An integrated planar antenna-mixer device for microwave reception utilizes a slot-ring antenna and a diode quad connected thereto. The device comprises a planar metallic sheet backed on one side by a dielectric layer. A circular ring pattern is cut from the metallic sheet forming a slot ring antenna with a central disc and a surrounding ground plane. Diodes of a diode quad are connected between the central disc and the ground plane with adjacent diodes being separated by 90.degree.. The incoming microwave signal is directed perpendicular to the device plane and polarized in a direction orthogonal to a local oscillator signal similarly directed. Operation is quasi-optical without waveguides.