Almost the entire lower half of the spectrum in the log scale (~1 Hz-1 THz) is now within the operational frequency range of integrated circuit technology. With material science advancements and heterogeneous integration, potentially even optical frequencies will, in future, be integrated with silicon. The synergy between high-frequency circuits, electromagnetics and digital, is an exciting field of research and we are just beginning to explore the plethora of opportunities in this new paradigm. Being able to synthesize, manipulate and control desirable electromagnetic near- fields in an integrated platform or otherwise, comprising of analog, digital and RF circuits, can create novel sensing and radar systems, new architectures in communication or even new methods for targeted drug delivery, therapy and imaging. The platform for implementation is not fundamentally important; however, in order to achieve an efficient end-to-end design, conventional ways of thinking of circuits, electromagnetics, devices will need to be revisited; novel architectures and techniques need to be explored and developed, systems will need to be optimized across different levels of abstractions. We are interested in exploring this close area between electromagnetic field synthesis and control in an integrated platform or otherwise to create systems for new applications.
Imagine the possibilities of a billion transistors with cut-off frequencies progressing towards THz frequencies. The unique ability to integrate very fast transistors, along with complex signal processing all in one chip, has opened up a portion of the electromagnetic spectrum in the mm-Wave and THz frequency ranges, previously unavailable to integrated technology. This can not only miniaturize bulky, expensive, custom optics-based instrumentation existing in this range, but the versatility of silicon technology can open doors to high-impactful new applications in ultra-high speed wireless communication, high-resolution imaging to spectroscopic analysis of biomolecules and security. The path-breaking innovations will not happen piggybacking on technology advancements with scaling, but through new architectures, design methodologies that can fully leverage the true potential of such versatile integrated platforms (THz Phased Arrays).
We proposed an Inverse Maxwell design philosophy in THz power generation, where we directly synthesize the surface currents responsible to create the desirable electromagnetic fields. This is in contrast to the traditional, partitioned way of designing where we are limited to the set of known classical circuit blocks. This opens up a new and broader design space, where concepts from different fields can synergistically merge together to create an integrated chip surface on which one can dynamically synthesize, control and manipulate the electromagnetic near-fields from DC-optical. The applications range from integrate lab-on-chip bio-molecular sensing, bioactuation to communication.
Silicon transistors have shrunk into dimensions, where variation in the countable number of dopant atoms cause significant change in performance and behavior. Added to this, parasitic and process variations, modeling inaccuracies, aging, environmental changes cause a severe degradation in system performance. The question arises if we can create systems where we remove the need of testing with expensive offchip equipment and build all the necessary testing into the chip itself. Further, can we build onchip sensing mechanisms that monitor the `health' of the circuits and sub-systems and takes appropriate actuation measures to automatically `heal' and optimize system performance in case of unintentional failures, process variations, mismatches, design errors or environmental changes . Building such efficient close-loop autonomous systems in the RF and mm-Wave frequencies can be very challenging , but rewarding at that same time since such concepts can be extended to programmable, flexible RF transceivers which are spectrally aware, that can dynamically switch between available spectral bands and where communication standards can be programmed post-fabrication. We are exploring novel techniques, architectures to explore this area. Our work at Caltech demonstrated self-healing in a fully integrated mm-Wave power amplifier capable of automatic onchip optimization in gain, power dissipation and efficiency at backoff in presence of process variations and load-mismatch events and even when some of the amplifier transistors are intentionally destroyed (IEEE RFIC 2012 best paper award).