Implementation of a fuzzy controller to tune the response of a waveguide cavity filter

Abstract

This paper demonstrates the utility of a modern technique to tune the frequency response of a microwave bandpass cavity filter as a complex nonlinear system with a new type of controller. The considered plant in the regulation process is a 4th order cavity filter with four resonators operating at a resonance frequency of 916 MHz, with a fixed return loss quantity of 21dB. Yet our method is based on the fuzzy logic principle, by retrieving and recalling the knowledge of microwave experts and duplicating it through linguistic rules to achieve the objective and optimize the reflection coefficient of our filter. The regulation process will be effectuated by using seven tuning screws, the insertion of these screws will create a discontinuity at the insertion position. Meanwhile, adjusting the discontinuities depth of penetration will lead to the variation of the frequency response of the considered structure. The fuzzy controlling algorithm will actuate on the screws to achieve the target.