Indian AESA Radar Developments
- Thread starter ni8mare
- Start date
A very interesting read about Networking of Tracking Radars of two different SAM systems(Pechora and Flycatcher) by DRDO to make them jamming tolerant.
View of Networking of Tracking Radars of Two Different SAM Weapons to Protect the Missile in Intensive Jamming Environment
@vstol Jockey @Falcon @Ashwin @Parthu. This should tickle your interests a bit, sirs.
I didn't understand most of it
View of Networking of Tracking Radars of Two Different SAM Weapons to Protect the Missile in Intensive Jamming Environment
@vstol Jockey @Falcon @Ashwin @Parthu. This should tickle your interests a bit, sirs.
I didn't understand most of it
A very interesting read about Networking of Tracking Radars of two different SAM systems(Pechora and Flycatcher) by DRDO to make them jamming tolerant.
View of Networking of Tracking Radars of Two Different SAM Weapons to Protect the Missile in Intensive Jamming Environment
@vstol Jockey @Falcon @Ashwin @Parthu. This should tickle your interests a bit, sirs.
I didn't understand most of it
Nothing that emits a signal remains jam proof. You can only reduce the 'blind' phases by significant factors to almost negligible, but they will still be there.
During the Aero India 2009 Air Show, the then Director General of DRDO & Scientific advisor to India's Defence Minister Dr. V.K Saraswat delivered a fascinating lecture in which he talked about the evolution of India's Missile Development Program & the various projects that have been successfully undertaken & those that are currently under way for the future deployment. There were many detailed analysis made in various Indian defence forums about that one 2 hours long lecture. One thing that struck me was how many of what was talked about in that lecture seem to be coming to fruition, ASAT is one prime example. Some others are already in service : Astra BVRAAM for example. Also it seems to me that the speed of achieving results is steadily increasing.
With that being said I bring to you the one specific slide from the lecture I wanted to talk about :
If you notice the points, you will see some of it has been achieved(imaging radar seekers, Data fusion, electronic scanning) some others are under development(dual band, dual mode, mems based T/R modules).
The one thing here that interests me the most is the "Conformal Antennas". Much to my great delight I have come across a some recent research papers which point to the development and testing of the said technology.
This one is from September 2018. It is about the : "Design and Development of Compact Conformal Microstrip Antenna at S-Band". It also states : "This paper addresses the conformal antenna design for missile requirements.". If I recall correctly as @randomradio once told me S-band radio waves produce high resolution radar picture for target discrimination, acquisition, tracking and engagement. For example the Kolkata class destroyers use the EL/M-2248 MF-STAR radar which is a S-band radar. The paper also states : "One of the major advantages of microstrip patch antenna is that it can be flush mounted to a curved host surface such as an aircraft, UAV, missile and satellite. It provides omni-directional coverage(when number of elements are used) for onboard application to ensure uninterrupted link between ground station and space vehicle". I assume that this Conformal Micro-Strip Antenna(CMSA) will be used to receive and send targeting information to and from fire control radars(ground based, sea-bourne, air-bourne) and on-board missile seekers. Please do correct me if I am wrong.
Performance evaluation of the CMSA :
Source : View of Design and Development of Compact Conformal Microstrip Antenna at S-Band
continued on next post..
With that being said I bring to you the one specific slide from the lecture I wanted to talk about :
If you notice the points, you will see some of it has been achieved(imaging radar seekers, Data fusion, electronic scanning) some others are under development(dual band, dual mode, mems based T/R modules).
The one thing here that interests me the most is the "Conformal Antennas". Much to my great delight I have come across a some recent research papers which point to the development and testing of the said technology.
This one is from September 2018. It is about the : "Design and Development of Compact Conformal Microstrip Antenna at S-Band". It also states : "This paper addresses the conformal antenna design for missile requirements.". If I recall correctly as @randomradio once told me S-band radio waves produce high resolution radar picture for target discrimination, acquisition, tracking and engagement. For example the Kolkata class destroyers use the EL/M-2248 MF-STAR radar which is a S-band radar. The paper also states : "One of the major advantages of microstrip patch antenna is that it can be flush mounted to a curved host surface such as an aircraft, UAV, missile and satellite. It provides omni-directional coverage(when number of elements are used) for onboard application to ensure uninterrupted link between ground station and space vehicle". I assume that this Conformal Micro-Strip Antenna(CMSA) will be used to receive and send targeting information to and from fire control radars(ground based, sea-bourne, air-bourne) and on-board missile seekers. Please do correct me if I am wrong.
Performance evaluation of the CMSA :
Source : View of Design and Development of Compact Conformal Microstrip Antenna at S-Band
continued on next post..
Another research paper is from July 2018 on the topic : "Frustum Shaped Conformal Antenna for Spinning Aerial Platform"
The paper seeks to achieve the following :
"A novel approach to design and develop frustum shaped conformal antenna for transmission of telemetry data from a missile like spinning aerial platform is described. The requirement necessitates for an omni directional radiation pattern in the roll plane. However, the criteria is not feasible to achieve by using a monopole or a dipole as the omni coverage due to these antennas are restricted only in yaw or azimuth plane of the aerial platform. A conformal antenna appropriately wrapped on to the surface provides potential solution and accordingly has been configured for meeting the requirements of a practical application. The antenna artwork has been designed to conform to the exterior geometry of the intended portion of conical surface and printed on a microwave substrate which is essentially thin and flexible. A corporate feed distribution scheme has been designed and tailored to match with the impedance of the microstrip radiator at multiple locations and also printed along with it making the frustum antenna very compact and of aerodynamic supportive form. The antenna produces required omni coverage in the plane normal to the roll axis. A step-wise method for the design and development of the frustum conformal antenna through simulation and experiment approach has been discussed."
