Abstract

A novel design of a circular microstrip antenna with an additional small circular patch excited by a single feed for achieving a dual band frequency operation with circular polarization (CP) is presented. The implemented dual band circularly polarized antenna has a compact configuration that serves the technology demands requirements in mobile unit systems for smaller volume. Simulation and experimental results show that the 10 dB return-loss impedance bandwidth is better than that of a conventional single circular microstrip patch antenna. In addition, a dual frequency band operation at 2.45 GHZ and 5.2GHZ is obtained. A second antenna design suitable for an integrated circuits demand is also presented. Results demonstrate that both sense left hand and right hand circular polarization (RHCP, LHCP) can be achieved using this technique. A comparison between theoretical and experimental results is provided and shows good match. The resonance frequencies and quality of the axial ratio can be controlled by changing the radii of the two circles, and the orientation of the additional circular patch relative to the main patch. For other desired frequencies, the design of the antenna can be carried out by calculating the radii of the main and additional patch using empirical equations acquired for this design. The empirical formulas are developed based on a comprehensive parametric study where different designs and material parameters are varied to achieve an optimum antenna performance. A 64-element uniform linear array of circular microstrip patch antennas is designed and simulated for achieving circular polarization (CP) with more than (20 dB) directivity. Since the axial ratio bandwidth of the implemented antenna is narrow, a sequential rotation of radiating patches with suitable excitation phase shifting has been applied to improve the polarization purity over a wide range of frequencies with higher gain compared to a single patch