GaAs micromachining technology was used for fabricating coplanar trans
mission lines on Si3N4 and polyimide membranes deposited on GaAs subst
rates. On-wafer measurements of scattering parameters up to 75GHz for
several line configurations show a constant phase velocity of 2.9 10(8
) m/s and a predominance of metallic losses with a square root frequen
cy dependence.