Characteristic Impedance Control for Branch-Line Coupler Design

This letter presents a new approach to control impedance for branch-line coupler (BLC) design. With the proposed method, the highest impedance of the two-section BLC can be set to a realistic value (below
$100~\Omega$
), so that it can be implemented with ordinary planar technology. The measured results are compared with the simulated results to validate the proposed theory and design approach.