Cable-current effects of miniature UWB antennas

Since the FCC legalized the operation of ultra-wideband (UWB) enabled products in the US, many novel, very broadband antenna designs have emerged. The paper discusses the cable-current effects of a common, miniature printed monopole antenna with a shaped ground plane and of a miniature printed dipole antenna. A CPW-fed pseudo monopole antenna is used to demonstrate that cable currents affect the low frequency performance when the antenna is fed by a coaxial line. A UWB dipole antenna is presented with significantly reduced cable-current effects. It is fed with a CPW line which transitions rapidly into a CPS line. The surface area of the PCBs for the dipole and the pseudo monopole are about the same. It is shown that using a balun and avoiding a finite-sized ground plane reduce the effect of cable currents on the antenna performance.