Theory and implementation of exceptional points of degeneracy for oscillators and array radiators based on spatial combiners

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High performance electronics is important in a variety of societal applications. Improvements based on the proposed research effort are expected to be significant in terms of energy-efficient electronics and of the quality of the generated oscillating frequency, which are both key features in modern electronic systems. The proposed work explores a new method to generate electromagnetic waves with stable frequencies with low noise and without wasting power. It is expected that the power necessary to provide oscillations is between one-half and one-tenth of that used by conventional oscillators design techniques. The other major outcome of the proposed research is an improved way to generate radiated high power in an efficient fashion, while being technologically simpler than other current solutions. It is known that high power generation at millimeter waves is notoriously challenging because single sources realized using semiconductors cannot provide high power levels. The solution adopted in this work is based on combining the power radiated by many individual radiating oscillators; thanks to a self-locking effect due to the degeneracy condition the oscillation frequency is expected to be pure, i.e., have low noise, and to produce high power radiation levels at a specific direction. Although the research is focused on exploring how to use for the first time the degeneracy condition in radio frequency systems, the acquired theoretical knowledge will also be useful for solving a variety of other problems, such as making highly sensitive sensors. The investigators will provide interdisciplinary training to participating graduate students through research; they will mentor undergraduate students in research fostering diversity in science and technology; and they will disseminate research to both scientific and layman audiences for the broad population to foster interest in electromagnetics and electronics. The proposed research activity aims at providing first a theoretical foundation of microwave and millimeter wave (mm-wave) circuits that are based on the exceptional point of degeneracy (EPD) in coupled-mode circuits and transmission lines. Second, this research will explore and implement various novel applications such as robust conditions of oscillation in distributed oscillators and spatial power combiners made of array grid oscillators. The novelty is based on the recently discovered physical phenomenon of giant resonance in coupled waveguides that support a degenerate band edge (DBE). A DBE is a very special degeneracy condition occurring when critical coupling is established between two or more guided modes. This proposal targets two related outcomes: (1) Theory and demonstration of a novel principle of operation for oscillators in silicon-based technology, including CMOS, based on the DBE; (2) Theory and demonstration of a novel principle of operation of radiation by spatial power combiners made of arrayed, tightly locked oscillating elements operating at an exceptional point of degeneracy (EPD) present in planar coupled-mode structures. The new principle of operation will be theoretically and experimentally investigated at microwaves and millimeter waves, and compared to existing technology of oscillators and spatial combiners. The proposed research is expected to provide advantages in terms of energy efficiency, more robust oscillation in the presence of load variations, lower phase noise, and improved stability of the frequency of oscillation and radiation. The proposed concepts related to degeneracy conditions have not yet been explored or even proposed in the area of microwave or millimeter-wave circuits. Outcomes of this project may enable future generations of high-efficiency oscillators, distributed amplifiers, as well as novel grid oscillators, which are the backbone of any communication system at microwave and mm-waves.