Dual-passband adjustable spatial filtering periodic structure

Abstract

The invention provides a dual-passband adjustable spatial filtering periodic structure, and belongs to the technical field of electromagnetic metamaterials. Comprising an upper metal unit layer, a middle dielectric layer and a lower metal feeder unit layer, the upper metal unit layer and the lower metal feeder layer are both of a periodic structure; four aperture rings are etched in each period of the upper metal unit layer, and the four aperture rings are distributed on four quadrants; the four aperture rings have two sizes, and the sizes of the aperture rings on the same diagonal line are the same; four active lumped elements are loaded on each aperture ring in a central axis symmetric manner; the center of the aperture ring is electrically connected with the lower metal feeder unit layer through a metal via hole; each period of the lower metal unit layer is of a cross-shaped metal patch structure, the metal via holes are connected with the cross-shaped metal patches through the metal patches, and each metal patch connected with the cross-shaped metal patches and the metal via holes is loaded with a passive lumped inductance element.

Description

Technical Field

[0001] The invention belongs to the technical field of electromagnetic metamaterials, and in particular relates to a dual-passband adjustable spatial filtering periodic structure. Background Art

[0002] Electromagnetic metamaterials are artificial structural materials composed of periodic or non-periodic arrangements of structural units at the subwavelength scale. Electromagnetic metamaterials have important application value in the fields of antennas and radar communications. In particular, artificial periodic structural materials composed of periodic arrangements of metal units of specific shapes, also known as frequency selective surfaces (FSS), can control the spatial filtering characteristics of transmission and reflection of incident electromagnetic waves at specific frequencies, so they can also be regarded as a special spatial filter. Due to its special electromagnetic wave control characteristics, frequency selective surfaces are usually applied to radomes to achieve the stealth characteristics of radomes.

[0003] At present, existing research focuses on the design of passive FSS periodic structures. Although it can solve the out-of-band stealth problem of the antenna cover, it cannot solve the in-band stealth problem of the antenna at the same time. The active FSS periodic structure can realize the artificial regulation of spatial filtering characteristics by loading a series of active devices in the passive periodic structure, which can reduce the risk of the target being detected by the radar while ensuring the normal operation of the antenna.

[0004] At present, there are few studies on the design of radomes using active FSS periodic structures in China. At the same time, there are few studies on how to reduce the influence of the feed structure loaded with active devices on the wave transmission characteristics of the periodic structure itself, and there are also few studies on the multi-band regulation of active FSS periodic structures. However, the design research of active FSS periodic structures will be a hot topic in the future of the FSS field, and it has very important research value in the fields of active radar, radomes, etc. Summary of the invention

[0005] The present invention provides a dual-passband adjustable spatial filtering periodic structure, which realizes the dual-passband frequency adjustable characteristics by loading active devices, solves the feeding circuit design problem of loading active devices, and has good polarization stability. It can be used to cope with radar electronic detection systems with variable working frequency bands and improve the survivability in complex electromagnetic environments.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A dual-passband adjustable spatial filtering periodic structure, comprising: an upper metal unit layer, an intermediate dielectric layer and a lower metal feeder line layer; the upper metal unit layer and the lower metal feeder line layer are both periodic structures;

[0008] Four aperture rings are etched in each period of the upper metal unit layer, and the four aperture rings are distributed in four quadrants; the four aperture rings have two sizes, and the aperture rings on the same diagonal have the same size; four active lumped elements are loaded on each aperture ring in a central axis symmetrical form; the center of the aperture ring is electrically connected to the lower metal feeder unit layer through a metal via;

[0009] Each period of the lower metal unit layer is a cross-shaped metal patch structure, the metal via is connected to the cross-shaped metal patch through the metal patch, and each metal patch connecting the cross-shaped metal patch and the metal via is loaded with a passive lumped inductor element.

[0010] Furthermore, each periodic unit of the upper metal unit periodic structure described in the present invention is a large square unit of the same size, the large square unit is divided into 4 small square units of the same size, 4 aperture rings are etched on the 4 small square units of the same size, and the center of the aperture ring coincides with the center of the small square.

