable integrated frequency selective surface structure with two absorption frequency bands of the present invention consists of a curved strip metal patch 1, an Isola FR408 square dielectric substrate 2, and a model 0603 resistance value of 62 Ohmic chip resistor 3, air layer 4, F4B square dielectric substrate 5, square metal patch 6 and square ring metal patch 7. The absorbing and permeable integrated frequency selective surface structure with two absorption frequency bands of the present invention comprises an upper lossy layer, an intermediate air layer and a lower lossless layer, and the upper layer lossy layer is aligned with the center of symmetry of the lower lossless layer.

As shown in Figure 2(a), in the unit structure of the upper lossy layer, four curved strip-shaped metal patches 1 are attached to the first type of square dielectric substrate 2, and four identical chip resistors 3 are sequentially connected to the curved strip-shaped The spacing c between the metal patch 1 and the curved strip-shaped metal patch 1 needs to ensure the welding of the chip resistor 3 , and the symmetrical centers of the four curved strip-shaped metal patches 1 are aligned with the center of the square dielectric substrate 2 . The choice of chip resistor 3 is not only considering the model size is suitable for c, but also the resistance value should be selected so that the impedance of the FSR and the free space impedance match best when absorbing waves. The length of the curved strip metal patch 1 affects the resonant frequency band of the lossy FSS. The simulation results verify that if l1 in Figure 2(a) increases, the resonant frequency band of the lossy FSS will shift to the left accordingly; When the width w of sheet 1 increases, the equivalent inductance of the lossy FSS decreases accordingly, so the resonant frequency band will shift to the right, and it is found through simulation that the peak value of the transmitted wave will also gradually decrease. As shown in Figure 2(b), there is an air layer 4 with a certain thickness between the upper lossy FSS and the lower lossless FSS. To better match the free space impedance, the most suitable thickness h2 of the air layer 4 should be selected.

As shown in Figure 3, the lower lossless layer is composed of a square metal patch 6, a second type of square dielectric substrate 5, a square ring metal patch 7, a second type of square dielectric substrate 5, and a square metal patch 6 that are closely bonded in sequence. . The square ring metal patch 7 is composed of a square patch whose side length is the same as the unit length of the dielectric board and cut out another square patch with a smaller side length that coincides with it in the center. The square metal patch 6 and the square ring metal patch The centers of the sheets 7 are all aligned with the center of the square dielectric substrate 5 . The larger the side length s of the square metal patch 6 is, the larger the equivalent capacitance is, and the resonant frequency band of the lower lossless FSS moves to a lower frequency. The ring width w of the square ring metal patch 7 increases, the equivalent inductance decreases, and the equivalent capacitance increases, so the resonance bandwidth narrows. After simulation, it is found that the right frequency point of the resonance frequency band is hardly affected, and the left frequency point Move right. The thickness h of the square dielectric substrate 5 greatly affects the bandwidth of the lower lossless FSS, the larger h is, the narrower the bandwidth is.

It should be noted that n*n (n is a positive integer and greater than or equal to 3) units are generally selected to form a complete structure in the actual processing of the frequency selective surface to reflect its periodic characteristics, which is (n*a)mm*(n*a)mm , where a is the unit length of the frequency selective surface.

In this embodiment, the commercial software CST STUDIO SUITE 2016 is used to assist in the optimization of the specific parameters of the frequency selective surface and the fine-tuning of the wave-transmitting/absorbing characteristics. The final parameters are shown in Table 1 below.

Table 1

Copper-clad laminate technology is used to produce the designed absorbing and permeable integrated frequency-selective surface product; among them, the processed sample of the frequency-selective surface contains at least 3*3 unit arrays, and the metal patch layer is made of metal with excellent electrical conductivity. The best material is silver (resistivity 15.86ρ/nΩ·m), and copper (resistivity 16.78ρ/nΩ·m) is generally used to have a better effect. The electrical performance is not significantly affected, and the pattern shape of the patch is etched using the standard process of the national specification for printed circuit boards (QJ3103-99). The air layer can be supported by a rigid foam board of corresponding thickness, which is used to fix the positions of the upper lossy FSS and the lower lossless FSS.

