Measurement of dielectric constant using a microstrip ring resonator

An approach for measuring the permittivity of dielectric materials by means of a microstrip ring resonator is presented. The method is used in conjunction with the variational calculation of the line capacitance of a multilayer microstriplike transmission line to compute the effective permittivity and hence the resonant frequency of the ring. The results are compared with measurements made in X-band waveguide cavity-by-cavity perturbation techniques and tend to confirm that microstrip resonators can be used for dielectric measurements. However, for materials having a large dielectric constant, comparative results seem to diverge rapidly