Composite right/left-handed λ-resonator ring antenna for dual-frequency operation

A novel ring structure operating as a dual-frequency resonating antenna is presented. The ring analysis and design is based on the concept of the composite right/left-handed transmission line (CRLH TL), with the particularity that the ends of the line are connected together so as to form a closed loop. As in the case of conventional ring resonators, multiples of full wavelength (nλ) field distributions are supported. The key feature of the proposed resonator is that an identical field distribution along the ring is achieved at two different operating frequencies. This phenomenon is due to the dual nature of the CRLH dispersion characteristic. The lower operating frequency corresponds to the λ mode in the left-handed (LH, backward wave, β<0) range, while the higher resonance frequency corresponds to the λ mode in the right-handed (RH, forward wave, β>0) range. The main benefit of having the same field distribution is that identical performances (radiation, polarization and matching) are achieved at each of the two frequencies. The proposed antenna structure has been simulated with commercial MoM/FEM tools and validated with measurements on fabricated prototypes.