Q Factor of a Radiator

Q factor is a parameter for describing the resonance behavior of a resonator or an oscillator. For time harmonic resonators with higher Q factors, they may oscillate with higher amplitude and attenuate slower. The frequency range that they can oscillate tends to be narrower. However, in practical engineering, Q factors may be defined in different ways in different problems. This chapter will give a brief introduction to the commonly used definitions of Q factors for circuits and antennas.