A Stripline-Fed Stacked Spiral Antenna with Improved Performance

Abstract

This paper presents a stacked spiral antenna with directional radiation pattern and improved bandwidth. The proposed antenna consists of two stacked spirals which are connected by two copper posts. To feed the antenna, a tapered stripline is applied to transform the input impedance of stacked spiral from $90 \mathrm{\Omega}$ to $50 \mathrm{\Omega}$ , which also makes the antenna easy to be fed by a coaxial cable directly. Simulated results show that the proposed antenna can achieve an excellent impedance bandwidth from 1.19 GHz to more than 5 GHz, which is wider than the bandwidth of a single spiral with the same turns. Moreover, it is demonstrated that unidirectional radiation pattern can be realized without using any reflectors, which is quite different to the radiation characteristic of conventional spirals without reflectors backed. The peak gain of the stacked spiral is also improved compared with a single stripline-fed spiral antenna.