LORANC Band Data Collection Efforts at Ohio University
LORAN-C Band Data Collection Efforts at Ohio University Presented by Curtis Cutright to the International LORAN Association 32 nd Annual Convention and Technical Symposium Boulder, CO November 6, 2003
Outline • 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
Task • 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
Purpose • 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
Purpose • Identify all trade-off’s for E and H-field antennas, SNR, phase error, saturation, bandwidth Ohio University • Avionics Engineering Center
To 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 Collection • Simultaneous ground aircraft RF data collection (Using Data. Grabber) • 2 channels, 16 -bits samples, 400 k. Samples/s • LORAN receivers for performance assessment • GPS WAAS for position reference Ohio University • Avionics Engineering Center
Data 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 airborne noise • Compare airborne E-field and H-field noise Ohio University • Avionics Engineering Center
Data Collection System Overview
Airborne Data Collection Equipment • Aircraft – King Air C-90 B – Pressurized twin turboprop – 240 knot cruise speed • Equipment – Novatel OEM 4 GPS receiver – LORADD-DS Data. Grabber – WX-500 Storm. Scope – Apollo 618 – Data collection PC Ohio University • Avionics Engineering Center
Whip antenna GPS antenna (e-field) Apollo 618 Data Collection PC Data Collection Equipment WX-500 Storm. Scope Pre-amp ADF antenna Stormscope (h-field) antenna Ohio University • Avionics Engineering Center
Data Collection PC • Cyber. Research dual backplane with 933 MHz P-III CPU cards • 512 MB RAM • 160 GB of hard-drive space Ohio University • Avionics Engineering Center
WX-500 Stormscope • RS-232 data output • 200 nmi 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 Antennas E-Field (Electric) • Large effective height – Little voltage amplification needed • High impedance (MW) – Charge build-up (cannot be terminated) • Antenna phase pattern is omnidirectional • Whip or wire antenna H-Field (Magnetic) • Small effective height Ø Large voltage amplification needed (low noise pre-amp) • Low impedance (1 W) Ø No charge build-up (antenna is grounded) • One loop creates 0 and 180 degrees. • Conformal antenna Ohio University • Avionics Engineering Center
Aircraft Data Collection Equipment Ohio University • Avionics Engineering Center
Antennas E-Field II Morrow A-16 H-Field King Radio KA 42 A Ohio University • Avionics Engineering Center
Rackmount chassis for data collection equipment AC in DC Power Supply LORADD-DS Data. Grabber GPS Novatel GPS Receiver GPS antenna LAN Antenna Interface H-field E-field Ohio University • Avionics Engineering Center
LORADD-DS Data. Grabber • Sampling rate: 400 k. Hz • Resolution: 16 bits • Dynamic range: 96 d. B • Two input channels – sampled simultaneously • Differential input amplifiers for the antennas • TCP/IP data output • Clock stability: 1 ppm Ohio University • Avionics Engineering Center
Antenna Interface Boxes • Adjust received signal level • Provide interference isolation for the antenna cable • Impedance matching for the Data. Grabber antenna inputs Ohio University • Avionics Engineering Center
Novatel GPS Receiver • 1 -20 Hz position data • Time synchronization • RS-232 data output (ASCII or binary) Ohio University • Avionics Engineering Center
Lab Data Collection Equipment • LORADD-DS Data. Grabber – 400 k. Hz sampling – Dual channel • Data collection PC Ohio University • Avionics Engineering Center
Antennas • E-field – IIMorrow A-16 Whip antenna with integral preamplifier/impedance transformer – Powered by an Apollo 618 LORAN receiver Ohio University • Avionics Engineering Center
Antennas • H-field – King KA 42 A ADF Loop antenna – Requires a separate preamplifier/impedance transformer tuned to the LORAN-C band – Powered by 5 -10 VDC Ohio University • Avionics Engineering Center
Initial Data Collection Results • The next 2 slides show screen captures from the initial lab data collection test using both antennas • Channel 1: h-field • Screen capture 1 shows the RF data from each antenna Channel 2: e-field – 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 100 k. Hz is apparent – Several CW interference sources are evident Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Example of collected data: Time domain Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Example of collected data: Spectrum Ohio University • Avionics Engineering Center
Current Status of the Data Collection Task
Airborne Collected Data • “Clear” – 10 hrs • Overcast – 4 hrs • Close t-storm (<20 nmi) – 20 min • Nearby t-storm – 2 hrs • Other – 4+hrs Ohio University • Avionics Engineering Center
Data Collection Flight Tracks Ohio University • Avionics Engineering Center
Thunderstorm Data Conditions Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Ohio University • Avionics Engineering Center
Future Work • Continue data collection effort – Varying environmental conditions – Different locations – Correlate National Lightning Detection Network (NLDN) data – Mobile ground data collection equipment • Calibrate the Data. Grabber • Aircraft noise analysis Ohio University • Avionics Engineering Center
Acknowledgements • Mitch Narins (FAA) • Wouter Pelgrum (Reelektronika) • Bryan Branham (Ohio University) • Jay Clark (Ohio University) Ohio University • Avionics Engineering Center
Questions?
- Slides: 37