Why frustrum shaped, I wonder.
continued...
The paper seeks to achieve the following :
"A novel approach to design and develop frustum shaped conformal antenna for transmission of telemetry data from a missile like spinning aerial platform is described. The requirement necessitates for an omni directional radiation pattern in the roll plane. However, the criteria is not feasible to achieve by using a monopole or a dipole as the omni coverage due to these antennas are restricted only in yaw or azimuth plane of the aerial platform. A conformal antenna appropriately wrapped on to the surface provides potential solution and accordingly has been configured for meeting the requirements of a practical application. The antenna artwork has been designed to conform to the exterior geometry of the intended portion of conical surface and printed on a microwave substrate which is essentially thin and flexible. A corporate feed distribution scheme has been designed and tailored to match with the impedance of the microstrip radiator at multiple locations and also printed along with it making the frustum antenna very compact and of aerodynamic supportive form. The antenna produces required omni coverage in the plane normal to the roll axis. A step-wise method for the design and development of the frustum conformal antenna through simulation and experiment approach has been discussed."
Why frustrum shaped, I wonder.
continued...
Project Conclusion :
Source : file:///C:/Users/GAUTAM/Documents/12217-Article%20Text-38956-3-10-20180709.pdf
A few months back I found a research paper that talked about the development of "large area flexible electronics". The paper didn't talk about the uses of the said technology. I posted those pictures in this thread post #61. It seems to me that the flexible electronics technology was one of the building blocks to the conformal antenna that we see on these papers.
Your thoughts : @Parthu @randomradio @vstol Jockey @Falcon @BlackOpsIndia @Milspec @_Anonymous_ @Sathya and everyone else I missed.
If we really have this tech, we can create a conformal radar for LCA MK1 and that will free up lot of space in the nose allowing for fitting the IRST and also ASPJ by relocating few boxes from fuselage to nose.
Excellent article, a bit old but updated.
Is LRDE developing an Ultra-Wideband (UWB) AESA Radar for AMCA?
November 22, 2018
An active phased array radar composed of tapered slot antenna elements (TSA) undergoing testing in an anechoic chamber
AESA radars are becoming the centerpiece of next-generation sensors suites. This new type of radar has greatly enhanced the situational awareness of modern combat aircraft. An AESA radar offers several advantages over legacy passive phased array (PESA) radar such as- higher range, beam agility, low probability of intercept (LPI), enhanced performance, increased ECCM resistance, high effective radiated power and more. An AESAR has an active phased array antenna composed of hundreds (or thousands) radiating element. These radiating elements are arranged in a geometrical pattern. The most commonly used radiating elements for phased array radar are dipoles, open-ended waveguides, slotted waveguide, microstrip antenna, helix, and spiral antennas.
Electronics and Radar Development Establishment (LRDE) has already developed several advanced AESA radars such as Aslesha, Arudhra, L-STAR, Swordfish LRTR, etc. Currently, LRDE is working on several radars such as Uttam AESA radar, High Power Radar, 360° coverage AESA radar for AEW&CS India and it is also working on some futuristic RF technologies which one day might go into Indian 5th generation Advanced Medium Combat Aircraft (AMCA). One of the new technologies LRDE is working on is shared aperture radar.
What is a shared aperture radar?
In simple terms, a shared aperture radar combines the functionality of multiple antennas into one, for example - using a radar antenna for electronic warfare and long-range tactical communication. The aperture can be shared in multiple ways. One way is time-interleaving, when radar functions aren't being used, the aperture can be used for other purposes. Another way is to subdivide the aperture into smaller segments, with each segment performing a specific task simultaneously, furthermore, each segment can be time-interleaved, for ex. radar segment may have interleaved modes. Finally, a shared aperture may also use multiple independent beams to perform multiple functions simultaneously. The last approach is the most advantageous as well as complex (isolating beams and intermodulation products is a challenging task).
Primary requirements of a shared aperture radar are 1. Wide bandwidth radiating elements 2. Multiple polarizations. Isolating beams and intermodulation products require state of the art filters and amplifiers. LRDE is developing critical components for a shared aperture radar- wideband radiating elements and associated TR module technology.
LRDE developed a 16x16 element planner array antenna to investigate the technology. The small antenna array provided sufficient functionality to study associated radiation characteristics and tradeoffs. Since the primary requirement is wide bandwidth ( >50% of center frequency) and dual polarization, it prevents the use of the common type of antennas such as microstrip patches, printed dipoles, and open-ended dipoles as the bandwidth of these antennas is <=30% of center frequency.
Therefore, TSA (Tapered slot antenna) AKA Vivaldi flared notch antenna was selected. TSA antenna meets all the requirements mentioned above. It has symmetrical radiation pattern, high gain, and wide bandwidth. The most recognizable feature of the TSA antenna is its V-shaped flared notch. The narrower region of the notch radiates RF signals of high frequency, whereas broader part radiates RF signals of low frequency.
