OPS Forum ESTRACK Transmitters 25.09.2009


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Satellite telecommunication links cover astounding distances; ESA missions need to communicate with spacecraft orbiting at distances up to 900 million kilometres away. The uplink signal must be strong enough to travel these enormous distances and still deliver data to a satellite's receiver. High Power Amplifiers (HPAs) are used at ESA ground stations to provide the requisite high power levels required for the uplink.

HPAs have certain distinctive characteristics. They are heavy (up to 1500 kg), energy intensive (up to 100 kW) and they must be handled with a lot of care - any mishandling can lead to severe damage not only to the amplifier itself but also to the station - or, in the worst case, even cause serious injuries or death station personnel.

This forum provides a short introduction to high-power amplifiers and their technology, to solid state power amplifiers, why we still use klystrons (a vacuum tube invented in the 1930s) and the usage of HPAs at ESA ground stations.

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  • To decide if keeping the mention to “hardware” or to made less strong the point keeping the mention to bulky and hot. S and X Band HPAs weight more than one ton (1000 kg) Define the acronyms HPA, SSPA and KPA
  • Definition of enough strength: The signal arrives stronger than the noise High power handled -> The HPAs of the Deep Space Stations have a power consumption around 100 kW. They are the bigger power demander of the station by far. Power dissipated -> Apart of the problem of extracting the power and avoid the amplifier burning, forces to spend money on the air conditioning and cooling systems
  • Explain that the maximum care shall be taken because an error on the design or the operation of the HPAs will lead in almost all the cases to the destruction of the unit and possibly other elements of the system. Errors have a high impact in terms of cost of the repair. An important part of the amplifier complexity is the implementation of the required protection circuits that minimise the risk of destroying the unit. Interlock RF Mute VSWR monitoring Blockage of dangerous combinations Forcing heating time in Klystrons
  • Describe the different parameters Insist on the low power received even when transmitting 20.000 Watts That explains why so much power is required and if more is available, it is always welcome.
  • Explain the main requirements on the installation of the amplifier. Very close to the feed (power conduction is waveguide, expensive and difficult to install and introduces losses) At the end of the uplink chain On the 15 meters stations the X-SSPA is mounted on the APEX cabin (just on the back of the dish) Several amplifiers may be available at the station. We can select ONLY ONE SIMULTANEOUSLY for a certain band (S or X). We can work with the optimum one for the particular application ESA stations are designed to support simultaneously one HPA transmitting on S Band and one HPA transmitting on S Band. NNO is able to transmit 20 kW in S and 20 kW in X simultaneously.
  • Different technologies Vacuum tubes (TWT, Klystron Gyrotrons) are bulky, expensive, dangerous, have limited life, … but reach power levels that solid state can not deliver Solid state: Based on transistors. Several materials and continuously innovating (SI, AsGa, SiC, GaN) and topologies of transistors (MESFET, pHEMT, LDMOS) There are may uses that require high power levels of microwaves. There is a wide market but with very different requirements depending on the application. High power for communications is a limited market with different demands that other power applications, but may benefit from advances on other power fields. The Active Denial System (ADS) is a non-lethal , directed-energy weapon developed by the U.S. military . [1] It is a strong millimetre-wave transmitter primarily used for crowd control (the "goodbye effect" [2] ).
  • 1 transistor delivers not too much power (1 to 100 Watts). The advantage of the SSPA is the much lower cost of one transistor, they are small, stable and repeatable and can be combined in parallel easily. The total output power is the sum of individual powers (minus some losses in the combination process). There is need to combine in phase. The tuning is delicate. Focus on the complexity of the power combination. We can made some parallelism with parallel processing. Show from the SSPA one of the modules explaining where is the combiner.
