A rectangular waveguide-microstrip transition based on the principle of magnetic coupling for millimeter-wave

A novel rectangular waveguide-microstrip transition for millimeter-wave frequency band is presented in this paper. The transition circuit is based on the principle of magnetic-field excitation. The triangular ring circuit, which is placed on the dielectric substrate inserted to the E-face of the waveguide, is used to achieve the mode conversion of the main mode between the rectangular waveguide and microstrip line. The structure has the advantages of low insertion loss, wide frequency range, small size and non-debug. The measured results show that the insertion loss of the back-to-back transition is less than 2.5 dB in the whole Ka-band.