Design of 10-dB Symmetric Broadband Multi-Sectional Directional Coupler

A 10-dB symmetric broadband multi-sectional directional coupler applied to the 0. 7-3.7 GHz band is introduced to address the high bandwidth requirement of directional couplers for microwave systems. The coupler is designed with a double-layer parallel stripline structure and extends the bandwidth of the coupler by using a three-section coupling line. Higher directionality is also achieved by adding branches at the coupling line connections. The simulation is optimized by HFSS simulation software. The simulation results show that the isolation (S
41
) of the coupler is greater than 35 dB, the return loss (S
11
) is greater than 27 dB, and the in-band fluctuation of coupling (S
31
) is less than ± 1dB in the range of 0.7 -3.7 GHz, which meets the design requirements of 10-db coupler.