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SCPNT Symposium
November 7, 2007
Systems Technology for Remote
Sensing of Near-Earth Space
Umran S InanProfessor of Electrical Engineering
Director, Space, Telecommunications and Radioscience (STAR)
Laboratory
Electrical Engineering Department
Stanford University, Stanford, California 94305
http://www-star.stanford.edu/~vlf/
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Very Low Frequency (VLF) Group
Largest group within Space, Telecommunications &
Radioscience (STAR) Lab, one of five EE Labs
VLF Group Personnel
3 Senior Research Associates, 3 Research Associates
Several active Emeriti & Consulting Professors
1 to 2 full-time engineers, 1 Data Aide
Currently 26 MS/PhD Students, graduated 27 PhDs since 1990
Experimental & theoretical research on waves & energetic
particles in near-Earth space, ionosphere, radiation belts, very
low frequency remote sensing, lightning discharges & high
altitude effects, such as sprites, elves Design & construction of sensitive receivers and autonomous
systems, deployed worldwide
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Electromagnetic Waves in
Near-Earth Space
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Electromagnetic Waves in
Near-Earth Space
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Electromagnetic Emissions in
Near-Earth Space
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Stanford at Palmer & South Pole
Stations, Antarctica
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Lightning-generated
Whistlers
Very Low Frequency (VLF)waves launched by lightningpropagate in the Earth-ionospherewaveguide (v p=c )
Wave energy also couplesupward to the radiationbelts, propagating along
filamentary “ducts” of enhanced ionization
The magnetospheric plasmais a dispersive slow wavemedium (v p=0.01 c )
Signal arriving at theconjugate region sounds like
a “whistler”
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Lightning-induced Electron
Precipitation (LEP) on DEMETER
LEP bursts on DEMETER.(top to bottom) (left)Broadband VLF data and(right) narrowband VLF datafrom ground stationsshowing sferics caused bylightning strokes;
Spectrograms of electricfield from ICE onDEMETER showing 0+whistlers from the samelightning strokes;
Electron spectra from IDPon DEMETER showing bursts of precipitated
electrons; integral flux (99.6to 304.3 keV).
The map shows thetrajectories of DEMETER satellite; blue and greenrespectively for the cases onthe left and right.
GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L07103, doi:10.1029/2006GL029238, 2007
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Lightning-induced Electron
Precipitation (LEP)
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Subionospheric VLF Remote
Sensing
Many VLF
transmitters operate
worldwide, providing
a range of coherentlaser-like signals
with which to probe
the ionospheric
regions through
which they
propagate
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Measurement: Simple Receivers
Allow Continuous Monitoring
VLF receivers at 13 high schools
Provides excellent opportunities for outreach
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Non-ducted LEP Events
(a)
(b)
(c)
(d)
In general whistler
waves propagate in
non-ducted mode,
illuminating large
regions of the
radiation
In each event, onsetdelay ( t)an onset
duration (t d) are
measurable,corresponding to
wave/particle travel
times and duration
of LEP pulse
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Subionospheric VLF Signatures
of LEP Events: Spatial Extent
Dashed line VLF paths perturbed;solid line ones are not; theoretical
precipitation region superposed
VLF Amplitude Data for 24 March 2001
Full extent of the ionospheric
disturbance produced by an LEP burst
(due to a single flash) is captured
Corresponding region of the inner
radiation belt is affected by whistler
waves from a single lightning flash
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Theoretical Modeling
Peter and Inan [2006]
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Stanford VLF Receivers(sun never sets on Stanford VLF )
Transmitter at Pole(7-km antenna)
Palmer Station
Antarctica
Line Receiver
Preamp
Antenna
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IHY/UNBSS Program
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Antarctic Unmanned Receivers
Single-chip LNA
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ELF/VLF Applications with HAARP
100 km
ELF / VLFRadio Waves
60 km
Detect Submarine
Comm Submarine Imaging Buried TargetsComm Buried Receiver
Control of Charged ParticleEffects on Satellite Operations
HAARP HFTransmitter
ELF / VLFRadio Waves
ELF / VLFRadio Waves
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High-Frequency Active Auroral
Research Program (HAARP)
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HAARP VLF Signals at Chistochina,Alaska (~30 km from HAARP)
