Analysis of reactive and resistive open waveguide filters for use in microwave-heating applicators

Purpose - The purpose of this paper is to analyze the limitations of conventional reactive and resistive filters employed in the open ports of microwave-heating applicators, in order to know the limits of these filters as a function of the permittivity of the inner materials.Design methodology approach - CST Studio Suite™ commercial electromagnetic software has been employed to simulate the behaviour of singly and doubly corrugated reactive filters. Additionally, several configurations for resistive filters implemented with water are assessed. Optimization procedures based on genetic algorithms have been used by modifying some geometric parameters of the filters in order to obtain the best possible bandstop response.Findings - Results show the serious limitations of these filters depending on the electric permittivity of the inner materials.Practical implications - These limitations restrict the type of the materials that can be processed, so there is a need for new structures which solve these problems.Originality value - Although extensively used in many applications, there are few works that analyze the behaviour of these filters as a function of the geometric parameters or the sample permittivity, and therefore this influence needs to be studied.