Development and verification of an accurate FEM electromagnetic model for a complex multi-stage RADAR limiter

A predictive model for a complex waveguide-based multi-stage solid-state X-band radar limiter has been developed using Ansoft HFSS. The treatment of the PIN diode semiconductor material is described and its parameters detailed. The S-parameter response of the model is compared to measured results and shown to match extremely well. The onset of impact ionization and avalanche breakdown in reverse biased diodes due to peak RF voltage level is also accurately predicted. The model enables accurate estimation of the RF current flow and power dissipation in the forward biased diodes while taking into account high frequency resistance effects. As such the model is eminently suitable for coupling to a numerical thermal solver to investigate temperature effects in the structure and vicinity of the diodes.