A new broadband microstrip quadrature hybrid with very flat phase response

A new broadband microstrip branch-line quadrature hybrid with very flat phase response is presented. The device is made by cascading four branch-line couplers with arbitrary power division. The novel design is based on the microstrip transposition of a broadband waveguide polariser [4]. Across a 32% bandwidth centred at 9.3 GHz, the RL and the IL are respectively ¡15 dB and ¡3 dB/¡4 dB; the phase difference is very flat, i.e., 90°±1:5°