Aspects of the present disclosure relate to determining a layout of a racetrack that forms part of a radio frequency (RF) isolation structure of a packaged module and forming the resulting RF isolation structures. Based on electromagnetic interference data for a module, an area of the module that is less sensitive to external radiation is identified. A racetrack layout can be determined based on identifying the area that is less sensitive to external radiation. The racetrack layout can include a narrowed section in the area that is less sensitive to external radiation or a break in the area that is less sensitive to external radiation.