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VLF Interferometer. Defense University Research Instrumentation Program (DURIP). Project Advisor: Umran Inan Project Team: Jeffrey Chang, Katie Braden, Timothy Chevalier, Andrew Park, Joseph Payne. What Is the Interferometer?.

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vlf interferometer

VLF Interferometer

Defense University Research Instrumentation Program (DURIP)

Project Advisor: Umran Inan

Project Team: Jeffrey Chang, Katie Braden, Timothy Chevalier, Andrew Park, Joseph Payne

what is the interferometer
What Is the Interferometer?
  • Nine element array of time synchronous receivers.
  • Capable of simultaneous recording in 3 channels, like an expensive VCR.
  • Low power, battery operated, standalone units.
  • Modular design for easy upgrade.
purpose of interferometer
Purpose of Interferometer
  • Measure near field of HAARP modulated electrojet currents.
    • Determine spatial distribution of currents.
    • Help to maximize ELF/VLF wave production.
  • Standalone receiver that can truly be deployed anywhere anytime.
interferometer v2 0
Validate Sampling method

Test Connection to CF media.

Fix any gotchas

Cleanup design

Improve Stability

Get ready for Production

Interferometer V2.0

Version 1.0

Version 2.0

interferometer capabilities
Interferometer Capabilities
  • Capture from ~100 Hz to ~10 kHz.
    • Upper bound is largely variable by changing filter and sample rate.
  • Sensitivity of 1.5*10-6 v/m-Hz-1/2 at 1khz.
  • Low power consumption, ~6W.
  • Store 1 GB of data.
block diagram of receiver
Block Diagram of Receiver


Line Receiver


Anti-aliasing LPF Filter


16-Bit A/D (250 ksps)


1GB Storage Device

CPU (i386)

Control Logic (FPGA)

UT+ Oncore GPS


Line Receiver

time synchronization
Time Synchronization

1PPS GPS Clock

Control Signals


16-Bit A/D

Temp. Controlled Crystal Osc. ~10MHz

Control Signals

Data Bus


main equipment
Main Equipment
  • Tern i386 controller.
  • IBM Microdrive.
  • Motorola Oncore UT+.
equipment cont
Equipment Cont.
  • 1 x 6V, 189 A-Hr Batteries

2 x 12V, 55 A-Hr Batteries

  • Laptop.
  • Wagon!
preamp cards
Preamp Cards
  • Matches the impedence of the square loop antenna with a transformer.
  • Amplifies and filters signal.
  • Output driver with a transformer.
  • Voltage regulation.
  • Mounts for CPU and GPS cards.
  • FPGA for glue logic.
  • ISA type slots for adapter cards.
cpu card
CPU Card
  • Manufactured by Tern.
  • I386 u-controller with lots of goodies…
  • Two serial lines, one for programming, one for LCD display and GPS.
  • 16 Bit data bus, 7 Bit Addressing (but word access only)
  • Port pins as CS for ADC or CF card.
gps card
GPS Card
  • Motorola Encore GPS card.
  • Small form factor.
  • For timing use, +/- 500ns timing accuracy.
  • Serial I/O
filter card
Filter Card
  • Instrumentation Amplifier – differential input to single ended output.
  • Selectable 8 pole or 16 pole Chebyshev filter.
  • Selectable output gain from unity to 40dB.
cf storage card
CF Storage Card
  • CF connector, capable of docking with both Type I or Type II CF cards.
  • CF cards in IDE mode.
  • Otherwise, nothing special.
  • Future version might have two flash card slots on it.
sampling card
Sampling Card
  • 3 LTC1606 ADC chips, simultaneous sampling (rated @ 250 ksps each).
  • Sampling controlled by FPGA, with CS from processor.
  • 16 bit tri-state buffers as hacked remedy to power problem
  • Temperature controlled oscillator…for accurate timing.

Near transmitter

Power lines nearby

Lake Louise & Paxton

~45 Minutes away

In the middle of no-where

No power lines nearby

Low Noise