[0011] Furthermore, the active lumped element loaded in the upper metal unit periodic structure of the present invention is a PIN or a varactor diode.

[0012] Furthermore, the aperture ring of the present invention is in the shape of a square ring, a hexagonal ring or a circular ring.

[0013] Furthermore, in the lower metal unit periodic structure of the present invention, each periodic unit is a large square unit of the same size, and the size is the same as that of the upper metal unit periodic structure;

[0014] The cross-shaped thin strip metal patch structure is arranged on the central symmetry axis of the large square unit, and the large square unit is divided into 4 small square units of the same size. The center position of each small square unit in the lower layer is connected to the cross-shaped thin strip metal patch through a thin strip metal patch, and together with the cross-shaped thin strip metal patch, it forms a central axis symmetric structure patch unit;

[0015] The center positions of the four small square units in the lower layer are electrically connected to the center positions of the four small square units in the upper layer through metal vias; four passive lumped inductor components are loaded onto the four small square metal unit patch structures in a central axis symmetrical form.

[0016] Furthermore, the thickness of the upper and lower metal unit layers of the present invention is 0.025 mm, the metal is Cu, the thickness h1 of the middle dielectric layer is 0.25 mm, the dielectric material is F4B, and the relative dielectric constant is 2.2.

[0017] Furthermore, the unit period P of the large square of the present invention is 4 mm, and the two sizes of aperture rings are respectively recorded as Y1 and Y2. The distance between the aperture ring Y1 and the boundary of the large square is d1=0.5 mm, and the width is s1=0.5 mm; the distance between the aperture ring Y2 and the boundary of the large square is d2=0.3 mm, and the width is s2=0.3 mm.

[0018] Furthermore, the active lumped element of the present invention is a varactor diode C1, and the capacitance value of C1 ranges from 0.01 pF to 1 pF.

[0019] Furthermore, the width d3 of the slender metal patch of the present invention is 0.2 mm.

[0020] Furthermore, the passive inductor element L1 loaded at the metal patch in each small square unit of the present invention has an inductance of 20nH.

[0021] Beneficial Effects

[0022] The upper metal unit layer and the lower metal feeder layer of the present invention are both periodic structures, and the lower layer is electrically connected to the upper layer through an intermediate metal via; active lumped elements (such as PIN, varactor diode, etc.) are loaded in the upper metal unit periodic structure, and passive lumped inductor elements are loaded in the lower metal unit periodic structure. Through reasonable structural design, as the varactor diode C1 changes from 0.1pF to 0.5pF, the periodic structure can realize dual-band bandpass adjustable characteristics in the C, X, and ku bands, and has good polarization stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is an overall schematic diagram of the periodic structure of the spatial filter with dual passband adjustment;

[0025] Figure 2 It is the structural layer diagram of the upper metal unit;

[0026] Figure 3 It is the structural layer diagram of the lower metal unit feeder;

[0027] Figure 4 It is a simulation curve of the S21 transmission characteristics of the dual-passband adjustable spatial filtering period. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0029] It should be noted that the following embodiments and features in the embodiments may be combined with each other in the absence of conflict; and, based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work are within the scope of protection of the present disclosure.

[0030] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0031] Figure 1 A schematic diagram of a dual-passband adjustable spatial filter periodic structure is provided for an embodiment of the present invention, wherein the periodic structure comprises an upper metal unit layer, an intermediate dielectric layer, and a lower metal feeder unit layer, wherein both the upper metal unit layer and the lower metal feeder layer are periodic structures;

[0032] Four aperture rings are etched in each period of the upper metal unit layer, and the four aperture rings are distributed in four quadrants; the four aperture rings have two sizes, and the aperture rings on the same diagonal have the same size; four active lumped elements are loaded on each aperture ring in a central axis symmetrical form; the center of the aperture ring is electrically connected to the lower metal feeder unit layer through a metal via;

[0033] Each period of the lower metal unit layer is a cross-shaped metal patch structure, the metal via is connected to the cross-shaped metal patch through the metal patch, and each metal patch connecting the cross-shaped metal patch and the metal via is loaded with a passive lumped inductor element.