The geometry of Tapered Slot Antenna(TSA)/Vivaldi Antenna
Closeup of an active phased array radar composed of X-band TSA radiating elements
Antenna element and planks developed for wide-band TR modules by DARE (Image: Delhi Defence Review- DDR)
Antenna arreay for revolving body. Credit on pic. (I added this, wasn't in the article)
Wideband TRM developed by DARE features Vivaldi Notch Antenna Array (Image: Delhi Defence Review- DDR)
Actual image of LRDE developed Tapered Slot Antenna (TSA) ( Image of associated MMIC isn't available)
DRDO has invested a lot of money in gallium nitride MMIC development projects and there are plans to set up a state of the art GaN foundry at IISc. It's likely that TR modules of AMCA's radar will use GaN-based solid-state RF amplifiers. GaN MMIC combined with latest LNA tech will greatly enhance detection range (greater than 200km for a 1 sqm RCS target). It also eliminates the requirement of a liquid coolant circulation based cooling system. Existing radars in IAF service use traveling wave tube amplifier (TWTA) and slotted waveguide antenna (planer array of slots). The bandwidth of these radars is relatively narrow (600-800MHz). More advanced radars such as Uttam and EL/M-2052 have a much wider bandwidth (1-3GHz). A wideband radar using TSA radiating element may have a bandwidth no less than 5 GHz and an enhanced probability of detection+classification and it's much more difficult to jam. The associated wideband/multi-channel MMIC is however very complex and expensive. It is in an early development stage and the technology in question is futuristic. If this radar tech indeed goes to the AMCA, then the development period is perfectly aligned with the timeline of the aircraft being inducted into the IAF i.e beyond 2035.
Article written by - Disha (ECE Department, Malaviya National Institute of Technology, Jaipur)
Is LRDE developing an Ultra-Wideband (UWB) AESA Radar for AMCA?
Is LRDE developing an Ultra-Wideband (UWB) AESA Radar for AMCA?
November 22, 2018
An active phased array radar composed of tapered slot antenna elements (TSA) undergoing testing in an anechoic chamber
AESA radars are becoming the centerpiece of next-generation sensors suites. This new type of radar has greatly enhanced the situational awareness of modern combat aircraft. An AESA radar offers several advantages over legacy passive phased array (PESA) radar such as- higher range, beam agility, low probability of intercept (LPI), enhanced performance, increased ECCM resistance, high effective radiated power and more. An AESAR has an active phased array antenna composed of hundreds (or thousands) radiating element. These radiating elements are arranged in a geometrical pattern. The most commonly used radiating elements for phased array radar are dipoles, open-ended waveguides, slotted waveguide, microstrip antenna, helix, and spiral antennas.
Electronics and Radar Development Establishment (LRDE) has already developed several advanced AESA radars such as Aslesha, Arudhra, L-STAR, Swordfish LRTR, etc. Currently, LRDE is working on several radars such as Uttam AESA radar, High Power Radar, 360° coverage AESA radar for AEW&CS India and it is also working on some futuristic RF technologies which one day might go into Indian 5th generation Advanced Medium Combat Aircraft (AMCA). One of the new technologies LRDE is working on is shared aperture radar.
What is a shared aperture radar?
In simple terms, a shared aperture radar combines the functionality of multiple antennas into one, for example - using a radar antenna for electronic warfare and long-range tactical communication. The aperture can be shared in multiple ways. One way is time-interleaving, when radar functions aren't being used, the aperture can be used for other purposes. Another way is to subdivide the aperture into smaller segments, with each segment performing a specific task simultaneously, furthermore, each segment can be time-interleaved, for ex. radar segment may have interleaved modes. Finally, a shared aperture may also use multiple independent beams to perform multiple functions simultaneously. The last approach is the most advantageous as well as complex (isolating beams and intermodulation products is a challenging task).
Primary requirements of a shared aperture radar are 1. Wide bandwidth radiating elements 2. Multiple polarizations. Isolating beams and intermodulation products require state of the art filters and amplifiers. LRDE is developing critical components for a shared aperture radar- wideband radiating elements and associated TR module technology.
LRDE developed a 16x16 element planner array antenna to investigate the technology. The small antenna array provided sufficient functionality to study associated radiation characteristics and tradeoffs. Since the primary requirement is wide bandwidth ( >50% of center frequency) and dual polarization, it prevents the use of the common type of antennas such as microstrip patches, printed dipoles, and open-ended dipoles as the bandwidth of these antennas is <=30% of center frequency.
Therefore, TSA (Tapered slot antenna) AKA Vivaldi flared notch antenna was selected. TSA antenna meets all the requirements mentioned above. It has symmetrical radiation pattern, high gain, and wide bandwidth. The most recognizable feature of the TSA antenna is its V-shaped flared notch. The narrower region of the notch radiates RF signals of high frequency, whereas broader part radiates RF signals of low frequency.
The geometry of Tapered Slot Antenna(TSA)/Vivaldi Antenna
Closeup of an active phased array radar composed of X-band TSA radiating elements
Antenna element and planks developed for wide-band TR modules by DARE (Image: Delhi Defence Review- DDR)
Antenna arreay for revolving body. Credit on pic. (I added this, wasn't in the article)
Wideband TRM developed by DARE features Vivaldi Notch Antenna Array (Image: Delhi Defence Review- DDR)
Actual image of LRDE developed Tapered Slot Antenna (TSA) ( Image of associated MMIC isn't available)
DRDO has invested a lot of money in gallium nitride MMIC development projects and there are plans to set up a state of the art GaN foundry at IISc. It's likely that TR modules of AMCA's radar will use GaN-based solid-state RF amplifiers. GaN MMIC combined with latest LNA tech will greatly enhance detection range (greater than 200km for a 1 sqm RCS target). It also eliminates the requirement of a liquid coolant circulation based cooling system. Existing radars in IAF service use traveling wave tube amplifier (TWTA) and slotted waveguide antenna (planer array of slots). The bandwidth of these radars is relatively narrow (600-800MHz). More advanced radars such as Uttam and EL/M-2052 have a much wider bandwidth (1-3GHz). A wideband radar using TSA radiating element may have a bandwidth no less than 5 GHz and an enhanced probability of detection+classification and it's much more difficult to jam. The associated wideband/multi-channel MMIC is however very complex and expensive. It is in an early development stage and the technology in question is futuristic. If this radar tech indeed goes to the AMCA, then the development period is perfectly aligned with the timeline of the aircraft being inducted into the IAF i.e beyond 2035.