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Natural and HAARP-
injected ELF/VLF Signals
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Whistlers, Auroral Hiss and
HAARP ELF/VLF Signals
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Very Strong HAARP
ELF/VLF Signals
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Amplified Signals and TriggeredEmissions on Tangaroa & Alaska
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Multiple Traverses
Between Hemispheres
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ELF/VLF Wave-InjectionExperiments with HAARP
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Quickly Developing Storm Systems
Feet
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Stanford VLF Buoy in NewZealand: Integration & Launch
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HAARP VLF Buoy in
Construction
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Buoy Electronics Integration
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Stanford VLF Buoy at Sea
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Stanford VLF Buoy at Sea andback in New Zealand
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Photos
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Photos
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Systems Overview
ChargeController
Solar Panels
Batteries
Electronics Package
Preamp
Loop Antennas
IRIDIUMs
Antennas
ARGOS
GPS
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Main Electronics
IRIDIUM
Interface
VLF Filter
Power
Filtering/Housekeeping
IRIDIUMInterface
Main
Atmel
GPS
IRIDIUM Atmel
IRIDIUM Atmel
DSP
ADC
Data Bus
Main Power Bus
IRIDIUM Serial Data
GPS Serial Data
IRIDIUM Power
VLF Filter Power
CF
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Motherboard, DSP. ADC, CF &
Iridium Interfaces
Motherboard
• ATMega128 Main Controller
• 100Mhz Bus interface for all subsystems
• 100khz Sample Clock Generation
• ATMega128 Iridium controllers
DSP TI TMS320C6711 DSP
• 150 MHz, 100MHz bus
• Floating point capabilities
• 64MB Ram
• Onboard FPGA
ADC
• 3 Channels
• 16 Bit ADC, up to 200Khz sampling
• 512 deep 18bit FIFO buffers
• CPLD
• Bus interface controller
• ADC Controller
CF Interface
• Direct interface to Compact Flash –
full throughput• Stackable design
• Max 15 per memory space
• Subject to bus signal integrity
Iridium Interface
• Iridium Modem brick interface
• Rx/Tx Indicators
• Optically isolated from main system
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GPS, Line Receiver,
Housekeeping/power, & AAF
GPS• Low Power Motorola
• Battery Backup
• 1PPS Generation
Line Receiver
• Three differential channel
• Selective Gain (0,2,5,10,20dB)
• 8th Order Min-Q Elliptic Filter
Housekeeping/Power
• Switching 5V, 12V regulators
• Housekeeping filter and ADC
• Reset Circuitry
• Modem Power Controls
• Power Indicators
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Buoy 1.5 Hardware Stack
Pic needed
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Buoy 1.5 Hardware Stack
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Stack In Mumetal Can
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Charger Section
Solar
PanelSwitch
Charge
Control
Battery Battery
Battery Battery
External Power
14.45VSystem
x4Battery
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Buoy 1.5 Power Box
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Iridium Enhancements
Performed a study in May 2005 on colocated Iridium terminals
Interference and blanking detected at 3’ separation
Rooftop antenna array created to minimize interference and maximize horizon
exposure
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Roof Testing
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Roof Testing
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HAARP VLF Buoy 2.0
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Stanford Buoys Launched
from the Tangaroa
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Deployment of Buoy
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Amplified ELF Signals on the
HAARP Stanford Buoy
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15 dB/s Amplification & Triggered
Emissions
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Transmitter-Induced Precipitationof Electron Radiation (TIPER)
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VLF Receiver at Kwajalein Atoll
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VLF Receiver at Waimea High
School, Kauai
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Stanford System at Midway Atoll
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Tern Island Autonomous System
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VLF Data from Tern Island
F r e q u e n c y ( k
H z )
10
20
30
40
Time (sec)1 2 3 4
VLF Transmitters
Radio Impulses
from Lightning
