Multifrequency Monopole Antennas by Loading Metamaterial Transmission Lines with Dual-shunt Branch Circuit

The theory and design of a new family of multifrequency monopole antennas by smartly loading a set of complementary metamaterial transmission line (CMTL) unit cells are investigated. The distributed CMTL elements, epsilon negative (ENG) or double negative (DNG) through incorporating additional capacitive gaps, contain a Koch-shaped extended complementary single split ring resonator pair (K-ECSSRRP) etched on the signal strip. The KECSSRRP features dual-shunt branches in the equivalent circuit model, rendering a distinguished resonator with dual zeroth-order resonant (ZOR) modes. By smartly controlling the element layout and loading different numbers of unit cells, ten antennas covering different communication standards (GSM1800, UMTS, Bluetooth, DMB and WIMAX) are designed and four of them are fabricated and measured. At most of operating frequencies, the antennas exhibit impedance matching better than −10 dB and normal monopolar radiation patterns. Numerical and experimental results both confirm that the single-cell or dual-cell ENG and DNG CMTL-loaded monopoles exhibit almost identical dual ZOR modes. Moreover, the loaded elements also contribute to the radiation, which is the major advantage of this Received 24 December 2012, Accepted 21 February 2013, Scheduled 12 March 2013 * Corresponding author: He-Xiu Xu ([email protected]).