A microwave antenna assembly includes a first dielectric layer, a second dielectric layer, a conductive layer, a first conductive patch, and a second conductive patch. The conductive layer is disposed in an inner region between the first dielectric layer and the second dielectric layer. The conductive layer includes a slot. A first conductive patch is surrounded by the slot. The second conductive patch is disposed against the second dielectric layer outside the inner region, and is electromagnetically coupled to the first conductive patch.