Three-passband frequency selective surface with high selectivity and small passband ratio

Abstract

The invention discloses a three-passband frequency selective surface with high selectivity and a small passband ratio. The frequency selective surface is formed by periodically arranging identical unit structures in the horizontal two-dimensional direction, and each unit structure is formed by combining a square metal waveguide and a square dielectric resonator. Each square dielectric resonator comprises three square metal rings in the upper surface, a dielectric substrate and three square metal rings in the lower surface, and the three square metal rings in the upper / lower surface are the same in size and are concentrically distributed. Under the effect of electromagnetic coupling, an original single resonance mode is coupled and split into an odd mode and an even mode, so that a plurality of transmission zero poles are generated, three second-order flat passbands are formed, and the frequency selection performance is greatly improved. The perimeters of the three square metal rings inthe same surface are very close, so that the generated resonant frequency is very close, and a small passband ratio is realized. Meanwhile, the frequency selective surface has high angle stability ina dual-polarization mode.

Description

technical field [0001] The invention belongs to the technical field of electromagnetic fields and microwaves, and in particular relates to a three-band frequency selective surface with high selectivity and small passband ratio. Background technique [0002] In the past ten years, Frequency Selective Surface (FSS) can be applied to radar radomes, antenna sub-reflectors, microwave absorbing materials, electromagnetic shielding, and signal enhancement in indoor wireless environments. In a satellite communication system, in order to increase the communication capability of a multi-frequency antenna, it is usually required that the FSS can work in corresponding multiple frequency bands. At the same time, when the three communication channels work at similar frequencies, it is necessary to design a three-band FSS with a small passband ratio. [0003] Coiled, complementary, and fractal structures are often used in the design of three-band FSS, but this type of designed FSS is usua...

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Problems solved by technology

[0003] Coiled, complementary, fractal and other structures are commonly used in the design of three-band FSS, but this type of designed FSS is usually a first-order FSS, and each passband contains only one transmission pole, resulting in an insufficiently flat passband

Some researchers have also realized the three-pass band FSS by stacking square metal ring arrays or hexagonal metal ring arrays, but only realized two second-order flat pass bands; at the same time, with the increase of the incident angle, this type of FSS will have grating lobe effect in the high frequency band, which directly affects the overall performance of FSS

As an alternative method, the concept of three-dimensional FSS was proposed. Based on two resonant structures of ladder impedance and uniform impedance, some scholars designed a tee-band FSS with second-order response by using multilayer printed circuit board technology. Although it is guaranteed However, the three-dimensional FSS can only work in a single polarization mode, and there is no transmission zero outside the band, and its frequency selection performance is average

In addition, the researchers loaded circular metal patches of different sizes on the upper and lower layers, and loaded circular apertures on the middle layer. With the help of aperture coupling, a dual-polarization, second-order three-pass band FSS was realized. However, its out-of-band No transmission zero is introduced, and its frequency selection performance needs to be improved; at the same time, due to the large electrical size of the FSS unit structure, the angular stability is poor

At the same time, the passband ratio of the adjacent passband of the existing three-pass band FSS is relatively large, which affects the practical application to a certain extent

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