Design of a Dual-Band Metamaterial Antenna with CRLH Transmission Line for Wi-MAX Applications

Abstract

This paper presents the design and evaluation of a dual-band antenna featuring a circular ring patch and an inner concentric circular patch. The antenna is designed to operate at two distinct frequency bands, with the outer ring patch optimized for the lower frequency band and fed through a grounded coplanar waveguide (CPW). The integration of Composite Right- and Left-Handed Transmission Line (CRLH-TL) elements within the inner patch introduces additional resonance frequencies and enhances impedance bandwidth. The inner patch is directly fed by the CPW conductor, while the outer ring is connected to the ground via microstrip lines to improve impedance matching and overall performance. The final antenna design achieves dual-band functionality, resonating at frequencies of 2.61 GHz and 4.45 GHz, and demonstrates broad impedance bandwidths suitable for Wi-MAX applications. Measurement of the S11 parameters confirmed a strong agreement with simulation results, validating the design approach. At 2.61 GHz, the antenna exhibits a gain of 2.22 dB and a directivity of 2.42 dB, while at 4.45 GHz, it shows a slightly higher gain of 2.23 dB and a directivity of 2.41 dB. The antenna achieves omnidirectional radiation patterns in the E-plane, indicating a uniform radiation distribution. The electric field distribution analysis reveals that, at lower frequencies, currents are concentrated along the patch and ground edges, whereas at higher frequencies, the CRLH-TL elements within the inner patch become more prominent. This behavior underscores the antenna’s capability to support different resonant modes, contributing to its effective dual-band performance.