Caltech Mixed-Signal, RF and Microwave Seminar
Nonlinear Radio Frequency Integrated Circuits
Nonlinearity is often regarded as nuisance in information processing and integrated circuits. Even in fundamentally nonlinear systems such as self-sustained oscillators, "excessive" nonlinearity is commonly ignored or intentionally subsided. There are plenty of examples in physics and engineering where nonlinearity, when judiciously exploited, offers additional and/or improved capabilities when compared to linear or weakly nonlinear systems. In this talk, I will cover a few examples of exploiting nonlinearity in radio frequency integrated circuits.
The first example covers self-sustained oscillators that utilize a nonlinear resonator. Resonator nonlinearity affects the dynamics and stochastics of self-sustained oscillators. In fact, recent experiments demonstrate improvements in oscillator phase noise where the nonlinearity of a nano-resonator is exploited properly. I will cover systematic formulation, analysis, design, and experimental verification of self-sustained oscillators that utilize a nonlinear miniature high-quality resonator. Specifically, I will demonstrate 1.5 GHz CMOS oscillators that uses a high-Q Film Bulk Acoustic Resonator (FBAR) to achieve a record jitter performance of < 10 fs.
The second example covers (extremely nonlinear) switching power amplifiers at millimeter-waves. It is well known that switching power amplifiers can offer higher power efficiency (reaching 100% in the limit) due to the non-overlapping current and voltage waveforms across the device. I will demonstrate that, proper switching of SiGe Hetero-junction Bipolar Transistors (HBT) enables increasing the voltage and current swings, leading to higher output power, in addition to achieving high power efficiency. I will also present generalized stacked architectures of SiGe HBTs, operating in switching mode (Class E), that achieve high power and efficiency at mm-waves. Specifically, 40-45 GHz power amplifiers with output power exceeding 23 dBm (200 mW), without power combining, and Power Added Efficiency (PAE) reaching 35%, utilizing the aforementioned concepts will be presented.