A strain engineered voltage tunable millimeter‐wave ferrite phase shifter

A 50‐GHz electric field tunable ferrite‐piezoelectric phase shifter based on a bilayer of single crystal M‐type hexagonal barium ferrite (BaM) and lead zirconate titanate (PZT) is discussed.A dc voltage applied to PZT results in a piezoelectric strain that manifests as an anisotropy field in BaM. A change in the voltage applied to PZT gives rise to variations in the anisotropy field and permeability of BaM and, therefore, a differential phase shift. A phase shift of 45° is measured when the voltage is increased from 0 to 400 V across a 0.5‐mm thick PZT. Theoretical estimates of the phase shift are in agreement with the data.