Processing of Light Emission Signals of Discharge Spot by FFT

Fast Fourier transform is an extremely important and widely-used method of extracting useful information from sampled signals. In this paper, the light signals of two types of discharge spot, the spot with a dim ring halo and the spot with a disc halo observed in dielectric barrier discharge in air, are recorded and compared through the Fast Fourier transform. For the spot with a disc halo, the Fast Fourier transform power spectrum of light signal only has the basic frequency F, which reflects its temporal periodicity. The Fourier transform power spectrum of the light signal of spot with a dim ring halo shows that there still exists subharmonic frequency 1/2F besides the fundamental frequency F. The subharmonic frequency is related to the changes of the amplitude of the signal periodically.