AESA Upgrade Option for
Eurofighter Captor Radar
M. Barclay
SeJex GaliJeo
u. Pietzschmann
EADS Defence Electronics
G. Gonzalez
Indra, Aranjuez
&
P. Tellini
Selex GaiNeo
ABSTRACT
The Euroradar Consortium has successfully developed
and demonstrated an Active Electronically Scanned
Array (AESA) technology upgrade for the Eurofighter
Typhoon Captor Radar. This technology demonstrator,
designated Captor Active Electronically Scanned Array
Radar (CAESAR), enables E-scan capability to be fully
exploited by the existing Captor radar, while retaining all
features and capabilities of the original system. Advanced
waveforms, designed and optimized for
electronically-scanned radar systems, have been
evaluated in recent CAESAR flight trials. Production of
the CAESAR system will address repackaging of the
AESA and associated components to minimize mass and
volume, reduce cost, and ensure ease of supportability.
CAESAR has demonstrated that AESA benefits can be
provided within the existing Captor framework,
enhancing seDsor capability while retaining existing
Euroflghter Typhoon interfaces.
INTRODUCTION
Radar systems based on Active Electronically Scanned
Array (AESA) technology have now been introduced on
operational fighter aircraft. Eurofighter Typhoon, which can
accommodate a large diameter antenna and provide high
prime power, would derive particular advantage from
incorporation of AESA technology.
The availability of AESA technology will confer many
significant operational, performance, and Through Life
Capability Management (TLCM) benefits [1, 2]. The
instantaneous beam-pointing capability, when governed by
energy management algorithms, enables spectacular
performance to be achieved. This is particularly true in air
combat scenarios where the AESA system can be operated as
a number of independent "virtual" radar systems, allowing
dedicated tracking of individual targets while maintaining
full search coverage.
Minimisation of logistic support requirements and
reduction of through-life costs are major drivers for
upgrading to-scan. These are facilitated by the inherent high
reliability of AESA technology and the ability to introduce
new functionality through software development alone.
The Euroradar Consortium - comprising Selex Galileo
(UK), EADS Defence Electronics (Germany), Selex Galileo
(Italy), and Indra (Spain) - has developed an AESA antenna
and associated hardware/software modifications which
enable E-scan capability to be exploited by the existing
Captor radar, while retaining all features and capabilities of
the original system. This technology demonstrator upgrade
package, known as CAESAR, has been flight tested on
Eurofighter Typhoon and utilizes existing aircraft interfaces.
CAPTOR RADAR SYSTEM
Author's Cumnt Addresses:
M. Barclay, Selex Galileo, Edinburgh, UK; u. Pietzschmann, EADS Defence Electronics,
U1m, Gamany; G. GouzaIez, Indra, Aranjuez, Spain; and P. Tcllini, Sclex Gali1eo,
Pomczia, Italy.
Based 011 a prcsentatiOll at Radar 2008.
088518985/101 $26.00 USA C 2010 IEEE
IEEE A&E SYSTEMS MAGAZINE. JUNE 2010
The Captor radar is the most adv!lllced multi-mode
pulse-Doppler radar of its generation. It is the primaty
sensor on the Typhoon platform, currently in service with
the four Eurofighter partner national (UK, Germany, Italy,
and Spain).
IS
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Low Voltage
DCP..-
Existing
Aircraft
Interfaces
Unchanged
RFOrive
AESA
RFOUI
Status/BIT
Con,""
Fig. 1. CAESAR System Block Diagram
The Captor radar system currently comprises six Line
Replaceable Items (LRIs).
CAESAR: AESA UPGRADE
The CAESAR (Captor Active Electronically Scanned
Array Radar) design concept replaces existing Transmitter,
Waveguide Unit and Scanner/antenna LRIs with a new
AESA. Associated power and control functions are provided
by Antenna Power supply and Antenna Control Unit LRIs.
All other CAPTOR LRIs are retained with minimal
modification, while aircraft interfaces remain unchanged (see
Figure 1).
Aircraft installation is illustrated in Figure 2.
