Higher isolation solutions for printed circuit board mounted antenna and waveguide interfaces are provided herein. An example device includes any of a dielectric substrate or transmission line, an antenna mounted onto the dielectric substrate, and an elongated waveguide mounted onto the dielectric substrate so as to enclose around a periphery of the antenna and contain radiation produced by the antenna along a path that is coaxial with a centerline of the waveguide, the elongated waveguide having a first cross sectional area and a second cross sectional area, and the first cross sectional area differs from the second cross sectional area.