mechanical resonances in small mechanical components can present trouble in certain environments

1. M
ICROW
AVE
CAVITY
FILTER
SHOCK
AND
VIBRATION
M
ODAL ANALYSIS
Don Blanchet
3B Associates
4/12/1999
sighting electronics

2. POSSIBLE SITUATIONS OF CONCERN – NOISE SOURCES

3. GOALS
Identify the modal vibration resonant frequencies of a microwave cavity
filter and its tuning elements.
Provide the results to the electronic engineering staff.
Understand self generated electrical signal noise due to mechanical
shock sources such as:
pyrotechnic explosive events – shipboard rapid gun fire
HALT testing with hammer blows

4. WARNING HALT/HASS
Microwave engineers – please note HALT “vibration” machines use
hammer blows to generate 3 axis excitation.
The exciting signal felt by the tested units will have significant shock
components above 2KHz.
Very small components can be damaged during HALT and HASS.

5. MODEL MICROWAVE CAVITY FILTER
Gold plated 6061-t6 aluminum

6. MODEL – COVER REMOVED
Interdigital microwave filter elements

7. FINITE ELEMENT MESH
71,000 degrees of freedom

8. RESULTS FEA EIGENVALUE EXTRACTION

9. MODE SHAPE 1

10. MODE SHAPE 2

11. MODE SHAPE 3

12. MODE SHAPE 4

13. MODE SHAPE 5

14. MODE SHAPE 6

15. MODE SHAPE 7

16. MODE SHAPE 8

17. MODE SHAPE 9

18. MODE SHAPE 10

19. MODE SHAPE 11

20. MODE SHAPE 12

21. MODE SHAPE 13

22. MODE SHAPE 14

23. MODE SHAPE 15

24. MODE SHAPE 16

25. MODE SHAPE 17

26. MODE SHAPE 18

27. MODE SHAPE 19

28. MODE SHAPE 20

29. MODE SHAPE 21

30. MODE SHAPE 22

31. MODE SHAPE 23

32. MODE SHAPE 24

33. MODE SHAPE 25

34. MODE SHAPE 26

35. MODE SHAPE 27

36. MODE SHAPE 28

37. MODE SHAPE 29

38. MODE SHAPE 30

39. RESULTS SUMMARY