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AESA- A Huge Leap Forward in Radar Technology

Development of radars based on AESA technology has substantially enhanced the operational capabilities of surveillance radars and developed countries use them in their airborne & surveillance systems. The author elaborates way forward for India.

Active Electronically Scanned Arrays (AESA) are considered a phased array system, which consists of an array of antennas which form a beam of radio waves that can be aimed in different directions without physically moving the antennae themselves. The first AESA systems were developed in the 1980s and had many advantages over the older PESA system.  Unlike a PESA, which uses one transmitter/receiver module, AESA uses many transmitter/receiver modules which are interfaced with the antenna elements and can produce multiple, simultaneous radar beams at different frequencies. Development of radars based on AESA technology has substantially enhanced the operational capabilities of surveillance radars as well as fighter aircraft. Countries, all over the world are now introducing AESA based radars into their airborne & surveillance systems.

Main Advantages of AESA

Resistance to Electronic Jamming

One of the major advantages of an AESA system its high degree of resistance to electronic jamming techniques. In addition to changing frequencies, AESA systems can distribute frequencies across a wide band, even within individual pulses, a radar technique called “chirping”. This combination of traits makes it much harder to jam an AESA system than other forms of radar.

Low Interception

AESA systems also have a low probability of intercept by an enemy radar warning receiver (RWR). An RWR allows an aircraft or vehicle to determine when a radar beam from an outside source has struck it. In doing so, it can also determine the beam's point of origin, and thus, the enemy's position. AESA systems are highly effective in overcoming RWRs. Because the “chirps” i.e,  change frequency so rapidly, and in a totally random sequence, it becomes very difficult for an RWR to tell whether the AESA radar beam is, in fact, a radar signal at all, or just part of the ambient “white noise” radio signals found all over the world.

Increased Reliability

Yet another benefit of using AESA systems is that each module operates independently, so a failure in a single module will not have any significant effect on overall system performance. AESA technology can also be used to create high-bandwidth data links between aircraft and other equipped systems.

Multi-Mode Capability

This radar technology also supports multiple modes that allow the system to take on a wide variety of tasks including:-

  • Real beam mapping
  • Synthetic Aperture Radar (SAR) mapping
  • Sea surface search
  • Ground moving target indication and tracking
  • Air-to-air search and track

Limitations/Challenges

As with most technology, there are a few challenges that manufacturer's face during the development of AESA radar technology. For optimisation of the design, some of the areas which need to be critically examined include power output, cooling due to high heat dissipation in the circuit, weight and of course price. Moreover, with a half wavelength distance between the elements, the maximum beam angle is approximately ±45°. With a shorter element distance, the highest Field of view (FOV) for afloat phased array antenna is currently 120°(±60°), although this can be combined with mechanical steering for better results.

Luckily, advancements have already been made and are continuing to advance, as technology continues to improve. For example, the weight of these radars has decreased by over half within the past few years along with a decrease in size, mainly due to the use of Nanotechnology. This allows the AESA to be mounted in areas other than just the nose of an aircraft. The radar will be able to be oriented in multiple directions and provide a wider perspective.

The Future of AESA

As AESA technology has advanced, it has become smaller and more affordable. This has allowed many countries to incorporate AESA into legacy systems on the ground, in the sea, and in the air. Countries around the world are adding AESA radar into their military aircraft, missiles and this has spurred the global demand for AESA systems. Top global defence manufacturing companies are now engaged in design & development of AESA radars and achieved considerable success as indicated in Table- 1.

It is worthwhile to note that US companies have established a considerable lead in AESA development. In 2016, Raytheon made headlines in the defence tech world by debuting its gallium nitride (GaN)-based AESA upgrade to the Patriot. By pairing two of these upgraded systems facing in opposite directions, they can cover a complete, 360-degree range. In Europe, Thales has its AESA installed on Rafale. In fact, AESA was a key requirement for India's MMRCA (Medium Multi-Role Combat Aircraft) competition, and the 36 Rafale jets being acquired from France should have both the AESA as well as the Infra-Red Search and Track (IRST) system. India recently contracted an Israeli firm ELTA to furnish its fleet of Jaguar fighter jets with new AESA radar systems. While these jets are old, incorporating AESA radar capabilities will allow these and other legacy craft to remain relevant in a world where electronic warfare is becoming ever more important. Simply put, without AESA, modern conventional military radars are obsolete. It's no longer optional, and it's going to become more widespread as time goes on.

Indigenous development

To meet the twin objectives of modernisation of our armed forces & achieving self-reliance, indigenous development of AESA radar is a step in the right direction. Electronics Research & Development Establishment under DRDO is India's premier Radar design and development establishment and is deeply involved in the development of Indigenous radars for the military. Its primary production partners include Bharat Electronics Ltd and various private firms like Mistral in Bangalore, Astra microwave in Hyderabad and Data pattern in Chennai.

