A Study on the Non-Uniform Rectangular-Ring Slot Antenna for Broadband Circular Polarization Operations

Abstract

A non-uniform rectangular-ring slot antenna is presented to achieve both wider impedance and axial-ratio (AR) bandwidths. A simple design process, composed of three steps, is developed to obtain the required performances. Because of the better performances and less design time, the proposed antenna will be a good choice for the wideband circularly polarized operation. The first one of the three design steps is to determine the size of the uniform square-ring slot and feeding point by the required center frequency. The second one is to achieve circular polarization operations by widening the upper slot. However, the center frequency of the proposed antenna is shifted to higher frequency owing to the shortening of the average current path. Finally, the center frequency of the proposed antenna is fine tuned to the required center frequency by resizing the parameters of the proposed antenna. An antenna design example is given for the application of WLAN 2.4 GHz. Following the three design steps, the simulated results show that the center frequency and bandwidth of impedance are 2.5 GHz and 50.4%, respectively, and those of axial ratio are 2.45 GHz and 17.1%, respectively. The measured center frequencies of the impedance and AR are 2.63 GHz and 2.53 GHz, respectively, and the corresponding data for the bandwidths are 49.2% and 12.1%, respectively. Hence, the experimental results are in good agreement with the simulated data. Furthermore, the radiation patterns are broadside radiation with right-hand-circular-polarization (RHCP), and the antenna gain is about 4.2 dBic.