Pirazzi Gabriele Intecs 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
Dec 31, 2015
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
Slide 2 of 20
Agenda
• SDR Definitions• SDR Applications• GNSS receiver• Acquisition Phase
• GPS• Giove-A(Galileo)• SBAS
• Tracking Phase• GPS• Giove-A(Galileo)• SBAS
• Space Software Receiver
Slide 3 of 20
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.
Slide 4 of 20
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
Slide 5 of 20
Applications (1)
SDRSDR
One Terminal, multiple Applications.
Slide 6 of 20
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
Slide 7 of 20
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
Slide 8 of 20
• 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
Slide 9 of 20
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.
Slide 10 of 20
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
Slide 11 of 20
Incoherent Integration SBAS
Slide 12 of 20
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
Slide 13 of 20
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.
Slide 14 of 20
Tracking Giove-A E1B
Slide 15 of 20
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)
Slide 16 of 20
Giove-A Message Decoded (Viterbi)
Packets 5-8
First Frame
Packets 1-4
Packets 1-4
Packets 5-8
Carrier Status Nav. Data Health
Slide 17 of 20
MIOSat mission
MIssione Ottica su microSATellite
Slide 18 of 20
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
Slide 19 of 20
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
Slide 20 of 20
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