A narrow-band waveguide to microstrip transition in Ka band

The structure and design procedure of a resonant waveguide to microstrip transition in Ka band are studied in this paper. The method of lines is applied to calculate the resonant frequency of planar circuits used for the transition, and a modified resonant approach is proposed. The microstrip is in the same direction with the waveguide. Experimental results of a test model verify the validity of the design. The pass bandwidth of the transition is about 3% and the insertion loss is less than 2.5 dB at Ka band. The modified resonant approach is also adequate for designs of other kind of narrow-band passive devices.