Miniaturized Circularly-Polarized Antenna Based on Four Meandered Monopoles

This paper presents a miniaturized circularly-polarized antenna based on four meandered monopoles. The proposed antenna is a dual-substrate type, where four meandered monopoles printed on the upper substrate are fed by a series feed network on the lower substrate. Two substrates are connected by a metal post enclosed by a teflon cylinder. The antenna miniaturization is realized by highly meandering monopole arms and transmission lines of the feed network with the size reduction of 78%. Short-circuit stubs for impedance matching of meandered monopoles are employed on the lower substrate for structural simplicity. The fabricated antenna has a dimension of 0.11×0.11×0.022 λ0, -1.9dBic gain, 1.4dB axial ratio, and 11.5dB front-to-back ratio at 915MHz.