Advanced Design of Planar Spiral Antenna with Novel Feeding Network

In this paper, a planar type four-arm rectangular spiral antenna with a novel feeding network is presented. Compared with the Archimedean and log spiral antennas, a planar spiral antenna with rectangular arms has short coming of narrow axial ratio bandwidth. To overcome this weakness, a novel feeding scheme utilizing CRLH metamaterial transmission line is proposed. The network consists of a Wilkinson power divider, metamaterial delay lines, and two half-wave baluns. The measured '10 dB return loss' impedance bandwidth spans over 2.43 GHz from 1.09 GHz to 3.52 GHz. An excellent axial ratio performance (<3dB) over broad band of 1.2 GHz from 1.3 to 2.5 GHz and RHCP gain of 4 dBi over all the frequency band of interest are obtained.