Study of a SDR GNSS Receiver

1

M.Sc. In Advanced Communication and Navigation
Satellite Systems
Chapter of Rome
AFCEAs Student Conference 2008
Study of an SDR GNSS receiver
Pirazzi GabrieleIntecs S.p.A
Bruxelles, 10/04/2008
2
Agenda

• SDR Definitions
• SDR Applications
• GNSS receiver
• Acquisition Phase
• GPS
• Giove-A(Galileo)
• SBAS
• Tracking Phase
• GPS
• Giove-A(Galileo)
• SBAS
• Space Software Receiver

3
Definitions

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

4
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

5
Applications (1)
SDR
One Terminal, multiple Applications.
6
Applications (2)
Radar
Galileo
GPS
UAV
SatCom
Installing, upgrading software module
Application Layer
Software Layer(management, control and
configuration)
Hardware Layer
User Terminal
Control Center
7
GNSS Receiver Structure
Hardware
Software
AGC
Channel n Software Correlator
Canale 2 Software Correlator
LNA
Channel 1 Software Correlator
Downconversion
A/Dconverter
IF Digital
RF
IF Analogue
Reference oscillator
Frequency synthesizer
Acquisition
Tracking
Navigation processing
8
Front-end

• RF Carrier
• Single IF conversion
• Bandwidth (-3dB)
• 2 bit ADC (sign and mag)
• Sampling frequency
• AGC
• TCXO

9
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.

10
GPS, Giove-A real data acquisition
11
Incoherent Integration SBAS
12
Unexpected Signal GAGAN!

• Geostationary satellite acquired, tracked and
  decoded
• AOR-E
• Artemis
• IOR-W
• Gagan

GAGAN
EGNOS
Analisis of Message 18 (Ionosperic Grid
Points Mask, IGP) and Message 9 (Geo Navigation
Message) confirm its Gagan!
First signal transmitted at the end of December
2007
13
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.

14
Tracking Giove-A E1B
15
Tracking GPS real data
16
Giove-A Message Decoded (Viterbi)
Packets 5-8
Packets 1-4
Carrier Status
Nav. Data Health
Packets 5-8
First Frame Packets 1-4
17
MIOSat mission
MIssione Ottica su microSATellite
18
SSR Requirements
19
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

20

Q A SESSION
Study of an SDR GNSS receiver
Thank you for your attention
Pirazzi Gabriele Intecs S.p.A.
Bruxelles, 10/04/08