Magnetospheric Radio Tomography: Observables, Algorithms, and Experimental Analysis

This grant supported research towards developing magnetospheric electron density and magnetic field remote sensing techniques via multistatic radio propagation and tomographic image reconstruction. This work was motivated by the need to better develop the basic technique of magnetospheric radio tomography, which holds substantial promise as a technology uniquely capable of imaging magnetic field and electron density in the magnetosphere on large scales with rapid cadence. Such images would provide an unprecedented and needed view into magnetospheric processes. By highlighting the systems-level interconnectedness of different regions, our understanding of space weather processes and ability to predict them would be dramatically enhanced. Three peer-reviewed publications and 5 conference presentations have resulted from this work, which supported 1 PhD student and 1 postdoctoral researcher. One more paper is in progress and will be submitted shortly. Because the main results of this research have been published or are soon to be published in refereed journal articles listed in the reference section of this document, we provide here an overview of the research and accomplishments without describing all of the details that are contained in the articles

Q-based design equations for resonant metamaterials and experimental validation

Practical design parameters of resonant metamaterials, such as loss tangent, are derived in terms of the quality factor $Q$ of the resonant effective medium permeability or permittivity. Through electromagnetic simulations of loop-based resonant particles, it is also shown that the $Q$ of the effective medium response is essentially equal to the $Q$ of an individual resonant particle. Thus, by measuring the $Q$ of a single fabricated metamaterial particle, the effective permeability or permittivity of a metamaterial can be calculated simply and accurately without requiring complex simulations, fabrication, or measurements. Experimental validation shows that the complex permeability analytically estimated from the measured $Q$ of a single fabricated self-resonant loop agrees with the complex permeability extracted from $S$ parameter measurements of a metamaterial slab to better than 20%. This $Q$ equivalence reduces the design of a metamaterial to meet a given loss constraint to the simpler problem of the design of a resonant particle to meet a specific $Q$ constraint. This analysis also yields simple analytical expressions for estimating the loss tangent of a planar loop magnetic metamaterial due to ohmic losses. It is shown that $\tan \delta \approx 0.001$ is a strong lower bound for magnetic loss tangents for frequencies not too far from 1 GHz. The ohmic loss of the metamaterial varies inversely with the electrical size of the metamaterial particle, indicating that there is a loss penalty for reducing the particle size at a fixed frequency

Adaptivni filtar za ekstrakciju signala pogonjenog događajem

This paper introduces a new adaptive filter structure for a class of event-based signals corrupted by quasi-periodic noise. The event driven adaptive filter emerges from Widrow\u27s adaptive filter, exploiting specific properties of event-based signals such as unpredictable time appearance and limited time duration. This filter can be used when reference input to Widrow\u27s filter, which essentially has to be correlated to the noise, is unavailable, but is known for a fact that it is quasi-periodic. Experimental tests verify improved filter performance of the proposed solution.U ovom radu predstavljen je novi tip adaptivnog filtra za klasu signala pogonjenih događajem onečišćenih sumirajućom, pseudoperiodičnom smetnjom. Adaptivni filtar pogonjen događajem nastaje razvojem iz Widrowog adaptivnog filtra, iskorištavajući specifična svojstva signala pogonjenih događajem kao što su nepredvidiv trenutak pojave signala i njegovo vremenski ograničeno trajanje. Ovaj filtar se može primijeniti kada je referentni ulaz u Widrow filtar, koji treba biti koreliran sa smetnjom, nedostupan, ali je sa sigurnošću poznato da je pseudoperiodičan. Eksperimentalni rezultati potvrđuju napredna svojstva predloženog rješenja