A Wideband Conical Log Spiral Antenna with Broad Circularly Polarized Beam

A wideband conical log spiral antenna is proposed in this communication. The antenna is composed of two arms that are wrapped around each other in a log-periodic manner. It is excited by a microstrip feed printed on the opposite side of the substrate having a dielcetric constant of 2.65 and thickness of 1mm, which is regard as a balun, providing the antenna with the appropriate impedance matching between the two arms. A parametric study is performed for providing practical design guidelines. The simulation results indicate that an impedance bandwidth for VSWR ≤ 2.0 from 3.2GHz to 7GHz is covered. Stable radiation pattern with broad beam-width is maintained among the working frequencies. In addition, a flexural structure is devised to reduce the size of the antenna.. Compared with the traditional helical antenna, the antenna has a wide band and a broad beamwidth. The results indicate that the electric characteristics of the antenna meet the application requirements in working frequency.