Three dimensional FEM (Finite Element Method) with edge elements is used to numerically study the 2.45G Hz electromagnetic wave propagation in an ECR (Electron Cyclotron Resonance) waveguide coupler. Compared with the traditional node-based FEM, it is found that edge elements do not produce so-called spurious solution problems.
The simulation structure is composed of the circular waveguide with different tapering angle and two different load conditions, i.e. one with short termination and the other which treats the ECR plasma as an effective dielectric media with proper dielectric constant as well as loss.
The results of our simulation clearly show that $TM_01$ mode propagates much smoothly than the dominant $TE_11$ mode without generating higher modes, that the reflection by tapering becomes smaller as the taper angle reduces, and that the ECR coupler proposed in our laboratory is nearly optimized one.