Article written by - Disha (ECE Department, Malaviya National Institute of Technology, Jaipur)
Is LRDE developing an Ultra-Wideband (UWB) AESA Radar for AMCA?
Attachments
Everything You Will Ever Need to Know About Gallium Nitride (GaN) HEMT Technology
June 20, 2018
The Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) has been considered primary technology for realizing solid state high power, high-frequency power amplifiers. The amplifiers based on GaN Technology are being widely used in various application such that Radar, electronic warfare, communication links etc. While GaAs HEMT is already available in the market and widely used as Power amplifiers, TWT VED is still used in high power applications. The primary focus of GaN HEMT has been high power, the focus is now shifting to further advantages such as high efficiency and low energy consumption and GaN is making its way into green technology. GaN HEMT utilizes high-density two-dimensional electron gas (2DEG) accumulated in the boundary layer between GaN and AlGaN through their piezoelectric effect and natural polarization effect. This makes it possible to realize low on-state resistance(Ron) combined with a high breakdown voltage.
The basic configuration of GaN HEMT (Image: Fujitsu)
Advantages of a High Electron Mobility Transistor (HEMT)
GaN HEMT is manufactured by growing a single-crystal GaN film on different substrates such as silicon carbide (SiC), sapphire (α-Al2O3) and silicon, SiC. Threshold Voltage Vth and mobility parameters of a transistor depends on temperature. As the temperature decreases device performance improves and vice versa. It makes thermal profile management an imperative task. Thermal conductivities of Si, SiC and sapphire are shown in the figure below.
Thermal conductivities of Si, SiC, Sapphire, W and Mo( Image courtesy: Development of High-Reliability GaN HEMT- Fumikazu YAMAKI)
Despite being expansive, thermal and mechanical properties of SiC makes it possible for it to be used in high power applications. Accelerated life test data for GaN HEMTs on SiC indicate that 'GaN-on-SiC' technology is very robust, with predicted lifetimes at application conditions in excess of 1 million hours.
Cost reduction is also an important factor for GaN HEMT commercialization. GaN-on-Si technology has been developed that allows cost reduction by adopting a large diameter Si substrate.
Operational Advantages of GaN HEMT technology
Operation at a relatively high voltage and temperature:
Owing to wide gape(~3.4eV direct band gap), these devices can operate at significantly higher voltages which is further translated into high power operations. Silicon and other common materials have a bandgap on the order of 1 to 1.5eV, which implies that such semiconductor devices can be controlled by relatively low voltages. However, it also implies that they are more readily activated by thermal energy which interferes with their operation. It limits silicon-based devices to operational temperatures below 100°C, beyond which the uncontrolled thermal activation of the devices makes it difficult for them to operate correctly. Wide-bandgap materials typically have band gaps on the order of 2 to 4 eV allowing them to operate at much higher temperatures on the order of 300°C. It makes wide bandgap semiconductors highly attractive for military applications.
In Wide Band Gap Semiconductor (WBGS-RF) trials it was found that GaN HEMT based Solid State Power Amplifiers(SSPA) were capable of operating at 150˚C continuously for almost 100000 hours. Higher temperature tolerance of GaN HEMT leads to lesser cooling requirements which have its own advantages for space and airborne applications because cooling system adds extra weight and power consumption. Owing to the superior thermal conductivity of SiC substrate, removal of heat from the junction is easier and GaN HEMT based SSPA can be operated with a less complex cooling mechanism. Existing Gallium Arsenide (GaAs) HEMT based MMICs require complex liquid coolant circulation.
High-Efficiency Operation:
Compared to Silicon transistors widely used in amplifiers, GaN HEMT shows low power loss during on state with low Ron . Power amplifiers for transmitters of wireless communication systems and radar systems need high power output and high-efficiency operation. For instance, if a transmitter needs 100w of output, to achieve the power of 100w order, a parallel combination of multiple devices is required if conventional GaAs MESFET or Si LD-MOSFET are used. On the other hand, single GaN HEMT can achieve 100w or higher. In case of RF power amplifiers, efficiency is characterized by drain efficiency that is the ratio of output RF power and DC power supply. Power added efficiency (PAE) is more inclusive and widely used term to describe the efficiency of RF SSPA., it is the ratio of the difference between output-input RF power to DC supply.
GaN HEMT based Solid State Power Amplifier compared to the power amplifier based on other technologies. (Image: GaN HEMT: Dominant Force in High-Frequency Solid-State Power Amplifiers by James J. Komiak)
GaN HEMT based SSPA power output-frequency and PAE-frequency curve( Image: GaN HEMT: Dominant Force in High-Frequency Solid-State Power Amplifiers J.J Komiak)
High reliability and ruggedness:
Reliability is characterized by Mean Time To Failure (MTTF), ruggedness is also important to for SSPA to remain operational under heavy RF stress. In WBGS-RF program, RF step stress and VSWR ruggedness tests were conducted which confirmed no significant degradation under a wide range of RF stress. MTTF was estimated to be 1.07 × 106 hours (approximately122 years) at 200°C.
