Complex permittivity measurements of dielectric plates using a dielectric loaded cavity resonator in UHF band

Abstract

Abstract A method is proposed for the measurement of complex permittivity (ϵ s and tan δ s ) of a dielectric plate with 50 × 50 mm 2 at 1 ∼ 2 GHz. A dielectric loaded cavity resonator in which a high permittivity, low‐loss dielectric rod (a relative permittivity of δ r and a loss tangent of tan ϵ r ) is divided into two and a dielectric plate to be measured is inserted between them. The advantage of the present measurement method lies in the fact that the edge effect at the contact planes of the cavity and the sample can be neglected since the energy is concentrated near the dielectric rod. Actually, various plate samples are measured at 2 GHz and the measurement errors are evaluated. For the conventional plate samples with fluctuations in sample thickness 2 t = 1.0 mm and the ambiguity Δ2 t = 0.01 mm, the measurement accuracy of ϵ s is less than 8 percent for ϵ s = 2, 3 percent for ϵ s = 5, and 2 percent for ϵ s = 10. If the manufacturing process allows Δ2 t = 0.003 mm, the measurement accuracy of ϵ s can be improved to 3 percent, 1 percent, and 0.7 percent, respectively. Also, the measurement accuracy of tan δ is 30 percent for tan δ = 10 −4 and 2 percent for tan δ s = 10 −3 . The present method is available in the UHF band for the plate samples in the range of ϵ s = 2 ∼ 20, tan δ = 10 −3 ∼ 10 −4 , and 2 t = 0.3 ∼ 2 mm.