Design and Implementation of New 3-dB Quadrature Couplers Using PCB and Silicon-Based IPD Technologies

In this paper, new 3-dB quadrature couplers based on the two-layered edge-coupling mechanism are designed and implemented in the printed circuit board (PCB) and silicon-based integrated passive device (IPD) technologies. To achieve strong edge-coupling, the proposed coupler consists of two sets of parallel-connected lines, which are placed on the top and bottom metallic layers of the substrate slab, respectively. The design concept and procedures are first exemplified by implementing a 3-dB coupler in the PCB technology at 2 GHz. In addition, since the proposed circuit structure avoids using bonding wires or air bridges, it has the advantage of applying in the millimeter-wave range. However, as the proposed coupler designed in the multilayered IPD substrate, it will lead to an obvious phase velocity difference between two orthogonal modes, c-and π-mode waves. To compensate this phenomenon, two millimeter-wave IPD couplers with different slow-wave structures are proposed, designed, and experimentally verified at 38 GHz.