Adjacent Channel Power Contributions of Silicon MOSFET Switches in RF and Microwave Systems

Spectral regrowth is a major design issue confronting the wireless transmitter and system designer. Considerable work has been performed by a number of investigators into the level of spectral regrowth produced by power amplifiers but little work to date has studied how the spectral regrowth is influenced by FET-based switches in the same RF path. This paper looks at the adjacent channel power generated by silicon MOSFET switches. A methodology based on a Taylor series expansion of both the channel resistance and the diffused region capacitance nonlinearities show how nonlinear signal contributions by silicon MOSFET switches influence spectral regrowth and how the MOSFET geometry may be changed to control this contribution.