A Broadband High Gain Circularly Polarized Antenna System for Cognitive Radio

Abstract

This paper proposes a broadband high gain LHCP (left hand circular polarized) antenna system using a microstrip line fed slot antenna, reflecting surfaces, and linear polarization (LP) to circular polarization (CP) transformer screen. Gain enhancement principle adopts Fabry-Perot (FP) method using phase compensation in partially reflecting surface (PRS) for increasing bandwidth from 720 MHz to 1.14 GHz. For linear polarization, the system gain is 20.1 dBi at 13.8 GHz with a bandwidth of 1.01 GHz. Using a polarization transformer screen for circular polarization, marginally decreases the gain to 18.8 dBi pulling down the frequency to 13.75 GHz with 3 dB axial ratio. Simulated results agree well with measured results from a fabricated prototype.