Design and experiments of the conical sinuous antenna fed by microstrip Balun

The structure design and experiments of the conical sinuous antenna for the dual polarized passive radar application are researched. The planar sinuous antenna with four arms was designed to be conformal with the surface of the cone and the conical sinuous antenna was fabricated through microstrip adhering technique. The conical sinuous antenna with four arms was fed in balanced mode by two microstrip exponentially tapered balanced-to-unbalanced transformers (Balun). The specific antenna structure and microstrip Balun were designed within the frequency range from 2 GHz to 5 GHz. The fabricated antenna was measured. Over the operating frequency range, the measured average input voltage standing wave ratio (VSWR) is about 2; the measured gain of each port is higher than 4 dBi, the measured isolation degree between two ports is about less than -20 dB and the radiation pattern has good polarization purity. The research results provide references for practical engineering application.