David Scott Whitefield

Recent advances and future trends in SOI for RF applications

In recent years, RFCMOS on Silicon-on-Insulator has rapidly evolved as a mainstream technology for switches used in wireless applications. Requirements of lower insertion loss, better isolation and better linearity have driven RFCMOS-SOI roadmap. Ron*Coff, a key figure-of-merit for switch application, has scaled from > 300fs to <; 200fs. In this paper, we review commonly adopted techniques to further improve Ron*Coff, along with their limitations.

High voltage SOI stacked switch with varying periphery FETs

The breakdown voltage of a FET stack is limited by the unequally divided voltage drop among the stacked FETs. A novel stack composed of varying periphery FETs is proposed. Uniform voltage distribution, and thus much higher breakdown voltage, can be achieved by carefully designing the periphery of each FET. A FET stack with varying periphery was designed and fabricated. Significant improvement in breakdown voltage was experimentally confirmed. Unlike the approach of inserting feed-forward capacitance, the breakdown voltage increase is achieved without isolation degradation.

Accurate capacitance/current-voltage based lookup-table diode model

A capacitance and Current look-up table based large-signal Phemt-diode model is presented based on an ensemble of bias-dependent small-signal equivalent circuits. The model is capable of accurate simulation of bias-dependent small-signal S-parameters and current performance over the data-acquisition bias range. Instead of charge model in conventional Root diode model, capacitance as function of voltage is used. Compared to charge model, capacitance gives more accuracy that fits to higher order of derivatives and avoids potential data instability. The model has also accurate leakage model and can be used for a variety of applications where accurate nonlinearity is of primary concern. The validity of the model is demonstrated by comparing the simulation of DC curves, leakages, and small-signal S-parameters over a wide bias range, by comparison of the measured data.

Accurate scalable capacitance/current-voltage based lookup-table diode model

A capacitance and Current look-up table based large-signal Phemt-diode model is presented based on an ensemble of bias-dependent small-signal equivalent circuits. The model is capable of accurate simulation of bias-dependent small-signal S-parameters and current performance over the data-acquisition bias range. Instead of charge model in conventional Root diode model, capacitance as function of voltage is used. Compared to charge model, capacitance gives more accuracy that fits to higher order of derivatives and avoids potential data instability. The model has also accurate leakage model and can be used for a variety of applications where accurate nonlinearity is of primary concern. The validity of the model is demonstrated by comparing the simulation of DC curves, leakages, and small-signal S-parameters over a wide bias range, by comparison of the measured data.