  • Power transistors are presently evolving and new technologies provide better performances continuously There are different materials for use on SSPA Si: the cheapest, better know but with limits on frequency 9up to 3 GHz) and power. The extension of LDMOS to L Band provided a jump on power capability. GaAs: Classic material for microwaves. Well established technology at higher frequencies than Si (up to 30 GHz). General purpose on microwaves from LNAs to SSPAs SiC and GaN: Very recent material able to deliver higher power than GaAs. Technologies not completely controlled and very expensive. The first commercial devices are already in the market. InP: Works at very high frequencies (up to 200 GHz) and with very low noise, but handles little power. The best choice for cryogenic LNAs Also different types of transistors are available: LDMOS: Recently introduced on L Band for the base stations of mobile phones. Very cheap. Used in the new S-SSPA MESFET and HEMT: classical choice for microwaves. Work at higher frequencies than standard bipolar transistors
  • Klystron are vacuum tube Expensive and bulky because they have many pieces, shall be assembled individually and are complex to assemble due to the need of being completely sealed (high vacuum inside the tube) Explain the beam velocity modulation: During half cycle the field goes against the electrons and the electrons are dragged and go slower, during the other half cycle the field goes in the direction of the electrons and the electrons are accelerated and go faster. Along the klystron, faster electrons catch slower ones and the constant beam of electrons becomes a series of bunches with the frequency of the microwave signal. The electrons are charges moving and generate a powerful electromagnetic field that is extracted at the output. Later the electrons are stopped in the collector and the remnant kinetic energy dissipated (low efficiency). The tube needs several ancillary systems Heater supply circuit Beam power supply (High voltage) Magnetic field for focusing Cooling system to extract the heat Securities and alarms Being a thermo ionic device, the life is limited to the life of the cathode.
  • The size of the tube depends on the frequency and limits the maximum power that can be dissipated specially at high frequencies. Medium size for microwave frequencies (typ 1-10 GHz). Big as a meeting table for UHF (350 MHz) Show the examples on the room and indicate that they have a permanent magnet. More powerful klystrons need a more powerful magnetic field to keep the beam focused.
  • The klystron was developed just before WW2. During the war perfectioned and was one of the keys to made a reality the RADAR. They allowed very high power at high frequencies allowing RADARS suitable for airplane detection. The concept has little evolved since the 50’s. Some minor evolutions have allowed to go to higher frequencies and obtain higher power levels, efficiency, reliability or longer life.
  • GSI in Darmstadt has bought a 2.5 MW peak (pulsed) at 350 MHz for the new accelerator they are building. Look to the dissipation -> 700 kW shall be extracted as heat!!
  • This one works at higher frequency -> The tube is smaller and the power handling is also lower
  • An exceptional outstanding tube used by JPL in Goldstone. This is not an operational transmitter (reliability not at the level required for a station), but an “experiment”
  • Explain differences between both
  • ESTRACK amplifiers have some specific requirements on top of the frequency and power. All amplifiers are CW Requirements on linearity, stability and control are very important on ESTRACK amplifiers Reliability is a key parameter to guarantee the availability of the station All these requirements limit the maximum power we can get There are other bands that will be used in the medium-long term. Transmitters will be required 22 GHz for Lunar links 40 GHz for EES uplink
  • Regulations do not allow to use commercial equipment for X and Ka Bands Agency market is too small and no interesting to manufacturers by itself alone Sometimes minor changes are required from COTS (military bands are close to X uplink)
  • Emphasis on the reduction of: Size Price Power consumption Additional functions Key: New technology available. From AsGa FETs to much more powerful Si LDMOS. Successful use of a COTS component. Additional functions added Each module delivers 4 times more power P
  • Single amplifier in all the network (no license in other stations). The replacement is under discussion (2 kW KPA or 500 W SSPA). A 2 kW SSPA would be similar in cost but is not yet developed since commercial operators do not need so high power.
  • Only other 203-S know in the world (ISRO in Bangalore) JPL uses the same klystron tube but develops and manufactures their own amplifiers Big equipment -> 4 cabinets (not possible to make a complete picture in the station)
  • CPI is a COTS, DNK7703 is a development for ESOC. DNK includes Double preamplifier ESA Basic M&C (standard M&C protocol for ESA GS) Log file for problem debugging
  • Outstanding tube Designed on the 70’s and still state of the art ETM unit design of the 80’s – 90’s RhI includes Switching 20kV, 100kW power supply Basic M&C Redundant preamplifiers sizing of the amplifier chain for worst case
  • Di cooling system transfers the heat from the HPA to the Station chiller Very important to maintain the chemical purity of the water. The collector of the tube is OFHC copper (very pure copper) for good heat conductivity and the water flows through many small ducts (in the order of the mm). Any rusting block the flow, the heat cannot be evacuated and the tube dies. Many securities and alarms.
