This letter presents a new generation of radiofrequency interferometric sensors. Herein, an original, simple and monolithic interferometer based on substrate integrated waveguide technology is introduced for the first time. In order to demonstrate its potential for measurement applications, the proposed structure has been studied as a humidity-sensing element. Its detection principle is based on the variation of the effective dielectric constant of a sensitive branch due to the variation of the humid air dielectric constant. The sensitive characteristics of the structure have been investigated in the range of 20%-70% relative humidity. An analytical model that predicts the frequency shift and estimates the humidity level is proposed. The substrate integrated interferometer can be used in many measurement applications such as dielectric material characterization and environmental detection.
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