A Note on the Simple Two-Element Low-Pass Filter of Two and Three Sections

An analytical study of the simple two-element low-pass filter of two and three sections is presented. Making certain approximations, applicable to the majority of such structures, the most economical distribution of a given sum total capacity and inductance between the various sections of the filter is determined. The advantage of the third section is shown by obtaining a simple expression for the filtering ratio of the three-section filter in terms of the ratio of the first two sections, taken alone, and the parameters of the last section.