CPW-FED multi-band omni-directional planar microstrip antenna using composite metamaterial resonators for wireless communications

A novel approach for the design of a compact multi-band planar microstrip antenna is presented. This type of antenna is composed of composite metamaterial resonators (including conditional microstrip resonators and metamaterial resonators), and fed by signal feed. A sample antenna with composite closed-ring resonator and split-ring resonator (SRR) fed by 50 Ω coplanar waveguide (CPW) developed on FR4_epoxy substrate for multi-band wireless communication applications is presented. Appropriate design of the composite structure resulted in three discontinuous resonant bands. The fundamental magnetic resonant and electric resonant frequency of SRR and the first electric resonant frequency of the closed-ring resonator were combined to form low, middle, and high resonant band. The properties of this antenna are investigated by theoretical analysis and finite element method (PEM) simulations. The numerical results show that the proposed antenna has good impedance bandwidth and radiation characteristics in the three operating bands which cover the required band widths of the 2.4/5.2/5.8GHz wireless local-area networks (WLAN) and 3.5/5.5GHz worldwide interoperability for microwave access (WiMax) with return loss of better than 10 dB. The antenna also has stably omni-directional H/-plane radiation patterns within the three operating bands.