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BPM Signal Processing with Log Amps

BPM Signal Processing with Log Amps. DITANET Workshop CERN 16-18 January 2012 José Luis Gonzalez – CERN/BE/BI. Outline. Introduction Logarithmic Amplifiers Basics Position Measurement Electrostatic BPM Principle Log Derivation Position Measurement with Log-Amps Shoe-box and Button BPM

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BPM Signal Processing with Log Amps

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  1. BPM Signal Processing withLog Amps DITANET Workshop CERN 16-18 January 2012 José Luis Gonzalez – CERN/BE/BI

  2. Outline • Introduction • Logarithmic Amplifiers Basics • Position Measurement • Electrostatic BPM Principle • Log Derivation • Position Measurement with Log-Amps • Shoe-box and Button BPM • Applications • Summary JL Gonzalez - CERN/BE/BI

  3. Introduction • BPM signal processing methods • Difference over Sum • Multiplexing (RF Receivers) • Normalization (Amplitude to Time Conversion) • Log processing (High Dynamic Range) • Main Applications • Orbit Measurements • Trajectory JL Gonzalez - CERN/BE/BI

  4. Logarithmic Amplifiers • What do they do? • Convert signals of high dynamic range to a substantially smaller dynamic range • The output is readily scaled to represent the decibel value of the input • This is a nonlinear conversion of the signal representation From Barrie Gilbert (Analog Devices) JL Gonzalez - CERN/BE/BI

  5. Logarithmic Amplifiers • Fundamental Function where VWis the Output voltage VX . . . . . Input voltage VY. . . . . Slope voltage VZ. . . . . Log Intercept voltage JL Gonzalez - CERN/BE/BI

  6. The Basic Logarithmic Relationship JL Gonzalez - CERN/BE/BI

  7. Logarithmic Function Approximation 4AEK 3AEK A EK 2AEK • The backbone is a chain of simple Amplifier Cells • FUNCTION is a type of PIECEWISE LINEAR APPROXIMATION JL Gonzalez - CERN/BE/BI

  8. The A/0 Amplifier (Limiter) JL Gonzalez - CERN/BE/BI

  9. Progressive Compression 4-Stage Example Vx very low (< EK) • Linear response: VW = (1+A+A2+A3+A4)VX • EK remains hidden JL Gonzalez - CERN/BE/BI

  10. Progressive Compression 4-Stage Example • For Vx = EK/A3 • Then VW = (A+1+A-1+A-2+A-3)EK JL Gonzalez - CERN/BE/BI

  11. Progressive Compression 4-Stage Example • For Vx = EK/A2 • Then VW = (2A+1+A-1+A-2)EK JL Gonzalez - CERN/BE/BI

  12. Progressive Compression 4-Stage Example • For Vx = EK • Then VW = (4A+1)EK JL Gonzalez - CERN/BE/BI

  13. Progressive Compression 4-Stage Example • For Vx > EK • Then VW = 4AEK + Vx JL Gonzalez - CERN/BE/BI

  14. Log-Amp Slope and Intercept • Slope (V/dB): • Intercept (V): Adding an offset to the output lowers the intercept JL Gonzalez - CERN/BE/BI

  15. Position Measurement Principle • Electrostatic BPM From P. Forck et al. (GSI, Darmstadt, DE) JL Gonzalez - CERN/BE/BI

  16. Position Measurement Principle • Logarithmic derivation of normalized position JL Gonzalez - CERN/BE/BI

  17. Position Measurement Principle BP Filter LogAmp A Vout ADC Diff.Amp. BP Filter B LogAmp Position = K*Vout JL Gonzalez - CERN/BE/BI

  18. Theoretical Log Response JL Gonzalez - CERN/BE/BI

  19. Log Conformance Error JL Gonzalez - CERN/BE/BI

  20. Button BPM Response a=25mm, =00, =300 B A JL Gonzalez - CERN/BE/BI

  21. Button BPM Linearity Error a=25mm, =00, =300 B A JL Gonzalez - CERN/BE/BI

  22. Commercial Log-Amp From Bergoz (sales@bergoz.com) JL Gonzalez - CERN/BE/BI

  23. CERN Transfer Lines Log-Amps AD8306 BPM Front-end From Thierry Bogey (CERN) JL Gonzalez - CERN/BE/BI

  24. Log-Amp performance AD8306 • 100 dB Dynamic Range (±3dB) : –91 to +9 dBV • Input Frequency Range: 5-400MHz • ±0.4 dB Log Linearity: -67 to +13dBm • Stable Log Scaling: 20 mV/dB Slope • Input noise: < 1.5 nV/√Hz JL Gonzalez - CERN/BE/BI

