Microwave and millimeter wave CMOS Characterization, modeling, and design

Doctoral thesis, 2008

The use of CMOS technologies for microwave and millimeter wave applications has recently been made possible as a result of increased transistor performance. The fT and fmax have, for example, passed 100 GHz at the 130 nm node and 200 GHz at the 65 nm node. This thesis deals with several issues related to the use of CMOS-technologies for microwave and millimeter wave applications. The main focus is above 10 GHz, i.e. above the majority of today’s commercial applications. The thesis is divided into three parts: Characterization, transistor modeling and design. In the characterization of devices, a new statistical equivalent circuit-based method is derived, validated, and compared to existing methods. The method is found to be more general while maintaining or improving accuracy. Large-signal measurements using load-pull are performed on 130 nm, 90 nm, and 45 nm CMOS transistors to evaluate their use for microwave and millimeter wave power amplification. Two empirical transistor models are also presented; a large signal model, including noise and simple scaling rules, and a small-signal noise model. The influences of gate resistance and gate leakage currents on the high frequency noise are described. The empirical large-signal model is used in the design of the first published millimeter wave CMOS frequency doublers. They were implemented in a 90 nm CMOS process and work from 20 GHz to 40 GHz and 30 GHz to 60 GHz. Conversion losses of 15.8 dB and 15.3 dB respectively, are achieved, together with good suppression of the fundamental frequency. Furthermore, the design and characterization of a set of different power amplifiers at K-band (18-27 GHz) in a 130 nm RF-CMOS process are treated. State-of-the-art output power levels of 63 mW at 20 GHz are achieved for the most complex design. For the power amplifier designs, RF extensions of compact models are extracted, and the use of cascode transistors studied. Finally, the analysis and design of a new active balun with wide broadband performance, the matrix balun, are reported. Measured results show a common mode rejection ratio, CMRR, of greater than 15 dB between 4 GHz and 42 GHz while exhibiting 2 dB gain. The balun was realized in a 0.15m mHEMT process. The same matrix balun circuit may also be biased for amplification and used as a matrix amplifier, exhibiting 10.5 dB flat gain up to 63 GHz.