CN110676592A - Dual-polarized three-order band-pass three-dimensional frequency selection surface - Google Patents

Abstract

The invention discloses a dual-polarization third-order band-pass three-dimensional frequency selection surface. The frequency selective surface is composed of several identical unit structures arranged periodically, and each unit structure includes a metal square cylinder and a dielectric square. A metal square ring is etched at the center positions of the upper surface, the middle layer and the lower surface of the dielectric square. The metal square rings on the upper surface and the lower surface of the dielectric block have the same size, and the perimeters of the two metal square rings are larger than the perimeter of the metal square ring in the middle layer. Due to the electromagnetic coupling between the resonant units on the upper and lower surfaces of the unit structure, two transmission poles are generated; the metal square ring in the middle layer, the metal square cylinder and the dielectric square work together to form the third transmission pole, thus forming a third transmission pole. Flat third-order passband. Due to the reverse cancellation of the signal phases, three transmission zeros are introduced, so that the present invention has high frequency selectivity and wide out-of-band suppression, and at the same time has good angular stability in the dual-polarization working mode.

Description

A dual-polarized third-order bandpass three-dimensional frequency selective surface

technical field

The invention belongs to the technical field of electromagnetic fields and microwaves, and in particular relates to a dual-polarization third-order band-pass three-dimensional frequency selective surface.

Background technique

In the past few decades, Frequency Selective Surface (FSS) has been widely used in various microwave and millimeter-wave systems due to its superior spatial filtering properties. An FSS is usually a two-dimensional array of periodically arranged metallic cell structures capable of achieving either band-pass or band-stop filtering responses. Band-pass FSS requires flat transmission response and low insertion loss within the pass-band, high frequency selectivity and wide out-of-band rejection outside the band, good angular stability, dual polarization, and small electrical size.

The traditional second-order bandpass 2D FSS can be realized by means of multi-layer stacking coupling, etc., but there are often problems such as poor frequency selectivity, insufficiently flat passband, narrow out-of-band suppression bandwidth, and large electrical size. Later, the team of Professor Shen Zhongxiang of Nanyang Technological University in Singapore proposed a series of second-order band-pass three-dimensional frequency selective surface structures based on shielded microstrip lines. The above problems have been effectively improved, but these structures can only achieve single polarization, which greatly limits the their practical application. Later, many scholars load non-resonant units in the middle layer of the multi-layer structure, and use the electromagnetic coupling of the multi-layer resonant units to generate three or more transmission poles. The flatness is improved, but these third-order or higher-order bandpass FSSs can only introduce a single transmission zero on one side of the passband or one transmission zero on each side of the passband, and their frequency selectivity has been improved to some extent, But it is difficult to achieve wide out-of-band rejection. Therefore, in view of the above shortcomings, it is necessary to design a dual-polarization third-order bandpass 3D FSS with wide out-of-band suppression.

SUMMARY OF THE INVENTION

The invention provides a dual-polarization third-order bandpass three-dimensional frequency selective surface, which realizes stable frequency response under different polarizations and different incident angles, and has a flat third-order passband, wide out-of-band suppression, and small electrical size.

The invention provides a dual-polarization third-order band-pass three-dimensional frequency selective surface, which is composed of several identical unit structures arranged periodically, and each unit structure includes a metal square cylinder and a dielectric square. A metal square ring is etched at the center positions of the upper surface, the middle layer and the lower surface of the dielectric square. The metal square rings on the upper surface and the lower surface of the dielectric block have the same size, and the perimeters of the two metal square rings are larger than the perimeter of the metal square ring in the middle layer.

In the dual-polarized third-order band-pass three-dimensional frequency selective surface provided by the present invention, two transmission poles are generated due to the electromagnetic coupling between the upper surface and the lower surface of the unit structure resonance unit; the metal square ring in the middle layer and the The metal square cylinder and the dielectric square work together to form the third transmission pole, thereby forming a flat third-order passband. Due to the reverse cancellation of the signal phases, three transmission zeros are introduced, so that the present invention has high frequency selectivity and wide out-of-band rejection. Due to the symmetry of the unit structure, the invention realizes dual polarization; meanwhile, in the dual polarization working mode, it has good angular stability when incident at angles of 0°, 30° and 50°. Compared with the existing bandpass FSS, the frequency selective surface has dual polarization, flat third-order passband, high frequency selectivity, wide out-of-band rejection, good angular stability and small electrical size and other advantages.

Description of drawings

FIG. 1 is a three-dimensional schematic diagram of the unit structure of the dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention.

Figure 2 is a schematic diagram of the components constituting the unit structure of the present invention (a) a metal square cylinder; (b) a medium square.

FIG. 3 is a schematic diagram of the dimensioning of the unit structure of the dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention (a) perspective view and parameter labeling; (b) top view and parameter labeling.

FIG. 4 is a three-dimensional schematic diagram of a dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention.

FIG. 5 is a simulation result diagram of the transmission coefficient and reflection coefficient of the dual-polarization third-order band-pass three-dimensional frequency selective surface proposed by the present invention when electromagnetic waves are vertically incident.

6 is a simulation result of the transmission coefficient of the dual-polarized third-order bandpass three-dimensional frequency selective surface proposed by the present invention under different incident angles (a) TE mode; (b) TM mode.

