The physical foundation, developmental history, and ultra-wideband performance of SMM (spiral-mode microstrip) antennas

The paper reviews the physical foundation, developmental history, and ultra-wideband (UWB) performance of the SMM (spiral-mode microstrip) antenna (Wang, J.J.H. and Tripp, V.K., 1996; Wang, 1997; Wang et al., 2005). The paper is inspired by the recent article on self-complementary (SC) antennas by Y.Mushiake (see IEEE Antennas and Propag. Magazine, vol.46, 2004; IEEE Antennas and Propag. Symp. Dig., 2003), and shares with it considerable physical insight and technical relevance. However, it is worth pointing out that an SC structure offers only a real constant impedance, not necessarily a useful radiation pattern; both are needed to qualify as a UWB, or even a frequency-independent (FI) antenna, and this is where the geometries of spiral, log-periodic (LP), etc. come into play. Additionally, for practical reasons it is often necessary that the antenna be amenable to conformal mounting on a platform; this can be accomplished by the SMM antenna.