Membrane-supported coplanar waveguides for MMIC and sensor application

Membrane-supported coplanar waveguides (CPWs) are needed for low-dispersive and low-loss millimeter- and submillimeter waves as well as for power sensor applications. The authors demonstrate CPWs on polyimid membranes micromachined on gallium arsenide (GaAs) that meet the requirements of a typical microwave monolithic integrated circuit (MMIC) process. The influence of the design parameters is simulated by finite difference in frequency domain (FDFD), in excellent agreement with the experiment. For a membrane CPW with ground to ground spacing of only 50 μm and characteristic impedance of 115 /spl Omega/, relative effective dielectric constants near 1.02 and attenuation of 0.14 dB/mm at 25 GHz have been achieved.