Full-Wave Analysis of a Novel Branch-Line Coupler with Series Junctions Between Lines

A novel two-branch coupler with series junctions between microstrip lines and slotlines has been synthesized first by using the even-odd mode theory. The spectral domain approach (SDA) is then utilized to rigorously analyze such a new circuit. By the formulation of the exact Green's function in the spectral domain, the effects of surface wave and radiation phenomena are accurately accounted for. Experimental data has been shown to be in good agreement with the theoretical ones.