Unprecedented low
levels of ‘hum’
40
60
80
d B
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Transmitter-Induced Precipitationof Electron Radiation (TIPER)
Use subionospheric VLF
method (used for
detection of lightning
induced precipitation) to
observe transmitter
induced precipitation
D Layer
Ionosphere
Precipitating charged particles
modify ionosphere electron density
Diagnostic VLF
Transmitters
Diagnostic VLF
Receivers
Precipitation
Magnetic field lineEscaped VLF
waves from
lightning strikes
or powerful VLF
transmitter
e- e- e-
Signal Perturbation V L F a m p l i t u d e
Time
Powerful
VLF Xmtr
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Subionospheric VLF Detection of NPM-induced Precipitation
TIPER M ith Th ti ll
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TIPER Map with Theoretically
Determined Precipitation Region
Figure 1 of Inan et al. [2006] (in review at GRL)
Ob ti f NPM i d d
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Observations of NPM-induced
Precipitation on NLK & NLM
Figure 2 of Inan et al. [2006] (in review at GRL)
NPM i d d P i it ti
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NPM-induced Precipitation:
Model & Data Comparison
Figure 4 of Inan et al. [2006] (in review at GRL)
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Mission Payload: Particle Detector
Energetic Electron Detector Pattern after successful
DEMETER mission
French sat
High geometric factor
High-time resolution
1.2 cm2.ster Maximum
geometrical
factor
0.07-0.7(2.5) MeV
256 channels
Energy range
895 mWPower
525 gMass
6 mFoil for p+ andh rejection
2 mm AlExternal
shielding
Implanted SiS = 490 mm2 ( 25 mm)
Detector
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NPM-induced ElectronPrecipitation on DEMETER
NPM
NWC i d d P i it ti
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NWC-induced Precipitation on
DEMETER [from Sauvaud et al .]
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TIPER Optical Measurements
Current Plan for NWC
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Current Plan for NWC
Keying Experiments
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Wave-Particle Interactions &Radiation Belts
Wave
Generation
Wave
Propagation
Wave-Particle
Interaction
O Hi h Altit d N l D t ti
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High-altitude nuclear tests of 1958 and 1962 demonstrated wide-areaeffects with significant military impacts for numerous systems.
Radars: Blackout, absorption, noise, clutter, scintillation
Communications: Blackout, scintillation fading, noise, connectivity
Optical Sensors: IR, Visible, UV backgrounds, clutter; noise
Satellites: Trapped radiation; radiation damage to electronics
Electronics & Power: Electromagnetic pulse; electrical systems damage
STARFISH
1.4 MT at 400 km
ORANGE
3.8 MT at 43 km
KINGFISH
__ MT at __ km
TEAK
3.8 MT at 76.8 km
CHECKMATE
__ MT at __ km
One High Altitude Nuclear Detonation
Impacts Multiple Systems
From Defense Threat Reduction Agency/Mission Research Corp briefing, 15 Jan 2003
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How Could It Happen?
Collateral damage from regional nuclear war or TMD/NMD intercept:
Nuclear warning shot in a regional conflict;
Effort to damage adversary forces/infrastructure with
electromagnetic pulse;
Detonation of salvage-fused warhead upon
exoatmospheric intercept attempt.
Deliberate effort to cause economic damage with
lower likelihood of nuclear retaliation:
By rogue state facing economic strangulation or
imminent military defeat;
Pose economic threat to the industrial world withoutcausing human casualties or visible damage to economic
infrastructure.
Senior Pakistani officials have said that
Pakistan's nuclear warheads have
undergone shock and vibration tests and
are ready to be mounted on the country's
Ghauri, or Hatf V, intermediate-range
ballistic missile.
JANE'S DEFENCE WEEKLY
- 3rd JUNE 1998
R di ti B lt R di ti
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Radiation Belt RemediationWhat is the problem?
Remediation can: Accelerate the natural decay of trapped
particles in narrow HAND region
Save critical LEO space missions
Enable environment for replenishment within
30 days
HAND Belt
50 kT, 31.3 deg, 75.2 deg, 200km
Nuclear vs Natural Environment (~800km Polar Orbit)
1E+0
1E+1
1E+2
1E+3
1E+4
1E+5
1E+6
1 14 30 365Days
D o s e ( R a d s S i )
Nuclear
Natural
High Altitude Nuclear Detonation produces huge increase in radiation for satellites – all LEO s/c fail within months
0.1 1.0 10
40
30
20
10
Months After Burst
30 Krad (Si)
Bay of Bengal50 kT burst
At 250 km100 mil Al
N u m b e r
o f A s s e t s
R e m
a i n i n g
1.5 MeVElectron Flux
Defense Threat Reduction
Agency
Radiation Belt Remediation
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FOUOTenfold increase in particle removal rate requires ~ 17kW => a few
satellites!
