A linear‐to‐circular polarization converter based on a bi‐layer frequency selective surface

Abstract

In this work, a wideband linear-to-circular polarization converter is proposed based on a bi-layer band-pass frequency selective surface (FSS), whose unit cell consists of two layers of identical patterned metal films mounted on the two sides of a homogeneous dielectric layer, and the geometric pattern of each metal film is a square loop aperture surrounding a concentric square corner-truncated patch. Both measured and simulated results show that the polarization converter can realize linear-to-circular polarization conversion in the frequency range from 6.87 to 10.07 GHz, which corresponds to a fractional bandwidth of 37.8%; moreover, its response is almost independent of the polarization and incidence angle of the incoming wave. Compared with published designs, the proposed polarization converter has a simpler geometry but a wider bandwidth, higher transmittance and better stability, it may possess potential applications in the design of CP antennas.Polarization is an expression of the orientation of the electricflux-lines in an electromagnetic (EM) wave, which is one of important properties of the EM wave, it must be taken into consideration in its practical application. In various wireless systems, such as mobile communications, radar tracking, satellite communications and navigation systems, circularly polarized (CP) waves are preferred due to the advantages such as simplifying alignment and overcoming Faraday rotation effect and multi-path fading. 1 To generate a desired CP wave, in addition to the way to generate it directly using CP antenna, an alternative effective way is to generate a linearly polarized (LP) wave firstly and then convert the LP wave into a CP wave by using a polarization converter. Polarization converter is a kind of polarization control device which can convert an incident wave with a given polarization to a reflected or transmitted wave with a different polarization. Polarization converter can be realized in different ways. In the past decade, it has be found that frequency selective surface (FSS) and metasurface can provide a convenient way to control the polarization state of a EM waves, now different types of polarization converters, such as cross polarization converters, 2-12 and linear-to-circular polarization converters, [13][14][15][16][17][18][19][20][21][22][23] have been realized using various FSSs or metasurfaces.In this work, we propose a transmission-type linearto-circular polarization converter based on a bi-layer bandpass FSS. Its 3 −dB axial ratio bandwidth is up to 37.8%, and the total transmittance remains above −1.69 dB over the entire band; moreover, its response is almost independent of the polarization and incidence angle of the incoming wave and can maintain a stable performance over a wide range of incidence angles at both TE and TM incidences. Compared with published designs, 13-20 the polarization converter has a simpler geometry but a wider working bandwidth, higher transmittance and better stability, it may possess potential applications in the design of CP...

Approximate analytical method for hexagonal slot frequency selective surface analysis

“…In the past centuries, the research on the reflection and transmission characteristics of frequency selective surface (FSS) has attracted extensive attentions. [1][2][3][4][5] Numerous methods were developed for the analysis and optimization of FSS, such as the numerical algorithms [6][7][8][9][10][11][12][13] and the corresponding commercial software [1][2][3][4][5][14][15][16][17][18][19] and the approximate analytical methods. [20][21][22][23][24][25][26][27][28][29][30][31][32] Generally, the numerical algorithms are time consuming with fewer physical interpretation of the filter characteristic.…”

“…To the authors' knowledge, the analysis method of FSS composed of hexagonal slot/sloop and the similar inclined edge structures is mainly the commercial software. 5,[14][15][16][17][18][19] Although the equivalent circuit model can be established according to the geometric and the reflection/transmission coefficients, the corresponding transmission line parameters are not provided. One would have to adopt the curve-fitting scheme or a similar approach based on full-wave simulation.…”

“…One would have to adopt the curve-fitting scheme or a similar approach based on full-wave simulation. [1][2][3][4][5][21][22][23][24][25] Recently, an interference theory was developed for polygon-based broadband absorbers. However, the reflection and absorption rates are also simulated by commercial software.…”

Miniaturized dual stop band frequency selective surface with broadband linear co to cross polarization conversion ability

“…Frequency selective surface (FSS) is widely used in wireless and satellite communication as a periodic surface that can transmit or reflect the electromagnetic (EM) signal. 1 FSS founds different applications as microwave absorber, 2,3 radar cross section reduction, 4 antenna radome, 5 polarization converter, 6 sub reflector in cassegrain horn, 7 EM cloaking, 8 and as antenna superstrate for directivity enhancement. 9 Recently, circular array radiation theory is applied to represent the scattered field from a conducting cylindrical surface and the theory is extended for concentric array geometry to realize active cloaking at microwave frequency.…”

Dual‐band multifunctional metasurface for absorption and polarization conversion

“…They are regarded as an excellent method for controlling the polarization state of EM waves because they possess several distinctive features, such as high efficiency, ultrathin thickness, multiple bands, and broad band. Till date, several metasurface-based polarization conversion systems with various functionalities, such as linear-to-linear, 19,20 linear-to-circular, 21,22 and circular-to-circular 23 polarization conversion, have been reported. However, the above-mentioned absorbers and polarization converters, though very efficient, are based on single functions.…”