A new 'circuit-model' for slotline-to-coplanar waveguide asymmetrical trans
itions is presented and applied to the design of slotline resonators. Thr m
odel, based on the separation of coplanar-waveguide (CPW) modes into two di
fferent ports, overcomes limitations of previous models because it explains
the transition behaviour even if CPW air-bridges are not used.