ELF/VLF Waves Control Particle Lifetimes
L shell = distance/RE
Radiation Belt RemediationParticle Dynamics
Particles mirroring below100 km are “lost”
Electromagnetic
wave
Pitch-angle
To remove particles the magnitude of the velocity need not be changed - just the
angle between the velocity and magnetic field!
Radiation Belt Remediation
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Radiation Belt RemediationKey Processes
VLF wave
generation
Wave propagation
Wave-particle
interaction
Wave-particle scattering
• Are interactions diffusive or coherent?
• Can tailored wave forms improve efficiency?
Global wave propagation and amplification
• Where does wave power go in the far field?
• Can waves be amplified through plasma
processes?
ELF-VLF wave injection efficiency
• Can ground-based antennas radiate VLF
efficiently through the ionosphere?
• Can space-based antennas radiate VLF into the
far-field at high power levels?
Scientific
UnderstandingIonosphere
Outer-zone electrons
HAND belt electrons
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DSX / WIPER Spacecraft Mission
WIPER: Wave-Induced Precipitation of Electron Radiation
i) Characterize naturally occurring VLF signalsa. In the inner radiation belt
b. Slot region
c. Inner edge of the outer belt.
iii) Quantify pitch angle scattering a. Energetic electrons by
whistler-mode waves
b. Naturally occurring
or injected.
ii) In-situ injection of VLF waves a. Efficiency in injection
b. Propagation characteristics
c. Effect on energetic particles
Active and Passive Observation Objectives
DSX Spacecraft
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WIPER Block Diagram
LVDS
Receiver sensitivity vs frequency
IMAGE Spacecraft Instrument Deck
RPI
TATU
TATU
TATU
TATU
TCU
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WIPER Block Diagram
LVDS
Anti-aliasing filter
Low-noise amplifier
Op-amps
Capacitors
Transconductor
Test Circuitry Functional Circuitry
S t a g e
0
S t a g e 1
S t a g e 2
S t a g e 3
S t a g e 4(a)
(b)
PARX ADC Die Layout
Low Noise Amplifier
Silicon Germanium 0.25 m BiCMOS
Flat gain over 5 decades in frequency
Negligible flicker noise <100 Hz
>100 dB SFDR
Responds to Tens of nV (NF 2-5 dB)
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15 cm
20 cm
R e c e i v e r S l i c e s
P o w e r a n d
C o m m B o a r d
15 cm
P r e a m p
BBR Physical Dimensions
Components 5 receiver boards
Y Antenna (Electric FieldDipole)
Z Antenna (Electric FieldDipole)
Bx (Searchcoil)
By (Searchcoil)
Bz (Searchcoil)
1 preamp board
Z Antenna
1 combination power board and
communications board DC to DC converters,
RS422, and LVDS links.
