Design of Dual Band Circulary Polarized Microstrip Antenna

Abstract

Microstrip antennas are one of the most widely used antennas today. They are used in cellular phones, spacecraft, missiles, radars and satellite systems. For most applications, circularly polarized wave is preferred over linearly polarized wave, as with circular polarization, antenna orientations are not important and it is immune to multipath distortion. With little modifications in the patch element, circular polarized waves can be generated. Also multiband antennas are always useful as they increase the system capacity. Hence, dual band circularly polarized microstrip antennas are much preferred these days. The objective of this thesis is to design dual band circularly polarized antenna. Two designs are presented for which dual resonance and circular polarization is achieved successfully. Dual resonant frequencies are generated by inserting slots and circular polarization is achieved by feeding adjacent edges in one design and truncating square patch in another. Feeding technique used for both designs is microstrip line feeding. Antenna designs are simulated using FDTD based CST Microwave studio software. Corresponding reflection coefficient and axial ratio obtained on simulation are discussed.