Transcript Introduction

Development of Global navigation
satellite system (GNSS) Receiver
Veena G Dikshit
Sc ‘E’
ADE, Bangalore
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Introduction
Global Navigation Satellite Systems (GNSS) involve satellites,
ground stations and user equipment to determine positions around
the world and are now used across many areas of society
•
GNSS
GPS (USA), GLONASS (Russia), Galileo(Europe), Augmentation
Systems (SBAS, GBAS), IRNS (India), QuasiZenth (Japan)
•
Fuelling growth during the next decade will be next generation GNSS
that are currently being developed.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
GNSS SYSTEM
GPS Modernization
•
Improved code on the L2 frequency of GPS (called L2C) –
•
ionospheric error,
•
more immune to RF interference and
•
multipath.
•
The first Block IIR-M during October 2005.
•
Under currently published plans, that is not expected to occur until 2013
or beyond.
•
A third civil frequency at 1176.45MHz (called L5) on the Block IIF satellites. Full
operational capability is unlikely until 2015.
•
GPS-III, (extra L2 and L5 signals of the Block IIR-M and Block IIF satellites), Thirty
GPS-III satellites are planned for launch from about 2013 until 2018.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
GLONASS from Russia
•
GLONASS-M (L1 and L2 bands ) satellites with an improved 7-year design
lifetime.
•
2007 to 2008 planned to launch GLONASS-K satellites with improved
performance, also transmit a third civil signal (L3).
•
Stated intention is to achieve a full 24-satellite constellation transmitting
two civil signals by 2010.
•
Full constellation is planned to be broadcasting three sets of civil signals
by 2012.
•
Indian Government announced at the end of 2004 that it would be
contributing funds to assist Russia to revitalize GLONASS.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Galileo from the European Union
•
Constellation of 30 satellites, increased altitude (approximately 3000km higher
than GPS) which will enable better signal availability at high latitudes.
•
Exact signal structure is still liable to change,
•
Galileo satellites broadcast signals compatible with the L1(E5a E5b) and L5 GPS
signals. Galileo will also broadcast in a third frequency band at E6; which is not
at the same frequency as L2/L2C of GPS.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
•
Current plan is to offer 5 levels of service:
o
Open Service uses the basic signals, free-to-air to the public with performance similar to
GPS and GLONASS.
o
Safety of Life Service allows similar accuracy as the Open Service but with increased
guarantees of the service, including improved integrity monitoring to warn users of any
problems.
o
Public Regulated Service is aimed at public authorities providing civil protection and
security (eg police), with encrypted access for users requiring a high level of performance
and protection against interference or jamming.
o
Search and Rescue Service is designed to enhance current space-based services (such as
COSPAS/SARSAT) by improving the time taken to respond to alert messages from distress
beacons.
o
Commercial Service allows for tailored solutions for specific applications based on
supplying better accuracy, improved service guarantees and higher data rates.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
GNSS Signal Spectrum
Lower L-Band
5250MHz
5030MHz
5010MHz
Glonass
G2
1610MHz
Galileo E1
GPS L1
1587MHz
1591MHz
1593MHz
1559MHz
1563MHz
Galileo E2
Galileo C1
Galileo E4
Glonass
G2
1237MHz
1239MHz
1214MHz
1215MHz
ARNS
RNSS
Galileo E6
GPS L2
1188MHz
1164MHz
1151MHz
960MHz
GPS L5
RNSS*
1254MHz
1258MHz
1260MHz
1261MHz
Galileo E5/B
Galileo E3
Galileo E5/A
RNSS*
C-Band
ARNS
RNSS
1300MHz
ARNS
RNSS
Upper L-Band
RNSS* shared with other services
06/09/07
Galileo E5/A or E5/B frequency band options
Veena G Dikshit, Sc 'E' , ADE, Bangalore
BENEFITS OF GNSS
•
Availability of Signals
•
Extra satellites improve continuity
•
Extra satellites and signals can improve accuracy
•
Extra satellites and signals can improve efficiency
•
Extra satellites and signals can improve availability (of satellites at a
particular location)
•
Extra satellites and signals can improve reliability
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
GNSS RECEIVERS DESIGN APPROACHES
A typical GNSS Receiver
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Software Receiver (SDR) Architecture
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Comparison of ASIC and SDR
Features
ASIC
SDR
Upgradability
•
•
A fixed platform.
Dictate the potential capabilities
of the receiver
•
•
Re-programmable
Re-configurable
Separation of
Hardware
•
Multi system upgrades changes
in base band processing
Hardware
•
Simple software
change
Acquisition
•
•
•
Serial search Acquisition
Convolution in the time domain
Using correlation technique
•
Parallel Search
Acquisition
FFT, Multiplication in
the frequency domain
Buffering memory
•
•
Tracking
•
•
More efficient
Cost effective
•
Power
Consumtion
•
Less power consumtion
More power consumption
Cost
effectiveness
•
More Hardware, More cost
Depends on the
processor MIPS
availability
Less Hardware less cost
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Development of GNSS Receiver
•
•
•
•
•
•
GPS L1 (Current)
GPS L1 & L2
GPS + GLONASS + SBAS
GPS + L5 + GLONASS + GALILEO
GPS + L5 + GLONASS + GALILEO + SBAS + GBAS
GPS + L5 + GLONASS + GALILEO + SBAS + GBAS + IRNS
BY 2015 position every where with decimeter and even centimeter
accuracy will be widely available and affordable
ISSUSES
• Lack of uniform compatibility
• Differing Timing of Operational availability
Hybrid receiver Architecture required
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
architecture.
Software receiver approach is nearly ideal in terms of
cost and system integration, as only a single front end
is needed to process all of the signals
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Challenges in the next generation receivers
•
•
Antenna Unit
•
Two Narrow band separated by 402 MHz
•
Broad band antenna covering multiple band signals
•
Challenge low cost satellite navigation receiver antenna requires – circular
polarization with adequate axial ratio and the medium gain.
RF Front end
•
Challenge proper on/OFF chip filter design and component selection will
improve the system performance.
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Digital Signal processing (A Big Challenge !?)
•
Multi-system receivers - Increased number of correlator channels
•
Dual band 2 correlator
•
Demand on the processing power depend on implementation
•
Implementation depend on the dynamics of the application
•
Approach either software correlator or trditional hardware correlator on
FPGA
•
To process a single C/A code channel with one chip correlator spacing
reqire a processing capacity of 4 MIPS
•
Increase in band width 2 t0 20 MHz wide band signals MIPS requirement
increases by factor of 10
•
To reduce the noise level 2 bit signal sampling further MIPS requirement
increases by factor 3
•
Finally for 48 channel 5760 MIPS are required
Demands are on the edge of currently available DSP
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore
Conclusion
Modernization trend, complexity, multitude of users and application,
Availability of different systems, differing time scale of availability are
Considered the development of the GNSS receiver for the defense
application offers a great challenge which need to be tackled right
from now
06/09/07
Veena G Dikshit, Sc 'E' , ADE, Bangalore