BBR Commanded bySoftware Receiver (SRX)code running in theExperiment Control
System (ECS) as an
Physical Integration of BBR into
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Physical Integration of BBR into
DSX
TASC
WIPER
TCU
VLF BBR
RECEIVER
2X TATU
X: 517 mm
Y: 133 mm
Z: 288 mm
X: 204mm
Y: 206mm
Z: 295mm
X: 300 mm
Y: 300 mm
Z: 300 mm
X: 200mm
Y: 150mm
Z: 150mm
CAD model courtesy Microsat Systems
TASC
WIPER
TCU
VLF BBR
RECEIVER
2X TATU
X: 517 mm
Y: 133 mm
Z: 288 mm
X: 204mm
Y: 206mm
Z: 295mm
X: 300 mm
Y: 300 mm
Z: 300 mm
X: 200mm
Y: 150mm
Z: 150mm
TASC
WIPER
TCU
VLF BBR
RECEIVER
2X TATU
X: 517 mm
Y: 133 mm
Z: 288 mm
X: 204mm
Y: 206mm
Z: 295mm
X: 300 mm
Y: 300 mm
Z: 300 mm
X: 200mm
Y: 150mm
Z: 150mm
CAD model courtesy Microsat Systems
Main BBR Functional
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Main BBR Functional
Requirements
BBR shall measure the electric fieldfrom 100 Hz to 50 kHz and at highsensitivity (~1×10-16 (V/m)2 /Hz) with 16-bits of quantization
BBR shall measure the magnetic fieldfrom 100 Hz to 50 kHz and at highsensitivity (~1×-11 nT2 /Hz) with 16-bitsof quantization
BBR shall have a minimum SpuriousFree Dynamic Range of 100dB for allchannels Measured at 1.0 kHz for the Electric Field
channels
Measured at 7.0 kHz for the Magnetic Fieldchannels
BBR SFDR Measurement (Using
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BBR SFDR Measurement (Using
DS360)
Receiver Response Preamp Response
Fundamental Tone Scaled to 0 dB
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System Architecture
Electricdipole
antenna
AAF FPGA
To On-board
Computer or
TelemetryLNA
Preamplifier ASIC
ADC
ADC ASIC
LNA Key Specifications
Adjustable Gain
Bandwidth
Input-referred Noise
Input ImpedanceSFDR
Power
0-20 dB
100 Hz - 1 MHz
10 nV/m/Hz1/2
1 Gohm || 100 fF100 dB
5 mW
ADC Key Specifications
ResolutionSampling Rate
SFDR
Power
13 bits5 MS/s
100 dB
75 mW
AAF Key Specifications
Architecture
Adjustable 3-dB Bandwidth
Stopband Attenuation
SFDR
Power
6th-order Chebyshev (Type I)
30 kHz, 180 kHz, 1080 kHz
-80 dB (3*f c), -96dB (4*f c)
100 dB
70 mW
Fig. 1 Plasma wave receiver block diagram.
LNA M d R l
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LNA Measured Results
Feedback is well-suited to this application
Linearity Feedback increases linear operating range Reducing gain is worthwhile trade-off Fidelity by reducing sensitivity to active devices
Programmable Gain
Feedback trades gain for bandwidth
Reduce low-frequency closed-loop gain is tolerable
Passive feedback allows gain programming without
power penaltyRadiation Tolerance
Feedback reduces gain sensitivity & improves hardness
Use of multiple series-series feedback loops
Prototype LNA performance
Flat passband gain over many gain settings in 3dB steps
Negligible flicker noise under 100 Hz
Further characterizations (SFDR) underway
LNA chip.
Fig. 3 Measured gain (upper) and input-referred noise power
spectral density (lower) for LNA.
Total Integrated Dose (TID) Test
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Total Integrated Dose (TID) Test
Results
Gain vs Dose No change < 100kHz
Measurement noise
At 2000krad -1dB at 1MHz
f -3dB drops by 22%
LNA irradiation biasing
Maximum gain setting (20dB)
Powered (all biasing nominal)
Power vs Dose Decreases with dose
Occurs by design
Conservative pMOSbiasing scheme
At 2000krad
Pmax drops by 7.1%
Irradiation in Co-60 chamber
High dose rate: 75rad(SiGe)/s
Log steps (1/2/5) up to 2000krad
Fig. 6 Bode response (upper) and power dissipation (lower) versus dose
Single-Event Effects (SEE) Test
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Single Event Effects (SEE) Test
Results
Illumination with mode-locked dye laser
Stimulates charge-pair production in substrate
Pico-second pulse width (tw); Variable intensity (Io)
Variable spot sizes ( o) on the order of 2-10 m2
Latch-up immunity
Scan entire die (I/O & core)
No latch-up detected over range of beam Io and o
Single-event transients
No supply glitches detected No saturation or oscillation
Signal transient ‘hot-spots’
< 2 s avg. recovery time
Measured Vdd , Out+, and Out- laser-induced SEE transients
Sample laser spot cross-section
Negative
output
Scaled
version of
supply
Positive
output
D i T h i ADC
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Design Techniques: ADC
Design PARXADC is a digitally calibrated, pipelined analog-to-digital converter for
capturing plasma wave signals in satellite applications. It leverages thespectrographic nature of such analysis to deliver high fidelity at low power.
