A comprehensive review of microwave system requirements on thin-film ferroelectrics

Abstract

The dual aspects of the relationship between microwave system requirements on thin-film ferroelectric (TF-FE) loss tangent (tanδ) and dielectric tunability (δεr,eff) and the performance enhancements TF-FE in turn offers as compared to existing technologies is comprehensively covered. Communication and sensor system requirements on TF-FE-based oscillators, filters, phase shift and true-time-delay phase shift circuits are thoroughly explained for many system-and-circuit combinations, and quantified where possible. In general, if TF-FE tanδ and Δεr,eff are low and high enough respectively, it can replace existing non-tunable, switched assemblies, resulting in lower size, weight, power, complexity and cost, especially as bandwidth widens. While there is substantial application-dependent variation, requirements on TF-FE performance as a function of system-circuit combination can be discerned. Of all four circuits, oscillators need the lowest tanδ (< 0.01) and modest Δεr,eff (< 4:1). Filters and phase shifters need modest tanδ (0.1 to 0.02) and Δϵr,eff, while true time delay requires modest tanδ and the highest Δϵr,eff, (4:1 - >10:1).