  We experimentally demonstrate a Purcell effect-based design technique for
improved impedance matching, and thus enhanced radiation efficiency from a
small microwave emitter. Using an iterative process centred on comparing the
phase of the radiated field of the emitter in air with that of the emitter in a
dielectric environment, we optimise the structure of a dielectric hemisphere
above a ground plane surrounding a small monopolar microwave emitter in order
to maximise its radiation efficiency. The optimised system shows very strong
coupling between the emitter and two omnidirectional radiation modes at 2.00
GHz and 2.84 GHz, yielding Purcell enhancement factors of 8360 and 430 times
increase respectively, and near perfect radiation efficiency.
