On-chip miniaturized 3-dB directional coupler using coupled synthesized CPWs on integrated passive device (IPD) process

An on-chip miniaturized 3-dB directional coupler is investigated in this paper using coupled synthesized coplanar waveguides (CPWs) on the integrated passive device (IPD) process. Coupled spiral inductors and MIM capacitors are used to achieve tight coupling between the lines. The proposed on-chip coupler is only 15% the length of a conventional design in CPW form on the same substrate. The design principles and experimental results are discussed. A comparison table with the state-of-the-art designs helps support the uniqueness of the proposed approach.