A small wideband multimode antenna

This paper presents a multi-resonant spherical antenna with a normalized size ka~0.54 and excellent bandwidth performance (k is the wavenumber and a is the radius of the sphere circumscribing the maximum dimension of the antenna). The spherical geometry is chosen in order to establish a baseline Q-factor against which to compare the bandwidth: a Q at 1.5x the lower bound is known to be achievable for optimized small, single resonance spherical antenna designs. The antenna presented here is designed to support two natural resonances, one low-Q and one high-Q . It postulates that the high-Q mode acts in a manner analogous to a higher-order matching circuit.