摘要

A dual-band coupled-line 90 degrees unequal coupler is proposed in this paper. It is simply composed of three pairs of coupled lines and four port extensions. Analytical design methodology and detailed design guidance are given, which significantly simplifies the design procedure. Due to the utilization of coupled lines, the proposed coupler possesses tight circuit configuration, and since the degree of freedom is increased for the even- and odd-mode characteristic impedances, the coupled lines enable the dual-band operation. Meanwhile, the coupler can operate with unequal power division. Furthermore, the employment of port extensions eliminates the additional insertion loss caused by additional port lines. Eventually, two prototypes of the proposed coupler are designed and fabricated. The good agreement between the expected and measured results confirms the design methodology in this work to be correct and effective.