Design of a compact and wideband branchline coupler using hybrid approach

A compact and wideband branch line coupler is designed that covers all the navigation bands starting form xx GHz to yy GHz. A single-section coupler with series stubs, half-wavelength at the mid-band frequency f0, is considered to obtain the wideband operation. Moreover, a hybrid approach, using both transmission line sections and lumped elements, is used for the size reduction without compromising the wideband operation. A prototype branch line coupler is fabricated. The coupler has a fractional bandwidth of aa% at f0 = 1.385 GHz and a compact size of bbλg×ccλg, λg being the microstrip line guided wavelength at f0.