Design of a Dual-Frequency Center-Fed Transmitting Antenna for Compact HF Surface Wave Radar

Multiple-frequency observation and mobile platform deployment are the promising directions of high frequency surface wave radar (HFSWR). To adapt to this trend, previous transmitting antenna is challenged by the compatibility of multifrequency operation and small size. In addition, the radiation efficiency of previous compact HFSWR antennas has always been troubled by the rigorous grounding requirement. We developed a novel dual-frequency center-fed transmitting antenna to address these concerns, which can be easily extended to multifrequency case. The high-power omnidirectional radiation pattern is achieved at two frequencies within a single pole, and no grounding system is required. This antenna also provides the wider bandwidths at both frequencies with respect to that of a single frequency antenna, which enables a more flexible radar band selection. The antenna design scheme and the associated mathematical model are illustrated in detail. In addition to the mathematical analysis, both simulated results obtained using Fourier series treatment and field experimental measurements are given to verify the rightness and validity of the antenna design.