  • Next unit in the network Phase stability is a key parameter
  • OPS Forum ESTRACK Transmitters 25.09.2009

    1. 1. Power amplifiers: The last kingdom of Vacuum Tubes Present and future of Power Amplifiers in ESTRACK
    2. 2. About …. <ul><ul><li>This is a forum about Hardware, not only hard, but also heavy, bulky and (when working) very hot! </li></ul></ul><ul><ul><li>We will talk about Transistors and also … vacuum tubes (in the XXI st century!) </li></ul></ul><ul><ul><li>No acronyms (OK, only three: HPA, SSPA and KPA) </li></ul></ul><ul><ul><li>No formulas </li></ul></ul><ul><ul><li>A lot of pictures, so … </li></ul></ul><ul><ul><li>Enjoy the show! </li></ul></ul>
    3. 3. What is a power amplifier <ul><li>Provides to the RF signal the required power level to reach the satellite with enough strength </li></ul><ul><li>Transform electrical power (from mains supply) into RF power </li></ul><ul><li>Capital performance: Efficiency </li></ul><ul><li>High power handled -> High power consumed and dissipated </li></ul><ul><li>The consumed power not transformed in RF power shall be dissipated </li></ul><ul><li>Limitations may come from maximum electrical field (peak power) or maximum thermal dissipation (average power) </li></ul>
    4. 4. What happens if we don’t take care
    5. 5. Why we need a power amplifier <ul><li>High power required to compensate path losses over 100’s million kilometres (Mars is between 50 and 400 million km) -> 270 dB of signal attenuation in the path. </li></ul><ul><li>How much power is received? </li></ul><ul><ul><li>Transmission of 20 kW </li></ul></ul><ul><ul><li>X Band (7.190 MHz) </li></ul></ul><ul><ul><li>Power focused in a narrow beam (64 dB gain of a 35m antenna) </li></ul></ul><ul><ul><li>Satellite antenna of 0.8 meters (33 dB antenna Gain) </li></ul></ul><ul><ul><li>Total power collected by the antenna: -100 dBm!! That is 0.1 pWatts </li></ul></ul><ul><ul><li>And … this is not the worst case! </li></ul></ul>
    6. 6. Where is the power amplifier <ul><li>New Norcia </li></ul>
    7. 7. Types of Power amplifiers <ul><li>HPA: High Power Amplifier </li></ul><ul><li>SSPA: Solid State Power Amplifier </li></ul><ul><li>KPA: Klystron Power Amplifier </li></ul><ul><li>Magnetrons, Travelling wave tube </li></ul><ul><li>Gyrotrons, …(2 to > 200GHz) </li></ul><ul><li>Other uses of Microwave high power amplifiers </li></ul><ul><ul><li>Radar </li></ul></ul><ul><ul><li>Nuclear magnetic resonance (NMR) </li></ul></ul><ul><ul><li>Microwave ovens </li></ul></ul><ul><ul><li>Induction furnaces </li></ul></ul><ul><ul><li>Nuclear fusion research (plasma heating) </li></ul></ul><ul><ul><li>Particle accelerators </li></ul></ul><ul><ul><li>Plasma discharge devices </li></ul></ul><ul><ul><li>Weapons (Active Denial System, ADS) </li></ul></ul>
    8. 8. Elements of a SSPA -0.5 57 Sortie RF / Output RF WR430 Info PR / R/P Info Info PS / O/P Info Test PS Output power sample Sortie analogique Analog output Détection ROS VSWR detection Combi- neur 4 voies 4 way combi-ner DNS2030 Divi- seur 4 voies 4 way divider RF switch Entrée RF RF input Télégestion RC&M Télégestion RC&M Supervision Supervision Cartes gestion / Control boards -4 -2 -2 +44 +28.5 -1 -2 -1 -5 -10 34 32 4x24 4x52.5 dB dBm DNS2030 DNS2180 G 1 dB P 1 dB Minimum Réseau / Mains 240 V 50 / 60 Hz Commu- tateur RF Diviseur 2 voies / Two ways divider DNS2180 DNS2180 DNS2180 Atténuateur variable 0-30dB Variable attenuator Limiteur Limiter
    9. 9. Elements of a KPA
    10. 10. What a SSPA looks like <ul><li>Old, Si BJT; </li></ul><ul><li>Now AsGa, LDMOS-Si </li></ul><ul><li>Coming GaN and SiC </li></ul><ul><li>Architecture: </li></ul><ul><ul><li>Driver chain </li></ul></ul><ul><ul><li>Parallel power stages </li></ul></ul><ul><ul><li>combiner (Radial, corporate, spatial combiner) </li></ul></ul>
    11. 11. SSPA technologies <ul><li>Different materials (Si, AsGa, GaN, SiC, …) </li></ul><ul><li>Different transistors (LDMOS, MESFET, HEMT, …) </li></ul>
    12. 12. How works a Klystron? <ul><li>Thermoionic device (works around an electron beam) </li></ul><ul><li>Very high voltages and strong magnetic fields involved </li></ul>
    13. 13. What a Klystron Looks Like?
