Design of CMOS RF-Switches for a Multi-Band Radio Front-End

• Main Author: Hedberg, Anders
• Format: Others
• Language: English
• Published: Linköpings universitet, Institutionen för systemteknik 2003
• Subjects: Electronics; Switch; CMOS; RF; front-end; radio; SoC; Elektronik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2037

A study has been made in CMOS RF-switches that can be used in the front-end of a multi-band radio targeting the 802.11a,b,g and W-CDMA standards and working in the frequency range 2.4-5.5GHz. Especially, one single-transistor switch and two types of transmission gates have been analyzed, simulated and compared with respect to loss, linearity, compression point and noise. From this, five different single-transistor switches have been designed for on-chip probing measurements. Special consideration has been taken to accommodate on-chip testing, thus additional structures have been designed. The simulations and design has been performed with Chartered 0.18um RF-CMOS process. The results from the simulations show that the single-transistor switch has better performance in loss, linearity, compression point and noise compared to the transmission gates. However, for the transmission gates the linearity can be increased beyond the linearity of the single-transistor switch if the widths of the transistors are made sufficiently large. For the single-transistor switch, simulation results show that the transistor length shall be kept to its minimum for best performance and that the number of fingers does not influence significantly. Also, there are optimum values for the loss in on-mode, the noise and the linearity and worst-case values for the loss in off-mode when the transistor width is varied. Consequently, the single- transistor switch can be tuned by its transistor width to accommodate desired performances.