Manish Lad Frank van Graas, Ph.D. David Diggle, Ph.D. Curtis Cutright
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Transcript of Manish Lad Frank van Graas, Ph.D. David Diggle, Ph.D. Curtis Cutright
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Characterization of Atmospheric Noise in the Loran-C Band
Presented to the International Loran Association (ILA-32) November 6, 2003 Boulder, CO
Manish Lad
Frank van Graas, Ph.D.
David Diggle, Ph.D.
Curtis Cutright
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Outline
• Data Processing Overview
• Flight Test Results “Quiet (normal conditions)” data
collected in Ohio“Thunderstorm” data collected in Florida
• Conclusions
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Flight Data Collection Equipment
• King Air C-90 B Aircraft
• LORADD-DS DataGrabber
• Novatel OEM4 GPS receiver
• WX-500 StormScope
• Apollo 618 (Loran receiver)
• Data collection PCKing Air C-90B
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Wire vs. Loop Antenna Gain
• Theoretically, the dual-loop antenna has a 3-dB gain advantage over the wire antenna
• Exact gain difference depends on the antenna installation
Gain = 0 dB Gain = 3 dB
Note: SNR results are determined at the output of the antenna.
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Processing Collected Data
• Read Loran-C data• Identify and remove CW interference• Remove Thunderstorm bursts• Read GPS data• Identify and remove Loran-C chains• Calculate signal-to-noise ratio• Characterize atmospheric noise
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Loran-C Data Processing Overview
Noise distribution
Collected data Find filter coefficients
Bandstop filters
GPS Time, Position
Noise Sequence
Track transmitters
Signal power
Remove pulses that
are above noise floor
Noise power
Calculate SNR
Loran Processor
Noise Characterization
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Removal of CW and Thunderstorm Bursts
Detect
CW
2-sec data block
Filter the CW from 2 second
data block
Bank of band-pass filters
2ix
2ix
1-500 Hz
501-1000 Hz
2ix
2ix
1001-1500 Hz
199.5-200KHz
Calculate bandstop filter
coefficients
Sampled data at
400 kSamples/sec
Calculate Energy in bins
Remove bins with Energy above a
set threshold
Integrate PCI’s for identifying different
chains
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Loran processor
Compute average noise power obtained after removal of pulses
Integrate signal as per PCI of chain
Identify Master and secondaries
Remove Loran-C pulses that are above noise floor
Compute signal power for each station
Calculate SNR for master and secondaries
Chain information
Antenna position
Calculate the noise distribution
Signal after removal of CWs and Thunderstorm Bursts (if present)
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Flight Test Data
• Results obtained for different data sets under diverse atmospheric conditions (clear and Thunderstorm)
• Data collected in Ohio: NEUS chain • Data collected in Florida: SEUS chain
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Flight Test Results
Normal conditions
Athens, Ohio
Collected on August 13, 2003
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Ground Path (Athens, Ohio)
Flight test trajectory near Athens, Ohio
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E–field Data Example: Time Domain
Note: Signal Amplitude is in A/D levels
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E–field Data Example (Cont’d)Before and after processing the 2-second data chunk
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E-field Noise Statistics (Athens, Ohio)
Noise Distribution
Number of samples
1010 to
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E-field Noise Statistics (Cont’d)
Calculated and Gaussian cdf
cdf
Cumulative probability
(1-cdf)
100 to010 to
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H–field Data Example (Athens, Ohio)
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H–field Data Example (Cont’d)Before and After Processing the 2-second data chunk
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H-field Noise Statistics (Athens, Ohio)
Noise Distribution
1010 to
Number of samples
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H-field Noise Statistics (Cont’d)
Calculated and Gaussian cdf
100 to010 to
(1-cdf)cdf
Cumulative probability
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Results (Athens, Ohio)
AntennaSNR M (avg)
Seneca, NY
SNR Z (avg)
Dana , IN
Wire
(E-field)10.5 13.3
Loop
(H-field)12.4 13.2
SNR measurements (average of 326 seconds) at the output of the antenna for NEUS chain
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Flight Test Results
Daytona Beach, Florida
Collected in the Vicinity of Thunderstorms on August 14, 2003
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Ground Path (Daytona Beach, FL)
Flight test trajectory near Daytona
Beach, FL
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E-field Data Example (Daytona Beach, FL)
Note: Dynamic range of data collection equipment is 96 dB (16 bits)
Signal Amplitude
Number of samples (2 seconds of data)
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E-field Data Example (Cont’d)Before and After Processing the 2-second data chunk
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Number of samples (2 seconds of data)
Signal Amplitude
E-field Data Example (Cont’d)
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Before and After Processing the 2-second data chunk
E-field Data Example (Cont’d)
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E-field Data Example (Cont’d)
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E–field Noise Statistics (Daytona Beach, FL)
Noise Distribution
1010 to
Number of samples
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E–field Noise Statistics (Cont’d)Calculated and Gaussian cdf
100 to010 to
(1-cdf)cdf
Cumulative probability
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H–field Noise Statistics (Daytona Beach, FL)
Noise Distribution
1010 to
Number of samples
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H–field Noise Statistics (Cont’d)Calculated and Gaussian cdf
100 to010 to
(1-cdf)cdf
Cumulative probability
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Results (Daytona Beach, FL)
Antenna SNR M (avg)
Malone, FL
SNR Y (avg)
Jupiter, FL
Wire
(E-field) 7.7 8.7
Loop
(H-field) 9.2 12.5
SNR (average of 326 seconds) measurements at the output of the antenna for SEUS chain
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Flight Test Results
Palm Coast, Florida
Collected in the Vicinity of Thunderstorms on August 14, 2003
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Ground Path (Palm Coast, FL)
Flight test trajectory near Palm coast, FL
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E–field Noise Statistics (Palm Coast, FL)
Noise Distribution
1010 to
Number of samples
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E–field Noise Statistics (Palm Coast, FL)
Calculated and Gaussian cdf
100 to010 to
(1-cdf)cdf
Cumulative probability
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H–field Noise Statistics (Palm Coast, FL)
Noise Distribution
1010 to
Number of samples
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H–field Noise Statistics (Palm Coast, FL)
Calculated and Gaussian cdf
100 to010 to
(1-cdf)cdf
Cumulative probability
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Results (Palm Coast, FL)
Antenna SNR M (avg)
Malone, FL
SNR Y (avg)
Jupiter, FL
Wire
(E-field) 12.6 15.2
Loop
(H-field) 13.8 18.4
SNR (average of 326 seconds) measurements at the output of the antenna for SEUS chain
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Conclusions
• SNR at the output of Loop (H-field) antenna is generally greater than the SNR at the output of Wire (E-field) antenna by 2-3 dB
• Noise distributionCore of distribution looks GaussianTail probabilities are much larger than Gaussian
with an equivalent rms value (looks like 3-sigma)
• Data collected from both the antennas closely match in the calculated cdf of the noise
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Acknowledgements
• Federal Aviation Administration (FAA)Mitch Narins (Loran Program Manager)
• Reelektronika B.V.Dr. Durk van Willigen, Wouter Pelgrum
• King Air CrewBryan Branham, Jay Clark
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Questions ?