High Quality-Factor Planar Inductors Compatible with Flexible Large-Area Electronics for Integrated IoT and 5G/6G Applications

Resonant operation, exploiting high quality-factor planar inductors, has recently enabled giga-Hertz applications in large-area electronics, opening up a new technology platform for large-scale and flexible wireless systems. This work presents the design, analysis, and characterization methodology of flex-compatible large-area planar inductors with a record-high quality factor of up to 65 in the 2.4-GHz frequency band. The inductor design and analysis address a key frequency limiter to recently demonstrated large-area and conformal wireless systems for integrated Internet of Things and 5G/6G applications.

I. Introduction

Large-area electronics (LAE) is a class of technologies that employ low-temperature processing and monolithic integration of semiconductors, metals, and dielectrics over large and flexible substrates of polymers or glass, that can span the order of meters. The rich functionality that LAE offers makes it a promising technology platform for next-generation flexible systems. Recent materials and devices progress has led to giga-Hertz (GHz) LAE systems, enabling large and conformal radiative apertures for future wireless applications in Internet of Things (loT) and 5G/6G [1], [2]. Large-area flex-compatible planar inductors are a critical technology feature, as they can achieve high quality factors (Q factors) by leveraging large geometries, wide metal traces, and low-loss substrates. Through resonant operation, these inductors have brought the frequency of LAE circuits/systems close to the LAE device limits in the GHz regime. Since this regime is of particular interest for low-power and long-range wireless communication (e.g., 2.4-GHz band for Wi-Fi and Bluetooth), a detailed understanding of the inductor is essential to further system improvements.