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This work proposes and experimentally evaluates a single layer bandpass frequency selective surface (FSS) that resonates at X-band (8-12 GHz). The metal plate of the unit cell has a half-Jerusalem cross slot of size 0.15λ 0 , where λ 0 is the wavelength corresponding to 10 GHz centre frequency. The effects of unit cell parameters on filter response are analyzed through parametric analysis. The results reveal that the proposed bandpass FSS exhibits good polarization stability and angular stability at oblique angles up to 45 • . Furthermore, negligible frequency deviations in both TE and TM polarizations have also been achieved using this structure. A prototype of the bandpass FSS was fabricated on an FR4 substrate to validate the proposed design which includes 10 × 10 elements in a dimension of 45 mm × 45 mm × 1.6 mm. Measurements show that the bandpass FSS has a fractional bandwidth of 40% centered at 10 GHz from 8 GHz to 12 GHz. The unique feature of the proposed filter is its ability to operate in the whole X band (8-12 GHz) by tuning the filter elements.

A compact exponentially tapered balanced antipodal Vivaldi antenna for modern radar systems is proposed in this paper. The proposed design implements slanted rectangular slots at the flare edges to improve impedance bandwidth typically at lower frequencies. The antenna is coupled to a 50 Ω microstrip line between the signal conductors of the middle layer and ground plane. A detailed parametric analysis has been carried out to determine the optimized dimensions and to achieve desired antenna performance. A prototype of the antenna (56 × 28 × 1.6 mm 3 ) was fabricated and measured to validate the simulation results. It is revealed that the antenna has a wide impedance bandwidth of 120% over 5-20 GHz and measured gain of the antenna increases from 2.6 dB to 8.0 dB in the whole operational frequency band. The small aperture width which is typically 28 mm is an attractive feature of the proposed design. Therefore, compact size, high gain, ultrawide bandwidth, and directional radiation characteristics of the proposed design may be suitable for advance radar systems.