Presented by Benedikt Scheid, Senior Engineer R&D, Broadcast Division, Radio Frequency Systems at IEEE Broadcast Symposium 2015

1. RADIO FREQUENCY SYSTEMS
Advanced Passive Components
for
UHF Broadcast Spectrum Reallocation
Benedikt Scheid
Senior Engineer R&D - Broadcast Division
Radio Frequency Systems
16th October 2015
Special thanks for their contributions to
Yan Cao, Jonathan Chi, Ernest Fardin, Dieter Pelz and Nick Wymant

2. RADIO FREQUENCY SYSTEMS
Overview
• The Australian repack experience & the looming US repack
• Old and New - adjacent channel high power combiner systems
• 1st adjacent channel combiner component: 50 kW fully tunable filter
• 2nd adjacent channel combiner component: High power 3 dB couplers
• Repack scenario: OK, I have a tunable 50 kW filter - who can tune it?

3. RADIO FREQUENCY SYSTEMS
RFS’ recent experience in the
Australian repack:
520 MHz 820 MHz
Before
520 MHz 694 MHz
After

4. RADIO FREQUENCY SYSTEMS
• Project timeframe: Feb. ‘13 - Sep. ’14
• Channels clustered into 5 x 6 adjacent channel blocks
• About 1300 channel changes
• MS project file contained 13,000 tasks with 100,000 dependencies!1)
Australian Frequency Repack Stats
1)Source: Broadcast Australia
1)

5. RADIO FREQUENCY SYSTEMSThe looming US repack
• Project timeframe: Mid ‘16 - End ’19 ?
• Post repack UHF TV Band 470 MHz - ~608 MHz ?
• Tunable and broadband equipment desirable to protect investment
from further changes – ATSC 3.0 ?
• Adjacent channel combining would offer the ability for everybody to
share a common antenna
The looming US repack

6. RADIO FREQUENCY SYSTEMS
• Adjacent channel combining – no problem
• High power handling capability (~250 kW)
• Relatively small footprint
• Fixed channel – not tunable
Traditional high power UHF combiner
technology
2008
RFS 10 CH ‚Superchain‘
Old and New - adjacent channel high power combiner systems

7. RADIO FREQUENCY SYSTEMS
• Combine any channels between CH 14 – CH 41
including adjacent channels
• Maximum individual channel input: 100 kW
• Maximum combined power output: 320 kW
• If channels change, simply re-tune on site!
6 CH tunable adjacent channel combiner
Fully tunable high power UHF combiner
2015
Old and New - adjacent channel high power combiner systems

8. RADIO FREQUENCY SYSTEMS
What was required to achieve this
product innovation?

9. RADIO FREQUENCY SYSTEMS
1st adjacent channel combiner component:
50 kW fully re-tunable UHF filter

10. RADIO FREQUENCY SYSTEMS50 kW Fully re-tunable UHF Filter
• 473 MHz – 635 MHz tuning range (Ch14-41)
• <0.2 dB insertion loss (>95.5% efficiency)
• Liquid cooled
• Very compact
(considering its power rating and tunability)
6PPXX325E – 50 kW re-tunable UHF TV filter

11. RADIO FREQUENCY SYSTEMS
• Input power: 50 kW
• Ambient: 77⁰ F
• Coolant temp.:131⁰ F
• Body: 138⁰ F
Thermal simulation
Liquid Cooling Ducts
Ansys thermal simulation using heat flux data from 3D EM simulation (Ansys HFSS)
50 kW Fully re-tunable UHF Filter

12. RADIO FREQUENCY SYSTEMS
Thermal verification – power test
Thermal imager picture of 50 kW filter during power test
50 kW Fully re-tunable UHF Filter
• Input power: 50 kW
• Ambient: 77⁰ F
• Coolant temp.:131⁰ F
• Body: 142⁰ F

13. RADIO FREQUENCY SYSTEMS
Low filter temperature – less filter insertion loss
50 kW Fully re-tunable UHF Filter
Copper conductivity [%] VS. temperature

14. RADIO FREQUENCY SYSTEMS
Why do we care about low average filter temperature?
50 kW Fully re-tunable UHF Filter
TX power 50 50kW
Filter loss (average over signal bandwidth) @ 68°F (20°C) 0.200 0.200dB
TX efficiency ( Pout_rf / Pin_ac ) 45 45%
Operating Life Time 20 20Years
Cost per kWh 15 15Cents
Filter operating temperature 68 176° F
Filter operational insertion loss 0.200 0.239dB
Filter efficiency 95.5 94.7%
Cost over operating life time 131.5 156.2k$
25k$ difference - an extra 0.1dB insertion loss would cost ~62k US$...