MTTF vs Channel Temperature curve for GaN HEMT (Image: Development of High-reliability GaN HEMT)
Application:
GaN HEMT is building the block of transmitter-receiver modules (TRM) used in radar and communication systems. GaN HEMTs are used to implement receive and transmit stage power amplifiers. As GaN HEMT based SSPA has higher power output than GaAs or Si-based PA, required power levels can be achieved by single GaN SSPA instead of using multiple GaAs/Si-based SSPAs with power combining circuits, which makes GaN SSPAs more efficient and obvious candidate for high-speed wireless communication systems (4G/5G), satellite transceivers and active phased array radar systems.
Wireless Cellular Communication:
Existing mobile base station used for cellular communication employs GaAs based SSPA. L-band GaN HEMT based high power amplifiers which enable high-efficiency operation, can be used to make existing cellular communication system more efficient and energy saving. A higher PAE(Power Added Efficiency) is also important for the efficient performance of a remote radio head(RRH). Among the high PAE HPA design, Class E operation is the most popular approach for L-or S-band which consists of an output matching circuit to achieve high efficiency. Sinceparasitic capacitance of a GaN HEMT is 23.6 times smaller than that of an LDMOS, it allows GaN HEMT to operate at higher power and frequency.
performance comparison of GaN-based HEMT with transistors based on GaAs and Si. GaN HEMT technology can increase PAE while reducing amplifier size and power consumption which is strongly required for wireless cellular communication and next-generation technologies such as 4G/5G.
Adaptive Active phased array antenna with advanced beamforming capability employing a large number of GaN HEMT based SSPA will be the backbone of 5G mobile communication systems- boosting power and minimizing interference between users (beamforming capability results in highly directional antenna).
Active antenna systems and massive MIMO (Image: EDN)
Space Application:
In space application such as satellite communication, the RF power amplifier is one of the key components and High PAE is essential to reduce the launch cost of the satellite( Higher PAE translates into reduced weight). GaAs based amplifiers cannot typically offer acceptable PAE for many satellite application. GaN HEMT SSPA with its high PAE is a likely candidate to replace TWTA(Traveling Wave Tube Amplifier).
Radar Application:
Typical Modern Active Phased Array radars use multiple(100-1000s in single antenna) TRMs(Transmitter-Receivers Modules). The first generation of AESA radar employed GaAs based TRM. While it provided radars with very high scanning and frequency hopping rates, it lacked in terms of brute power compared to TWTA based passive phased array radars. However, the second generation of AESA radars features GaN-based TRM which not only improves scanning performance but also outperforms TWTA based phased array radars in terms of range and peak output power. Thanks to higher PAE new phased array radars are lighter and energy efficient.
GaN-based TRM developed by Fujitsu
GaN/AlGaN-on-SiC wafer- DRDO
Everything You Will Ever Need to Know About Gallium Nitride (GaN) HEMT Technology
June 20, 2018
The Gallium Nitride (GaN) High Electron Mobility Transistor (HEMT) has been considered primary technology for realizing solid state high power, high-frequency power amplifiers. The amplifiers based on GaN Technology are being widely used in various application such that Radar, electronic warfare, communication links etc. While GaAs HEMT is already available in the market and widely used as Power amplifiers, TWT VED is still used in high power applications. The primary focus of GaN HEMT has been high power, the focus is now shifting to further advantages such as high efficiency and low energy consumption and GaN is making its way into green technology. GaN HEMT utilizes high-density two-dimensional electron gas (2DEG) accumulated in the boundary layer between GaN and AlGaN through their piezoelectric effect and natural polarization effect. This makes it possible to realize low on-state resistance(Ron) combined with a high breakdown voltage.
The basic configuration of GaN HEMT (Image: Fujitsu)
Advantages of a High Electron Mobility Transistor (HEMT)
- High electron mobility
- Small source resistance
- A high gain-bandwidth product, due to high electron velocity in large electric fields
- High transconductance due to small gate-to channel separation
GaN HEMT is manufactured by growing a single-crystal GaN film on different substrates such as silicon carbide (SiC), sapphire (α-Al2O3) and silicon, SiC. Threshold Voltage Vth and mobility parameters of a transistor depends on temperature. As the temperature decreases device performance improves and vice versa. It makes thermal profile management an imperative task. Thermal conductivities of Si, SiC and sapphire are shown in the figure below.
Thermal conductivities of Si, SiC, Sapphire, W and Mo( Image courtesy: Development of High-Reliability GaN HEMT- Fumikazu YAMAKI)
Despite being expansive, thermal and mechanical properties of SiC makes it possible for it to be used in high power applications. Accelerated life test data for GaN HEMTs on SiC indicate that 'GaN-on-SiC' technology is very robust, with predicted lifetimes at application conditions in excess of 1 million hours.
Cost reduction is also an important factor for GaN HEMT commercialization. GaN-on-Si technology has been developed that allows cost reduction by adopting a large diameter Si substrate.
Operational Advantages of GaN HEMT technology
Operation at a relatively high voltage and temperature:
Owing to wide gape(~3.4eV direct band gap), these devices can operate at significantly higher voltages which is further translated into high power operations. Silicon and other common materials have a bandgap on the order of 1 to 1.5eV, which implies that such semiconductor devices can be controlled by relatively low voltages. However, it also implies that they are more readily activated by thermal energy which interferes with their operation. It limits silicon-based devices to operational temperatures below 100°C, beyond which the uncontrolled thermal activation of the devices makes it difficult for them to operate correctly. Wide-bandgap materials typically have band gaps on the order of 2 to 4 eV allowing them to operate at much higher temperatures on the order of 300°C. It makes wide bandgap semiconductors highly attractive for military applications.
