Miniaturization of Microwave Devices by Using Three-Dimensional Strip Line Design

This paper offers a concise examination of three-dimensional designs of coupled strip lines and devices based on them. It includes examples of non-directional and trans-directional couplers, impedance transformers, and phase shifters. The 3D strip line structures are implemented on both horizontal and vertical substrates, enabling a strong connection between strips when placed on vertically oriented substrates. The paper discusses the advantages and disadvantages of the discussed devices based on such coupled lines. One significant drawback lies in the large dimensions of substrates when strips are executed as straight segments. To address miniaturization, it is proposed to implement coupled lines on both horizontal and vertical substrates in a meander-like configuration. The paper presents research results concerning the frequency dependencies of transmission coefficients, reflection coefficients, directional couplers, and non-reflective filters based on 3D designs with reduced dimensions while minimally affecting frequency characteristics and preserving their intended functions. This research opens new perspectives in the field of 3D coupled strip lines and their applications, including the reduction of device sizes for more efficient utilization across various technical applications.