Title: Modern Loran Receivers: Current Performance and Future Enhancements by Linn Roth, Ph'D' Locus, Inc'
1Modern Loran Receivers Current Performance and
Future Enhancementsby Linn Roth, Ph.D.Locus,
Inc.
Some of the data and work reported here was
supported under subcontract SK-00-18 between
Locus, Inc. and Advanced Management Technology,
Inc. under primary Federal Aviation
Administration Contract DTFA01-98-C-00061. Locus
gratefully acknowledges the support of Mitchell
J. Narins of the FAA.
2Modern Loran Receivers Current Performance
3Modern Loran Receivers vs 1990 Technology
Receivers. Example Differences
- DSP-based vs combined analog/digital technology
- All-in-view (40 stations) vs single chain
- 24dB improvement in SNRs
- 1 nS TD resolution vs 100 nS
- Substantially better
- - availability and coverage
- - dynamic performance
- - absolute and repeatable accuracy
- Ability to demodulate GPS messages
- Use of H-field antennas
- Other improvements in related technologies,
- e.g. computer modelling of ASFs
4Antiquated Loran Infrastructure Control Currently
Limits Loran System Performance
- Modern Receiver Resolution Identifies Timing
Control Problems - USCG Currently Modernizing Infrastructure
5Example Accuracy with Current Infrastructure
- 60 hours data
- Least squares fit from 12 - 18 stations
- Clusters suggest stability possible with modern
infrastructure
6FAA Tech Center Flight Tests - August 2001
- Compare all-in-view Loran technology to GPS and
- legacy Loran receiver technology E-field
antennas
7FAA Tech Center Data Sacramento AirportClose-up
View of Landing and Takeoff
GPS and SatMate only no SatMate ASF Corrections
8FAA Tech Center Data Sacramento AirportClose-up
View of Landing and Takeoff
SatMate and Legacy Receivers
9FAA Tech Center Data Atlantic City, NJ
AirportClose-up View of Aug. 20 Takeoff and
August 28 Landing
GPS and SatMate only no SatMate ASF Corrections
10Derivation of Quasi-ASFs and Example
Application to Flight Data
- On August 21, 2001, recorded GPS and SatMate
data for - 90 seconds at single airport location, then
calculated - position offset between GPS and Loran
- Measured SatMate TOAs were subtracted from the
- calculated TOAs to obtain ASFs for the
individual - stations used in the navigation solution - here
11 stations - These 11 ASF corrections were applied to SatMate
data - from return flight landing on August 28, 2001
- A plot of the August 28 data using these
week-old ASF - corrections was created
11Example SatMate Quasi-ASF ResultsClose-up of
Atlantic City Airport
GPS and SatMate SatMate with Quasi-ASF
Corrections
12Modern Loran Technology H-field AntennasE-field
H-field
SNR
ECD
- Higher signal levels and SNRs, lower ECDs
- Immunity to P-static interference
13H-field Tests April 30, 2002
14H-field mount under Saratoga
15SatMate 1020 Tests, H-field Antenna
- 5/1/02 flight tests with Ohio University in
Madison, WI - Included 10 ILS-guided approaches
- WAAS GPS - Green SatMate - Black
- Simultaneous recording, positions updated 1/sec
- SatMate 1020 using quasi-ASFs
16SatMate 1020 Tests, H-field Antenna
- 3 representative examples of ILS-guided
approaches - SatMate 1020 using quasi-ASFs generated 8
miles from airport - SNRs 5-10 dB lower than expect to achieve
- Results will improve with
- - better transmitter control, airport-generated
ASFs - - improved receiver software and antenna hardware
17SatMate 1020 Tests, H-field Antenna
Run 9
Run 8
Run 7
- 3 representative examples of ILS-guided
approaches - SatMate 1020 using quasi-ASFs generated 8 miles
from airport - SNRs 5-10 dB lower than expect to achieve
- Results will improve with
- better transmitter control, airport-generated
ASFs - improved receiver software and antenna hardware
18Same 10 ILS Guided Approaches, No ASFs
19Modern Loran Receivers Future Enhancements
20Evolution of all-in-view DSP receiver and
H-field antenna a. Reduce size 75 to Eurocard
format b. Develop ARINC 429 Interface c.
Incorporate WAAS message demodulation c. Develop
combined GPS/Loran antenna d. Integrate Loran
receiver into multimode GPS avionics system
for prototype testing
21SatMate Size Reduction
- New, all-in-view receiver board will be 100 x
160 mm - Standard ARINC 429 and RS-232 interfaces for
- integration with GPS
22Prototype MMR For FAA GPS/Loran
- Locus-developed Loran card embedded into Rockwell
Collins MMR - For FAA demo/evaluation purposes, independent
Integration Processor will be inserted to
minimize development risk - WAAS message data demodulated in Loran feeds into
GPS
23Combined GPS/Loran Antenna
- Loran H-field 130mm x 130mm x 50 mm
- GPS microstrip patch
- Prototype now operational
24Preliminary Conclusions
- Modern all-in-view Loran receivers provide
substantially - better performance than legacy receivers
- Modern H-field antennas provide many performance
and - size advantages
- USCG modernization of the Loran infrastructure
will - improve overall system performance even more
- As demonstrated by many, a combined GPS/Loran
system - offers better performance (e.g. availability,
continuity, etc.) - than either system alone
- Modern Loran technology is evolving to make
integration - with GPS a reality
25Modern Loran Receivers Current Performance and
Future Enhancementsby Linn Roth, Ph.D.Locus,
Inc.
Some of the data and work reported here was
supported under subcontract SK-00-18 between
Locus, Inc. and Advanced Management Technology,
Inc. under primary Federal Aviation
Administration Contract DTFA01-98-C-00061. Locus
gratefully acknowledges the support of Mitchell
J. Narins of the FAA.