Pirazzi Gabriele Intecs S.p.A

Pirazzi GabrieleIntecs S.p.A

Bruxelles, 10/04/2008

““Study of an SDR GNSS receiver”Study of an SDR GNSS receiver”

Chapter of Rome

M.Sc. In Advanced Communication and

Navigation Satellite Systems

AFCEA’s Student Conference 2008

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Agenda

• SDR Definitions• SDR Applications• GNSS receiver• Acquisition Phase

• GPS• Giove-A(Galileo)• SBAS

• Tracking Phase• GPS• Giove-A(Galileo)• SBAS

• Space Software Receiver

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Definitions

• Software Radio:the digitization is at the antenna and all of the processing required is performed for the radio by software.

• Software Defined Radio:the digitization is performed at some stage downstream from the antenna, typically after wideband filtering, low noise amplification, and down conversion to a lower frequency in subsequent stages.

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SDR purpose

• The purpose of the Software Radio:• Move the ADC (analog-to-digital) as close as possible to

the antenna. • Elaborate the samples obtained through a

reprogrammable processor.

• Advantages:• Removing analog components with non-linear

characteristics, depending on the temperature and age. • Single antenna for multi-constellation, multiband and

multi-modes systems . • High flexibility in the implementation of new algorithms:

update software without replace hardware. • Reducing costs and maintaining

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Applications (1)

SDRSDR

One Terminal, multiple Applications.

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Applications (2)

User Terminal

Hardware Layer

Software Layer(management, control

and configuration)

Application Layer

Installing, upgrading

software module

GPS Galileo

UAV

Radar

SatCom

Control Center

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GNSS Receiver Structure

Channel n SoftwareCorrelatorCanale 2

SoftwareCorrelator

Downconversion

Frequency synthesize

r

Reference oscillator

A/Dconverter

AGC

Channel 1 SoftwareCorrelatorIF

AnalogueRF

Acquisition

Tracking

IF Digital

Navigationprocessing

Hardware Software

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• RF Carrier:

• Single IF conversion:

• Bandwidth (-3dB):

• 2 bit ADC (sign and mag)

• Sampling frequency:

• AGC• TCXO

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

x 10-3

-3

-2

-1

0

1

2

3Segnale uscita ADC (IF)

Tempo [ms]

Am

pie

zza

0 1 2 3 4 5 6 7 8

-20

-15

-10

-5

0

5

Frequenza [MHz]

Ma

gn

itud

e [d

B/H

z]

Stima spettro di Densita di Potenza (Welch)

-4 -3 -2 -1 0 1 2 3 40

1

2

3

4

5

x 104 Istogramma

Campioni

Nu

me

ro d

i ca

mp

ion

iFront-end

MHzfL 42.15751

MHzf IF 1304.4

MHzBWIF 2.2

MHzfCamp 3676.16

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Acquisition phase

• Acquisition scope:

• Determinate the number of visible satellites.

• Coarse estimate of the beginning C/A code .

• Coarse estimate of the carrier included Doppler.

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GPS, Giove-A real data acquisition

PRN CodePhase Doppler [Hz] Amplitude2 6612 -500 7803731,65 10134 -500 125892056 4419 2000 193867257 15860 2000 121419409 14228 -3500 7486397

12 13644 -1500 1063796624 14005 3500 6385256,130 5942 500 1869288031 14096 3500 5739081,8

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Incoherent Integration SBAS

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Unexpected Signal: GAGAN!

• Geostationary satellite acquired, tracked and decoded:

AOR-E Artemis IOR-W Gagan

Constellation Name PRN Orbital

Position

EgnosInmarsat-3-F2

(AOR-E)120 15.5°W

Egnos Artemis 124 21.5°E

EgnosInmarsat-3-F5

(IOR-W)126 25°E

WAAS Anik F1R 138 107.3°W

WAAS Galaxy 15 135 133°W

MSAS MTSAT-1R 129 140°E

MSAS MTSAT-2 137 145°E

Gagan Inmarsat-4-F1 127 64°E

First signal transmitted at the end of December 2007

Analisis of Message 18

(Ionosperic Grid Points

Mask, IGP) and Message 9

(Geo Navigation Message)

confirm it’s Gagan!

EGNOS GAGAN

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Tracking

• Tracking scope: Tracking over time the carrier and the GPS code.

• Implemented Tracking closed loop: PLL (Phase Lock Loops) Costas 2° order. DLL (Delay Lock Loops) incoherent 2° order. FLL (Frequency Lock Loops) del 1° order.

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Tracking Giove-A E1B

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Tracking GPS real data

0 100 200 300 400 500 600 700 800 900 10000

0.5

1

1.5

2

2.5

3x 10

7

Tempo [msec]

Co

rre

lazi

on

e

SV 6 Componente in Fase (pull-in)

IPrompt2

ILate2

IEarly2

0 100 200 300 400 500 600 700 800 900 10000

0.5

1

1.5

2

2.5

3x 10

7

Tempo [msec]

Co

rre

lazi

on

e

SV 6 Componente in Quadratura (pull-in)

QPrompt2

QLate2

QEarly2

0 100 200 300 400 500 600 700 800 900 10001500

1600

1700

1800

1900

2000

Tempo [msec]

Fre

qu

en

za [H

z]

SV 6 Inseguimento in Frequenza (pull-in)

0 100 200 300 400 500 600 700 800 900 1000-6000

-4000

-2000

0

2000

4000

6000

Tempo [msec]

Am

pie

zza

SV 6 Dati di Navigazione (pull-in)

0 100 200 300 400 500 600 700 800 900 1000

-50

0

50

Tempo [msec]

Err

ore

su

lla fa

se [°

]

SV 6 PLL discriminatore errore (pull-in)

0 100 200 300 400 500 600 700 800 900 1000-1

-0.5

0

0.5

1

Tempo [msec]

Err

ore

su

l co

dic

e [c

hip

s]

SV 6 DLL discriminatore errore (pull-in)

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Giove-A Message Decoded (Viterbi)

Packets 5-8

First Frame

Packets 1-4

Packets 1-4

Packets 5-8

Carrier Status Nav. Data Health

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MIOSat mission

MIssione Ottica su microSATellite

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SSR Requirements

Function Value

Dimensions 100x100x90mm

Weight <0.7 Kg

Antenna weight <50g (cable excluded)

Power 5 V

Power consumption <12W

Antenna gain > 5 dBi at Zenith

Noise figure < 2.5 dB

Operative frequency L1 GPS e GALILEO

GNSS systems GPS (GALILEO HW-ready)

Receiver linearity TBD

ADC quantization bits 1

AGC Embedded in the receiver

Sampling frequency 16.8 MHz (TBC)

Oscillator stability TCXO typical

Electric interface RS 422

Launch vibrations compliance TBD (reference VEGA launcher suggested)

Mission lifetime 6 months ground, 2.5 years in flight

Operating temperature -20°/+50°

Radiation tolerance >10 Krad

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SSR Scheme

• Satellite or System on Chip (SoC).• Less volume and mass.• Reduced power consumption.• Fewer interconnects, solder joints e

bound wires.• Soft-core CPU: Leon3

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Pirazzi GabrieleIntecs S.p.A.

Bruxelles, 10/04/08

““Study of an SDR GNSS receiver”Study of an SDR GNSS receiver”

Q & A

SESSION

Thank you for your attention

Pirazzi Gabriele Intecs S.p.A

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