CMOS digital tunable capacitance with tuning ratio up to 13 and 10dBm linearity for RF and millimeterwave design

Abstract

Nowadays capabilities offered by advanced silicon technologies enable both mmw design and agile circuits development, then the development of high performance tunable capacitance is now mandatory. One of the challenge to develop this component is to be able to design capacitance with a tuning range higher than 4 from RF up to millimeter wave range. Variable capacitance like MOS varactor does not meet circuit specifications due to their low tuning range and very high non linearity. Digital capacitances are a good candidate to address that need and this paper review the design, optimization and characterization of digital tunable capacitance (DTC). Specific DTC with series or traveling wave architecture are also address, allowing to synthesize high performance capacitance up to 110GHz regarding 10dBm linearity and a tuning ratio equal to 13. Those developments have been carried out using STMicroelectronics BiCMOS 0.13um millimeter wave technology. Finally, the design of a 60GHz Reflection Type Phase Shifter (RTPS) using 4 bits DTC is presented showing insertion loss less than 6dB and a phase shift of 62°.