What everyone ought to know about Filter Tuning – Try your hand at it. The retuning process will include basic information and characteristics of filters, and the following detailed steps for returning: • Identification of equipment and tools • Analyzer set-up • Pre-setting and loading settings The step-by-step guide will ensure efficient tuning. We feel the hands-on approach is the most desirable method of explaining LPTV filter tuning technology.

1. Filter Tuning 101
Presented by: Jeremy D. Ruck, PE
Filter Tuning 101
Presented by: Jeremy D. Ruck, PE
SBE39 Symposium 2015

6. Definitions – Filter type
low pass high pass
band pass

7. Why Band pass Filters ?

8. Return Loss and Polar Displays
There are n-1 return loss “bumps” and n-1 smith chart loops

9. CHANGING CHANNEL ?
You can get there from here!!

10. Tuning Options
• Buy or rent vector network analyzer
(VNA) and try it your self
• Hire qualified field engineer
• Work with station group to use central
engineer / VNA and exchange filters
• Return filter to factory for re-tuning

11. Tuning Procedures
• Available at www.dielectric.com

12. Equipment Needed
Vector Network Analyzer (VNA) purchase
• Keysight Technologies (formerly Agilent)
• Rohde & Schwarz
• Anritsu
• Advantest
• Copper Mountain
VNA Rental
• Electro-rent
• Test Equity
• Advanced Test Equipment Rentals
• Metric Test
• TRS-RenTelco
• Calibration Kit and Cables
• Adaptors type N to 7-16
Or type N to 1 5/8” or 3 1/8”
• Allen keys and standard
wrenches

13. Filter dissection

14. Step 1 – Set coupling heights

15. Step 2 – Set input couplings

16. Step 3 – Bring in 2nd Resonators

17. Step 4 – Bring in resonator 3

18. Step 5 – Bring in last resonator
Result is filter on channel with the correct band width
and about 14 dB w/c return loss

19. Step 6 – fine tuning
• All fine matching screws, all
couplers
• Iterative adjustments

20. Coupling Depth
wider
deeper

21. Cross coupler depth

22. Resonator Depth – Tunable filters
lower
deeper
deeper

23. Thermal Stability
660.00 662.50 665.00 667.50 670.00 672.50 675.00 677.50 680.00 682.50
F [MHz]
-100.00
-80.00
-60.00
-40.00
-20.00
0.00
Y1
Ansoft LLC Nexxim1XY Plot 1
(cold)
Curve Info
dB(S(Port2,Port1))
LinearFrequency
dB(S(Port4,Port3))
LinearFrequency
T
T
ff
∆⋅−
∆⋅
=∆
α
α
1
0
α = material coefficient of thermal
expansion

24. Temperature Compensation
Minimal
Drift
(≤75 kHz)

25. Step 6 – fine tuning a methodical way
• Time domain tuning
• Agilent app note AN1287-8
• Requires VNA with time
domain transform (TDR)
option
• Response in time domain
corresponds to each physical
adjustment

26. Time Domain Tuning
• Important Step 1: Before
making any adjustments on
tuned filter save :
• input return loss (S11)
• transmission response (S21)
• output return loss (S22)
to VNA memory
These memory traces will serve
as template for tuning the filter
at the new channel

27. Time domain – S11 response
input coupling
resonator 1
1-2 coupling
resonator 2
2-3 coupling
resonator 3

28. Conclusions
• Get started on your planning now.
• Do not rely solely on corporate engineering for implementation.
• Establish necessary relationships for repack.
• Interim solution may be necessary.

29. Questions