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SPP FIELDS Preamplifier Peer Review 24OCT2013

SPP FIELDS Preamplifier Peer Review 24OCT2013. SPP FIELDS Instruments. Digital FIELDS Board (DFB) DC to 64kHz ( LF ) 20nV/√Hz noise floor, 120Vpp max signals Time Domain Sampler (TDS) 3kHz to 1MHz ( MF ) 20nV/√Hz noise floor, 20Vpp max signals Radio Frequency Spectrometer (RFS)

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SPP FIELDS Preamplifier Peer Review 24OCT2013

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  1. SPP FIELDS Preamplifier Peer Review 24OCT2013

  2. SPP FIELDS Instruments • Digital FIELDS Board (DFB) • DC to 64kHz (LF) • 20nV/√Hz noise floor, 120Vpp max signals • Time Domain Sampler (TDS) • 3kHz to 1MHz (MF) • 20nV/√Hz noise floor, 20Vpp max signals • Radio Frequency Spectrometer (RFS) • 30kHz to 20MHz (HF) • 3-4nV/√Hz noise floor, 4Vpp max signals

  3. SPP FIELDS Preamplifier

  4. SPP FIELDS Preamplifier Concept - V1-V4 V1 – V4

  5. SPP FIELDS Preamplifier Concept – V5 V5

  6. SPP FIELDS Preamplifier Requirements

  7. SPP FIELDS Preamplifier Requirements

  8. SPP FIELDS Preamplifier Environmental Radiation: 70krad total dose inside 0.1” aluminum box All parts are SQPL 100krad or better except JFET LSK389

  9. BACKUP SLIDES

  10. Original Design

  11. Testing

  12. Input Capacitance Test Measured 20pF and test box strays with meter Measured HF gain at low and high frequencies C in = (20pF/Hfgain)-20pF • Conclusions: • Find alternative clamp diodes (DPAD or 2N5547) • Consider eliminating? Evaluate risk • U404, 2N5547 Cin not much lower, have 40-60% higher noise and inadequate gain bandwidth • LSK389 HF gain = 20/(60+25+20) = 0.19 • Galaxy will = 10% increase in 3nV amp noise above 1MHz • 60pF C base mitigates effect of JFET C in • Results: • LSK389 = 50pFwith LSK389 as clamp diodes (not shown) • LSK389 = 25pFwithout clamp diodes • U404 and 2N5547 = 12-15pF

  13. Noise Test Setup

  14. HF Noise, Original Design

  15. LF Noise, Original Design

  16. Signal Evaluation Test Setup - Original Design

  17. Signal Evaluation Test Setup - Proposed Design

  18. MF Frequency Response Vs. Simulations

  19. MF Harmonics - Original Design

  20. MF Harmonics - Proposed Design

  21. MF Harmonics - Proposed Design, Improved

  22. Preamp Design To Do List • Evaluate tradeoffs in changes to mitigate harmonics • Do complete transfer function measurements with amplitude and phase • Measure thermal drifts from -80 to +80 • Choose overall values for high and low gains

  23. SPP FIELDS Preamplifier: LF Bootstrap

  24. SPP FIELDS Preamplifier: LF Biasing

  25. SPP FIELDS Preamplifier: HF antenna coupling

  26. SPP FIELDS Preamplifier - Signal Levels 0.25 AU (54 Rs): R plasma ~ 1MΩ C coupling = 20pF Gain = 0.25 @ >10kHz

  27. SPP FIELDS Preamplifier - Signal Levels 9.5 Rs: R plasma ~ 10kΩ C coupling = 20pF Gain = 0.25 @ >1MHz

  28. SPP FIELDS Preamplifier - HF Signals Assuming 20pF source capacitance 60pF input capacitance

  29. SPP FIELDS Preamplifier Requirements

  30. SPP FIELDS Preamplifier Requirements

  31. SPP FIELDS Preamplifier Requirements

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