15. RADIO FREQUENCY SYSTEMS
Less filter insertion loss – higher overall TX efficiency
50 kW Fully re-tunable UHF Filter
TX overall efficiency VS. filter insertion loss
( Pout_rf / Pin_ac )

16. RADIO FREQUENCY SYSTEMS
Filter Tuning Range
50 kW filter mask response plot summary
• 473 MHz – 635 MHz (Ch14 – Ch 41)
• Constant S21 response across
tuning range
• Adjustable selectivity to meet TX
requirements
50 kW Fully re-tunable UHF Filter

17. RADIO FREQUENCY SYSTEMS
2nd adjacent channel combiner component:
High Power 3 dB Couplers

18. RADIO FREQUENCY SYSTEMS
• Frequency Range: 470 MHz – 700 MHz
• Max. Power:
 80 kW with 7-3/16” output transmission line
 125 kW with 8-3/16” output transmission line (up to 614 MHz)
• Thermal Management: Remove heat from inner conductors via
a thermal connection1)
High Power 3 dB Couplers
Coaxial high power 3 dB coupler
Coaxial 3 dB coupler
1)Patent application filed

19. RADIO FREQUENCY SYSTEMSHigh Power 3 dB Couplers
Coaxial coupler used to combine TX cabinets
Coupling Response of high power coaxial 3dB coupler High power 3dB coupler used to combine TX racks
1)
1)Source: Rohde & Schwarz
~0.35dB coupling ripple

20. RADIO FREQUENCY SYSTEMS
• Frequency Range: 470 MHz – 640 MHz
• Max Output Power: 320 kW
• Compact design due to broad side coupling
Why does a waveguide coupler handle more power?
• No inner conductor
• 65% less average current density
Waveguide high power 3 dB coupler
Waveguide 3 dB coupler
High Power 3 dB Couplers

21. RADIO FREQUENCY SYSTEMS
High Power Tunable Combiner module
• Frequency Range: 470 MHz - 640 MHz
• Max. Input Power per Channel:
 100 kW
• Max. Combined Output Power:
 320 kW
• Adjacent channel combining across the UHF band
• Smart interface to waveguide coupler1)
100 kW tunable combiner module
1)Patent application filed

22. RADIO FREQUENCY SYSTEMS
6-Channel Combiner Example
Footprint (LxWxH)
19 ft x 5.2 ft x 10.8 ft
(5.8 m x 1.6 m x 3.3 m)
Combiner
Output
CH 6
CH 5
CH 4
CH 3
CH 2
CH 1
Typical group delay about <350 nS

23. RADIO FREQUENCY SYSTEMSBroadcast Computer Aided Tuning
Repack scenario:
OK, I have a tunable 50 kW filter – who can
re-tune it? With Broadcast Computer Aided
Tuning (BCAT), (almost) anyone

24. RADIO FREQUENCY SYSTEMS
Broadcast Computer Aided Tuning
(BCAT)

25. RADIO FREQUENCY SYSTEMSBroadcast Computer Aided Tuning
• Tuning software specific to broadcast
• Factory Tuning anytime/anywhere
• Stress-free re-tuning without trial/error
• Very fast algorithm for real time feel
• Only limited experience needed
BCAT general user interface
BCAT

26. RADIO FREQUENCY SYSTEMS
S-parameters
BCAT
Tuning Actions
The BCAT tuning cycle
Visualization of
tuning errors

27. RADIO FREQUENCY SYSTEMSBroadcast Computer Aided Tuning
Filter tuning demonstration using BCAT
BCAT tuning video
Video by: Upul Bulathsinhala and Serge Piastra

28. Conclusions
• A new class of products have been developed providing both high power and
frequency agility
• Computer Aided Tuning provides the ability to retune a mask filter on the spot
• Adjacent channel combiners enhance site flexibility and efficiency by removing the
need for multiple antennas.
• For good overall transmitting efficiency filter losses and operating temperatures should
be considered
• The repack in Australia has shown that with careful planning, a repack can be
successfully accomplished in a short period of time

29. www.rfsworld.com
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Dubai
Johannesburg
Kolkata
Madrid
Monza
New Delhi
Paris
Pacy
Trignac/Lannion
Coconut Creek
Mansfield
Meriden
Naperville
San Jose
Bangkok
Beijing
Guangzhou
Hong Kong
Jakarta
Kuala Lumpur
Melbourne
Shanghai
Singapore
Taipei
Tokyo
EUROPE
NORTH
LATIN
AMERICA
NORTH
AMERICA
ASIA
PACIFIC
SOUTH EUROPE, MIDDLE
EAST, AFRICA & INDIA
Thank You for your attention!
Bogota
Buenos Aires
Mexico City
São Paulo
Copenhagen
Haddenham
Hannover
Moscow
Warwick
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© Radio Frequency Systems
2015. All rights reserved

30. RADIO FREQUENCY SYSTEMS
Backup Slides

31. RADIO FREQUENCY SYSTEMS
How does a balanced combiner work?
50 kW Fully re-tunable UHF Filter