Miniaturised broadside coupler using coupled slow-wave artificial lines

A miniaturised broadside coupled-line coupler is presented. The coupler is fabricated on a six-layered printed circuit board and consists of a 90deg coupled slow-wave artificial transmission line section. Compared with previous works on printed circuit boards, the proposed design features the smallest occupied size. It also demonstrates a comparable operating bandwidth of 85deg. The design concept, methodology and results are investigated.