Miniaturized tuneable passive microwave devices based on transmission line metamaterials

Electromagnetic metamaterials (MTM) are effectively homogenous structures that are artificially created and not found in nature. Extensive investigation and theoretical analyses by researchers show that this material or structure exhibits simultaneous negative permittivity and permeability phenomenon. Due to the special double negative electromagnetic properties the material was named “left-handed material”. In 1967, V.G. Veselago a physicist from the Lebedjev Physical Institute in Moscow first proposed this metamaterials, and later on Pendry and Smith demonstrated the special electromagnetic properties can be realised practically using split ring resonators and metal strip structures. According to their investigation the split ring resonator´s (SRR) inherent capacitance and inductance interact to create the negative permittivity. Also the thin metal wire (TW) strip parallel arrangement through a dielectric substrate induces negative permeability within the substrate. The TW-SRR MTM structure is resonant at a particular frequency defined by the dimensions of the structure. It´s known that the quality-factor (Q) of the resonant structure is inversely proportional to its bandwidth, and transmission-loss is inversely proportional to the quality-factor. This means a high-Q will have a reduced bandwidth and be responsible for higher a transmission loss. After taking these resonant structures restrictions into consideration, in 2002, Caloz, Eleftheriades investigated the viability of the non resonant transmission-line approach to realise the metamaterial structure. They demonstrated the same electromagnetic properties could be realised using a series capacitor and shunt inductor circuit arrangement using microstrip technology. In this planar configuration, low loss and broad bandwidth can be achieved by proper