Synthesis of a polarisation‐rotating surface with reflective filtering response based on orthogonally inserted coupled slot‐lines

Abstract

In this article, a three-dimensional polarisation-rotation surface (PRS) with reflective filtering response based on two orthogonally inserted coupled slot-line is investigated, which can reflect a vertically/horizontally polarised incident wave by 90°. Each unit cell of the PRS is composed of a pair of meandered slot-line sections with open-short-ends etched on the vertically and horizontally inserted single-layer printed circuit boards. Under the incidence of a linearly polarised plane wave along the vertical/horizontal direction, the plane wave is converted into the guided wave by the open-circuited end of the slot-line section, and then the guided wave is obstructed by the short end of the slot-line section and coupled to the other slot-line section, thus leading to 90°polarisation rotation. To simplify the design procedure, a matrix coupling theory is applied to synthesise and design the proposed PRS. A sample with fractional bandwidth of 20% at the centre frequency of 5 GHz and return loss of 20 dB is designed, fabricated, and measured for verification. The measured and simulated results are in good agreement with the theoretical ones. The results confirm that the proposed PRS has low insertion loss, high polarisation conversion ratio, and stable filtering performance for oblique incident angle up to 60°. K E Y W O R D Sfiltering theory, frequency selective surfaces, polarisation | INTRODUCTIONFrequency selective surfaces (FSSs) are kinds of spatial filters manipulating electromagnetic (EM) waves that have been widely investigated for decades [1,2]. A traditional FSS is commonly composed of a two-dimensional (2-D) periodic array constructed by metallic patches or apertures etched on a dielectric substrate, which can exhibit bandstop or bandpass filtering performance for the spectral control of incident EM waves [3,4]. Unlike microwave filters, FSSs can not only control the amplitude response related to frequency, but also manipulate the incident angle and polarisation. Benefitting from these advantages, FSSs have been employed in a variety of applications including radomes [5], transmitarray [6], reflectarray [7], polarisation converters [8] etc.Polarisation-rotating surfaces (PRSs) are special kinds of FSSs, which can not only possess the frequency selective property for the incident EM waves, but also rotate the polarisation direction of the incident EM waves into a predictable direction. The special structures have been widely used in applications such as imaging radar [9], modern military stealth radar [10], and secret communication systems [11]. According toThis is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.