Advanced global navigation satellite system receiver design (797918), страница 32
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The secondtype provides robust reliable acquisition and tracking but has a significant reduction intiming sensitivity. In Chapter 6 the double estimation (DE) BOC tracking techniqueis detailed. This tracking technique is an entirely novel contribution to this field ofGNSS and as such forms much of the academic contributions of this research. TheDE tracking technique is shown to provide the full timing precision of the BOCmodulated GNSS signal, while maintaining robust acquisition and tracking.
The DEtechnique is more efficient with hardware resource than the BJ algorithm and insimulation shows a small improvement in multipath performance.The DE technique has no false-lock conditions within its discriminator function.Therefore, the integrity of a DE BOC receiver is less sensitive to inferring multipathsignals and distortions in the correlation function. In addition, slips in receiver219Discussion, conclusions and future worktracking can be automatically corrected, without the need for the a posteriori falselock detection synonymous with the BJ algorithm.
This research has identified theeffect of asymmetry in the received BOC spectrum and detailed the impact onreceiver tracking techniques. The DE technique is shown to be more robust todistortions in the received spectrum when compared to the BJ algorithm.The DE technique shows many advantages over the existing BOC tracking techniqueparticularly for high-accuracy and high-integrity applications. We hope this willresult in the DE technique will become widely accepted and used in future GPS andGalileo receiver designs.11.2 Practical contributionsThis research has made a number of practical contributions and provideddemonstrations of signal generators and receivers for the next generation of GNSSsignals.In Chapter 7 the architecture of the signal generator on-board the Giove-A satellite isdetailed. This architecture is capable of producing every GNSS signal currentlyspecified for the future systems.
The modulation of method of producing the in-phaseand quadrature carrier modulation in the DAC reduces the fundamental samplingfrequency of the FPGA baseband modulation by a factor of two.Chapter 8 and 9 describe the contributions of this research to the SSTL receiverdesign in the form of the prototype intermediate frequency PIF receiver and the singlechip receiver respectively. Both these receiver designs are based on re-programmableFPGAs. The move to FPGA based receiver architecture provides a number ofadvantages for future GNSS receivers.
The most obvious advantages of FPGA basedreceivers are removing the risk of obsolescence of chipsets, providing flexibility toreceiver designs and the option of radiation tolerant architectures. The option ofradiation tolerance is of particular importance to space receivers, which commonlyoperate in extreme environments.220Discussion, conclusions and future workThe prototype receiver designs developed during this research provided practicaldemonstration of the DE BOC tracking technique. Through these demonstrations thetechniques required to implement the DE technique in hardware were developed. Thedemonstrations also act to further our confidence in the theory developed during theresearch and models developed in order to simulate receiver operation.11.3 Future WorkThis research has resulted in the development of a theoretical novelty, namely thedouble-estimating (DE) BOC receiver.
During this research this technique has beendemonstrated with rigorous tests in both simulation and with practical receiverdesigns. The DE BOC tracking technique has been shown to be preferred choice oftracking scheme for BOC modulated GNSS signals with a natural extension to theGalileo AltBOC signal given. One area of further research on the DE BOC receiver isthe extension of the DE technique to MBOC signals. This extension is currentlybeing developed by Dr Hodgart with the expectation of filing a second patentapplication in the near future.The multipath performance of the DE BOC tracking technique has been assessed inthis thesis for standard correlator and narrow correlation techniques.
It seems clearthat the DE technique can be generalized to other forms of current multipathmitigation techniques, such as double-delta correlators and the early-late slopetechnique, the performance of such schemes with DE tracking is however yet to bedetermined.The strong practical emphasis of this research has resulted in development of bothGNSS transmitter and receiver architectures.
SSTL are currently further developingthe single-chip receiver in order to demonstrate the DE BOC tracking technique onthe BOC(15, 2.5) signal from Giove-A. The aim of this work will be to fullycharacterize the effect of distortion of the transmitter and the receiver front-end filterson the tracking of high-rate BOC signals and hence the advantages of the DE trackingtechnique.221Discussion, conclusions and future workAs detailed in Chapter 8 the FPGA-based correlator and processor architecture arecurrently under consideration for future SSTL receiver designs. Many spaceapplications require GNSS receiver hardware that is application specific, radiationtolerant and flexible.
Therefore, FPGA-based receivers provide the ideal solution forspace GNSS receivers.222References[Bello and Fante 2005]Bello P.A., Fante R.L., “Code Tracking Performance for NovelUnambiguous M-Code Time Discriminators”, Proceedings of ION NationalTechnical Meeting, San Diego, California, January 2005[Betz 1999]Betz J.W., “The Offset Carrier Modulation for GPS Modernisation”,Proceedings of ION 1999 National Technical Meeting, San Diego,California, January 1999[Betz 2001]Betz J.W., “Binary Offset Carrier Modulations for Radionavigation”,Navigation: Journal of The Institute of Navigation, Vol. 48, No.
4, Winter2001[Betz and Kolodziejski2000]Betz J.W., Kolodziejski K., “Extended theory of early-late code tracking fora bandlimited GPS receiver”, Navigation: Journal of The Institute ofNavigation, Vol. 47, No. 3, Fall 2000[Blunt et al 2004]Blunt P., Ebinuma T., Unwin M., Hodgart S., “FPGA-Based Dual-FrequencyGNSS Receiver Development for GPS and Galileo Signals”, Proceedings ofthe 2nd ESA Workshop on Satellite User Equipment Technologies, Navitech2004, Noordwijk, Netherlands, December 2004[Blunt et al 2005]Blunt P., Ebinuma T., Hodgart S., Unwin M., “A Demonstration of GalileoTransmitter / Receiver Architecture for Space Applications” Proceedings ofION GPS 2005, Long Beach, California, September 2005[Dafesh et al 1999]Dafesh P.