AESA
Key features of the CAESAR AESA design include:
Fig. 3. Transmit I Receive Module (TRM)
•
Circa 1500 transmit / Receive Modules (TRM)
arranged in a nominally circular outline,
Key features include:
•
•
Multi-role air-to-air and air-to-surface
capability,
•
All aspect automatic detection and tracking,
•
•
Low pilot workload,
•
Dedicated support for Eurojighter Typhoon
weapons,
•
•
High transmitted power, low antenna sidelobes,
•
•
Powerful and flexible ECCM, and
•
•
fully programmable and scalable signal and
data processors.
Wide bandwidth, light-weight, high dynamic
range, low noise, high power using GaAs
pHEMT HPA chipset,
> 30 sub-arrays,
Multiple Guard sub-antennas, offering various
options for gain and directional bias,
Liquid cooled "plank" architecture, and
Wideband, low-cost radiating element designed
for high performance overfull range of scan
angles, RFfrequencies, and waveforms.
Transmit I Receive Module (TRM)
The CAESAR TRM is a derivative of an existing light
weight design (see Figure 3).
Key TRM design features include:
Antenna
Control Unit
AESA
Existing Power
Conditioning Unit
Existing Receiver
•
Fully integrated Control ASIC,
•
GaAs core chip,
•
Dual pHEMT HPA,
•
Low Noise Figure « 3 dB),
•
High Linearity / TOI, and
•
Extensive BIT capability.
Power and Control
Fig. 2. CAESAR Aircraft Installation
Aircraft supplies are first rectified and conditioned in the
Power Conditioning Unit, then converted and further
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conditioned by the Antenna Power Supply before distribution
to the AESA via low voltage through-bulkhead cabling.
Control of the AESA is exercised by the existing Captor
Processor, with updated software. Beamshape and steering
commands are sent to the Antenna Control Unit which
calculates phase / amplitude weights, incorporating
corrections dependent on frequency, temperature, and
bandwidth. The data are distributed to individual TRMs using
a number of high-speed fault-tolerant serial links.
Fig. 5. CAESAR Installed on Captor Test-bed Aircraft
Fig. 4. Antenna Pattern (Boresigbt)
Modes and Functions
Advanced air-to-air prototype modes and associated
digital signal processing algorithms have been developed to
derive maximum advantage from electronic scanning
capability. Multiple waveforms, individually optimized for
search, target confirmation, and track maintenance [3] are
used to implement an alert-confirm target detection and
acquisition strategy, resulting in increased track formation
ranges, greatly improved track tenacity, and better
measurement accuracy when compared to a comparable
mechanically-scanned system. Furthermore, in contrast to
mechanically-scanned radar systems, track file capacity may
be scaled up without significant impact on search capability
or situational awareness.
Fig. 6. BAC I-II Captor Test-bed Aircraft
Initial AESA calibration and pattern performance
assessment was conducted on a test range. Excellent patterns
were measured up to, and including, the maximum theoretical
achievable electronic scan angles off boresight. A typical
antenna pattern is shown in Figure 4.
Sensing performance of the integrated system was
evaluated using a combination of standard Captor test
equipment and ground trials against cooperative fast jet
targets. Formal acceptance testing was concluded in
November 2005, enabling the system to be released for initial
flight trials.
System Test
The CAESAR system was fully integrated and tested
in roof-lab trials prior to being installed in the BAC I-II
Captor test-bed aircraft. Equal priority was given to
robustness and performance, to ensure that useful results
could be obtained from the earliest flights. Significant
effort was expended by all members of the Euroradar
Consortium to optimize the system in order to satisfy
these objectives.
CAESAR EVALUATION
THE CECAR PROGRAMME
Performance of the Euroradar CAESAR system is being
evaluated within the CECAR programme which is jointly
funded by the UK and German governments. This
programme involves three phases of flight trials programmes,
complemented by ground tests and parallel design studies.
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CAPTOR System, related to the clearance effort and
CAESAR development status, at that time.
