# Reconfigurable radiofrequency electronic functions designed with 3D Smith Charts in Metal-Insulator-Transition Materials

## TL;DR

This paper introduces 3D Smith charts for analyzing complex RF circuits with Metal-Insulator-Transition materials like VO2, enabling better visualization, modeling, and design of reconfigurable RF components across a broad frequency range.

## Contribution

It develops a novel 3D Smith chart framework based on geometric concepts to visualize and model frequency-dependent impedances in MIT materials, addressing theoretical inconsistencies in traditional charts.

## Key findings

- Fabricated VO2-based inductors with record quality factors.
- Demonstrated reconfigurable inductors operating from 4 GHz to 10 GHz.
- Designed and fabricated frequency-dependent dielectric constant extraction filters.

## Abstract

Recently, the field of Metal-Insulator-Transition (MIT) materials has emerged as an unconventional solution for novel energy efficient electronic functions, such as steep slope subthermionic switches, neuromorphic hardware, reconfigurable radiofrequency functions, new types of sensors, teraherz and optoelectronic devices. Designing radiofrequency (RF) electronic circuits with a MIT material like vanadium dioxide, VO2, requires the understanding of its physics and appropriate models and tools, with predictive capability over large range of frequency (1-100GHz). Here, we develop 3D Smith charts for devices and circuits having complex frequency dependences, like the ones resulting by the use of MIT materials. The novel foundation of a 3D Smith chart involves here the geometrical fundamental notions of oriented curvature and variable homothety in order to clarify first theoretical inconsistencies in Foster and Non Foster circuits, where the driving point impedances exhibit mixed clockwise and counter-clockwise frequency dependent paths on the Smith chart as frequency increases. We show here the unique visualization capability of a 3D Smith chart, which allows to quantify orientation over variable frequency. The new 3D Smith chart is applied as a 3D multi-parameter modelling and design environment for the complex case of Metal-Insulator-Transition (MIT) materials where their permittivity is dependent on the frequency. In this work, we apply 3D Smith charts to on Vanadium Dioxide (VO2) reconfigurable Peano inductors. We report fabricated inductors with record quality factors using VO2 phase transition to program multiple tuning states, operating in the range 4 GHz to 10 GHz. Finally, we fabricate new Peano curves filters used to extract the frequency-dependent dielectric constant of VO2 within 1 GHz-50 GHz for the accurate design of RF electronic applications with phase change materials

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Source: https://tomesphere.com/paper/1905.09701