A branch-line microstrip coupler is designed and
fabricated in this paper. The proposed coupler operates at 3 GHz,
which is suitable for WiMAX applications. The designed coupler
has a high performance, that is, a low phase difference of 0.49°,
low insertion loss, good coupling factor, and good isolation better
than −30 dB. Another advantage of the designed coupler is its novel
geometrical structure based on integrating the semi-circular and
step impedance cells. The design process is based on introducing and
analyzing an equivalent LC model to improve impedance matching
and reduce losses. To verify the design process, the designed coupler
is fabricated, where a good agreement between the simulation result
and measurement is achieved.