Highly Balanced Hybrid Ring Based on Microstrip Slotline Tight Coupling

This letter presents a compact, highly balanced broadband hybrid ring. The device replaces the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3\lambda /4$</tex-math> </inline-formula> segment of the traditional hybrid ring with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda /4~3$</tex-math> </inline-formula>-dB microstrip slotline coupled line to reduce the size. This hybrid ring only requires simple manufacturing techniques and a single-layer substrate with a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.32\times 0.34\lambda _{g}$</tex-math> </inline-formula>. The measured relative bandwidth with a return loss better than 10 dB is 80.6%, and the amplitude imbalance measured in 2.5–4.8 GHz is less than 0.1 dB. The simulation and experimental results are consistent.