Investigation of the transient EM scattering of a dielectric resonator

Dielectric resonators have gained interest in RF identification and localization system concepts. This contribution reports observations from experiments and EM simulation with special focus on the transient behavior of the EM scattering of a ceramic resonator in free space. Explanation and analysis of the transient behavior is given using equivalent circuit modeling and EM simulation. The time constant of the particular resonant mode excited is shown to depend on the loaded quality factor of the resonant mode and governs the exponential charging up process and the exponential decay process of "ringing" of the resonator at its Eigen frequency. For an exciting RF pulse much shorter than the time constant, the resonator scattering amplitude increases linearly with increasing pulse length which allows to determine the structural response also. Forced excitation at a frequency offset from the resonant frequency will still produce free "ringing" at the resonator's Eigen frequency. The scattering amplitude is related to the Radar Cross Section of a dielectric resonator, but this only applies to the steady state of excitation.