Abstract
This article presents the results of synthesis of a second-order single-frequency notch filter based on the Butterworth polynomial. The frequency response of this filter is improved by the feedback loop correction coefficient. A single-frequency notch filter with a feedback coefficient of 0.1 provides a steeper drop at the interference cutoff frequency, thereby improving the interference resistance and accuracy of the signal processing system. In addition, the discovered association characterizes the influence of the negative feedback loop coefficient on the accuracy, interference resistance and attenuation coefficient of single-frequency interference during experimental testing. Based on the processing of the experimental material, the operability of the Butterworth single-frequency notch filter was also confirmed when filtering sinusoidal interference generated at the output of the ESP32 microcontroller.