Electrically tunable materials for microwave applications

TLDR

Microwave devices using tunable materials are of vigorous current interest, with typical applications including phase shifters, antenna beam steering, filters, voltage‑controlled oscillators, matching networks, and tunable power splitters. The review aims to guide material selection for microwave applications by evaluating response time, tunability, operating temperature, and loss tangent. The authors compare the performance of ferroelectric ceramics, polymers, and liquid crystals, focusing on ferroelectrics for their favorable response time, dielectric loss, and tunability. Polymers and liquid crystals are emerging as promising candidates for new applications due to their mechanical flexibility, lower weight, and lower tuning voltages.

Abstract

Microwave devices based on tunable materials are of vigorous current interest. Typical applications include phase shifters, antenna beam steering, filters, voltage controlled oscillators, matching networks, and tunable power splitters. The objective of this review is to assist in the material selection process for various applications in the microwave regime considering response time, required level of tunability, operating temperature, and loss tangent. The performance of a variety of material types are compared, including ferroelectric ceramics, polymers, and liquid crystals. Particular attention is given to ferroelectric materials as they are the most promising candidates when response time, dielectric loss, and tunability are important. However, polymers and liquid crystals are emerging as potential candidates for a number of new applications, offering mechanical flexibility, lower weight, and lower tuning voltages.