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ANYWAVE August 2014 PRESENTATION TITLE: RF Transmitter Amplifiers - PowerPoint PPT Presentation

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ANYWAVE August 2014 PRESENTATION TITLE: RF Transmitter Amplifiers June 2014 Contents TV Transmitter Amplifier designs Performance (A discussion on SNR, EVM and MER) Distortions in TV Transmitters About Anywave Q&A Amplifier Designs

  1. ANYWAVE August 2014

  2. PRESENTATION TITLE: RF Transmitter Amplifiers June 2014

  3. Contents TV Transmitter Amplifier designs Performance (A discussion on SNR, EVM and MER) Distortions in TV Transmitters About Anywave Q&A

  4. Amplifier Designs Receiver  Tube technology was employed in first high power amplifiers .  Klystrons / Tetrodes / Diacrodes  Pulsed klystrons  MSDC klystrons LDMOS  Klystrodes which became… Transistor  Inductive Output Tubes (IOT) Klystron  Solid State  Increased in power capability IOT  Initially VHF then moved to UHF  5W (1960’s)  (LDMOS; laterally diffused metal oxide semicondutor)  250-300 W per pallet ( and up to 1kW per chassis)  One chassis can contain everything: protection, power supply and cooling  Liquid cooling typically doubles power density  New Technology… Doherty and Drain Modulation (Envelope Tracking) Tianjin Radio and Television Tower

  5. Amplifier Designs 6 Tianjin Radio and Television Tower

  6. Amplifier Designs Amplifier Digital Efficiency* Receiver 6% KLYSTRON 9% TETRODE 10% BI ‐ POLAR TRANSISTOR 22% TRADITIONAL IOT 26% LDMOS TRANSISTOR 50% MSDC INDUCTIVE OUTPUT TUBE (IOT) 36% LDMOS DOHERTY 38% ENVELOPE MODULATION 45%* ENVELOPE ‐ DOHERTY MODULATION * Estimate only

  7. Changes in Amplifier design  New amplifier types available  Dougherty modulation  Envelope modulation (Drain Modulation)  Combinations of above  Typical efficiency improvement from 25% to > 40%  Which to choose?  IOT  Traditional LDMOS  Doherty  Drain Modulation  ? Tianjin Radio and Television Tower

  8. Amplifier Designs IOT Technology Receiver  What is an IOT?  High Vacuum Electron tube  Water and Air cooled  Cathode High Voltage, ion pump, filaments and focus power supply required  Crowbar or similar protection system  Gain 20 dB  The efficiency of an IOT dramatically increased due to the introduction of the Multi-State Depressed Collector technology (taken from the MSDC klystron).  Efficiencies in ATSC increased from 20% to 50%  Still the most efficient amplifier on the market today IOT

  9. Amplifier Designs Doherty Modulation (or Doherty Power Amplifier DPA) Receiver  William Doherty - 1936  Bell Labs (Westin Electric)  Successful developments by Continental Electronics (James B. Weldon / Joseph Sainton)  50kW AM transmitters  Various version including parallel Class AB and C tubes (Continental 317C)  9 tubes versus RCA’s 32 tubes!  Follow on development by NXP (Ex-Philips)  LDMOS design using standard format two transistor pallet  Current model BLF888D – 250W output (average power – UHF)  50% Drain Efficiency (at the transistor) –  “Ultra Wide Band Doherty (NEW) Bandwidth approx. 200MHz i.e. Two types will cover the UHF Band

  10. Amplifier Designs Klystron Receiver IOT TO SCALE LDMOS Amplifier 2.5kW LDMOS Transistor 300W LDMOS Transmitter 25 ‐ 30,000 Volts 50 Volts Tianjin Radio and Television Tower 30kW

  11. Amplifier Designs Doherty Modulation (or Doherty Power Amplifier DPA) Receiver Main PA = Class A/B Carrier Amplifier Wilkinson Splitter 0 ᴼ 90 ᴼ Input Phase Shift 90 ᴼ Output Matching Section ~ 36 ‐ 40% Efficiency Peak PA = Class C (Peeking amplifier)

  12. Amplifier Designs Doherty Modulation (or Doherty Power Amplifier DPA) Receiver Class A/B Class C Efficiency 28% Efficiency 43% Temperature 75 ᴼ C Temperature 66 ᴼ C Class A/B Class A/B Average Junction Average Junction temperature 140 ᴼ C temperature 117 ᴼ C

  13. Amplifier Designs Doherty Modulation (or Doherty Power Amplifier DPA) Receiver Summary:  Average Drain Efficiency over UHF band = 42% versus 25% for standard Class AB;  Transmitter energy consumption savings  (for a 5kW transmitter, efficiency improves from 24% to 34%);  Less heat dissipated on transistors => Higher MTBF and thus higher reliability  A reduction of 20 degrees C in junction temperature represents four times more in reliability  Broadband through a new design by NXP that almost covers the entire UHF band  Extra savings due to simpler cooling system and less internal fans

  14. Amplifier Designs Envelope Modulation (Drain Modulation) Receiver Energy Dissipated Transmitted as Heat Radio Signal

  15. Amplifier Designs Envelope Modulation (Drain Modulation) Receiver V DC Class A/B Amplifier Modulator/Exciter Energy Dissipated ~ 25% Efficiency as Heat 75% Wasted energy as heat

