Analysis and design of two-arm conical spiral antennas

The two-arm, conical spiral antenna is analyzed using the finite-difference time-domain method. The analysis is validated by comparison with measurements of the input impedance and the realized gain. A parametric study is performed with the analysis, and the results from the study are used to produce new design graphs for this antenna. These graphs supplement and extend the existing, mainly empirical, design base for this antenna. Two resistive terminations, intended to improve the low-frequency performance, are examined. One is a termination formed from two lumped resistors, and the other is a new termination formed from a thin disc of resistive material. These terminations are shown to improve the front-to-back ratio and axial ratio for the antenna.