A clover-shaped single-ring element based RA for high efficiency and wideband application in X-band

This communication presents an X-band RA using a meandered clover-shaped single-ring element of variable size. A good linear phase range is realized by varying edges of the rectangle. The periodicity of the unit cell is 0.5λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</inf>. λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</inf> is wavelength in vacuum at 10 GHz. The substrate utilized is Rogers RT/duroid 5880 of dielectric constant Ɛ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf>=2.2 with tan = 0.025. Additionally, an air layer of thickness 2mm is used. RA has a circular diameter of 300mm with total elements of 316. A pyramidal X-band horn antenna as standard waveguide WR-90 having an aperture size of 4.5×3.5 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and gain of 13 dBi at operating frequency to excite RA. This RA offers a peak gain of 26dBi and an aperture efficiency of 40% at central frequency. The side lobe level and cross-polarization levels in both planes (E and H) are lower than -15dB and -80dB individually. Besides 3-dB gain bandwidth is 22.2% while 1-dB gain of 12.6 % is obtained.