AFCEA’s International Student Conference 2009

Brussels, October 28 2009

SDR GNSS ReceiverAcquisition Module

LabVIEW Implementation Lt. Pasquale Digregorio

Introduction : Workgroup

GNSS Ricever : Hw-based vs Sw-based

Acquisition Module : Hw e Sw approach

LabView : implementation

Results : real GPS signal acquisition

Conclusions

SUMMARY22

Cpt. Francesco Bartolozzi

Cpt. Alberto De Sanctis

Gabriele Mariani

Lt. Efer Miotti

3

RF to IF converter

Antenna GNSS

Acquisition Tracking Navigation

Code-phase Delta Doppler

ObservablesNavigation Data PVT

A/D converter

RF to IF converter

Antenna GNSS

Acquisition Tracking Navigation

Code-phase Delta Doppler

ObservablesNavigation Data PVT

SOFTWARSOFTWAREE

HARDWAREHARDWARE

SUMMARY44

A/D converter

Acquisition

SOFTWARESOFTWAREHARDWAREHARDWARE

GPS signalLocal Code

Satellite in view (PRN code)

Delta Doppler

Code-phaseCode-phase

Search in 3 dimention space:

0 100 200 300 400 500 600 700 800 900 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1Acquisizione

Chip

Corr

ela

zio

ne

0 100 200 300 400 500 600 700 800 900 1000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1Acquisizione

Chip

Corr

ela

zio

ne ∆∆tt

GPS SiS

GPS Signal at the receiver

Reciver Local Code

Shifted local code

GPS SiS reachs the reciver after dt delay

SUMMARY55

Code-phaseCode-phase

Search Space

1023 Chip

±10

KH

z

∆f = 500 Hz

∆τ = 1/fc ≈ 1μsFase Codice PRNF

req

. Do

pp

ler

SUMMARY66

MODULO ACQUISIZIONE

Hw-Based

1023 Chip

±10

KH

z

∆f = 500 Hz

∆τ = 1/fc ≈ 1μsPRN code phaseF

req

. Do

pp

ler

SUMMARY77

Sw-Based

1023 Chip

±10

KH

z

∆f = 500 Hz

∆τ = 1/fc ≈ 1μsPRN code phaseF

req

. Do

pp

ler

MODULO ACQUISIZIONESUMMARY88

Computational issues

Fast Fourier Transform Parallel Code Phase Search Acquisition Algorithm

with high computing efficiency

Parametric Acquisition Configurable time and frequency bin size Trade-off : accuracy and sensitivity versus computational weight

MODULO ACQUISIZIONESUMMARY99

Acquisition Module

MODULO ACQUISIZIONESUMMARY1010

Parametric GUI

MODULO ACQUISIZIONESUMMARY1111

MODULO ACQUISIZIONESUMMARY1212

SV N°22 SV N°2

Acquired SV

MODULO ACQUISIZIONESUMMARY1313

SV dynamicDoppler Shift (kHz)

-5

-4

-3

-2

-1

0

1

2

3

4

5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Sat.

MODULO ACQUISIZIONESUMMARY1414

Pseudorange (ms)

0

0,2

0,4

0,6

0,8

1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Sat.

MODULO ACQUISIZIONESUMMARY1515

Goals achieved: Implemented PRN Code generator

(test gold sequence properties) Acquisition module (Parametric function, FFT)

(testing with a Real digital GPS signal)

Future development: Tracking module Navigation solution module

MODULO ACQUISIZIONESUMMARY1616