A wide band transition from waveguide to differential microstrip lines

A novel transition from rectangular waveguide to differential microstrip lines is illustrated in this paper. It transfers the dominant TE10 mode signal in a rectangular waveguide to a differential mode signal in the coupled microstrip lines. The common mode signal in the coupled microstrip lines is highly rejected. The transition was designed at 75 GHz, which is the center frequency of E band and simulated by a 3D EM simulator. It has a wide bandwidth of 19 GHz for -15 dB return loss of the waveguide port. Several prototypes of the transitions were fabricated and measured. The measurement results agree very well with the simulation. The compact size and the simple fabrication enable the transition to be employed in a number of millimeter-wave applications.