A coplanar waveguide fed two arm archimedean spiral slot antenna

Abstract

Spiral antennas gained a lot of popularity due to their circularly polarized radiation with a relatively constant input impedance and radiation pattern over wide frequency range.The conventional spiral antenna is fed from the center with the need for a balun and an impedance matching network. However, this way of feeding increases the size of the antenna and put more constraints and difficulties in the designing process. In this project a coplanar waveguide fed two-arm Archimedean spiral slot antenna loaded with a chip resistor with improved circular polarization bandwidth and reduced size is presented and investigated.The antenna is studied through simulation and fabricating a prototype to verify the simulated results.The geometry of the antenna is similar to the conventional Archimedean spiral antenna. However, the antenna is situated in one plane and fed without the need for an external balun or an impedance matching network which allows compact and completely planar structure. Moreover, the proposed antenna, possesses the advantage of wide band impedance bandwidth and circularly polarized radiation pattern, less than 3dB axial ratio, with good radiation efficiency, larger than 60%, over 1.6:1 bandwidth. Furthermore, two techniques to improve the axial ratio bandwidth, have been studied and investigated. Finally, the characteristic impedance of the antenna and the lower operating frequency can be designed to match the requirements for many systems.