In this paper, the initial part describes the types of filters and their division, approximations for obtaining their transmission functions, and describes the cascade structure and the structure of the biquart for which calculations were performed. After the above, the time and frequency characteristics are described, as well as the method of calculating them. The noise of the filter elements and the way in which the noise is calculated are explained. The second chapter will show the division of filters and ways to calculate them. After the above, the time and frequency characteristics of the cascade structure realized by Butterworth's approximation and the values of the elements of the same are presented. The calculation of cascade structure forests was performed, and the results of time and frequency characteristics were obtained, and the forests were checked using the LTSpice program. Then the values of the elements of the biquart structure and the biquart noise were calculated, which was also checked in the LTSpice program. After the above, a comparison of the approximations used and the models of tiles in the KiCAD program was made. The last chapter presents the results of measurements obtained using a network analyzer.