Analysis of edge effect on millimeter-sized planar logarithmic spiral antennas

Effect of edge configurations of millimeter sized planar-logarithmic-spiral-antenna (PLSA) was analyzed. It is found that an external ring electrode and taper conducting arms contribute to lowering a lower side of critical frequency at which the VSRW becomes two. The low VSWR domain extends up to terahertz region for all types of edge configuration. The size dependence of the critical frequency and spatial Poynting's power distribution are estimated for different edge configuration.