A high-impedance tunable composite right/left-handed (CRLH) coplanar-waveguide (CPW) transformer provides an effective means of matching a 200-Ω load to a 50-Ω line. By applying DC magnetic bias, it is possible to tune the bandwidth of the transformer, with the center frequency changing from 2.8 to 3.4 GHz.
With a length of 2.4 mm, this transformer represents about a 78% reduction compared to a conventional transformer in the same frequency band. The CRLH transformer’s CPW configuration employs a horizontally magnetized ferrite substrate with small demagnetization field so that very little DC magnetic bias is needed for tuning compared to microstrip configurations.
Composite right/left-handed (CRLH) transmission lines (TLs) have been proposed as a form of transmission line with novel properties. These TLs have been shown to have effective negative dielectric permittivity and magnetic permeability. The CRLH TLs have been incorporated in many compact, multiband microwave components (phase shifters, power dividers, filters, oscillators, and antennas). From these components, microwave impedance transformers based on CRLH TLs have been developed, characterized by small size and wide bandwidth.