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
155 Rs
Venus
54 Rs
0.25 AU
20 Rs
9.5 Rs
Alfven
Waves
Expected
Range (mV/m)
Frequencies
0.5 mV/m
(0.01 – 10)
DC – 9 Hz
10 mV/m
(0.01 – 100)
DC – 63 Hz
150 mV/m
(0.01 – 1000)
DC – 134 Hz
1000 mV/m
(0.1 – 10000)
DC – 326 Hz
Whistler
1 mV/m
DC – 500 Hz
(0.01 – 500)
DC – 2 kHz
100 mV/m
DC – 15 kHz
500 mV/m
(0.05 – 5000)
DC – 59 kHz
Langmuir
15 mV/m
(0.01 – 150)
30 kHz
70 mV/m
100 kHz
300 mV/m
(0.03 – 3000)
300 kHz
750 kHz
Non Linear
Structures
DC – <30 kHz
DC – <100 kHz
DC – <300 kHz
DC – <750 kHz

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
SURVEY
Signals
Range
Resolution
Native Rate
(Samples/S)
TM Rate
(Nominal)
(Sample/S)
DC E Survey
E12, E34, E5X
+/-10000
mV/m
HG: +/- 1000
0.3
0.03
131,072 2
DC V Survey
V1, V2, V3, V4, (V5)
+/-100 V
0.003
16,384
Filter Banks
3E, 3B
See Below
Spectra Survey
0.5 Hz –
64 kHz
df/f ~ 10%
(128 bins) NA
1 Spectra every 8 s
Xspectra
Survey???
1 Matrix every 8 s
Dust
1 or 4
Counts in amplitude bins.

9. DFB Signal Processing Plan
BURST 1
(10%)
Signals
Range
Resolution
Native Rate
(Samples/S)
TM Rate
(Nominal)
(Sample/S)
DC E Burst 1
E12, E34, (E5A)
+/-10000
mV/m
HG: +/- 1000
0.3
0.03
131,072
128
V Burst 1
V1, V2, V3, V4, (V5)
+/-100 V
AC: +/- 10V
0.003 V V
16,384
SCM Burst 1
SCM1, SCM2, SCM3
Gain States?
65,536

10. DFB Signal Processing Plan
BURST 2
(0.01%)
Signals
Range
Resolution
Native Rate
(Samples/S)
TM Rate
(Nominal)
(Sample/S)
DC E Burst2
E12, E34, (E5A)
+/-10000
mV/m
HG: +/- 1000
0.3
0.03
131,072
V Burst2
V1, V2, V3, V4, (V5)
+/-100 V
AC: +/- 10V
0.003 V V
SCM Burst 2
SCM1, SCM2, SCM3
Gain States?
65,536

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 RS science. 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.