Measurement of the Complex Permittivity of Curved Dielectric Radome Specimens using an Open Resonator

A technique for the measurement of the complex permittivity of curved dielectric radome specimens using an open resonator is reported. By using perturbation theory, a modified compensation term has been derived to deal with relatively large deviation of the specimen geometry from that ideally required in such measurements. Preliminary measurements, made at 11.6 GHz on concave perspex samples having various radii of curvature down to 300mm and with a judicious choice of resonator configuration, show errors in the relative permittivity and loss tangent of less than 3% and 20% respectively. The large errors in the loss tangent are thought to be due to the energy refracted out of the resonator not yet having been taken into account.