Electrothermal Design and Analysis of Dielectric TE01-mode Resonator Filters

Abstract: The use of dielectric resonator filters is very common in the telecommunications industry for applications with demanding filtering requirements. For high power applications in particular, TE01-mode dielectric resonators are often used because of its low losses and excellent peak power handling capabilities. The essence of this work is to great extent focused around the fact that even a small amount of dissipated power can give rise to a large temperature increase if the heat transfer is insufficient. A temperature increase due to self-heating translates into a degradation of filter performance. Understanding the mechanisms behind this degradation is vital in order to compensate for these effects. Computer simulations can successfully be used to characterise the electrical and thermal behaviour of these devices. However, if the filter in question is not properly tuned when running the analysis the results will bring little or no value. This work outlines an efficient filter design flow based on Port Tuning in order to overcome this tuning issue. By carefully studying both a single resonator and a realistic filter example using CFD analysis the heat transfer mechanisms can be quantified and the dominant terms can be identified. Based on these results, a simplified model for the thermal analysis can then be established. A coupled analysis including electromagnetic, thermal and structural analysis is then demonstrated that predicts the performance degradation of the filter response. It is also demonstrated how these effects can be compensated for.