Airborne Early Warning & Control (AEW&C) is a broad term used to describe the airborne capability to detect air, land or water threats and direct a response, typically from a large distance. The radar, control and aircraft platforms are diverse but high performance semiconductor devices and electronic technologies enable them. The rationale behind airborne surveillance is simple: the more you see, the more you know. High altitude aircraft and powerful radars achieve the "more-you-see" capability and sophisticated sensor, onboard processing and communications capabilities satisfy the "more- you-know" dimension.
Earlier versions of these capabilities were called Airborne Warning and Control System (AWACS) or Airborne Early Warning (AEW). In fact, one of the most widely deployed platforms, the E-3 Sentry, has become commonly known as "AWACS." These systems play a major role on the modern battlefield by providing real-time intelligence and the control needed to maintain air superiority over the combat area. These platforms are not solely for wartime use. Several nations devote resources exclusively to enable surveillance of borders in peacetime.
Current airborne surveillance includes, not only detection, tracking and identification of targets, but also execution of actions that result from data derived from its suite of sensors. These actions may be offensive, like the control of other aerial assets (mainly interceptors), or defensive, like initiation of electronic countermeasures. As the processing capabilities on these aircraft have increased, their control capabilities have also improved and expanded to the point where the mission is now exclusively AEW&C.
Airborne Early Warning and Control capabilities provide a fundamental building block of a national defense or combat strategy. Until recently, design and development of AEW&C platforms had been the near-exclusive domain of U.S. military OEMs, but as countries acknowledge the importance of the mission, more AEW&C development effort is being undertaken in other regions and countries, including Europe, Israel, China, India and Russia.
The market is thus growing along two paths: countries with mature capabilities will seek to upgrade to the latest technology to outpace threats, and countries with rudimentary or no capability will purchase new AEW&C platforms. As existing users expand or upgrade their coverage and new countries implement services, Strategy Analytics believes the number of planes in service will see a steady increase with upgrades and retrofits.
Figure 1 Cumulative AEW&C platform market to 2020.
Strategy Analytics forecasts a market growing to more than $52 B by 2020 (see Figure 1). The total electronics content for radar, communications, computers, sensors and other related systems will increase over time as technology is upgraded, growing to $22 B.
All AEW&C platforms make extensive use of advanced electronics and component technology for radar, communications, EW, computer, sensor and other related systems. The diversity of AEW&C platforms incorporates a range of technologies including tubes, silicon/GaAs/GaN/other microelectronics and optoelectronics. The basic subsystems found onboard a typical AEW&C platform are as follows:
- Data processing
- Identification Friend and Foe (IFF)
- Radio & Data Communications
- Electronic Support Measures (ESM)
- Electronic Counter Measures (ECM)
These subsystems require a control system to ensure that all are functioning correctly at the right time. AEW&C aircraft also have individual electronic units for other systems, notably the flight controls and engines. Collectively these represent a substantial opportunity for electronic components and associated hardware.
Figure 2 Cumulative AEW&C electronics segmentation.
From an electronics perspective, even though the yearly increase in platforms is relatively small, the deployed base is very large. The attractive aspect of this market is the development time, longevity and expense of the airframe platform, which makes it uniquely suited to the upgrade market (see Figure 2). The most important system aboard the AEW&C platform is the main radar sensor. A typical AEW&C will have at least two radar systems: the main radar for the early warning functions and a smaller nose-mounted unit for general use in situations such as adverse weather alerts. New platform developments and upgrades are typically utilizing some form of phased array radar to perform these functions. There are two basic designations for electronically scanned arrays: passive and active. The phased array concepts are identical for both types, but the implementation is different, with the main difference being the transmit power source. Older AEW&C platforms predominantly use passive arrays utilizing TWT-based power sources with radars in rotating rotodomes, while new platforms are increasingly making use of GaAs-based T/R modules in active arrays.
