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


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


PurposePurpose

• Develop threat models for aircraft in flight

• Precipitation static (p-static)

• Atmospheric noise

• Man-made noise(cross rate, CW)

• Lightning


PurposePurpose

• Identify all trade-off’s for E and H-field antennas, SNR, phase error, saturation, bandwidth


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


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


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


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


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


Data Collection PCData Collection PC

• CyberResearch dual backplane with 933MHz P-III CPU cards

• 512MB RAM

• 160GB of hard-drive space


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


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)


Aircraft Data Collection EquipmentAircraft Data Collection Equipment


AntennasAntennas

E-FieldII Morrow A-16

H-FieldKing Radio KA42A


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


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


Antenna Interface BoxesAntenna Interface Boxes

• Adjust received signal level

• Provide interference isolation for the antenna cable

• Impedance matching for the DataGrabber antenna inputs


Novatel GPS ReceiverNovatel GPS Receiver

• 1-20 Hz position data

• Time synchronization

• RS-232 data output (ASCII or binary)


Lab Data Collection EquipmentLab Data Collection Equipment

• LORADD-DS DataGrabber

– 400kHz sampling

– Dual channel

• Data collection PC


AntennasAntennas

• E-field

– IIMorrow A-16 Whip antenna with integral preamplifier/impedance transformer

– Powered by an Apollo 618 LORAN receiver


AntennasAntennas

• H-field

– King KA42A ADF Loop antenna

– Requires a separate preamplifier/impedance transformer tuned to the LORAN-C band

– Powered by 5-10VDC


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



Example of collected data: Time domainExample of collected data: Time domain



Example of collected data: SpectrumExample of collected data: Spectrum

Current Status of the Data Collection Task


Airborne Collected DataAirborne Collected Data

• “Clear” – 10hrs

• Overcast – 4hrs

• Close t-storm (<20nmi) – 20min

• Nearby t-storm – 2hrs

• Other – 4+hrs


Data Collection Flight TracksData Collection Flight Tracks


Thunderstorm Data ConditionsThunderstorm Data Conditions




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


AcknowledgementsAcknowledgements

• Mitch Narins (FAA)

• Wouter Pelgrum (Reelektronika)

• Bryan Branham (Ohio University)

• Jay Clark (Ohio University)

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