Successive optimization of zeros of reflection characteristics for automated microwave filter tuning

This paper presents a novel automated microwave filter tuning method based on successive optimization of zeros of reflection characteristics. We develop an optimization procedure to determine how much adjusting screws of a filter should be rotated. The proposed method consists of two stages; coarse and fine tuning stages. In the first stage, called coarse tuning, the phase response error of the target filter is minimized so that the filter roughly approximates almost-ideal bandpass characteristics. Then in the second stage, called fine tuning, we optimize the position of zeros of reflection characteristics. Performance of the proposed tuning procedure is evaluated through some experiments of actual filter tuning.