An asymmetrical suspended stripline directional coupler

For a directional coupler using a low-loss suspended stripline, the structure of an asymmetrical suspended directional coupler with medium coupling of -5 dB to -9 dB is proposed and the design method and characteristic of the coupler are discussed. By using an asymmetric suspended stripline in the coupled section, medium coupling, which is difficult to achieve with a branched stripline directional coupler for tight coupling and an edge-coupled stripline directional coupler for weak coupling, can be realized. This type of coupler is advantageous for the supply circuit of a phased-array antenna using suspended striplines.