A Compact Circular Filtering Antenna for C-band Applications

In this paper, a compact circular filtering antenna for C-band application is presented. It comprises four main parts, including a circular patch with a U-shaped cutout at the bottom, inserted feeding, a half circle resonator with two curved arms, and a feeding microstrip line. The proposed circular filtering antenna has a size of 30 x 25 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a thickness of 1.67 mm. It has two nulls that represent the filter’s stopband at a lower frequency of 4.8 GHz and a higher frequency of 5.4 GHz. Additionally, the filter passband is presented by a max gain of 6.2 dBi at the center frequency of 5 GHz. Furthermore, the filter function is also shown by the surface current distribution at frequencies of 4.8 GHz, 5 GHz, and 5.4 GHz. Based on the simulated results, the strongest surface current distribution occurs in the radiator patch at a frequency of 5 GHz, while the strongest surface current distribution happens in the insert feeding at frequencies of 4.8 GHz and 5.4 GHz. The simulated result of impedance bandwidth (IBW) is achieved around 550 MHz, spanning from 4.83 GHz to 5.38 GHz. Next, it has a 3 dB beamwidth of 97° with the mainlobe at 6°. For C-band applications, the proposed circular filtering antenna has good filter function characteristics.