Waveguide-to-coupling microstrip transition structure of millimeter wave highly compact differential antenna

The invention discloses a waveguide-to-coupling microstrip transition structure of a millimeter wave high-compactness differential antenna, which belongs to the technical field of millimeter waves and comprises a rectangular waveguide, a rectangular cavity and a waveguide-to-coupling microstrip line transition circuit. The waveguide-to-coupling microstrip line transition circuit comprises a dielectric substrate, a transition structure on the front surface and a metal grounding plane on the back surface; the transition structure comprises a differential antenna located in the rectangular waveguide and a coupling microstrip line located in the rectangular cavity and partially inserted into the rectangular waveguide. The differential antenna comprises a rectangular metal sheet, a multi-stage stepped impedance conversion structure and two rectangular coupling branches. According to the invention, the differential antenna inserted into the rectangular waveguide is utilized to convert the main mode electromagnetic