In Wide Band Gap Semiconductor (WBGS-RF) trials it was found that GaN HEMT based Solid State Power Amplifiers(SSPA) were capable of operating at 150˚C continuously for almost 100000 hours. Higher temperature tolerance of GaN HEMT leads to lesser cooling requirements which have its own advantages for space and airborne applications because cooling system adds extra weight and power consumption. Owing to the superior thermal conductivity of SiC substrate, removal of heat from the junction is easier and GaN HEMT based SSPA can be operated with a less complex cooling mechanism. Existing Gallium Arsenide (GaAs) HEMT based MMICs require complex liquid coolant circulation.
High-Efficiency Operation:
Compared to Silicon transistors widely used in amplifiers, GaN HEMT shows low power loss during on state with low Ron . Power amplifiers for transmitters of wireless communication systems and radar systems need high power output and high-efficiency operation. For instance, if a transmitter needs 100w of output, to achieve the power of 100w order, a parallel combination of multiple devices is required if conventional GaAs MESFET or Si LD-MOSFET are used. On the other hand, single GaN HEMT can achieve 100w or higher. In case of RF power amplifiers, efficiency is characterized by drain efficiency that is the ratio of output RF power and DC power supply. Power added efficiency (PAE) is more inclusive and widely used term to describe the efficiency of RF SSPA., it is the ratio of the difference between output-input RF power to DC supply.
GaN HEMT based Solid State Power Amplifier compared to the power amplifier based on other technologies. (Image: GaN HEMT: Dominant Force in High-Frequency Solid-State Power Amplifiers by James J. Komiak)
GaN HEMT based SSPA power output-frequency and PAE-frequency curve( Image: GaN HEMT: Dominant Force in High-Frequency Solid-State Power Amplifiers J.J Komiak)
High reliability and ruggedness:
Reliability is characterized by Mean Time To Failure (MTTF), ruggedness is also important to for SSPA to remain operational under heavy RF stress. In WBGS-RF program, RF step stress and VSWR ruggedness tests were conducted which confirmed no significant degradation under a wide range of RF stress. MTTF was estimated to be 1.07 × 106 hours (approximately122 years) at 200°C.
MTTF vs Channel Temperature curve for GaN HEMT (Image: Development of High-reliability GaN HEMT)
Application:
GaN HEMT is building the block of transmitter-receiver modules (TRM) used in radar and communication systems. GaN HEMTs are used to implement receive and transmit stage power amplifiers. As GaN HEMT based SSPA has higher power output than GaAs or Si-based PA, required power levels can be achieved by single GaN SSPA instead of using multiple GaAs/Si-based SSPAs with power combining circuits, which makes GaN SSPAs more efficient and obvious candidate for high-speed wireless communication systems (4G/5G), satellite transceivers and active phased array radar systems.
Wireless Cellular Communication:
Existing mobile base station used for cellular communication employs GaAs based SSPA. L-band GaN HEMT based high power amplifiers which enable high-efficiency operation, can be used to make existing cellular communication system more efficient and energy saving. A higher PAE(Power Added Efficiency) is also important for the efficient performance of a remote radio head(RRH). Among the high PAE HPA design, Class E operation is the most popular approach for L-or S-band which consists of an output matching circuit to achieve high efficiency. Sinceparasitic capacitance of a GaN HEMT is 23.6 times smaller than that of an LDMOS, it allows GaN HEMT to operate at higher power and frequency.
performance comparison of GaN-based HEMT with transistors based on GaAs and Si. GaN HEMT technology can increase PAE while reducing amplifier size and power consumption which is strongly required for wireless cellular communication and next-generation technologies such as 4G/5G.
Adaptive Active phased array antenna with advanced beamforming capability employing a large number of GaN HEMT based SSPA will be the backbone of 5G mobile communication systems- boosting power and minimizing interference between users (beamforming capability results in highly directional antenna).
Active antenna systems and massive MIMO (Image: EDN)
Space Application:
In space application such as satellite communication, the RF power amplifier is one of the key components and High PAE is essential to reduce the launch cost of the satellite( Higher PAE translates into reduced weight). GaAs based amplifiers cannot typically offer acceptable PAE for many satellite application. GaN HEMT SSPA with its high PAE is a likely candidate to replace TWTA(Traveling Wave Tube Amplifier).
Radar Application:
Typical Modern Active Phased Array radars use multiple(100-1000s in single antenna) TRMs(Transmitter-Receivers Modules). The first generation of AESA radar employed GaAs based TRM. While it provided radars with very high scanning and frequency hopping rates, it lacked in terms of brute power compared to TWTA based passive phased array radars. However, the second generation of AESA radars features GaN-based TRM which not only improves scanning performance but also outperforms TWTA based phased array radars in terms of range and peak output power. Thanks to higher PAE new phased array radars are lighter and energy efficient.
GaN-based TRM developed by Fujitsu
GaN/AlGaN-on-SiC wafer- DRDO
Everything You Will Ever Need to Know About Gallium Nitride (GaN) HEMT Technology
Uttam AESA radar: Everything you need to know
June 16, 2018
The Uttam is an advanced active phased array radar (APAR) system being developed by Electronics and Radar Development Establishment (LRDE) for the HAL Tejas and other combat aircraft of Indian Air Force. Development of Uttam started in 2008 and it was first unveiled at Aero India 2009. Uttam is slated to be a successor to hybrid passive electronically scanned array radar EL/M-2032 currently equipping LCA Tejas. Radar is currently being integrated with an LCA.
