On Replacing the Quarter-Wave Section of a Directional Coupler with Lumped LC Elements

The presentation is devoted to the study of replacing quarter-wave sections in two-loop LC directional couplers with elements with a low-pass filter (LPF) structure. The main purpose of the presentation is to determine the values of LC elements that do not significantly degrade the coupler characteristics. By comparing the ABCD matrices of the LC structure and the <tex>$\lambda / 4$</tex> segment, it was possible to derive formulas for calculating the values of inductances and capacitances. Comparison of filters of the 3rd, 5th, 7th orders allowed to reveal a regularity and to find approximating relations for calculation of LC structure elements of any order. The results of the work provide engineers with an opportunity to evaluate the prospects of using LC structures in the design of compact microwave devices.