Precise measurements of the complex permittivity of dielectric materials at microwave frequencies

Overview of precise resonant measurement methods for complex permittivity determination of low and medium loss dielectrics is presented. The following techniques are discussed: split post dielectric resonator (SPDR), TE0 1 1 resonator, TE0 1 δ mode dielectric resonator, and whispering gallery mode resonators (WGMR). Applications of split post dielectric resonators (SPDR) for measurements of specific materials like ferroelectrics and thin laminar materials are highlighted. It is shown that TE0 1 δ mode dielectric resonator technique is one of the most accurate for permittivity, dielectric loss tangent and thermal coefficients of permittivity measurements of low and medium loss dielectrics having arbitrary permittivity value. Precise measurements of low permittivity dielectrics require spurious modes analysis and proper choice of sample size and its aspect ratio. Conductor and radiation loss limits are discussed for open and closed whispering gallery mode resonators.