A Circularly Polarized Microstrip-Fed T-Slot Antenna Array on a Conducting Cylinder

A circularly polarized T-slot antenna array wrapped on a conductive cylinder is presented in this letter. This cylindrical antenna array consists of four independent cavity-backed T-slot elements, which are fed by four microstrip lines. The designed array is to be used in a switched-beam mode so that the array's radiation beam can be selected using a single-pole 4-throw (SP4T) switching circuit. Simulated and measured results show that the radiation pattern of each element is able to cover a quadrant in the horizontal plane while the radiated wave in each quadrant is circularly polarized. Furthermore, the four elements are well isolated and exhibit wide bandwidth. Measured results of one slot element in the array configuration show that it has a 13.8% bandwidth for $10~ dB$ return loss and a 7% bandwidth for 3 dB axial ratio.