On the design, simulation and fabrication of multiple section coupled-line directional couplers at C-band using microstrip technology

This paper presents the design of coupled-line directional couplers using microstrip technology. It is verified that by attaching sections to a coupled-line directional coupler, the working bandwidth of the device can be increased, this increase is also achieved by varying the length (L), width (W) and separation (Se) of microstrip lines within the coupler sections. For such purpose, couplers of 1, 3 and 5 sections were designed. To validate the designs, two prototypes with 3 and 5 sections were fabricated using microstrip technology and tested at different working frequencies within the C-band. Finally, an appropriate procedure for tunning a coupler, by varying the L, W and Se parameters of the microstrip lines, is proposed based on experimental results.