Uttam AESA radar at Aero India 2017
Uttam being integrated with a prototype/LSP Tejas
Difference between AESA and PESA radar:
LRDE 3D MMR (left) and Uttam AESA radar (right). Notice the difference in size of the antenna array
(Image credits: shiv@BRF, Trishul)
Conventional passive phased array radars have a single high power RF source (usually Travelling Wave Tube) at ‘back-end’ and RF signals are fed into slotted array antenna via a waveguide or coaxial tube. Introduction of the phase difference between each transceiver element allows the radiation pattern to be steered electronically. In the reception cycle, a PESA antenna cannot transmit. PESA radar has a light antenna which can be mounted on a mechanical steering mechanism thereby giving it a wide frontal coverage area or FOV.
Active phased array antennas have transmitter-receiver modules or transceiver module (TRM) built right into the antenna. A single array may feature hundreds or thousands of TRMs depending upon antenna size and operational requirement. Each TRM can either operate independently or under a hierarchy. Each TRM can generate and radiate its own signal of different phase and frequency as required, thus the transmitted signal is wideband in nature. Unlike PESA radar, signals can be transmitted and received simultaneously in an AESA radar. Active phased array antennas are usually heavier than slotted planner array antenna so it is difficult to mount them on a steering mechanism, which limits their field of view (FOV). Electronic steering is faster compared to mechanical steering but at high steering angle (90-120 degree) it may also increase side lobe power which is undesirable. FOV limitation can be mitigated by using a swash-plate repositioner.
Euroradar CAPTOR mounted on a swash-plate repositioner for ultra wide FOV
Various aspects of Uttam AESA radar:
Uttam features an active phased array (APAR) which gives it superior scanning performance over legacy passive phased array radar. Unlike most contemporary radars, Uttam features Quad TRM i.e. a single plank consists of 4 TRMs. It allows the array to be more densely packed. Each TRM is equipped with low noise power amplifier, built-in test facility, digital phase-gain, and side lobe control elements. The inert model displayed at Aero India 2015 had ~184 QTRMs i.e. 736 TRMs. The array temperature is controlled by a liquid coolant circulation system. The QTRM configuration makes Uttam maintenance friendly. The radar can be scaled up or down depending on antenna size requirement.
Uttam's QTRM configuration
The radar is capable of tracking 100 targets simultaneously and engage 6 of them by SARH/ARH missiles in high priority tracking mode. For comparison, Elta EL/M-2052 is capable of tracking 64 targets in TWS mode.
In 2015 Uttam was stated to be capable of tracking a target having RCS of 2m2 at a distance of 92 kilometers. According to the new reports, the range has been increased to 150 kilometers for the target of the same RCS. In GMTT mode 2 targets can be tracked.
Uttam has over 16 different types of operational modes and the radar can operate in multiple modes simultaneously by changing modes pulse-to-pulse which gives the pilot exceptional situational awareness and mission flexibility.
Air-To-Air
June 16, 2018
The Uttam is an advanced active phased array radar (APAR) system being developed by Electronics and Radar Development Establishment (LRDE) for the HAL Tejas and other combat aircraft of Indian Air Force. Development of Uttam started in 2008 and it was first unveiled at Aero India 2009. Uttam is slated to be a successor to hybrid passive electronically scanned array radar EL/M-2032 currently equipping LCA Tejas. Radar is currently being integrated with an LCA.
Uttam AESA radar at Aero India 2017
Uttam being integrated with a prototype/LSP Tejas
Difference between AESA and PESA radar:
LRDE 3D MMR (left) and Uttam AESA radar (right). Notice the difference in size of the antenna array
(Image credits: shiv@BRF, Trishul)
Conventional passive phased array radars have a single high power RF source (usually Travelling Wave Tube) at ‘back-end’ and RF signals are fed into slotted array antenna via a waveguide or coaxial tube. Introduction of the phase difference between each transceiver element allows the radiation pattern to be steered electronically. In the reception cycle, a PESA antenna cannot transmit. PESA radar has a light antenna which can be mounted on a mechanical steering mechanism thereby giving it a wide frontal coverage area or FOV.
Active phased array antennas have transmitter-receiver modules or transceiver module (TRM) built right into the antenna. A single array may feature hundreds or thousands of TRMs depending upon antenna size and operational requirement. Each TRM can either operate independently or under a hierarchy. Each TRM can generate and radiate its own signal of different phase and frequency as required, thus the transmitted signal is wideband in nature. Unlike PESA radar, signals can be transmitted and received simultaneously in an AESA radar. Active phased array antennas are usually heavier than slotted planner array antenna so it is difficult to mount them on a steering mechanism, which limits their field of view (FOV). Electronic steering is faster compared to mechanical steering but at high steering angle (90-120 degree) it may also increase side lobe power which is undesirable. FOV limitation can be mitigated by using a swash-plate repositioner.
Euroradar CAPTOR mounted on a swash-plate repositioner for ultra wide FOV
Various aspects of Uttam AESA radar:
Uttam features an active phased array (APAR) which gives it superior scanning performance over legacy passive phased array radar. Unlike most contemporary radars, Uttam features Quad TRM i.e. a single plank consists of 4 TRMs. It allows the array to be more densely packed. Each TRM is equipped with low noise power amplifier, built-in test facility, digital phase-gain, and side lobe control elements. The inert model displayed at Aero India 2015 had ~184 QTRMs i.e. 736 TRMs. The array temperature is controlled by a liquid coolant circulation system. The QTRM configuration makes Uttam maintenance friendly. The radar can be scaled up or down depending on antenna size requirement.
Uttam's QTRM configuration
The radar is capable of tracking 100 targets simultaneously and engage 6 of them by SARH/ARH missiles in high priority tracking mode. For comparison, Elta EL/M-2052 is capable of tracking 64 targets in TWS mode.