The radar perfonned beyond expectation on all flights on
both aircraft. The main achievements of CAESAR flight
trails to date include:
•
Full demonstration 0/ all operational and radar
modes, using conventional and agile-beam
scanning strategies, including multiple target
fonnations, look-up and look-down,
•
Acquisition o/key data /or ojJ1ine analysis,
covering digitized radar returns, internal and
external communications traffic, and monitoring
of power and cooling services, and
Fig. 7. CAESAR on Eurofighter DA5 Aircraft
•
CAESAR has demonstrated that high
performance E-scan radar technology can be
introduced as an upgrade to existing equipment,
maintaining compatibility with existing AlC
interfaces (mechanical, electrical, cooling, and
databus).
Fig. 8. Eurofighter Typhoon DA5 Aircraft
It is within the CECAR programme that the operational
perfonnance benefits of CAESAR E-scan technology have
been successfully demonstrated in flight tests on the BAC
1-11 Captor test-bed and Eurofighter Typhoon aircraft
against a range of target types. Both aircraft are fitted with a
comprehensive instrumentation suite, which has been used
for more than 200 development flights on the main
development of the Captor radar for Typhoon. CAESAR,
being a member of the Captor radar family, is able to use the
instrumentation and recording suite without modification.
Initial BAC 1-11 flight trials were conducted from
Boscombe Down Airfield in the UK during the Spring of
2006. Initial shakedown flights provided the opportunity for
making adjustments to both radar and aircraft systems, as
final preparation for an intensive round of flight testing.
Exploitation of the trials data from the initial flights
enabled CAESAR to be fine-tuned, enhancing E-scan
perfonnance on subsequent flights.
Flight Tests on Eurofighter Typhoon (Development
Aircraft DA5) followed in the Spring of 2007, conducted
from Manching in Gennany [4]. The bulk of this work was
funded by the Gennan MoD, supported by all Euroradar
partners, as an adjunct to the CECAR programme. These
focused on a reduced set of functional modes compared to the
18
OFF BORESIGHT
NEAR BORESIGHT
Range
Fig. 9. Comparison of E-scan Clutter Maps
Fig. 10. High Resolution SAR Map
Offline analysis of radar data enabled confinnation of
achieved perfonnance, detailed interpretation of observed
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�
events and artifacts, calibration of supporting models, and
definition of key design improvements.
An example of clutter maps produced from the processed
radar data is shown in Figure 9. This clearly shows the
expected change in clutter distributions as the antenna is
scanned away from boresight.
The most significant performance aspect of all flight tests
was the range at which stable and robust tracks could be
formed on small, fast, and highly maneuverable air targets,
when compared to conventional mechanically-scanned
systems.
The CECAR programme will continue with a further
round of flight trials to be conducted on the BAC I-II Captor
test-bed aircraft. This element of the programme, which is
scheduled to commence in the Spring of 2008, will introduce
advanced capability covering both air-to-air and
air-to-ground roles. Air-to-air performance will be extended
through innovative adaptive waveforms aimed at providing
further detection and tracking performance benefits,
enhanced overall situational awareness, and robustness of
operation. Ground testing was completed in late 2007.
Air-to-ground performance enhancements will include the
ability to form high resolution maps, with improved
capability over that which can be supported by the existing
equipment standard (see Figure 10).
LOOKING FORWARD
CAESAR and the related CECAR programme have
provided extremely valuable knowledge which can now be
applied directly to production. Flight trials data has resulted
in waveform and algorithm modifications which, collectively,
will significantly improve both sensing performance and
energy management within the radar system. Further
advances are expected, following completion of forthcoming
flight tests.
A key element of the CAESAR programme involved
evaluation of new supportability strategies. This was aimed at
achieving manifold increases in reliability and
maintainability performance metrics when compared
alongside equivalent conventional mechanically-scanned
technology. In one exercise aimed at verifying robustness of
the calibration strategy, the AESA was intentionally stripped
down and rebuilt on a number of occasions. The lessons
learned from this, and similar exercises, will directly inform
future TLCM strategies, with longer term benefits accruing
from reduced logistic support requirements and lower
life-cycle costs.
Having successfully proven the technology concept on
both the BAC 1-1 I and Typhoon platforms, the focus of the
Euroradar companies has shifted to design changes geared
toward produceability of a cost-effective AESA upgrade
which could enhance future operational, logistical, and
performance capabilities of the Eurofighter Typhoon
weapons system (see Figure 11).
