  Sinuous antennas are capable of producing ultra-wideband radiation with
polarization diversity. Such a capability makes the sinuous antenna an
attractive candidate for wideband 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 outer truncation of the sinuous antenna
geometry. 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 parameters. In addition,
the resonance due to truncation may be mitigated by moving the circular
truncation to the tip of the outermost cell which has advantages over the
clipping method proposed in the literature.
