Low-loss mm-wave transition from on-chip microstrip to rectangular waveguide

A new method for coupling from an on-chip microstrip line to a rectangular waveguide oriented perpendicular to the chip is presented. The coupling is realized by a 3-pole bandpass structure, containing an on-chip microstrip resonator, a dielectric spherical resonator and a waveguide cavity resonator. Measurements show a transition loss of 2.6 dB at 64 GHz and less than 3 dB loss over a 4.5% bandwidth. Simulations indicate that less than 0.2 dB of this loss are due to radiation leakage. The structure occupies small on-chip area und provides features for electrical test before assembly and for simple yet precise assembly.