New inkjet printed wideband 3 dB branch line coupler

In this paper, a new inkjet printed wideband 3 dB branch line coupler is presented and compared with the identical coupler circuit fabricated in the conventional etching technique. The coupler circuit consists of four γ/4 open circuited coupled lines in a suspended microstrip structure, a conventional squared loop circuit in a microstrip structure, and a transition between these two different transmission media. The circuit has been realized with a silver nano particle ink on the Chukoh substrate with a thickness of 0.5 mm and a relative permittivity ε_r=2.6. A primer layer based on the epoxy, bistphenol A, has been additively laminated on the substrate. The coupler circuit has been simulated with HFSS and printed by the OmniJet 100 inkjet printing system. Measurement results show |;S₂₁| better than 3.6 dB and |S₃₁| better than 6.6 dB with a power imbalance of 0.8 dB; and |S₁₁| better than 20 dB and |S₄₁| characteristics better than 18 dB over 43% fractional bandwidth.