Miniaturised dual-band branch-line coupler

A novel topology of a miniaturised dual-band branch-line coupler with a 3 dB power split is presented. The compact design is achieved by folding the transmission line sections into the interior of a circuit. The initial dimensions are obtained at the equivalent circuit level. Design closure is conducted at the electromagnetic-simulation model level. The coupler operates on frequencies of 1 and 2 GHz, and features miniaturisation of 75% compared with the conventional structure. Experimental validation of the fabricated prototype is provided.