Dissipative Parameters in Ferrites and Insertion Losses in Waveguide Y-Circulators Below Resonance

Extensive microwave loss measurements have been performed at frequencies from 1.3 to 11 GHz on below-resonance waveguide Y circulators loaded with a wide variety of ferrite and garnet compositions. Dissipative internal and external magnetic parameters have been measured on the same compositions. Also, dielectric loss measurements have been carried out. Two classes have been distinguished, defined by the following conditions: ω_M / ω ≤0.8 and 0.85 ≤ω_M / ω ≤1.05. It is inferred that the (insertion loss) IL of such devices is independent of ΔH and mainly depends on the internal dissipative susceptibility x_i" and on the dielectric loss tan δ. The relation of the IL versus x_i" and tan δ in the case ω_M / ω ≤0.8 is independent of frequency and given by the semiempirical equation IL= 10 log₁₀ (1-2.85 x_i" - 1.60 tan δ - 0.017)^-1.