[0034] In one embodiment of the present application, an upper metal unit periodic structure, each periodic unit is a large square unit of the same size, each large square metal unit can be regarded as four small square units of the same size, two aperture gap structures of different sizes (such as square ring, hexagonal ring, circular ring and other arbitrary annular aperture units) are etched in sequence and at intervals on the four small square units, and four active lumped elements are loaded in a central axis-symmetrical form to the center position of each small square metal unit gap.

[0035] In one embodiment of the present application, the lower metal unit periodic structure, each periodic unit is a large square unit of the same size, and the size is the same as the upper structure. The cross-shaped thin and long metal patch structure is arranged on the central symmetry axis of the large square unit, and is also divided into 4 small square units of the same size as the upper structure. The center position of each small square unit in the lower layer is connected to the cross-shaped patch through the same thin and long metal patch, and together with the cross-shaped patch, it forms a patch unit with a central axis symmetrical structure; at the same time, the center positions of the 4 small square units in the lower layer are electrically connected to the center positions of the 4 small square units in the upper layer through metal vias. 4 passive lumped inductor components are loaded onto the 4 small square metal unit patch structures in a central axis symmetrical form.

[0036] In one embodiment of the present application, the thickness of the upper and lower metal unit periodic structure is generally less than 0.05 mm. The middle layer is a dielectric material base layer, which is a dielectric plate of the upper and lower metal layers. The relative dielectric constant is generally between 1.5 and 10. Depending on the selected dielectric material, the thickness is generally less than 5 mm.

[0037] Figure 1 The overall schematic diagram of the dual-passband adjustable spatial filter periodic structure is shown in Figure 1. The upper metal unit layer is provided with two aperture rings Y1 and Y2 of different sizes, which are arranged crosswise. The center of the ring is electrically connected to the lower metal feeder unit layer through metal vias. The thickness of the upper and lower metal unit layers is 0.025 mm, and the metal is Cu. The thickness of the middle dielectric layer h1 is 0.25 mm, and the dielectric material is F4B, with a relative dielectric constant of 2.2.

[0038] Figure 2 The upper metal unit layer size diagram of the dual-band adjustable spatial filtering periodic structure. The overall large square unit period P is 4mm, which can be divided into 4 small square units of 2mm. The specific dimensions of the two aperture rings Y1 and Y2 of different sizes are d1=0.5mm, s1=0.5mm, d2=0.3mm, and s2=0.3mm. A variable capacitance diode C1 is loaded on the top, bottom, left, and right of each ring gap unit, and the capacitance value of C1 ranges from 0.01pF to 1pF. Y1 resonates and transmits waves at a relatively high frequency, and Y2 resonates and transmits waves at a relatively low frequency. At the same time, the four variable capacitance diodes C1 loaded on the Y1 and Y2 units respectively make the FSS periodic resonance and wave transmission frequency adjustable.

[0039] Figure 3The dimensions of the lower metal feeder unit layer of the dual-passband adjustable spatial filtering periodic structure. The feeder width d3 is 0.2mm, and the passive inductor element L1 loaded at the feeder in each small square unit has an inductance of 20nH. The feeder layer adopts a cross-axis symmetrical design, and is more simplified than the traditional feeder network with a straight line connection at the center of each unit. At the same time, a large inductor is loaded at each ring unit, which helps to reduce the impact of the feeder layer on the passband insertion loss of the FSS periodic structure.

[0040] Figure 4 The S21 transmission characteristic simulation curve of the dual-passband adjustable spatial filtering period. The capacitance value of the varactor diode C1 is adjusted by applying an external voltage. As the varactor diode C1 changes from 0.1pF to 0.5pF, the periodic structure can achieve dual-band adjustable passband characteristics in the C, X, and Ku bands.