  25. Front-End Characteristics • Position and Intensity available • Large dynamic range without requiring gain switching • Two integration times are implemented (200 ns and 1 µs) • Auto-triggered • No requirement for external timing in the tunnel • Calibrator • Remotely triggered • Single or 40 MHz LHC bunch simulation • It offers 0 dB (center) and ± 5 dB ratio (slope) • Analog to digital conversion • Serial transmission of ADC data to surface buildings JL Gonzalez - CERN/BE/BI

  26. CNGS Beam Acquisition Example 10 s Batch (2.2E13 protons), 2000 bunches spaced by 5 ns Log A 2µS 2µS 2µS 2µS 2µS Pos turn 1 Pos turn 2 Pos turn 4 • Pos ≈ Log A- Log B Pos turn 3 Pos turn 5 • Integrator Out 1µS • Integrator Gate JL Gonzalez - CERN/BE/BI

  27. Dual Log-Amp Chips • Analog Devices AD8302 (Gain & Phase Det.) • Dynamic Range (60dB): -60 to 0dBm • Input Frequency Range: 0 to 2.7GHz • Scaling: 30 mV/dB • Small Signal Envelope Bandwidth: • DC to 30 MHz • Rise/Fall time (10%–90%): • 20 dB change: 60 ns • Settling time to 1%: • 60 dB change: 300 ns • Typical Nonlinearity (100MHz) • < 0.5 dB over 55 dB • < 0.2dB over 42 dB JL Gonzalez - CERN/BE/BI

  28. Dual Log-Amp Chips • Analog Devices ADL5519 (Dual Log Detector) • Dynamic Range (60dB): -55 to 5dBm • Input Frequency Range: 0.1-10GHz • Scaling: 22 mV/dB • Small Signal Envelope Bandwidth: • DC to 50 MHz • Rise/Fall time (20%–80%): • 40 dB change: 16 ns • Output noise: 10 nV/√Hz • Typical Nonlinearity • < 0.5 dB over 47 dB • < 0.2dB over 40 dB JL Gonzalez - CERN/BE/BI

  29. Dual Log-Amp Chips • Maxim MAX2016 (Dual Log Detector) • Dynamic Range (80dB): -70 to 10dBm • Input Frequency Range: 0.1-2.5GHz • Scaling: 20 mV/dB • Small Signal Envelope Bandwidth: • DC to 22 MHz • Rise/Fall time (20%–80%): • Log-output (8dB): 15ns • Diff-output (30 dB): 35 ns • Settling time to ±0.5dB: • Log-output (60dB): 100ns • Diff-output (30 dB): 300 ns JL Gonzalez - CERN/BE/BI

  30. SPS Beams • Protons (14 or 26-450GeV/c) charge dynamic range 54 dB (1e9 – 5e11) • RF swing: 199.94 or 200.26MHz  200.39MHz • Frevswing: 43.278 or 43.347kHz  43.375kHz • LHC-Ions Pb82+ (17.1-450GeV/c) charge dynamic range 46 dB (1e8 – 2e10) • RF swing: 199.93MHz  200.39MHz • Frev swing: 42.967kHz  43.375kHz JL Gonzalez - CERN/BE/BI

  31. SPS BPM Front-End JL Gonzalez - CERN/BE/BI

  32. Summary • Irradiation of a set of these components is on going to select the most robust • Front-end prototypes are under development • Log Amps are very powerful • Simple implementation • Wide dynamic range • Limitations • Don’t allow direct single bunch measurement yet JL Gonzalez - CERN/BE/BI

  33. Thanks for your attention! JL Gonzalez - CERN/BE/BI

  34. Spare slides JL Gonzalez - CERN/BE/BI

  35. Lead Ion Beam Acquisition 2 Ion Bunches (2x1.3E10 charges) spaced by 200 ns Integrator Gate • Pos ≈ Log A- Log B 200nS • Pb54 Ion Beam • Log A JL Gonzalez - CERN/BE/BI

  36. SPS Beam Position Monitors Total = 216 BPMs: 6 x 36 slots • Current MOPOS acquisition channels: 240 [6 x 40 slots] • Future needs [2-plane BPMs] ≥ 432 channels JL Gonzalez - CERN/BE/BI

  37. SPS BPM Resolution & Accuracy Resolution of the BPM system over ±15 mm aperture • Resolution for large intensity beams (>2.1010 p/b) • Orbit mode (averaging over 40 turns): 0.1 mm BPH [Na=77mm]: 0.1% BPV [Na=41.5mm]: 0.2% • Trajectory mode (single turn): 0.4 mm (should be much better in the center) BPH: 0.5% BPV: 1% • Resolution for single bunches[low/very low intensity] (LHC pilot [2.109 p], Pb ions [1…5.108 charges]) • Orbit mode (averaging over 40 turns): 0.4 mm BPH: 0.5% BPV: 1% • Trajectory mode (single turn): 1 mm BPH: 1.3% BPV: 2.4% JL Gonzalez - CERN/BE/BI

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