Numerical Study on Low Pressure Discharge of Microwave Stepped Impedance Transformer

The transient process of low-pressure air discharge in microwave stepped impedance transformer is described using three-dimensional (3D) spectral-element time-domain (SETD) method. The self-consistent coupling of electron fluid equation and Maxwell's equations is used to describe the electromagnetic-plasma system. The evolution of spatial distributions of discharge is obtained. The mechanism of low-pressure discharge is analyzed and explained. As time goes on, the electron distribution hot spot gathers toward the source end in the y-z plane. With the increase of the pressure, the electromagnetic field can be transmitted to the right side gradually, and the trend of electron density gathering to the incident side of the incident wave is weakened. Our research is beneficial to improve the matching performance of stepped impedance transformer.