Spectrum analysis of different types of high-power microwave pulses in air breakdown

When a high-power microwave (HPM) pulse propagation in the air with a breakdown threshold below the HPM field, may cause the breakdown of background gas and generate plasma which varies rapidly in space and time. Such a plasma can effectively modify the spectral content of the pulse. And the electrons produced will attenuate the field at the tail portion of the HPM. This erosion shortens the pulses and generates transmitted pulses with broadened bandwidth. Using finite difference time domain method (FDTD) can give numerical analysis about the spectrum broaden.