Finally, those skilled in the art should know that IsolaFR408 and F4B are not necessary for the selection of dielectric substrate materials, as long as the relative permittivity and thickness meet the resonance requirements. According to the required frequency band, bandwidth and other requirements, the corresponding size parameters of the FSR unit can be adjusted to meet the resonance requirements. According to the required wave transmission rate, wave absorption rate and other requirements, parameters such as the resistance value of the chip resistor can be adjusted to meet the resonance requirements.

As shown in Figure 4, it is the reflection curve, transmission curve and absorption curve diagram of the frequency selective surface of the present invention under the condition of normal incidence, and it can be seen that the FSR structure satisfies the insertion below -3dB between 4.54-6.36GHz Lossy bandpass characteristics, the -3dB bandwidth is 1.82GHz, and the insertion loss at 5.86GHz is only -0.71dB; the absorption rate is above 90% in the range of 2.65-2.95GHz and 7.58-7.94GHz, of which, 2.78 The absorption rate at GHz is 96%, and the absorption rate at 7.75GHz is as high as 98%.

As shown in FIG. 5 , it is a reflection curve and a transmission curve diagram of the frequency selective surface of the present invention under the incident condition of 0-30 degrees, wherein (a) is the TE mode, and (b) is the TM mode.

As shown in FIG. 6 , it is the absorption curve of the frequency selective surface of the present invention under the incident condition of 0-30 degrees. It can be seen that the absorbing and penetrating integrated frequency selective surface is not only insensitive to polarization, but also has good angular stability within 30 degrees, and the working center frequency band is highly stable.

Claims (6)

1. An absorbing and penetrating integrated frequency selective surface structure is characterized in that: it comprises an upper lossy layer, an intermediate air layer and a lower lossless layer; Wherein, the upper lossy layer includes four centrally symmetrical curved strip-shaped metal patches (1), four chip resistors (3) and a first-type square dielectric substrate (2); each metal patch It can be regarded as a straight strip metal patch formed by multiple bends, two adjacent curved strip metal patches are connected by a chip resistor, the four chip resistors are exactly the same, and the four curved strip metal patches The symmetrical center of the patch is aligned with the center of the square dielectric substrate; The lower lossless layer consists of two identical square metal patches (6), two identical second-type square dielectric substrates (5) and a square ring metal patch (7), according to the square metal patch, The order of dielectric substrate, square ring metal patch, dielectric substrate, and square metal patch is arranged in sequence; the square ring metal patch is cut from a square patch whose side length is the same as the unit length of the dielectric substrate, and the other center coincides with it. Composed of square patches with smaller side lengths, the centers of the square metal patch and the square ring metal patch are aligned with the center of the dielectric substrate; Between the upper lossy layer and the lower lossless layer is an air layer (4) with a certain thickness, and the symmetry centers of the upper lossy layer and the lower lossless layer are aligned. 2. The absorbing-through-integrated frequency selective surface structure according to claim 1, characterized in that: the material of the first type square dielectric substrate is Isola FR408. 3. The absorbing-through-integrated frequency selective surface structure according to claim 1, characterized in that: the material of the second type square dielectric substrate is F4BM220. 4. The absorbing and permeable integrated frequency selective surface structure according to claim 1, characterized in that: the thickness of the intermediate air layer is 5mm. 5. The absorbing and penetrating integrated frequency selective surface structure according to claim 1, characterized in that: the side length of the square metal patch is 9.8 mm. 6. The absorbing and penetrating integrated frequency selective surface structure according to claim 1, characterized in that: the model of the chip resistor is 0603, and the resistance value is 62 ohms.