Using a 3D-Printed Waveguide Filter with Ridge Resonators As a Dielectric Permittivity Sensor

This paper presents the use of a waveguide filter with ridge resonators that exhibits transmission zeros to implement a dielectric permittivity sensor. Thanks to its geometry, the electric field is intense under the ridge resonators, where the dielectric slab to be characterized is located. The operation principle is based on the evaluation of the frequency shift of transmission zeros, and exhibits high sensitivity and tolerance to vertical positioning errors. The designed sensor operates around the frequency of 10 GHz. The manufacturing process is based on the 3D printing with plastic material and the subsequent metallization. A set of commercial dielectric laminates have been adopted to validate the performance of the sensor.