What is the three-dimensional radiation pattern of an isotropic radiator?

Because an isotropic radiator is a theoretical point source that radiates electromagnetic energy equally in all directions, its three-dimensional radiation pattern forms a perfect sphere. Measuring the signal strength at a constant distance in any direction yields the exact same value. Distractors like the 'torus' (donut shape) describe the radiation pattern of a standard half-wave dipole antenna. A cardioid is heart-shaped and typical of directional arrays, while a hemisphere implies radiation in only half of the available space.