RFS Advanced Passive Components for UHF Broadcast Spectrum Reallocation
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
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
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
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
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