Multiplexers and Antennas Based on Metamaterial Transmission Line

Metamaterial transmission lines are able to control the phase response in the circuit, thereby making it possible to achieve multi-band characteristic in guided structures and full beam scanning ability in leaky-wave antenna applications. Isolation circuits use multi-band trait of a metamaterial transmission line for having infinite impedance at multiple frequencies. With isolation circuits, it is possible to connect microwave filters for having unique property, so called multiplexing functionality. This new approach provides unique advantageous features beneficial to system designer. For instance, there is no need to modify the components (filters and multiplexers) used in the system. Also, the design process is straightforward.Substrate integrated waveguide (SIW) is a novel guided-wave structure developed in recent years in microwave and millimeter wave areas. It can be synthesized on a planar substrate with linear periodic arrays of metallic vias by planar circuit processes. SIW has significant advantages such as low insertion loss, low cost and strong integration ability with other planar circuits. Based on the SIW technique and the metamaterial transmission line concept, circular polarized SIW leaky-wave antennas are designed and presented. The proposed frequency scanning antennas provide circular polarized fields using a single radiating transmission line, which can avoid the complexity of conventional approach