Measurement of Microwave Substrates Complex Permittivity with Distribution Uniformity (Invited)

The measurement method employed for precise acquisition of the complex permittivity of microwave substrates is investigated. A microwave resonant technique, combining resonant ring (RR) and transmission line (TL) circuits, is proposed for highly accurate measurement of the complex permittivity of microwave substrates operating in the 2~10 GHz frequency range. By utilizing a design featuring an enhanced coupled RR circuit and a TL with a transition section, the permittivity and loss tangent of a domestically produced microwave substrate were respectively measured at room temperature. The testing accuracy of the permittivity reaches 0.004, and the loss tangent increases with frequency. Based on the method, the spatial distribution uniformity of the dielectric properties of substrates is analyzed, with the results indicating that the microwave substrate used exhibited maximum differences in permittivity of 0.072 at 2 GHz and 0.044 at 10 GHz.