Tri-band and dual-polarized antenna based on composite right/left-handed transmission line

Relaxing the composite right/left-handed (CRLH) balance condition enables arbitrary tri-band CRLH resonant devices. This paper presents a tri-band and dual-polarized antenna based on this principle. The proposed CRLH antenna operates in the transversally-polarized zeroth order (ZO) shunt mode (n = 0) and in the two longitudinally-polarized half-wavelength (HW) modes (n = plusmn1). Explicit synthesis formulas are given for the CRLH tri-band operation. A specific microstrip design using MIM (metal-insulator-metal) series capacitors and shunt stub inductors is demonstrated. In this design, the three resonant modes n = -1, n = 0 and n = +1 exhibited similar input impedances (allowing a simple feeding structure), radiation patterns and efficiencies/gains.