LRDE has developed various radar systems for defence forces including surveillance radar (INDRA), Air defence (Rajendra), 3D - central acquisition radar, weapon locating radar(Swathi), battlefield- surveillance radar (PJT-531) etc. These projects and many other phased array radar projects have given LRDE plenty of experience in designing and developing cutting edge AESA systems and also help it realise critical technologies needed for such systems. Presently, LRDE/DRDO is working on a host of AESA projects. Some of these are:-

AESA for Indigenous AWAC systems

DRDO has taken the number of steps towards the development of the AESA radar for its current and future AEW&C applications.  An important aspect of the AEW&C system developed by DRDO and integrated on the Brazilian made Embraer aircraft is the AESA radar system. It provides coverage of 240 degrees. Development of the Transmit-Receive Multi-Modules (TRMM), a key component of AESA, was a significant and high-value indigenous effort as the technology, hitherto available only to a handful of advanced nations, could be, for the first time, engineered successfully to fully meet the needs of the Indian AEW&C system. A unique feature of the indigenous TRMM design is that eight trans-receive modules are combined compactly to form a single TRMM, thus facilitating high-density installation of 160 of them in the Active antenna array unit (AAAU) to power the surveillance radar. The important fact about the indigenous TRMM is that the quantity required for the Indian AEW&C program could be produced through the industry in the private sector at a cost less than one-fourth of that of its imported equivalent. The realisation of the TRMM is a boost to self-reliance in development of indigenous defence systems.

This AWAC system has already been inducted into service with IAF. It has given DRDO valuable experience in designing  & developing high power airborne radars and will be the bedrock for the future airborne radar projects including AWACS. A good example of this is the Airbus A330-200 based airborne early warning & control (AEW&C) system being developed by DRDO. The aircraft will be fitted with an AESA radar housed in external radome and provide coverage of 360 degrees and a range of more than 400 KMs. It will be a great leap forward towards developing high power airborne radars. This will also bridge the technology gap &do away with our dependence on external sources. Additionally, it will also enhance the export potential of our radar systems.

UTTAM: AESA Fire Control Radar

This will be the second airborne AESA program after the AEW&C project and intends to transfer the success DRDO has achieved in the Ground-based radar segment to airborne systems.

It is a multi-mode solid state phased array radar developed by LRDE. It is primarily a fire control radar for deployment in airborne platforms such as LCA Tejas aircraft as well as Jaguars & MIG-29Ks etc. It has a maximum power output of 3.6 kw &target detection range of 150 km for a 2 sqm target. It has the capability to track at least 20airborne targets and engage six targets with high accuracy suitable for firing missiles. It has densely packed compact Gallium Arsenide (GaAs) T/R modules. UTTAM has capabilities like Identification friend or foe (IFF), electronic and communication support measures, C-band line-of-sight and Ku-band SATCOM data links, etc., similar to those on the AWACS.

The important modes of operation of the UTTAM radar system are surface surveillance and air surveillance. The sensor has the abilities to search, track-while-scan, priority tracking, high-performance tracking, etc. Utilizing active aperture technology, the radar provides a fast-beam agile system that can operate in several modes concurrently.

As per the current status, hardware has been realized and a software update has been completed.  DRDO is now testing the radar in Air-to-Air& air-to-ground mode. Once the development will be completed, the radar will be able to carry out high-resolution mapping of the ground, detect & track multiple ground moving targets & operation of electronic countermeasures.

Prototypes of this radar have already been tested from helicopter & rooftop in all the required modes. The system is now undergoing flight trials on a flying test bed, appropriately one of the LCA -Tejas recently inducted. The initial timeline for the indigenous  AESA Radar was set at 2017. This process is likely to take at least 2-3 years more before meaningful production can commence.  UTTAM AESA radar once in production will be used on LCA Tejas-MKII while Tejas MK-IA most likely will be getting Israeli developed ELTA's EL/M-2052 aesa radar which is already being procured for Jaguar Darin III upgrade. However, LRDE is still hopeful that if all trials are completed in the decided time frame, it might still be selected to be used on last batches of MK-IA if desired by the IAF.

Future development & Industry Participation

The necessary core competence to evolve futuristic applications in AESA radar has thus been adequately established. DRDO/LRDE has now offered this technology to the Indian Industry and has asked them to submit proposals for transfer of technology (ToT). It is a good opportunity for the industry to assimilate the technology and create the necessary infrastructure for further development & production of this technology. Futuristic efforts by DRDO should focus on the development of 360 degrees antenna. Preliminary studies have been carried out at Center for Airborne Studies (CABS) for possible optimal design of a futuristic antenna with the desirable 360°vision for roles identified under various war situations. Moreover, the LCA radar developed for LCA is essentially a low power radar and technologies for high power radars for longer ranges need to be developed.  Since GaN devices can provide higher power output as compared to GaAs devices used in DRDO AESA, it can play an important role in the future design of AESA radars. But due to high heat dissipation required in GaN devices& less linearity, it may still be a trade-off between GsAs & GaN depending on the end use requirements. Moreover, as the volume of GaN increases & the cost decreases, it is expected that GaN will replace GsAs. There is already a proposal worth Rs 3000 crores with the Govt of India to set up a Foundry at Indian Institute of Science (IISc), Bangalore for producing GaN, a Nanomaterial. It will certainly help in the indigenous development of next-generation radars, seekers & communication systems. It will also enhance the effectiveness of our Antiballistic Missile Programme.

In view of the impending up gradation of our large (4th largest in the world) combat/other aircraft fleets, there will be a huge demand for these systems & enough scope for Electronic industry to participate in its production. The industry should come forward to meet this challenge under the make in India programme.

Conclusion

The foregoing summarises the efforts made by DRDO towards the development of the AESA radar for its current and future AEW&C & fire control radar applications as well as for realising essential allied technologies. For India, investing in this technology is imperative & need of the hour due to its operational necessity. With advanced Electronic warfare capabilities now available with our adversaries, we need to accord high priority to develop AESA radars.

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