A miniaturized branch-line coupler using finger-shape distributed capacitors

A miniaturized 3-dB branch-line hybrid coupler based on distributed capacitors is proposed. By altering the structure of the distributed capacitors, it can further minimize the size of the hybrid coupler compared to the pure distributed capacitors. Experimental results demonstrate that the proposed novel 3-dB branch-line hybrid coupler has a compact size of 23.5mm × 33.9mm at the designed frequency of 836.5MHz, which corresponds to 70% size reduction compared to the conventional one with similar performance. Compared to a previously reported topology using pure distributed capacitors to the ground, the size was reduced by 23%.