LORAN-C Band Data Collection Efforts at Ohio University Presented by Curtis Cutright to the...
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Transcript of LORAN-C Band Data Collection Efforts at Ohio University Presented by Curtis Cutright to the...
LORAN-C Band Data Collection Efforts at
Ohio University
Presented by Curtis Cutrightto the International LORAN
Association32nd Annual Convention and
Technical Symposium Boulder, CO
November 6, 2003
Ohio University • Avionics Engineering Center
OutlineOutline
• Task overview
• Data collection system overview
– Airborne data collection equipment
– Lab data collection equipment
– Initial data collection results
• Task progress
Ohio University • Avionics Engineering Center
TaskTask
• Field a data collection system capable of digitizing storing atmospheric noise for subsequent analysis
• Integrate this system into an airborne flight platform
• Perform data collection under varying atmospheric conditions
Ohio University • Avionics Engineering Center
PurposePurpose
• Develop threat models for aircraft in flight
• Precipitation static (p-static)
• Atmospheric noise
• Man-made noise(cross rate, CW)
• Lightning
Ohio University • Avionics Engineering Center
PurposePurpose
• Identify all trade-off’s for E and H-field antennas, SNR, phase error, saturation, bandwidth
Ohio University • Avionics Engineering Center
To be determinedTo be determined
• Is ground-based noise the same as airborne noise(E-field and H-field)
• Aircraft man-made noise
• CW interference environment
• Determine actual P-static mechanism
• Phenomena under thunderstorms
• Antenna and pre-amp performance
Ohio University • Avionics Engineering Center
Data CollectionData Collection
• Simultaneous ground and aircraft RF data collection (Using DataGrabber)
• 2 channels, 16-bits samples, 400 kSamples/s
• LORAN receivers for performance assessment
• GPS WAAS for position reference
Ohio University • Avionics Engineering Center
Data ProcessingData Processing
• P-Static
• Characterize E-field and H-field antenna performance
• Compare measured lightning noise with predicted noise based on the national lightning detection network(NLDN)
• Compare ground and airborne noise
• Compare airborne E-field and H-field noise
Data Collection SystemOverview
Ohio University • Avionics Engineering Center
Airborne Data Collection EquipmentAirborne Data Collection Equipment
• Aircraft
– King Air C-90B
– Pressurized twin turboprop
– 240 knot cruise speed
• Equipment
– Novatel OEM4 GPS receiver
– LORADD-DS DataGrabber
– WX-500 StormScope
– Apollo 618
– Data collection PC
Ohio University • Avionics Engineering Center
y
xData
Collection
Equipment
Pre-amp
Data Collection PC
WX-500 StormScope
Whip antenna
(e-field)
ADF antenna
(h-field)Stormscope
antenna
GPS antenna
Apollo 618
Ohio University • Avionics Engineering Center
Data Collection PCData Collection PC
• CyberResearch dual backplane with 933MHz P-III CPU cards
• 512MB RAM
• 160GB of hard-drive space
Ohio University • Avionics Engineering Center
WX-500 StormscopeWX-500 Stormscope
• RS-232 data output
• 200nmi range
• Heading stabilization
• Data will be used in conjunction with National Lightning Detection Network (NLDN) data
Ohio University • Avionics Engineering Center
Loran-C H-Field vs. E-Field AntennasLoran-C H-Field vs. E-Field Antennas
• Large effective height
– Little voltage amplification needed
• High impedance (M)
– Charge build-up (cannot be terminated)
• Antenna phase pattern is omnidirectional
• Whip or wire antenna
• Small effective heightLarge voltage
amplification needed (low noise pre-amp)
• Low impedance (1W)No charge build-up
(antenna is grounded)
• One loop creates 0 and 180 degrees.
• Conformal antenna
E-Field(Electric)
H-Field(Magnetic)
Ohio University • Avionics Engineering Center
Aircraft Data Collection EquipmentAircraft Data Collection Equipment
Ohio University • Avionics Engineering Center
AntennasAntennas
E-FieldII Morrow A-16
H-FieldKing Radio KA42A
Ohio University • Avionics Engineering Center
y
x
Rackmount chassis for data collection equipment
LORADD-DS DataGrabber
DC Power
Supply
AC in
GPS
H-field
E-field
GPS
antenna
LAN
Novatel GPS
Receiver
Antenna
Interface
Antenna
Interface
Ohio University • Avionics Engineering Center
LORADD-DS DataGrabberLORADD-DS DataGrabber
• Sampling rate: 400kHz
• Resolution: 16 bits
• Dynamic range: 96dB
• Two input channels – sampled simultaneously
• Differential input amplifiers for the antennas
• TCP/IP data output
• Clock stability: 1ppm
Ohio University • Avionics Engineering Center
Antenna Interface BoxesAntenna Interface Boxes
• Adjust received signal level
• Provide interference isolation for the antenna cable
• Impedance matching for the DataGrabber antenna inputs
Ohio University • Avionics Engineering Center
Novatel GPS ReceiverNovatel GPS Receiver
• 1-20 Hz position data
• Time synchronization
• RS-232 data output (ASCII or binary)
Ohio University • Avionics Engineering Center
Lab Data Collection EquipmentLab Data Collection Equipment
• LORADD-DS DataGrabber
– 400kHz sampling
– Dual channel
• Data collection PC
Ohio University • Avionics Engineering Center
AntennasAntennas
• E-field
– IIMorrow A-16 Whip antenna with integral preamplifier/impedance transformer
– Powered by an Apollo 618 LORAN receiver
Ohio University • Avionics Engineering Center
AntennasAntennas
• H-field
– King KA42A ADF Loop antenna
– Requires a separate preamplifier/impedance transformer tuned to the LORAN-C band
– Powered by 5-10VDC
Ohio University • Avionics Engineering Center
Initial Data Collection ResultsInitial Data Collection Results
• The next 2 slides show screen captures from the initial lab data collection test using both antennas
• Channel 1: h-field Channel 2: e-field
• Screen capture 1 shows the RF data from each antenna
– The presence of the LORAN signal can be seen in each channel
– E-field channel (bottom) has more amplification than h-field (this does not affect the SNR)
• Screen capture 2 shows the spectrum of the RF data
– The filter bandwidth around 100kHz is apparent
– Several CW interference sources are evident
Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Example of collected data: Time domainExample of collected data: Time domain
Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Example of collected data: SpectrumExample of collected data: Spectrum
Current Status of the Data Collection Task
Ohio University • Avionics Engineering Center
Airborne Collected DataAirborne Collected Data
• “Clear” – 10hrs
• Overcast – 4hrs
• Close t-storm (<20nmi) – 20min
• Nearby t-storm – 2hrs
• Other – 4+hrs
Ohio University • Avionics Engineering Center
Data Collection Flight TracksData Collection Flight Tracks
Ohio University • Avionics Engineering Center
Thunderstorm Data ConditionsThunderstorm Data Conditions
Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Future WorkFuture Work
• Continue data collection effort
– Varying environmental conditions
– Different locations
– Correlate National Lightning Detection Network (NLDN) data
– Mobile ground data collection equipment
• Calibrate the DataGrabber
• Aircraft noise analysis
Ohio University • Avionics Engineering Center
AcknowledgementsAcknowledgements
• Mitch Narins (FAA)
• Wouter Pelgrum (Reelektronika)
• Bryan Branham (Ohio University)
• Jay Clark (Ohio University)
Questions?