SOURCEFORGE » RALF » 2015 Software defined GPS receiver

h1. PART 5 : Implementation.

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h2. 1 - Starting point.

h3. a - Receiver scheme and milestones.

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h3. b - Quid about LabVIEW.

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Input : GPS signal of sampling frequency 38.192 MHz at intermediate frequency 9.55 MHz from CD *[1]* under GNSS_signal_records/GPSdata-DiscreteComponents-fs38_192-if9_55.bin

h3. c - Local C/A code generation.

The files involved are :

- _CA_Code.vi_

- _CA_generatorG1.vi_

- _CA_generatorG2.vi_

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h2. 2 - Acquisition.

*See the UML Diagram of Section 2 under :* attachment:"Acquisition.png"

The files involved are :

- _Main_Acquisition.vi_ : attachment:"SnapAcquisition.PNG"

- _Acquisition_subVI.vi_ : attachment:"SnapAcquisitionSub.png"

- _CA_Code.vi_

Justification acquisition method in terms of accuracy and time execution

Justification of the step of 500Hz

Methods to avoid the data bit transition while running acquisition

Frequency refine is needed for the PLL of the tracking to converge

Definition of the threshold and how it is implemented

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h2. 3 - Tracking.

Justification of the DLL discriminator

Correction of the blocksize to read as a function of the doppler shift

*See the UML Diagram of Section 2 under :* attachment:"Track.png"

The files involved are :

- _Main_Carrier_Tracking.vi_ : attachment:"SnapTracking.png"

- _CalcLoopCoeff.vi_ : attachment:"SnapCalcLoopCoeff.PNG"

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p=. !TrackingMin.PNG!

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h2. 4 - Navigation Data decoding.

*See the UML Diagram of Section 4 under :* attachment:"NavigationData.PNG".

h3. a - Delimiting subframes.

The files involved are :

- _FindPreamble.vi_

- _TestFindPreamble.vi_ : attachment:"SnapTestFindPreamble.PNG"

- _GenerateFrame.vi_

- _ParityCheck.vi_ : attachment:"SnapParityCheck.PNG"

p=. !Preamble1.PNG! !Preamble2.PNG!

p((((. *Figure 5. :* Cross-correlation between navigation frame and local preamble. *Figure 5. :* Subframes with index of delimitation.

h3. b- Decoding ephemeris and information within the frame.

The files involved are :

- _Ephemeris.vi_

- _BinaryArrayToDecimal.vi_ : attachment:"SnapBinaryArrayToDecimal.PNG"

- _twosComp2dec.vi_ : attachment:"SnapTwosComp2dec.PNG"

- _ParityCheck.vi__ : attachment:"SnapParityCheck.PNG"

- _TestEphemeris.vi_

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h2. 5 - Elementary blocks for localization.

*See the UML Diagram of Section 5 under :* attachment:"Localization.PNG"

h3. a - Satellite position.

The files involved are :

- _SatellitePosition.vi_

- _TestSatellitePosition.vi_ : attachment:"SnapTest_satellite_position.PNG"

- _Check_time.vi_ : attachment:"SnapCheckTime.PNG"

p=. !SatPos.PNG!

*Figure 5. :* Interface with ephemeris as input and illustration of the satellite position.

h3. b - Pseudoranges.

The file involved is :

_PseudorangesComputation.vi_

h3. c - Least Square solution for position determination.

The files involved are :

- _LeastSquarePosition.vi_

- _SatelliteRotationECEF.vi_ : attachment:"SnapSatelliteRotationECEF.PNG"

- _toTopocentric.vi_ : attachment:"SnaptoTopocentric.PNG"

- _CartesianToGeodetic.vi_ : attachment:"SnapCartesianToGeodetic.PNG"

- _TroposphericCorrection.vi_

h2. 6 - Receiver position computation.

*See the UML Diagram of Section 6 under :* attachment:"Receiver.PNG"

The files involved are :

- _ComputeReceiverPosition.vi_

- _NavigationProcess.vi_

- _CartesianToGeodeticForUTM.vi_ : attachment:"SnapCartesianToGeodeticForUTM.PNG"

- _CartesianToUTM.vi_

h2. 7 - Complete UML Diagram of the receiver.

*The UML diagram with real size is available under :* attachment:"UMLDiagram.png"

Here is a small overview of the structure :

p=. !UMLDoverview.PNG!

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*References :* 

*[1]* K. Borre, D. M. Akos, N. Bertelsen, P. Rinder, S. H. Jensen, A software-defined GPS and GALILEO receiver