Hybrid Analysis of Electromagnetic Interference Effects on Microwave Active Circuits Within Cavity Enclosures

We present a hybrid analysis technique based on a decomposition approach to evaluate electromagnetic interference (EMI) effects on RF active and passive circuit components enclosed within multilayer cavities exposed to external electromagnetic waves. The adopted decomposition concept separates the analysis of the passive printed circuits and shielding cavity from the nonlinear components. The method of moments with a layered media Green´s function is employed for the passive components and layered printed circuit board. For the nonlinear active devices circuit tools such as HSPICE or Agilent ADS are employed for their analysis. Using this approach, we investigated EMI effects on an enclosed RF power amplifier board with varying slot lengths on the shielding cavities. We found that external EMI could upset active circuits even in the shielded enclosure through a narrow slot aperture for certain frequencies of the interfering source.