As an example, the E-3D Sentry, best known as the AWACS, uses an older Passive Electronically Scanned Array (PESA) radar that continues to provide several major air forces with a system well matched to their needs. The main radar antenna is located inside a rotating rotodome mounted above the spine of the aircraft. This rotodome contains several systems, primarily the Northrop Grumman AN/APY-1/2 search radar on one side of a 30-foot long beam structure and, on the other, a set of aerials for the IFF AN/APX-103 interrogator, supplied by the Telephonics Corp., and data-link fighter-control (TADIL-C) antennas. A dual klystron-based amplifier system inside the fuselage generates the RF power that is sent to the antenna array via waveguides.
There have been several upgrades to this program, but there is no plan to replace the PESA radar with a solid-state Active Electronically Scanned Array (AESA) radar. One of the biggest upgrades for the AWACS was the Radar System Improvement Program (RSIP) that has been referred to as "Sharpening the Eye of the Eagle" and replaces aging original equipment. RSIP was a joint U.S./NATO development program involving major hardware and software-intensive modification and costing $1.2 B for the 32 U.S., 17 NATO and seven UK E-3 aircraft.
At the other end of the spectrum is the U.S. Navy E-2 platform, the most popular AEW&C plane in the world. The U.S. Navy has added incremental improvements, the most recent implemented in the Hawkeye 2000. The Navy is also performing a major platform upgrade with the E-2D Advanced Hawkeye. This variant will revamp the radar and include the Northrop Grumman APY-9 AESA based radar. Its new rotodome, developed by L-3 Communications Randtron Antenna Systems, will provide 360-degree scanning capability in a hybrid mechanical/electrical scanning arrangement.
In an AESA implementation, each element is driven by a transmit/receive (T/R) module. These T/R modules contain solid-state MMICs, typically GaAs for the transmit/receive paths and silicon for the control functions with future trends pointing toward GaN technologies being used in conjunction with SiGe.
Development time, cost, mission and radar performance are just a few of the trade-off characteristics that make platform upgrade such a multi-layered decision process. As described, most of the earliest, most popular aircraft platforms were modified to incorporate rotating rotodomes. A discussion of modifications and trade-offs must often be viewed in the context of the entire AEW&C platform and whether the improved performance and capability of an AESA radar does not offset the cost of retrofitting the rest of the platform.
Changing focus to communications, information must be disseminated quickly and efficiently to all assigned agencies working with the AEW&C aircraft. The users of this information generally fall into two categories: onboard and external staff. In practice, the AEW&C platform is at the center of a three-dimensional network of forces ranging from relay satellites and ground stations to strike aircraft and other assets. Other onboard communications capabilities include secure voice and data communication systems.
- The Erieye has a secure voice and data link communications suite with HF and VHF/UHF links. The VHF/UHF data link operates at 4800 bps.
- The Boeing Wedgetail has a communications suite that includes three HF and eight VHF/UHF communications systems together with Link 4A and Link 11 systems.
AEW&C platforms must ensure that all communications are secure from enemy eavesdropping. To address this issue, the Joint Tactical Information Distribution System (JTIDS) was developed and is now common to most airborne assets. An additional avenue to address this issue is AWACS systems providing anti-jam communication for information distribution, position location and identification capabilities.
As far back as 1989, an improved communication system named HAVE QUICK A-NETS was deployed to address secure communications. This system provides secure, anti-jam contact with other AWACS platforms, friendly aircraft and ground stations. It is also included in French and RAF systems. The AN/ARC-164 HAVE QUICK II radios are used for air-to-air, air-to-ground and ground-to-air communications and are deployed on all Army rotary wing aircraft. By 2007, nearly all U.S. military aircraft had adopted HAVE QUICK. Improvements include HAVE QUICK II Phase 2, and a "Second generation Anti-Jam Tactical UHF Radio for NATO" called SATURN. The latter features more complex frequency hopping.
Another system called enhanced TADIL-A Link-11 ensures high speed exchange of radar information. Also known as TADIL-J, or Link-16, it requires additional computer memory to anticipate new ESM and future enhancements. The Class 2H JTIDS terminal is a secure digital communications system that allows E-3 crew members to communicate with other participants such as fighter aircraft, Navy units and ground-based units during air battle. It has a capability to identify units using common points of reference.
