Miniaturization of microstrip directional coupler by means of artificial transmission lines

this paper presents a brief analysis of the existing methods of reducing microstrip device dimensions. This paper also presents a miniaturization method based on using artificial transmission lines, which possess characteristics similar to those of quarter-wave transmission lines. Based on this method, a compact directional coupler, which divides the power in a 1: 2 ratio, was designed and manufactured. FR-4 with dielectric permeability of epsilon = 4.4 and thickness of h = 1 mm serves as substrate material. Using the R&S vector network analyzer, the experimental characteristics were ob-tained, which coincided with simulation results with minor error. The proposed miniaturization method allowed reducing the bridge coupler dimensions by 70% compared to the standard design.