Arbitrary Shaped High-Voltage RF Switch

This paper deals with the improvement of voltage handling of stacked MOSFET-based RF switches on high-ohmic silicon substrates by optimizing the substrate capacitance for each transistor in stack. The layout of the proposed switch arrangement has a trapezoidal shape instead of a conventional rectangular layout. The substrate capacitance distribution in the trapezoidal switch is predicted using the inverted microstrip line model for the flip-chip IC mounted on a printed circuit board. The proposed idea is verified in hardware on two prototype switch ICs fabricated in a dedicated CMOS switch technology. The measured improvement in voltage handling brought by the trapezoidal switch over the convention rectangular configuration is 1.4 V for 60 V voltage handling class device.