Power-Handling Considerations of Narrowband Second-Order Absorptive and Reflective Bandstop Filters

This article compares the power-handling capabilities of narrowband second-order absorptive bandstop and reflective bandstop filters (BSFs) that have not been explored previously. The analysis considers two distinct perspectives: the maximum voltage and current that each filter can handle, as well as the average power dissipation. Both electrical and electrothermal analyses are conducted. Closed-form expressions are derived for the second-order absorptive and reflective BSF (RBSF) topologies, delineating voltage and power distribution among their resonators as a function of input power. Two second-order microstrip filters with lumped components are designed, fabricated, and measured to validate the analyses. These filters, centered at 500 MHz, are tailored specifically for direct, nonloading voltage measurement using an oscilloscope. Thermal profile measurements are also taken using an infrared (IR) camera, confirming theoretical trends that the absorptive BSF (ABSF) has a higher average power-handling capability (PHC) compared to the RBSF.