Abstract

Reconfigurability, especially in terms of the ability of adjusting the operating frequency, has become an important prerequisite in the design of modern microwave components and systems. It is also pertinent to microwave sensors developed for a variety of applications such as characterization of material properties of solids or liquids. This paper discusses uncertainty quantification of additive-manufacturing-based post-fabrication tuning of resonator-based sensors implemented using a microstrip technology. Therein, the operating frequency is altered by adding metallic patches of a specific size determined by the full-wave electromagnetic (EM) model of the system. The reliability of setting up the center frequency depends on both the accuracy of the patch size (manually cut out of the copper tape), and its allocation with respect to the resonator. A rigorous statistical analysis of the patch size and its allocation errors is carried out, including a quantification of their joint effects on the sensor operating frequency. Furthermore, the analysis of a possibility of compensating the patch size inaccuracies through its appropriate positioning is conducted. The details of the proposed approach are explained using a complementary symmetric split ring resonator (CSSRR)-based sensor designed to operate in X and Ku bands with the tuning range between 10 GHz and 20 GHz. The optimized sensor's fundamental resonant frequency is 9.4 GHz, its exterior size is 25 x 30 mm2, the quality factor of the fabricated sensor is 29, and the sensitivity of the considered design is 1.1 GHz/mm with the measurement error is 0.1 percent. The obtained measurement data are indicative of a practical utility of the additive-manufacturing-based tuning technique, in particular, a possibility of reliable center frequency tuning under mild assumptions on the accuracy of manual preparation of the tuning patches. Furthermore, a practical tuning scheme has been developed and experimentally validated, which allows for a precise allocation of the operating frequency with the error not exceeding 0.01 GHz (or 0.1% in relative terms), all under assumptions of a manual preparation and placement of the tuning patch.

Citations

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