Novel Zeroth-order Resonance in Composite Right/left- Handed Transmission Line Resonators

A novel resonator using a composite right/left-handed (CRLH) transmission line (TL) is presented and its extraordinary resonant characteristics with an infinite-wavelength wave are discussed. The resonance corresponds to the zeroth-order on the analogy of the conventional mode numbering. The zeroth-order resonant characteristics and loss mechanism are fully described by the circuit theory and it is shown that the resonant frequency of the zeroth-order resonator (ZOR) is independent of the physical length so that the resonator can be arbitrarily small under the condition that sufficient reactance is squeezed in a small length. Full-wave simulations and experiments for meta-structured ZORs implemented with the microstrip line technology agree well with the theoretical results and hence the validity of the theory is confirmed. A 61% size reduction from the conventional resonator with a good unloaded Q of 250 is obtained for a prototype ZOR made of 1.5-cell CRLH TL at 1.9GHz in the experiment.