RESEARCH ARTICLE Design of compact patch type curved frequency selective surface Nurnihar Begam | Snehasish Saha | Sushanta Sarkar | Debasree C. Sarkar | Parthapratim Sarkar Department of Engineering and Technological Studies, University of Kalyani, Kalyani, West Bengal, India Correspondence Nurnihar Begam, Department of Engineering and Technological Studies, University of Kalyani, Kalyani 741235, West Bengal, India. Email: nur.ice40@gmail.com; Abstract Miniaturized FSS is very useful in communication system. It is obtained by lowering the resonant frequency. Many good research works are reported on compact planar FSS, but it is challenging to decrease the resonant frequency in case of curved FSS. This article deals with the design and fabrication of compact patch type curved FSSs. Here maximum 50.31% compactness is achieved in semicylindrical curved FSS with square slit. Also the parametric studies have been analyzed by introducing same slit in circular and hexagonal patch elements of the curved FSSs. The proposed design has been fabricated. Simulated result has been ratified with experiment result. KEYWORDS curved frequency selective surface, FEKO, measurement, method of moment (MOM), patch type 1 | INTRODUCTION Frequency selective surface (FSS) can be defined as the periodic arrangement of metallic patches on dielectric substrate or that of slots on metal sheet. 1,2 In different technologies in communica- tion system such as radar, aircraft, satellite, and so forth, and household purposes, the filtering properties of FSS is used abundantly. 1,3,4 A novel-shaped compact FSS has been discussed in Reference 5 having simultaneous dual filtering characteristics (band pass and band stop) along with stable response at different incident and polarization angles of plane wave. For practical applications of FSS, the filtering response with the variations of incident angle and polarization angle should be analyzed. 6-8 It may be also used to increase the gain and reduce back radiation of an antenna. 9 The center frequency is reduced for the novel structure by 29.60% and 60% compared to swastika and cross dipole design, respectively. 7 For application in mobile handsets, a compact FSS is very useful to implement high impedance sur- face (HIS). 10 A compact FSS comprising of anchor shape exhibits dual band stop at 2.4 and 5 GHz for WLAN application with the stable response for variation of incident and polarization angles from 0  to 60  . 11 A miniaturized FSS is presented with 4.33 GHz broad pass band with stable response at different inci- dent angles. 12 Miniaturized FSS can be formed by spiral or annular type elements due to its longer electrical length and also for small unit cell size. 13,14 Fourth generation of the Hilbert curve (convoluted structure) is used as unit cell in the design of planar FSSs. The FSSs are resonating at different frequencies for vari- ous generation of Hilbert curve. The FSS consists of Hilbert curve, resonates at 5.6 GHz. Here compactness has been achieved for planar FSSs with convoluted elements. 15 A novel compact two-layer planar FSS resonates at 1.39 GHz with dimension of unit cell 0.035λ × 0.035λ. 16 But it is very challeng- ing to achieve compactness in curved FSS. Some research on curved FSSs have been done. 18-26 But the works are not related to the compactness improvement of curved FSSs. Begam et al. presented in their paper, 18 the roll off and bandwidth improve- ment of a curved FSS (aperture type)-loaded with plus-shaped slots. They investigated that both planar and curved double layer FSSs showed higher roll off, that is, 94.07 and 66 dB/GHz, respectively. 18 The same authors in another paper 19 analyzed the parametric studies for both aperture and patch-type curved FSSs loaded with hexagonal loop elements with simulated and mea- sured results. In Reference 20, an equivalent circuit model was developed to illustrate the square loop elements-loaded finite and curved FSS numerically. There was no measured result for ratification. Begam et al. demonstrated broadband (up to 19.45 GHz) and multiresonating frequencies in simulated Received: 21 January 2019 Revised: 25 March 2019 Accepted: 6 April 2019 DOI: 10.1002/mmce.21803 Int J RF Microw Comput Aided Eng. 2019;e21803. wileyonlinelibrary.com/journal/mmce © 2019 Wiley Periodicals, Inc. 1 of 8 https://doi.org/10.1002/mmce.21803