Study of a two-arm sinuous antenna and the relevant wideband balun

In this work, we focus on the research technique of the sinuous antenna. We have studied and designed a wideband two-arm sinuous antenna for 2.5-7.5 GHz operation and its matched balun, and the antenna has been fed by a 50 Omega coaxial-cable. The balun, matched the balance structure and the wideband character of the antenna, is microstrip linearly gradual tapered type. The simulation results show that the antenna with the balun has wideband character, and the radiation pattern of the E- and H-plane are more uniform compared with those of the traditional spiral antennas.