1. Wang Juan Lin Yihua Dec 25th,2010
Discussion of resonant cavity and the simulation by software COMSOL
Wang Juan Lin Yihua
Dec 25th,2010

2. Content 1.Theoretical deduction of TM wave function
2.Practical simulation of TE & TM wave in resonant cavity by COMSOL
3.Some interesting questions in the process of simulation

3. I. Theoretical deduction

4. I. Theoretical deduction
According to:
Z=0:
Z=d:

5. I. Theoretical deduction

6. I. Theoretical deduction
Resonance frequency:
In a cubical resonant cavity:
Discussion of degree of degeneracy:
Define:
, the degree of degeneracy is 1;
, the degree of degeneracy is 3;
, the degree of degeneracy is 6;

7. II. Practical simulation
TE (0,1,1) Mode:

8. II. Practical simulation
Section: z=0
a=0, b=1
Section: x=0
b=1, c=1
Section: y=0
a=0, c=1

9. II. Practical simulation
Section: y=0
a=0, c=1

10. II. Practical simulation
TE (2,1,1) Mode:
Section: y=0
a=2, b=1

11. II. Practical simulation
Calculating the power flow:

12. II. Practical simulation
The power flow in TE (2,1,1) Mode:

13. Problem 1
1. When simulating electrical density in COMSOL:

14. Key point
The power density in the pipe is 2~3 ranges larger than that in the resonant cavity:

15. Solution

16. Problem 2
There exists a “power hole” in the process of simulating electrical density:

17. Key point
The sub sources interfered the inner distribution of electric density! Then the challenge comes: 1. How to smooth the edges to avoid the occurrence of sub sources? 2.How to “break” the symmetry of the wave source to avoid the same phase position?

18. Solution
1. How to smooth the edges to avoid the occurrence of sub sources?

19. Solution
2.How to “break” the symmetry of the wave source to avoid the same phase position?

20. Solution
The result:

21. Conclusion
Having known how to take advantage of simulation software to test the theoretical result;
Try to think hard to find ways to eliminate all the problems when putting the model into practice!

22. Thanks!