A waveguide-microstrip structure for millimeter-wave spatial power combining

In this paper, a novel structure is proposed for power dividing and combining at millimeter-wave bands. It presents lower loss compared to circuit level power combining since its power-combining occurs in air space; in comparison with the traditional spatial power combining, it uses metal enclosures to prevent possible radiation loss. Simulations were performed on the proposed structure and a prototype was developed and tested. It was found that efficiencies of power combining in the Ka band and E band are 93.3% and 71.6%, while the bandwidths of return loss less than -20dB are more than 3GHz in the Ka band and 6GHz in the E band, respectively. The advantages of it include: low loss since power combining occurs in free space; simple structure and easy fabrication due to the use of conventional waveguide and microstrip structures; easy integration with MMICs because of the use of microstrip lines; good efficiency performance.