Via-Free CPW-Based Composite Right/Left-Handed Transmission Line and a Calibration Approach to Determine Its Propagation Constant

In this paper, a via-free compact CPW-based composite right/left-handed transmission line (CRLH TL) is presented. The structure is realized by metal-insulator-metal (MIM) series capacitors and shunt coplanar waveguide (CPW) stub inductors. A calibration approach to accurately extract the propagation characteristics of CRLH TLs is also proposed. To demonstrate the extraction technique, three unbalanced CRLH TLs of different lengths are designed and fabricated. The LH-passband with anti-parallel phase and group velocities and the LH/RH-stopband with zero phase constant are successfully determined. For the proposed CRLH TL a LH-passband extending from 0.5 to 2.5 GHz is measured. In comparison with the conventional methods based only on the overall S-parameters of the CRLH TL, the proposed technique offers an accurate extraction of single-mode propagation characteristics. Simulation results are in good agreement with the measurement.