A Right-Angle Wideband Transition Between Differential Microstrip Line And Rectangular Waveguide

In this letter, a right-angle full Ka-band differential microstrip line (DML) to rectangular waveguide transition is proposed. A novel coupling probe configuration, which is considered to be a combination of a strip loop and a slot loop, is developed to improve the bandwidth of the transition. The 15 dB fractional bandwidth is increased from 33 to 40.6% compared with the right-angle DML-to-waveguide transition using multilayer PCB structure. To verify this transition, a back-to-back prototype is fabricated and measured. It provides an insertion loss of less than 1.2 dB and a return loss of better than 15 dB within a wide frequency range from 26.5 to 40 GHz. The measurement results show good agreements with the simulation ones.