This exercise addressed:
IEEE A&E SYSTEMS MAGAZINE, JUNE 2010
Powe<
Status/BIT
Con"'"
An"' ....
Power
Supply &
Comma
Power
Conditioning
Conlroller
Existing
Aircraft
AESA
Interfaces
RF 0riYe
RFOut
o
Processor
Receiver I
exciter
Existing Captor LRI
RadarOat&
...
New or Modified Captor LRI
Fig. 1 1. Production CAESAR
•
•
•
•
•
•
Production of AESA components to reduce depth
and mass, increase transmitted power, and
reduce cost,
Refinement of design to maximize intrinsic
supportability advantages,
Increased level of integration, resulting in a
reduced number of LRIs,
Upgrade of Power Supply & Control interfaces
to increase capacity and simplify LRI
inter-connects,
Extension of existing BIT capability, and
Introduction of provisions to allow for future
further exploitation of E-Scan technology via
software upgrades.
This configuration will deliver advanced functionality and
capability, including:
•
•
•
•
Multi-channel adaptive beamforming,
Space-Time Adaptive Processing (STAP) and
Adaptive Beam Forming (ABF),
Advanced air-to-ground target identification
based on ultra high resolution Synthetic
Aperture Radar (SAR) capability, and
Support for Network Enabled Capability, both
as gatherer and distributor of high value 1STAR
data.
We intend to conduct advanced flight trials using a
production-standard configuration at our earliest opportunity.
CONCLUSION
The Euroradar CAESAR programme has demonstrated
AESA capability within a variant of the successful Captor
Typhoon radar. Following extensive ground testing, the
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system was successfully flight tested on the BAC 1-11
Captor Test-bed aircraft and on the Eurofighter Typhoon
DA5 aircraft. The expected E-scan advantages were fully
demonstrated in both air-ta-air and air-ta-ground roles,
operating against a range of air and ground targets.
The reliability of the CAESAR equipment was excellent,
in keeping with expectations for AESA technology in
general. The supportability strategy for future AESA
products will benefit greatly from valuable lessons learned on
the CAESAR programme.
CAESAR has demonstrated that AESA benefits can be
provided within the existing Captor framework, enhancing
sensor capability while retaining compatibility with existing
Eurofighter Typhoon interfaces. The programme has
contributed to establishing a route for future upgrades of the
Eurofighter Typhoon weapon system [5]. Series production
of a more advanced variant could, with appropriate emphasis,
be achieved within a relatively short time frame. AESA
technology will provide an excellent basis for further
development of multi-role capability and ensure that
capability is maintained in the longer term. Furthermore, this
would be achieved with a reduced Through Life Capability
Management (TLCM) burden.
ACKNOWLEDGEMENTS
The authors extend their grateful thanks to many
colleagues within the Euroradar Consortium who are / were
involved in the design, development, and evaluation of
CAESAR.
The efforts and support of the Eurofighter partner
companies was essential to successful flights in the
Typhoon aircraft.
20
Finally, much gratitude is due to key government agencies
within the UK and German Ministries of Defence, including:
Bundesamt fUr Wehrtechnik und Beschaffilng, DE&S (SANS
& Air EW IPT), DEC (TA), DSTL, and FGAN. Collectively,
they have provided direct support in various forms,
particularly funding for flight trials and evaluation of the
CAESAR system via the CECAR programme.
REFERENCES
[1] P.E. Holbourn,
The Future Evolution of Airborne Radar,
Military Technology,
Vol.
[2] W.
23, Issue 8, pp. 57-64, August 1999.
Holpp,
The Future of Radar has Begun,
Military Technology,
Vol.
30, Issue 7, pp. 100-102,2006.
[3] PJ. Fielding and A.M. Kinghorn,
Waveform Optimisation for Efficient Resource Allocation
in Airborne AESA Radar Systems,
lEE Radar Conference, November
2001.
[4] W. Holpp,
E-Scan for Eurofighter and the Pilot's View,
International Radar Symposium,
Cologne, September
2007.
[5] W. Holpp,
New AESA Radar to Enhance Combat Effectiveness
of Eurofighter,
Military Technology, Issue
7, 2007.
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