Wideband Directional Coupler Using 3D Copper Additive Manufacturing Technology

In this paper, a wideband directional coupler is designed using three-dimensional (3D) additive manufacturing technology. To solve the mismatch issue of the odd-even mode impedance at high frequencies, a compensate method is proposed to make up the electrical length and the odd-even mode impedance for a flat coupling response over wide frequency range. For demonstration, a 5.1-34.8 GHz directional coupler is designed using a nine-layer additive manufacturing technology. The coupling degree is 20.8±1.4dB, the directivity is better than 15dB in the working band, and the insertion loss is as low as 0.3dB.