[0041] The periodic structure of the present invention can be designed to obtain an active FSS structure with dual passband adjustable within 2 to 40 GHz by rationally optimizing the structural parameters of each layer unit, and at the same time has good polarization stability. The periodic structure of the present invention can be applied to the stealth design of radar antenna cover, effectively reducing the RCS within the antenna band and improving the survivability of the radar.

[0042] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention. It should be understood that the above is only a further explanation of the implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A dual-passband adjustable spatial filtering periodic structure, characterized in that: include: An upper metal unit layer, an intermediate dielectric layer, and a lower metal feeder unit layer; The upper metal unit layer and the lower metal feeder layer are both periodic structures; Four aperture rings are etched in each period of the upper metal unit layer, and the four aperture rings are distributed in four quadrants; the four aperture rings have two sizes, and the aperture rings on the same diagonal have the same size; four active lumped elements are loaded on each aperture ring in a centrally symmetrical form; the center of the aperture ring is electrically connected to the lower metal feeder unit layer through a metal via; Each period of the lower metal unit layer is a cross-shaped metal patch structure, the metal via is connected to the cross-shaped metal patch through the metal patch, and each metal patch connecting the cross-shaped metal patch and the metal via is loaded with a passive lumped inductor element.

2. The dual-passband adjustable spatial filtering periodic structure according to claim 1, characterized in that: Each periodic unit of the upper metal unit periodic structure is a large square unit of the same size, the large square unit is divided into 4 small square units of the same size, 4 aperture rings are etched on the 4 small square units of the same size, and the center of the aperture ring coincides with the center of the small square.

3. The dual-passband adjustable spatial filtering periodic structure according to claim 1 or 2, characterized in that: The active lumped element loaded in the upper metal unit periodic structure is a PIN or a varactor diode.

4. The dual-passband adjustable spatial filtering periodic structure according to claim 1 or 2, characterized in that: The aperture ring is in the form of a square ring, a hexagonal ring or a circular ring.

5. The dual-passband adjustable spatial filtering periodic structure according to claim 1 or 2, characterized in that: The lower metal unit periodic structure, each periodic unit is a large square unit of the same size, and the size is the same as that of the upper metal unit periodic structure; The cross-shaped thin strip metal patch structure is arranged on the central symmetry axis of the large square unit, and the large square unit is divided into 4 small square units of the same size. The center position of each small square unit in the lower layer is connected to the cross-shaped thin strip metal patch through a thin strip metal patch, and together with the cross-shaped thin strip metal patch, it forms a central axis symmetric structure patch unit; The center positions of the four small square units in the lower layer are electrically connected to the center positions of the four small square units in the upper layer through metal vias; four passive lumped inductor components are loaded onto the four small square metal unit patch structures in a central axis symmetrical form.

6. The dual-passband adjustable spatial filtering periodic structure according to claim 5, characterized in that: The thickness of the upper and lower metal unit layers is 0.025 mm, the metal is Cu, the thickness of the middle dielectric layer h1 is 0.25 mm, the dielectric material is F4B, and the relative dielectric constant is 2.

2.

7. The dual-passband adjustable spatial filtering periodic structure according to claim 1, characterized in that: The unit period P of the large square is 4 mm, and the two sizes of aperture rings are denoted as Y1 and Y2 respectively. The distance between aperture ring Y1 and the boundary of the large square is d1=0.5 mm, and the width is s1=0.5 mm; the distance between aperture ring Y2 and the boundary of the large square is d2=0.3 mm, and the width is s2=0.3 mm.

8. The dual-passband adjustable spatial filtering periodic structure according to claim 7, characterized in that: The width d3 of the slender metal patch is 0.2 mm.

9. The dual-passband adjustable spatial filtering periodic structure according to claim 2, characterized in that: The active lumped element is a varactor diode C1, and the capacitance value of C1 ranges from 0.01pF to 1pF.

10. The dual-passband adjustable spatial filtering periodic structure according to claim 9, characterized in that: The passive inductor element L1 loaded at the metal patch in each small square unit has an inductance of 20nH.

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