RADIO FREQUENCY DEVICES BASED ON CIRCUITS WITH FOURTH ORDER MODE DEGENERACY
With wide adaption of 5G technology just around the corner, and ever-increasing shift of daily life and activities into the mobile world, every facet of an RF communication system becomes a critical component in its design, with oscillator being one of the most important ones. Oscillators in today’s world must have an impeccable properties such as stable oscillation frequency, high efficiency, low power consumption, as well as a small form factor to fit into the ever-shrinking but yet more densely packed devices. In our modern mobile devices, it is important for an oscillator to be as low-power consuming as possible; long battery life being one of the biggest selling points for any mobile device. This dissertation’s main focus is on a new class of electromagnetic/RF devices, primarily oscillators, which rely on dispersion engineering, and more precisely on phenomena known as Degenerate Band Edge (DBE). When electromagnetic propagation eigenmodes of a waveguide coalesce into one in the state space of a system, a special point in the parameter space of the waveguide is formed and is known as an Exceptional Point of Degeneracy (EPD). Degenerate band edge (DBE) refers to a special case where an infinitely long and lossless system supports four propagating eigenmodes that, given proper operational condition, can coalesce. In practice, since we cannot have an infinitely long and lossless system, operation of a device near this condition can lead to unique and beneficial properties such as enhanced quality factor and giant gain enchantment, both properties being an integral part of highly efficient and stable oscillator. First, a relatively simple, double-ladder, lumped element circuit is introduced that can support DBE, which will serve as the basis of a first variation of DBE oscillator. Comparison to a well-known single-ladder oscillator shows that a double-ladder oscillator exhibits all around better performance despite its relatively more complex structure. Then, the idea of DBE oscillator is further explored and is actually realized in a microstrip technology. We demonstrate its measured performance and compare it to simulations, showing that the behavior is very predictable and controllable due to the DBE phenomenon. Finally, the high-Q structure is used as a pulse generation device, where it is first fed with energy until it reaches steady-state and then this energy is quickly extracted to produce a narrow in time pulse.