On the Design of Sinuous Antennas for UWB Radar Applications

Sinuous antennas are capable of producing ultrawideband (UWB) radiation with polarization diversity. This capability makes the sinuous antenna an attractive candidate for UWB polarimetric radar applications. Additionally, the ability of the sinuous antenna to be implemented as a planar structure makes it a good fit for close-in sensing applications such as ground penetrating radar. However, recent literature has shown the sinuous antenna to suffer from resonances, which degrade performance. Such resonances produce late time ringing, which is particularly troubling for pulsed close-in sensing applications. The resonances occur in two forms: log-periodic resonances on the arms, and a resonance due to the sharp ends left by the outer truncation. A detailed investigation as to the correlation between the log-periodic resonances and the sinuous antenna design parameters indicates the resonances may be mitigated by selecting appropriate design parameters. In addition, a novel truncation method is proposed to remove the sharp end resonance. Both simulation and measured results are provided to support the developed sinuous antenna design guidance.