High Power Analysis of Filters and Diplexers

Abstract

The ever-increasing popularity and usage of communication devices has resulted in power density becoming more demanding due to crowding of frequency spectrums and narrowing of bandwidths. Consequently, the power-handling capability of filters has emerged as an important research area. With the size and mass of filters shrinking to accommodate the needs of the latest technology, designing narrowband filters necessitates the operation of filters close to their maximum power capacities. Hence, there is an urgent need to properly measure and estimate power-handling capability in filter-based products such as satellite multiplexers and wireless diplexers. In this research, the design of filters and diplexers capable of handling higher power was investigated using modifications of available methods to predict the maximum input power that a filter can handle before breakdown. This method was utilized to improve the power-handling capability and quality factor of the conventional coaxial resonator while avoiding time-consuming EM simulations. A novel coaxial resonator configuration was proposed using this method and the performance of suggested configuration was validated by designing 2-pole filters using both conventional and novel configurations. A 4-pole chebyshev filter was also designed and realized using the proposed configuration, and a power-handling analysis utilizing HFSS was compared with that of the estimated value. A novel approach in the design procedure of coaxial diplexers was proposed that provided a faster design method using step-by-step group delay matching of EM simulation results with a diplexer equivalent circuit. A method for predicting air breakdown was also applied to the diplexers to determine maximum power-handling capability.