Key Specifications Effective Number of Bits 13
Spurious-Free Dynamic Range 100 dB Averaging of circuit and quantization noise over FFT bins allows reduction of
number of bits and hence the power dissipation. Number of bits chosen tomaintain 100dB SFDR, assuming a 20000 point FFT (4ms at 5MS/s).
Nyquist/Sampling Rate 5 MS/s Input signal bandwidth of 100 Hz – 1 MHz. Converter samples faster than Nyquist
to accommodate analog anti-aliasing filter transition bandwidth.
Power Dissipation (analog portion) < 60 mW Power Supply Voltage 2.5V
Maximum Input Signal ±1.0V fully differential
Radiation Tolerance > 100krad total dose
ADC I l t ti
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ADC Implementation
Converter composed of twoparts: the PARXADC integratedcircuit and an Actel A54SX32AFPGA Actel FPGA houses calibration
engine, performs reconstruction, anddefines output interface
Calibration Calibration corrects DAC errors in
pipeline converter, linearizing theconversion
Feedforward (inherently stable) andfully digital (no analog trimmingfeedback loops)
Re-calibration can be initiated at anytime
May compensate for radiation induced
circuit degradation
Integrated Circuit Design Incorporates radiation hardness of
design techniques Enclosed layout transistor switches,
latchup prevention layout methods
Actel
A54SX32A
FPGA
R E C O N S T R U C T I O N
A L G O R I T H M
C A L I B R A T I O N
E N G I N E
OUTPUT
DRIVER
STAGE 7
STAGE 6
STAGE 5
STAGE 4
STAGE 3
STAGE 2
STAGE 1
TRACK AND
HOLD
CLOCK
VREFP
VREFN
ANALOGINPUT
PARXADC
Integrated Circuit
OD
RESET
PRESET
DOUT[15:0]
CALIB
DAV
calibrationcoefficients
Fig. 1. Functional diagram of PARXADC converter implementation.
ADC St t
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ADC Status
First version tested Complete system, composed of
PARXADC silicon and Actel FPGA,operates at 2MS/s.
Performance characterization isunderway.
Second version fabricated
Returned mid-2005 Expanded calibration
Corrects gain error as well as DACerrors.
Additional breakout sections for radiation characterization of constituent functional blocks.
Radiation Tests underway
Fig. 2. Reconstructed output from PARXADC converter functioning on PARXADC (version 1) Test Board in time and
frequency domains (under 1024-pt FFT). Actel FPGA running
UINT code (Rev.04) performs reconstruction; output is shown
after calibration. Data is captured directly by logic analyzer.
Converter operating at 2MS/s with 50kHz, 500mV amplitude
input sinusoid transformer coupled.
ADC Di L t PARXADCV2
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ADC Die Layout, PARXADCV2
Fig. 3. PARXADCV2 (PARXADC, version 2) die layout. Taped out July 2005. Total silicon dimensions 3.5mm by 3.5mm.
operational
amplifier analog
biasing breakout
for radiation
testing
operational
amplifier (from
track and holdstage) breakout
for radiation
testing
8-level flash
(from stages #1,
2, and 3) breakout for
radiation testingselect enclosed
terminal device
breakouts for
radiation testing
6-stage pipelined
analog-to-digital
converter with
dedicated track
and hold stage
N S f d C SCPNT
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New Stanford Center: SCPNT
Stanford Center for Position Navigation and Time(SCPNT) http://scpnt.stanford.edu/
Formed by faculty from EE, AA, Physics Per Enge (AA), Director
U. Inan (EE) and M. Kasevich (Phys), Vice-Directors
Centimeter accuracy anywhere, anytime
Research includes new signals (e.g., GPS, Galileo),integrated sensors, inertial & atomic clock technologies,directional antennas & signal processing, atmospheric &orbital science
Funded by industry & government Provides basis for new faculty appointments
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The End
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