Reduction of parasitic coupling in packaged MMICs

Electromagnetic coupling between circuit elements within a package is often significant, or even catastrophic, at frequencies near a package resonance. In future, large, highly integrated, millimeter-wave MMICs, this resonant coupling will be difficult to avoid. The addition of lossy materials to the enclosure will reduce the coupling, but not eliminate it. A rigorous application of the method of moments is used to determine the relative amount of power coupled from a microstrip circuit in an enclosure to a resonant mode. The full-wave analysis is used to analyze a large gap in a transmission line and a transmission line with a single shunt open-circuit stub attached midway between the input and output connectors. The scattering parameters and the power lost to the resonant modes of the enclosure are determined. The results indicate that a further reduction in the coupling of power to the resonant modes is possible by repositioning the circuit within the enclosure.<>