    14. 14. Are the klystrons so old? <ul><li>Russell and Sigurd Varian invented the klystron in August 1937 at Stanford University, based on the velocity modulation theory from A.Arsenjewa-Heil and Oskar Heil (wife and husband) (1935) and Hansen works on electrons focusing and acceleration </li></ul>
    15. 15. Klystron limits (TH2089) <ul><li>Use in synchrotron applications </li></ul><ul><li>1.3 MW CW at 350 MHz </li></ul><ul><li>100 kV Beam voltage, 20 A </li></ul><ul><li>5 meters long, 2500 kg </li></ul>
    16. 16. Klystron limits (TH2100-TH2155) <ul><li>Use in synchrotron applications </li></ul><ul><li>45 Mw peak, 20 kW average at 3 GHz </li></ul><ul><li>300 kV Beam voltage, 340 A </li></ul><ul><li>70 kg, 1.65 meters </li></ul><ul><li>80 kg, 1.5 meters </li></ul>
    17. 17. Klystron limits (VKX7864A) <ul><li>Interplanetary Radar Applications </li></ul><ul><li>IEEE MTT Vol 48no 6 June 1992 </li></ul><ul><li>VKX 7864A </li></ul><ul><li>250 kW @ 8510 MHz </li></ul><ul><li>Collector dissipation 4.3 kW/in 2 </li></ul><ul><li>735 lb </li></ul><ul><li>51 kV beam Voltage, 11 A </li></ul><ul><li>Efficiency 45% </li></ul><ul><li>Linearity is important </li></ul>
    18. 18. SSPA vs. KPA Focus magnet Protections Heater supply Divider + Combiner Ancillary elements High (8kV … 200 kV) Low (10 … 50 V) Supply voltage Single Point Failure Graceful degradation degradation ~ 20.000 hours (Tube exhaustion) > 100.000 hours Reliability > 1 MW (L Band) ~300 W/TRT (L Band) ~ 2 KW amplifier Max. Power (L Band) ~ 100 GHz ~ 20 GHz Max. Frequency 1937 ~ 1980’s Origins KPA SSPA
    19. 19. ESTRACK Amplifiers <ul><li>S Band (2025-2120 MHz) </li></ul><ul><ul><li>S-SSPA 500 W </li></ul></ul><ul><ul><li>S-LPA 2 kW </li></ul></ul><ul><ul><li>S-HPA 20 KW </li></ul></ul><ul><li>Ka Band (34200-34700 MHz (future) </li></ul><ul><ul><li>Ka-KPA 500 W </li></ul></ul><ul><li>X Band (7145-7235 MHz) </li></ul><ul><ul><li>X-SSPA 500 W </li></ul></ul><ul><ul><li>X-LPA 2 kW </li></ul></ul><ul><ul><li>X-HPA 20 KW </li></ul></ul>
    20. 20. COTS for ESA? <ul><li>ESA employs the following bands: </li></ul><ul><li>S Band (2025-2010 MHz): </li></ul><ul><ul><li>Also used by commercial operators. Increasing restrictions </li></ul></ul><ul><ul><li>COTS available up to 500 … 2kW </li></ul></ul><ul><ul><li>20 kW only used by Agencies in Deep Space (no COTS) </li></ul></ul><ul><li>X Band (7145-7235 MHz) </li></ul><ul><ul><li>Band only for Agencies’ use (no commercial operators) </li></ul></ul><ul><ul><li>No commercial COTS in the market </li></ul></ul><ul><ul><li>20 kW only used by Agencies in Deep Space (no COTS) </li></ul></ul><ul><ul><li>Closer cots are military bands (7.9 to 8.4 GHz) </li></ul></ul><ul><li>Ka Band (34200-34700 MHz) </li></ul><ul><ul><li>Same problematic than X Band (only Agencies) </li></ul></ul><ul><ul><li>Closer cots are Ka Uplink bands (27 – 31 GHz ) </li></ul></ul><ul><ul><li>Less developed than X Band </li></ul></ul>
