Coupling between neighboring CPWs in MMICs

Coupling between neighboring coplanar waveguides (CPWs) is simulated and measured. Simulation is based on two-dimensional (2-D) electromagnetic analysis and a network description. The investigations show that, in general, coupling may be neglected (lower than -30 dB) if the distance between the CPWs is more than twice their ground-to-ground spacing. However, this does not hold in the conductor-backed case with a connection between CPW ground and backside metal. Then, one finds sharp resonance peaks in the coupling exceeding -10 dB.