Shadi Saberi Ghouchani CMU

Millimeter-Wave Frequency Generation

In mm-wave transceivers operating at 60 GHz and above in CMOS, there exists a great need for wide-band, low noise local oscillators. Due to the low gain of CMOS transistors that operate close to their f_T, and the poor quality of passive elements, including varactors, fundamental frequency mm-wave VCOÕs are typically power hungry to provide sufficient voltage swing and phase noise. The tuning range is often very limited due to significant parasitic capacitors. Also, the center frequency is more sensitive to process variations and parasitics, which can be substantial at mm-wave frequencies.

To overcome the above shortcomings of mm-wave VCOs, an alternative approach is considered. Frequency multiplication of a lower frequency VCO to generate the final output frequency can relax most VCO requirements. Since the VCO now oscillates at a fraction of the output frequency, power consumption is greatly reduced. The overall phase noise is most likely improved despite the 20log₁₀N (dB) degradation caused by frequency multiplication. The tuning range is extended by the multiplication factor, while sensitivity to parasitics and process variations is greatly reduced.

In this talk a quadrature VCO and a frequency doubler-tripler, designed and fabricated in 0.13 μm CMOS, are presented. The quadrature VCO uses magnetic coupling of transformers to generate quadrature outputs and to extend the frequency tuning range. The QVCO can generate frequencies in the range of 12-17.2 GHz with 102-109 dBc/Hz phase noise in its tuning range. The frequency multipliers operate in the frequency range of 23-48 GHz with more than -20dBm output power into 50Ω, consuming only 12.6mW dc power from 1.2V supply.

Bio:

Shadi Saberi Ghouchani is currently a PhD candidate in Electrical and Computer Engineering Department at Carnegie Mellon University, advised by Prof. Jeyanandh Paramesh. She received her Masters in Electrical and Computer Engineering from CMU in 2007 and her Bachelors degree in Electrical Engineering from the Sharif University of Technology (Tehran) in 2005. Her research interests include RF and mm-Wave circuit design as well as high-speed I/O and analog design. She was awarded Intel/SRCEA Graduate Fellowship in 2008.