A., Nguyen M. T., Lazar S., “Coherent adaptive subcarriermodulation (CASM) for GPS modernization”, Proceedings of ION 1999National Technical Meeting, San Diego, California, January 1999[Dafesh et al 2000]Dafesh P. A., Cooper L., Partridge M., “Compatibility of the InterplexModulation Method with C/A and P(Y) code Signals”, Proceedings of IONGPS 2000, Salt Lake City, Utah, September 2000[De Wilde et al 2004]De Wilde W., Sleewaegen J.-M., Van Wassenhove K., Wilms F., “A Firstof-a-Kind Galileo Receiver Breadboard to Demonstrate Galileo TrackingAlgorithms and Performances” Proceedings of ION GNSS 2004, LongBeach, California, September 2004[Duncan et al 2006]Duncan S., Hodgart S., Unwin M., “Investigation of GPS attitudedetermination for microsatellites” Proceedings of ENC 2006, Manchester,England, May 2006.[Dutton et al 2002]Dutton L., Rumens D., Forrest W., Ruiz L., “Galileo’s Services”,Proceedings of ION GPS 2002, Portland, September 2002.[Ebinuma et al 2004]Ebinuma T., Unwin M., Myatt R., Rooney E., Hashida Y., Garutti A., “GEOGPS Receiver Demonstration on a Galileo System Test Bed Satellite”,Proceedings of ION GNSS 2004, Long Beach, California, September 2004[ESA and GJU 2006]European Space Agency, Galileo Joint Undertaking, “Galileo Open ServiceSignal In Space Interface Control Document” Draft 0, Available at:http://www.galileoju.com, Accessed in May 2006223References[Falcone et al 2006]Falcone M., Lugert M., Malik M., Crisci M., Jackson C., Rooney E.,Trethewey M., “GIOVE-A In Orbit Testing Results” Proceedings of IONGNSS 2006, Fort Worth Texas, September 2006.[Fante 2004]Fante R.L., “Unambiguous Tracker for GPS Binary-Offset-Carrier Signals”,ION 59th Annual Meeting / CIGTF 22nd Guidance Test Symposium,Albuquerque, New Mexico, June 2003.[Fine and Wilson1999]Fine P., Wilson W., “Tracking Algorithm for GPS Offset Carrier Signals”,Proceedings of ION 1999 National Technical Meeting, January 1999[Gardener 1979]Gardener F., “Phase lock Techniques, 2nd Edition” Wiley and Sons, pp.
54,April 1979[Gaisler 2006]Gaisler Research, “LEON 3 GRLIB product brief”, Available at:http://www.gaisler.com/doc/Leon3%20Grlib%20folder.pdf Accessed in Dec2006[Gleason et al 2005]Gleason S., Adjrad M. and Unwin M., “Sensing Ocean, Ice and LandReflected Signals from Space: Results from the UK-DMC GPSReflectometry Experiment”, Proceedings of ION GPS 2005, Long Beach,California, September 2005[Gold 1967]Gold R., “Optimal Binary Sequences for Spread Spectrum Multiplexing”,IEEE Transactions in Information Theory, Vol.
33, pp. 619 – 621, October1967[GPS ICD 2007]GPS Navstar interface control documents, Available at:http://www.navcen.uscg.gov/gps/geninfo/ , Accessed in May 2007[Graf and Günther2006]Graf S., Günther C., “Analysis of the Giove-A L1-signals”, Proceedings ofION GNSS 2006, Fort Worth Texas, September 2006.[Hein et al 2006]Hein G.W., Avila-Rodríguez J.-A., Wallner S., Betz J.W., Hegarty C.J.,Rushanan J.J., Kraay A.L., Pratt A.R., Lenahan S., Owen J., Issler J.-L.,Stansell T.A., “MBOC: The New Optimized Spreading ModulationRecommended for GALILEO L1 OS and GPS L1C”, Proceedings ofIEEE/ION PLANS 2006, San Diego, California, April 2006[Heiries et al 2004]Heiries V., Roviras D., Ries L., Calmettes V., “Analysis of Non AmbiguousBOC Signal Acquisition Performance”, Proceedings of ION GNSS 2004,Long Beach, California, September 2004[Irsigler et al 2004]Irsigler M., Hein G. W., Eissfeller B., “Multipath Performance Analysis forFuture GNSS Signals” Proceedings of ION National Technical Meeting, SanDiego, California, January 2004[Jordan and Smith1997]Jordan D.W.
and Smith P., “Mathematical Techniques”, Oxford UniversityPress, Second Edition, pp. 420, 1997[Kaplan and Hegarty2006]Kaplan E.D., Hegarty C.J., “Understanding GPS principles and applications,second edition”, Artech house Inc., Second Edition, pp. 133-134, 170 –202,264,572, 2006[Kilvington 1986]Kilvington J., “Receivers for Navigation Satellite Systems”, US Patent4601005, 15th July 1986.224References[Komjathy et al 2001]Komjathy A., Armatys M., Masters D., Axelrad P., Zavorotny V.U.,Katzberg S.J., “Developments in Using GPS for Oceanographic RemoteSensing: Retrieval of Ocean Surface Wind Speed and Wind Direction”,Proceedings of ION National Technical Meeting, Long Beach, California,January 2001[Lehmer 1951]Lehmer D.H., “Mathematical methods in large-scale computingUnits”, Proceedings 2nd Symposium on Large-Scale Digital ComputingMachinery, Harvard University Press, pp.
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