In 2015 Uttam was stated to be capable of tracking a target having RCS of 2m2 at a distance of 92 kilometers. According to the new reports, the range has been increased to 150 kilometers for the target of the same RCS. In GMTT mode 2 targets can be tracked.
Uttam has over 16 different types of operational modes and the radar can operate in multiple modes simultaneously by changing modes pulse-to-pulse which gives the pilot exceptional situational awareness and mission flexibility.
Air-To-Air
- TWS (Track While Scan): Combination of search and track, essentially a surveillance mode.
- HPT – High priority Target: Dedicated tracking mode, also referred to as “Hard Lock”.
- AACQ/ACM (Auto-Acquisition/Air Combat maneuvering): radar searches a certain area and detected targets are automatically locked on transferred to HPT allowing the pilot to fire missiles quickly- Rapid target engagement.
- AJ (Anti-Jam): Rapid frequency changes and other techniques to cut through heavy jamming.
- RA (radar altimeter): measures altitude of the aircraft.
- Weather: Weather observation
- Air-To-Sea
- Sea TWS: Search and tracks targets on the water surface, high processing requirement to cut through the clutter. It also includes SSS (sea surface search)
- RS (Range Signature): Generating 1D profile of sea target, essentially a ‘quick look’, assessing the area of interest in a target, such as its length, position of high reflectivity area
- ISAR (Inverse Synthetic Aperture Radar): Imaging the target for classification, RS and ISAR are usually coupled with an automatic classification library
- STCT (Sea Target Continuous Track): Similar to air-to-air HPT but for sea targets
- Air-To-Ground
- AGR (Air-To-Ground Ranging): Radar uses a continuous single beam for ranging, similar to a laser rangefinder. Range information is used to assist gunfire (strafing run) and visual bombing.
- RBM (Real Beam Mapping): Radar scans the terrain to generate a topographic map. Pilots can use this map for terrain avoidance. It allows the aircraft to fly low while avoiding collision with a feature or ground.
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- Terrain Avoidance- The valley in front of the aircraft is black indicating that there is no terrain at the current altitude
- SAR/DBS/HRM (Doppler Beam Sharpening/ High-Resolution Mapping): Enhanced Imaging mode used for high-resolution imaging of ground. Since the actual aperture of radar is very small compared to wavelength and energy is spread in a wide area, DBS is used to enhance the resolution.
- GMTI/GMTT (Ground Moving Target Tracing/Indication): Detection of a moving target on the ground, other objects such as trees and buildings are filtered out. These modes can be interleaved with RBM/SAR to produce terrain map and track the target at same time.
- Navigation
- Weather
- Terrain Avoidance.
- Advanced Electronic Counter-Countermeasure capabilities of Uttam AESA radar:
- Wide bandwidth: Since each TRM can generate and transmit radiate its own signal of different phase and frequency, a large number of spectral components can be generated in a single pulse i.e. radar can spread its frequencies across a wide band in a single pulse.
Chirp pulse The ability to quickly switch the frequency and wide bandwidth make Uttam a Low-Probability-of-intercept (LPI) radar i.e. it is difficult for an RWR to intercept it - .
- Frequency agility: The Radar can rapidly+randomly switch through a large number of frequencies spread across wide bandwidth to counter certain types of jamming.
- Sidelobe Cancellation (SLC): SLC is a technique used to removing interference in which the processor subtracts the interference from the antenna output. It is designed to operate against active jammers. It is assumed that the jamming signal is entering the radar antenna through one of the sidelobes. In SLC, auxiliary antennas are used to gather information about interfering signal, the resulting signal is sent to rest of radar receiver and processor via SLC channels and interference is neutralized. Having multiple SLC channels allows Uttam to neutralize multiple jammers simultaneously.
- Ultra-low sidelobe antenna: Uttam has an ultra-low sidelobe antenna which allows it to generate very sharp pencil beams. In AESA radars low sidelobe regions can be created with TRMs using independent phase control at each element. Having low sidelobe level not only improves steering/tracking performance but also increase immunity against jammers. It also helps the aircraft to avoid detection by passive RF tracking systems (Emitter locator systems).
- Wide bandwidth: Since each TRM can generate and transmit radiate its own signal of different phase and frequency, a large number of spectral components can be generated in a single pulse i.e. radar can spread its frequencies across a wide band in a single pulse.
M-MOTR is a scaled down version of MOTR ( MULTI OBJECT TRACKING RADAR ) being built by SDSC SHAR
MOTR ( MULTI OBJECT TRACKING RADAR ) used by ISRO.
MOTR ( MULTI OBJECT TRACKING RADAR ) used by ISRO.
It has already been built and is undergoing tests , it has passed some of the same , it was mentioned in the original post which you overlooked
I did, my bad. Wasn't the ISRO's MOTR used for tracking debris created by ASAT test ?
Yes, infact I have reasons to believe it was tracking the satellite too before the hit.
ISRO did not publish any info because of the obvious reasons.
That would be pretty reasonable. The VC11184 features a version of the MOTR and is meant to track RVs, planes, satellites etc. By the way is there any relation between the MOTR and the Swordfish radar ?
Why do you think MOTR is related to the DRDO MMSR ?
There is a very interesting poster of ISRO motr which gives out one of the primary capability of the radar ,which has nothing to do with ISRO , since all space debries burn up in atmosphere upon reentry. I saw it in one of P_K posts long time back
Motr and swordfish different
Motr connection with mmsr , I have no idea , you will have to ask the original poster.