Abstract: Today's CMOS transistor has a cutoff frequency approaching 1 THz, can switch effectively at mmWaves and can be integrated to the tune of millions on a single chip, but exhibits poor linearity and power handling and increased variability. Over the past five years, CoSMIC lab at Columbia University has attempted to answer the following two questions: "Can we think of new circuits and architectures enabled by this RF-to-THz switch where complex signal processing, conventionally performed in digital, is moved to RF?" and "What are the fundamental limits of performance achievable in CMOS in terms of frequency of operation, power generation and power handling?".

At RF, I will describe techniques for RF self-interference cancellation and filtering in radios right at the antenna that significantly enhance transmitter/receiver dynamic range and enable wideband software-defined frequency-division-duplex and full-duplex operation. Specifically, we have devised new digitally-controlled and switched-capacitor-based RF active self-interference cancellation and filtering circuits that cancel or filter their own noise and distortion, and achieve wideband cancellation through frequency-domain equalization of the selective antenna interface transfer function. Such RF signal processing techniques enable new functionalities at the communication system and network layers such as full-duplex networks that is the subject of future collaborative research.

mmWave power amplifiers have traditionally been limited to output power levels that are lower than 100mW and efficiencies lower than 20% due to the need to use scaled technologies with low supply voltages of around 1V. In this presentation, I will describe techniques developed in my group, including device stacking, switch-mode (Class-E) operation at mmWave, low-loss on-chip power combining and direct digital-to-mmWave conversion that have enabled the first watt-class mmWave PA in CMOS. Watt-level direct digital-to-mmWave power generation in complex CMOS SoCs enables new mmWave communication system paradigms such as mmWave massive MIMO, a topic of future collaborative research in my group.

Terahertz frequencies lie beyond the maximum operating frequencies of today's CMOS devices. I will briefly touch upon techniques that leverage device non-linearity to enable terahertz signal generation in CMOS in the milliwatt power envelope. Specifically, we have demonstrated a Maximum-Gain Ring Oscillator topology that achieves the theoretically-maximum oscillation frequency possible in a given technology as well as a nonlinearity-engineering technique that significantly enhances output power in a terahertz power mixer.

~BME Faculty Host: Pedro Irazoqui~

***Coffee and juice will be provided at West Lafayette***

(via teleconference to SL165 at IUPUI)