Accurate modelling and optimization of inhomogeneous substrate related losses in SPDT switch IC design for WLAN applications

This paper teaches the way to achieve an optimum substrate isolation in RF switch design thanks to Deep Trenches Isolation (DTI). The role of Deep Trench Isolation in substrate coupling around active blocks is analysed in link to its ability to break the conductive buried layers in the substrate. Then, an accurate modelling approach based on quasi-static approach developed for inhomogeneous substrate is investigated. The efficiency of this methodology is first demonstrated thanks to a comparison with a standard numerical method based on FEM (Finite Element Method). Then, experiments data are provided to support this theoretical analysis. The methodology is fully integrated in a commercial design flow and offers a perfect trade-off between accuracy and run time simulation. From available test data on single device and a full SP3T, a correlation better than 0.1dB is obtained between simulation and measurement up to 8 GHz.