Detailed ways

In order to describe the technical solutions disclosed in the present invention in detail, further description is made below in conjunction with the accompanying drawings and specific embodiments of the description.

FIG. 1 is a three-dimensional schematic diagram of the unit structure of the dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention. Each unit structure includes a metal square cylinder 1 and a medium square 2 . Both the upper and lower surfaces of the unit structure form a resonance unit composed of a metal square ring and an upper end face of a metal square cylinder.

Figure 2 shows a schematic diagram of the components constituting the unit structure of the present invention. FIG. 2( a ) is a metal square cylinder 1 ; FIG. 2( b ) is a medium square 2 . The metal square ring 21 , the metal square ring 22 and the metal square ring 23 are etched respectively at the center positions of the upper surface, the middle layer and the lower surface of the dielectric block 2 . The size of the metal square ring 21 and the metal square ring 23 are the same, and the circumference of the two metal square rings is larger than the circumference of the metal square ring 22 in the middle layer.

FIG. 3 is a schematic diagram of the dimensioning of the unit structure of the dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention. The design parameters are d _x = _dy =11.4mm, l ₁ =8.5mm, l ₂ =7.1mm, w ₁ =w ₂ =0.2mm,h=10mm,t=0.5mm,the dielectric relative permittivity of the dielectric square is 3.5.

FIG. 4 is a three-dimensional schematic diagram of the dual-polarization third-order bandpass three-dimensional frequency selective surface proposed by the present invention, which is formed by the periodic arrangement of the unit structure shown in FIG. 1 in the two-dimensional plane direction. FIG. 4 only shows a schematic diagram of the arrangement of 4×4 unit structures, and usually hundreds of unit structures need to be fabricated in actual processing and testing.

FIG. 5 is a simulation curve of the transmission coefficient and the reflection coefficient of the present invention when the electromagnetic wave is vertically incident. It can be seen from the figure that the three transmission poles are located at f _p1 = 5.46 GHz, f _p2 = 5.74 GHz and f _p3 = 5.87 GHz respectively, forming a flat third-order passband, the center frequency of the passband is 5.605GHz, and the passband 3dB is relatively The bandwidth (RBW _3dB ) was 10.9%. In addition, the three transmission zeros generated out-of-band are located at f _z1 = 6.08 GHz, f _z2 = 6.35 GHz and f _z3 = 7.1 GHz, and the frequency selectivity is improved; the suppression depth is in the frequency range of 5.99 GHz-8.69 GHz Below -20dB, the 20dB relative bandwidth (RBW _20dB ) of its stopband is 48.2%; the electrical dimension (d _x ×dy ×h) of its unit structure is _{0.21λ 0} ×0.21λ ₀ ×0.187λ ₀ (λ ₀ is the free-space wavelength). Thus, the frequency selective surface has a flat third-order passband, high frequency selectivity, broad out-of-band rejection, and small electrical dimensions.

FIG. 6(a) and FIG. 6(b) are simulation curves of transmission coefficients corresponding to different incident angles under two polarization modes of TE and TM, respectively. It can be seen from the figure that in the two polarization modes of TE and TM, the electromagnetic wave has good angular stability when incident at angles of 0°, 30° and 50°, which fully proves that the present invention has good practicability.

The invention discloses a dual-polarization third-order band-pass three-dimensional frequency selection surface. The frequency selective surface is composed of several identical unit structures arranged periodically, and each unit structure includes a metal square cylinder and a dielectric square. A metal square ring is etched at the center positions of the upper surface, the middle layer and the lower surface of the dielectric square. The metal square rings on the upper surface and the lower surface of the dielectric block have the same size, and the perimeters of the two metal square rings are larger than the perimeter of the metal square ring in the middle layer. Due to the electromagnetic coupling between the resonant units on the upper and lower surfaces of the unit structure, two transmission poles are generated; the metal square ring in the middle layer, the metal square cylinder, and the dielectric square work together to form the third transmission pole, thus forming a third transmission pole. Flat third-order passband. Due to the reverse cancellation of the signal phase, three transmission zeros are introduced, so that the present invention has high frequency selectivity and wide out-of-band suppression; the present invention realizes dual polarization due to the symmetry of the unit structure; In the working mode, it has good angular stability when the incident angle is 0°, 30°, 50°. Compared with the existing bandpass FSS, the frequency selective surface has dual polarization, flat third-order passband, high frequency selectivity, wide out-of-band rejection, good angular stability and small electrical size and other advantages.

Claims (4)

1. A dual-polarization third-order band-pass three-dimensional frequency selective surface, consisting of several identical unit structures periodically arranged, characterized in that the unit structure is comprised of a metal square cylinder and a dielectric square. 2 . The dual-polarization third-order bandpass three-dimensional frequency selective surface according to claim 1 , wherein a metal square ring is etched at the center position of the upper surface, the middle layer and the lower surface of the dielectric square. 3 . 3 . The dual-polarization third-order band-pass three-dimensional frequency selective surface according to claim 2 , wherein the metal square rings on the upper surface and the lower surface of the dielectric square have the same size. 4 . 4 . The dual-polarization third-order bandpass three-dimensional frequency selective surface according to claim 2 , wherein the circumference of the metal square ring on the upper surface and the lower surface of the dielectric square is greater than the circumference of the metal square ring of the intermediate layer. 5 . .

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