Looking at the communications systems in general, common trends across the board include a move toward higher frequencies and wideband performance, driven by a need to have multi-mode, multi-band capabilities that will enable these radios to act as nodes in the total battle space. This is coupled with an increasing emphasis on data and efficient spectrum use that will drive linearity requirements as well as the continued development of SDR and cognitive radio capabilities. While Si-based power amplifiers are the incumbent technology, these factors will provide opportunities for other RF technologies that can couple high power outputs with wideband performance, linearity and higher efficiencies.
Electronic Support Measures (ESM) provide for a passive detection, electronic surveillance capability to detect and identify air and surface-based emitters. The ESM system passively detects signals from hostile, neutral, friendly, and unknown emitters and identifies targets, augmenting present on-board sensors. ESM equipment consists of sensitive direction finding radar-warning receivers coupled to an extensive software threat library to permit the calculation of bearing and type tracks. These are made available in a format readable by the data processing software, allowing the operators to passively identify sources of transmission, oftentimes at ranges nearly double those of active radar and with useful receive sensitivity.
Electronic Counter Measures (ECM) are now considered essential for all military and even some chartered civil aircraft. There may be times when high-value platforms, such as AEW&C, will have to rely on self-defense when enemy fighters or missiles get too close. Lacking offensive armament, the AEW&C relies on special ECM and electronic counter-countermeasures (ECCM) to confuse and deflect incoming threats. The concept of Smart Jamming, for example, involves detecting the oncoming missile, classifying it by identifying its seeker signature and then sending a jamming signal in a particular band to break its lock. These types of concepts are leading to what may be described as a "no-channel" concept in which the systems are tasked with looking at a complete frequency range resulting in multiple channels being handled by one receiver. For jamming applications, this has to be coupled with high power capabilities across the frequency range and this has opened the door for GaN-based systems in this area.
The enabling RF technologies, of which there is a wide range, include Si, SiGe, GaAs, GaN as well as TWTs.Each technology offers specific advantages.
- Si LDMOS/MOSFET technologies provide good saturated power capabilities, but have a relative limited frequency range. While operating along the same frequency ranges, SiC offers higher power.
- SiGe offers broader frequency capabilities, but is limited in power. However, the integration capabilities will see SiGe used in the receive function while SiGe-based ADC and DAC components will see increasing penetration of the radar, EW and communications systems as phased array capabilities are coupled with digital receivers.
- GaAs offers a strong mix of power, frequency and linearity capabilities that have driven the use of this technology but still has limitations compared to TWT capabilities.
- TWTs offer the broadest frequency operation, very high efficiencies and reliability coupled with high power but scaling can be an issue, depending on the platform.
- GaN appears to offer the best solution in terms of power, efficiency, wide frequency operation and reliability though linearity can be an issue.
The AEW&C platform is a good example of the trends in the defense industry that will drive demand for RF technologies. For communications, electronic warfare and radar systems, both in AEW&C as well as in the broader defense sector, capabilities are expanding around specific parameters such as broadband performance, power, linearity and digitization. No one semiconductor technology solution will singularly satisfy every system requirement, and we will see different technologies used side-by-side depending on the requirements of the system and platform. While global economics have forced governments to rethink defense priorities, the desire for technology differentiation will lead to continued opportunities for electronic systems and the enabling of semiconductors in both emerging platforms as well as through upgrade/retrofit channels.
Asif Anwar is a Program Director within the Strategic Technologies Practice at Strategy Analytics. He develops insights and analysis in the advanced electronics markets through research into key sectors, including defense and aerospace, wired and wireless communications, automotive systems and consumer electronics. Anwar's career spans both engineering and marketing roles in the metals, minerals and electronics industries. He graduated from the University of Teesside, UK, in 1993 with a B.Eng Honours degree in Chemical Engineering and is a member of the IChemE and IEEE.