    21. 21. S-SSPA 500 W <ul><li>DNS 2400 </li></ul><ul><ul><li>Old unit from the 80’s </li></ul></ul><ul><ul><li>Still working in KRU, KIR, PER, VIL </li></ul></ul><ul><ul><li>Modular </li></ul></ul><ul><ul><li>Graceful degradation </li></ul></ul><ul><ul><li>redundant preamplifier </li></ul></ul><ul><li>DNS 2703 </li></ul><ul><ul><li>Installed in MSP and RED </li></ul></ul><ul><ul><li>Will be installed in NNO </li></ul></ul><ul><ul><li>Smaller </li></ul></ul><ul><ul><li>Cheaper </li></ul></ul><ul><ul><li>TCP-IP </li></ul></ul><ul><ul><li>Additional functions (O/P power TM, Log File, ALC, …) </li></ul></ul><ul><ul><li>More reliable (we expect, still not time to verify!!) </li></ul></ul>
    22. 22. S-LPA 2 kW <ul><li>Old DNK 2703 </li></ul><ul><ul><li>NNO, KRU and VIL-2 </li></ul></ul><ul><ul><li>Obsolete. No maintainable </li></ul></ul><ul><ul><li>K3S64D (Only possible COTS) </li></ul></ul>
    23. 23. S-HPA 20 KW <ul><li>Needs a DI cooling system </li></ul><ul><li>203-S from ETM in NNO </li></ul><ul><li>Single unit in the network </li></ul><ul><li>No way to transmit S band 20 kW in other station (regulatory issues) </li></ul>
    24. 24. X-SSPA 500 W <ul><li>DNS 7703/500 from SODIELEC </li></ul><ul><ul><li>Developed end of 90’s </li></ul></ul><ul><ul><li>Modular </li></ul></ul><ul><ul><li>double preamplifier </li></ul></ul><ul><ul><li>Graceful degradation </li></ul></ul>
    25. 25. X-LPA 2 kW <ul><li>DNK 7703 for NNO and DS3 </li></ul><ul><li>K3C for CPI (COTS) for CEB </li></ul><ul><li>Former RSI and Vertex units already removed </li></ul>
    26. 26. X-HPA 20 kW <ul><li>Needs a DI cooling system </li></ul><ul><li>ETM 203-X for NNO and CEB </li></ul><ul><li>RhI TRA 000AA for CEB and DS3 </li></ul>
    27. 27. De-Ionized Cooling System <ul><li>The cooling system is required to extract 90 kW of heat from a klystron smaller than a bottle of wine. </li></ul><ul><li>De-ionized and very pure water required to avoid corrosion of the copper body of the tube </li></ul>
    28. 28. Ka-KPA 500 W (future) <ul><li>Option for Cebreros and DS3 stations </li></ul><ul><li>Ka Band uplink required for RS experiments of Bepi Colombo </li></ul><ul><li>Presently still in project. </li></ul>
    29. 29. Deep Space Stations in the future <ul><li>JPL and ESA studies point to arrays as future solution to get better performances than present Deep Space Antennas </li></ul><ul><li>Arrays demand many small to medium power amplifiers -> SSPA are the natural solution </li></ul><ul><li>Expected EIRP values in excess 1 TW (120 dBW) </li></ul><ul><li>Arraying in transmission is not completely solved </li></ul><ul><li>Reliability, cost, repeatability, … Some parameters, previously secondary, now become critical </li></ul>
    30. 30. Thanks to … <ul><li>Andreas Scior </li></ul><ul><li>Giancarlo Alessi </li></ul><ul><li>And of course … </li></ul><ul><li>Thank You for your attention </li></ul>
    31. 31. … and SSA – One step beyond <ul><li>Frequency 1250 MHz (TBC) </li></ul><ul><li>Power around or over 1 MW (1 million Watts) </li></ul><ul><li>Phased array architecture: around xx modules of yy Watts each </li></ul><ul><li>Packed in an overall dimension of cccc meters per ddd meter </li></ul>
    32. 32. Klystron limits (TV2022) <ul><li>Industrial accelerators applications </li></ul><ul><li>30 Mw peak, 60 kW average at 1.3 GHz </li></ul><ul><li>240 kV Beam voltage, 200 A </li></ul><ul><li>1600 kg, 1.8 meters </li></ul>
    33. 33. Where is the power amplifier <ul><li>Kourou (15 meters) </li></ul><ul><li>(Actualizar con banda X) </li></ul><ul><li>Think if remove this slide and let only the 35 mters </li></ul>