  16. Amplifier Designs Envelope Modulation (Drain Modulation) Receiver Average Power Tracking V DC DC ‐ DC Converter Class A/B Amplifier Modulator/Exciter Energy Dissipated ~ 30% Efficiency as Heat 70% Wasted energy as heat

  17. Amplifier Designs Envelope Modulation Receiver Envelope Power Tracking V DC Envelope Detector Supply Modulator Class A/B Amplifier Modulator/Exciter Envelope doesn’t ~ 40% Efficiency track to zero 60% Wasted energy as heat

  18. Amplifier Designs Doherty Modulation (or Doherty Power Amplifier DPA) Receiver Drain Modulated Efficiency 46% Temperature 62 ᴼ C Drain Modulated Average Junction temperature 112 ᴼ C

  19. Amplifier Designs Envelope Modulation or Drain Modulation Receiver Summary:  Average Drain Efficiency over UHF band = 48% versus 30% for standard Class AB and 42% for Doherty  Transmitter energy consumption savings  (for a 5kW transmitter, efficiency improves from 24% to 38%);  Less heat dissipated on transistors => Higher MTBF and thus higher reliability  A reduction of 20 degrees C in junction temperature represents four times more in reliability  Extra savings due to simpler cooling system and less internal fans

  20. Amplifier Designs Envelope Modulation Receiver  Efficient 48%  Broadband  Complex (PSU) Doherty Modulation  Efficient 42%  Ultra Wide band transistors from NXP still drop off in power at high and low frequencies  Significant reduction in efficiency as power level moves away from maximum Warning  As transmitter power is reduced from maximum efficiency does not stay the same  It is an important factor when deciding on technology

  21. Amplifier Designs Amplifier Efficiency as a % of Maximum Power Amplifier Efficiency as a % of Maximum Power 55 50 50 48 48 47 45 45 41 39 40 38 38 38 37 37 37 CEA 35 Drain Modulation 35 33 Doherty 30 30 LDMOS 30 Convention IOT 27 25 25 25 24 25 22 22 21 20 19 20 18 16 15 15 50 60 70 80 90 100

  22. Amplifier Designs LDMOS – Performance versus Output Power reduction 57 56 55 53 51 49 47 46 43 41 40 40 39.5 39 39 38 38 38 36 32 33.5 35 30 28 27 26 26 25 25 0 2 8 16 24 32 40 48 56 65 73 81 89 97 Shoulders SNR ‐ ** Without re ‐ correction

  23. Amplifier Designs Comparison of High Efficiency (HE) transmitters versus Standard LDMOS (Fixed Drain) $25,000 POWER CONSUMPTION COST $24,000 HIGH EFFICIENCY VERSUS STANDARD LDMOS $20,000 Cost per Year ($) Cost LDMOS Cost HE $16,000 $15,000 $10,000 $5,000 $1,200 $1,000 $0 0 . 5 1 2 4 5 6 1 0 Transmitter Power (kW) ** Based On: 24 hour/365 day operation, $0.07 kW/h, 25% LDMOS Efficiency, 38 % Doherty Efficiency

  24. Amplifier Designs Comparison of High Efficiency (HE) transmitters versus Standard LDMOS (Fixed Drain) TOTAL SAVINGS Total Savings $19,140 $15,105 $11,087 $6,070 $2,052 $742 $535 ‐ $179 ‐ $293 ‐ $448 ‐ $397 ‐ $483 ‐ $586 0.5 1 2 4 5 6 10 12 15 20 25 30 40 ** Based On: 24 hour/365 day operation, $0.07 kW/h, 25% LDMOS Efficiency, 38 % Doherty Efficiency and 10% premium on capital investment

  25. Amplifier Designs Comparison of High Efficiency (HE) transmitters versus Standard LDMOS (Fixed Drain) TOTAL SAVINGS Total Savings Doherty or $19,140 Drain Modulation $15,105 Standard LDMOS $11,087 Optional $6,070 $2,052 $742 $535 ‐ $179 ‐ $293 ‐ $448 ‐ $397 ‐ $483 ‐ $586 0.5 1 2 4 5 6 10 12 15 20 25 30 40 ** Based On: 24 hour/365 day operation, $0.07 kW/h, 25% LDMOS Efficiency, 38 % Doherty Efficiency and 10% premium on capital investment

  26. Amplifier Designs So which high power device to choose  IOT’s  Still the highest efficiency… but  High Voltage  Complex  Less redundancy  Envelope Tracking or Drain Modulation  High redundancy  Higher efficiency than Doherty  Complex  Doherty  Lowest efficiency that all, but  Simpler and easier to implement  Band limited but easy enough to change if necessary  PRICE…. ALL about the same!

  27. Contents TV Transmitter Amplifier designs Performance (A discussion on SNR and MER) Distortions in TV Transmitters About Anywave Q&A

  28. SNR

  29. EVM

  30. MER

  31. SNR, MER and EVM  SNR is defined in real domain: only approximate relationship between MER, SNR and EVM can be obtained. MER and EVM differ from each other, only by the reference value  EVM (dB) = MER (dB) + 3.679 dB  SNR = 39.3 – 20 * log10 (EVM%) dB Tianjin Radio and Television Tower

  32. Constellation and Eye Diagrams  The “Eye Diagram” Measurement  The “Constellation” Measurement  8 Cross over points (8VSB)  8 Vertical Lines (virtual)  The bigger the “eyes” the better the  Thinner the vertical line, better the signal. signal Tianjin Radio and Television Tower

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