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A novel, dual‐band frequency‐selective surface (FSS) is presented. The designed and fabricated FSS structure has closely spaced operation bands and high selective frequency response at each operation band. Two‐dimensional compact U‐shaped slot resonators are used in each FSS unit cell to obtain this ability. Also, each slot resonator is composed of straight slot section at the centre connected to two U‐shaped arms at each end. The dimensions of the slot resonators are optimised using via full‐wave electromagnetic simulations using CST Microwave Solver. The proposed FSS structure is independent of incident polarisation and angle because of 90° rotation of the unit cell. The validity of the proposed FSS is confirmed by both simulation and measurement results. In the experimental verification, a waveguide measurement setup is chosen. Both measurement and simulation results show that the FSS structure operates at the designed frequencies of 8.80 and 9.54 GHz, which are very close to each other.

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In this study, a single layer reflectarray antenna is proposed with variable patch sized unit cells and suggested for enhancing the bandwidth with small overall dimensions for X‐band applications. The novel unit cell consists of double cutted ring geometry. 13 × 13 unit cells reflectarray is covering an 162.5 × 162.5 mm2 ultrathin square substrate with εr = 6.15 dielectric permittivity and 0.042 × λ0 thickness. In order to obtain larger and smoother phase curve, 2 mm air gap is inserted between substrate and ground plane. The required phase delay is compensated by using variable size unit cell elements. The main beam is directed to the desired direction (θ = 0°). A 169‐elements reflectarray is illuminated by a pyramidal horn antenna which is located at F = 148 mm. The designed reflectarray antenna is simulated and fabricated to validate the design method. The measurements are made in a shielded anechoic chamber. The simulation and measurement results are in agreement with each other. The maximum gain value is 22.93 dBi at 12 GHz, 1‐dB gain bandwidth is 18% between 10 and 12 GHz and 3‐dB gain bandwidth is 24% between 9.4 and 12 GHz.

In this study, a novel axe‐shaped ultra‐wideband (UWB) antenna with low‐backscattering radar cross‐section (RCS) is designed. The designed UWB antenna bandwidth is 3.4–15.5 GHz covering the entire band assigned for the UWB applications. The RCS of the designed antenna is reduced by modifying the geometrical shape. This technique is based on the subtraction of the metal areas which have the minimum current distributions on the surface of the printed antenna. Therefore the backscattering RCS of the modified axe‐shaped UWB antenna is reduced up to 10 dB in the whole frequency band while maintaining the radiation performance. The size of the antenna is 0.32λl ×0.39λl, where λl is the wavelength at the lower operation frequency and the fractional bandwidth is 128%. The radiation patterns, scattering characteristics and the RCS of both the modified and reference axe‐shaped UWB antennas are simulated and experimentally verified. The simulation and measurement results are in a good agreement.