The interdigital coplanar waveguide: a new low-impedance micromachinable planar structure

The authors describe a new type of coplanar waveguide (CPW) which we call interdigital coplanar waveguide (ICPW). ICPW has three advantages over CPW. First, ICPW can have a lower characteristic impedance for the same minimum feature size and overall line width. Second, at low impedances it can obtain reduced high-frequency resistive loss. Finally, thickening the conductor reduces the ohmic losses more rapidly in the ICPW than in the CPW. The authors present an analysis comparing CPW and ICPW, assuming a TEM mode of propagation. Calculations are performed using finite-element analysis, and volume filament and surface ribbon methods