High-speed Track and Hold Amplifiers in CMOS for Enabling Pulse-based Direct Modulation, Secure Communication and Precision Localization
Master of Science
Last few decades have seen a puissant desire for fast communication links that has shaped the evolution of high-speed circuits and silicon- based technology. This desire accompanied with a large consumer market has fueled the development of ever-shrinking, faster technology nodes. These advanced nodes open doors for designers to develop new ways of transferring data with unprecedented speed and accuracy. There are a number of challenges in building high-speed, secure communication links, one being the lack of availability of fast Analog to Digital Converters (ADCs), which form the front end of a receiver. Even in advanced technology nodes, the leakage in the transmission gate due to parasitic source-drain capacitance provides an alternate path for signals to pass, thus lowering the performance of the ADCs at high frequencies. Second, the current communication schemes use beam-forming or Direct Antenna Modulation (DAM) to narrow the information beam and point it in the direction of communication. Such techniques still have a wide information beam compared pulse-based directional modulation, as discussed in this thesis. In this dissertation, we address the issue of parasitic leakages in the transmission gate of a fast sampler by introducing active cancellation. A track-and-hold amplifier with active cancellation is designed and fabricated in 45nm CMOS SOI technology, which can operate at 40GSample/second real-time. In addition to this, we also study a pulse-based directional modulation scheme which can be used for secure communication, imaging and localization. Two coherent pulse generators with pulse width less than 200ps were used to attain an information beamwidth of less than 1 degree and localize objects with millimeter accuracy.