Shared-radiator design of broadband and dual-mode antenna for personal role radio applications

Shared-radiator design of a broadband and dual-mode antenna that simultaneously covers the VHF/UHF band and satellite navigation band is presented for personal role radio (PRR) applications. Quadrifilar helix antenna (QHA) is devised to be a circularly polarized radiator which as well acts as a part of the upper half radiation arm of the dipole antenna and be equivalent to a linearly polarized radiation current carrier at VHF/UHF band, forming a symmetrical dipole antenna with a sinusoidal current distribution. A 5th-order balanced matching network comprised of five cascade L-sections is adopted to obtain the maximum possible working band-width and a 3.76:1 band-width (116 %) at VHF/UHF band is achieved. Strong mutual coupling effect of the two operating modes is observed near 1.5 GHz originated from QHA shared-radiator design, and a new balun structure is applied to achieve high isolation and self-decoupling, subsequently |S21| of the two operating modes is significantly reduced from about to below −32 dB at satellite navigation band without affecting the reflection coefficient and radiation efficiency. The measured results show that radiation patterns of the manufactured prototype is basically consistent with corresponding simulation counterparts.