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

The dual aspects of the relationship between microwave system requirements on thin-film ferroelectric (TF-FE) loss tangent (tan delta) and dielectric tunability (Delta epsilon(r,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 tan delta and Delta epsilon(r,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 tan delta (< 0.01) and modest Delta epsilon(r,eff) (< 4:1). Filters and phase shifters need modest tan delta (0.1 to 0.02) and Delta epsilon(r,eff), while true time delay requires modest tan delta and the highest Delta epsilon(r,eff), (4:1 - >10:1).