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SP + DFB

SP + DFB. REE 12/01/ 12. DFB – Top Level Requirements. SENSOR INPUTS: 5 Electric Field Inputs:+/- 100 V 4 SCM Inputs: +/- 5 V (TBD) 2 (TBD) Witness Plate Inputs : +/- 10 V (TBD) POWER: +/- 12 V Analog (TBD); must be > +/- 8 V +/- 5 V Analog +5 V Digital (May go away.)

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SP + DFB

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  1. SP+ DFB REE 12/01/12

  2. DFB – Top Level Requirements SENSOR INPUTS: • 5 Electric Field Inputs:+/- 100 V • 4 SCM Inputs: +/- 5 V (TBD) • 2 (TBD) Witness Plate Inputs: +/- 10 V (TBD) POWER: • +/- 12 V Analog (TBD); must be > +/- 8 V • +/- 5 V Analog • +5 V Digital (May go away.) • +3.3 V Digital Regulated; • >+1.8 V Digital; (We regulate to +1.5 V)

  3. DFB – Top Level Requirements DIGITAL INPUTS/OUTPUTS: • 16 MHz Clock • Command/Data Interface: Designed after MAVEN • Time: Need time at marker • Configuration: We are considering adding an EEPROM to DFB to hold: • (a) 16 (TBD) modes • (b) Teledyne code. • Reconfiguration / Reprogramming • TBD

  4. DFB Measurement Requirements

  5. Design Options LASP is exploring three options for DFB board. The goals are to lower power and mass while maintaining science requirements: • (1) Teledyne sidecar. Four flight-qualified parts found. Cost still a problem (but not insurmountable). We expect board area <400 cm2 with power < 1.8 W. • (2) Low-power A/D qualification. This option is now a back-up to option 1. Testing is underway. Evaluation board and radiation board are finalized. If this option is exercised, we expect board area ~400 cm2(squeezed) with power < 2 W (TBD), depending on which A/D converters are qualified. • (3) Fall-back to heritage use of LTC 1604 A/D converters. Board area ~500 cm2 and power of 3 W exceed resource allocation. May need science trades.

  6. DFB Signal Processing Plan

  7. DFB Block Diagram (obsolete)

  8. DFB Signal Processing Plan

  9. DFB Signal Processing Plan

  10. DFB Signal Processing Plan

  11. Gain States We plan to include a gain 10x state for >20 RS science. • Gain = 1/8 (nominal) allows for largest signals that preamps can measure, +/- 10 V/m. Gain = 1.25 allows for DC fields +/- 1V/m. • AC-coupled electric fields high-gain state on Gac = 5 allows for +/- 250 mV/m Langmuir waves with better sensitivity at >20 RSscience. AC pole at 10 Hz. • Are gain states needed on SCM? DFB nominally includes 5-pole Bessel filters at 40% sampling rate.

  12. Filtering DFB nominally includes 5-pole Bessel filters at 40% sampling rate (40% of 128 K samples/s = 52 kHz) . With Teledyne or “chip” A/Ds, we plan to “over-sample and filter”. This plan includes 3-pole Bessel filters at 20% sampling rate (20% of 256K samples/s = 52 kHz). Native sampling rate can be moved to 256 kSamples/s. Any desire to use higher sample rates for better frequency overlap?

  13. Filtering

  14. Filter Banks DFB nominally includes filter banks on E and SCM channels.

  15. DFB – FFTs Two 1024 or FFTs at different sample rates. Frequency bins compressed to 128 bins to achieve df/f ~10%. Data compressed to 8-bit pseudo log. +/-10% with large dynamic range. X-spectral matrices can be derived. Propose to use RTAX4000. Can do N FFT’s, where N is large.

  16. DFB – Open Questions • Gain state on electric fields? We envision having a gain state changing ranges between (a) 0.3 mV/m – 10 V/m (b) 0.03 mV/m – 1 V/m. • Do we want to match SCM and E low-pass filters? • Do we want 36-element matrices (actually 19 parameters)? • Do we want V to V cross spectral analysis? • Details of filter bank design not final.

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