arXiv subjects

Dmitry Oshmarin

Publications and source records attributed to Dmitry Oshmarin.

6 recordsLinked to original sources

arXiv2022

Pulse Generation Based on a Microstrip Circuit with Fourth Order Degenerate Band Edge

A pulse generation scheme is proposed based on a structured resonance in a cavity where the non-conventional energy distribution is concentrated in its middle part. The cavity is first used as an oscillator during the energy charging step and when a switch is activated the signal is extracted from its center. The key component of the proposed scheme is the periodic microstrip waveguide with a fourth-order degenerate band edge (DBE) of its wavenumber-frequency dispersion diagram. The DBE is an exceptional point degeneracy condition that is responsible for the energy to be localized at the cavity center and that can also have the quality factor easily destroyed by a perturbation. The waveguide is designed to have a DBE frequency of 2.86 GHz and produces pulses of approximately 0.1 V peak and 1.1 ns width.

physics.app-ph↗

arXiv2021

Experimental Demonstration of Sixth Order Degenerate Band Edge in Coupled Microstrip Waveguides

We show the physical realization and experimental demonstration of an exceptional point of 6th order degeneracy in a triple ladder (or three-way) microwave waveguide realized using three coupled microstrips on a grounded dielectric substrate. This threeway waveguide supports six Bloch eigenmodes and all coalesce onto a degenerate single eigenmode at a given frequency. The three-way waveguide is gainless, and this exceptional point is associated to a vanishing group velocity and its multiple derivatives. Indeed the wavenumber-frequency dispersion diagram, that we call 6th order degenerate band edge (6DBE) has six coalescing branches. We provide the experimental verification of a 6th order exceptional point by evaluating the degenerate wavenumber-frequency dispersion diagram from the measurement of scattering parameters of a six-port unit cell. We also show the resonant behavior of a cavity made of the three-way waveguide with finite length. The unique properties of 6DBE can be exploited in designing innovative high-Q resonators, oscillators, filters, and pulse shaping devices.

physics.app-ph↗

arXiv2021

Experimental Demonstration of a New Oscillator Concept Based on Degenerate Band Edge in Microstrip Circuit

The first experimental demonstration of an oscillator based on a periodic, resonant microstrip circuit with a degenerate band edge (DBE) is presented. The DBE is a fourth-order exceptional degeneracy of the eigenmodes in a lossless periodic waveguide that is visible in the wavenumber-frequency dispersion diagram, and the periodic microstrip behaves as a frequency selective medium. The presence of the DBE condition and the associated DBE resonance allow for a stable, single-mode oscillation as well as stability with varying the load resistance.

physics.app-ph↗

arXiv2020

Distributed Degenerate Band Edge Oscillator

We propose a new class of oscillators by engineering the dispersion of two-coupled periodic waveguides to exhibit a degenerate band edge (DBE). The DBE is an exceptional point of degeneracy (EPD) of order four, i.e., representing the coalescence of four eigenmodes of a waveguide system without loss and gain. We present a distributed DBE oscillator realized in periodic coupled transmission lines with a unique mode selection scheme that leads to a stable single-frequency oscillation, even in the presence of load variation. The DBE oscillator potentially leads to a boost of the efficiency and performance of RF sources, thanks to the unique features associated to the EPD concept. This class of oscillators is promising for improving discrete-distributed coherent sources and can be extended to radiating structures to achieve a new class of active integrated antenna arrays.

physics.app-ph↗

arXiv2019

Exceptional Points of Degeneracy in Periodic Coupled Waveguides and the Interplay of Gain and Radiation Loss: Theoretical and Experimental Demonstration

We present a novel paradigm for dispersion engineering in coupled transmission lines (CTLs) based on exceptional points of degeneracy (EPDs). We develop a theory for fourth-order EPDs consisting of four Floquet-Bloch eigenmodes coalescing into one degenerate eigenmode. We present unique wave propagation properties associated to the EPD and develop a figure of merit to assess the practical occurrence of fourth-order EPDs in CTLs with tolerances and losses. We experimentally verify for the first time the existence of a fourth EPD (the degenerate band edge), through dispersion and transmission measurements in microstrip-based CTLs at microwave frequencies. In addition, we report that based on experimental observation and the developed figure of merit, the EPD features are still observable in structures that radiate (leak energy away), even in the presence of fabrication tolerances and dissipative losses. We investigate the gain and loss balance regime in CTLs as a mean of recovering an EPD in the presence of radiation and/or dissipative losses, without necessarily resorting to Parity-Time (PT)-symmetry regimes. The versatile EPD concept is promising in applications such as high intensity and power-efficiency oscillators, spatial power combiners, or low-threshold oscillators and opens new frontiers for boosting the performance of large coherent sources.

physics.app-ph↗

arXiv2017

Oscillator Based on Lumped Double Ladder Circuit with Band Edge Degeneracy

An oscillator design based on a periodic, double ladder resonant circuit is proposed. The circuit exhibits a degenerate band edge (DBE) in the dispersion diagram of its phase-frequency eigenstates, and possesses unique resonance features associated with a high Q-factor resonance, compared to a single ladder or a conventional LC tank circuit. This oscillator is shown to have an oscillation threshold that is half that of a single LC ladder circuit having the same total quality factor, and thus is more robust than an LC oscillator in the presence of losses. It is also shown that the output and amplitude of the double-ladder oscillator is much less sensitive to the output loading compared to single-ladder oscillators. We show the analysis and design of such oscillators that potentially lead to enhancing the efficiency of RF components and sources.

physics.class-ph↗