Design of compact microstrip branch line coupler using semi-circular and rectangular resonators with wide range suppressed harmonics

In this paper, a novel compact branch line coupler (BLC) with 10 suppressed harmonics is proposed. To achieve small size, four semi-circular and eight stepped impedance resonators are used instead of 35 Ω and 50 Ω conventional branch line coupler transmission lines. The operational frequency of the presented branch line coupler is 0.85 GHz. The size of the proposed circuit is reduced about 78% in compared with the conventional branch line coupler. To verify the design and analysis, the proposed coupler is simulated using full-wave EM simulator Advanced Design System and fabricated. Simulation results are in good agreement with measurement results.