New radar applications are certainly helping to propel RF/microwave technology forward. Yet it is the upgrades of existing systems that are currently calling for many advances in high-frequency electronics. These range from upgrades that will expand and enhance current capabilities to full replacements of legacy systems (see sidebar, "Cobra Judy Replacement: The Legacy Continues"). For example, Raytheon Co.'s new radar transmitters for the Federal Aviation Administration's (FAA's) Long Range Radar Service Life Extension Program (SLEP) can see further than the previous generation while improving detection and clutter-management capability. Each radar provides surveillance over a 400-nautical-mile coverage area. In doing so, it detects both commercial and military aircraft and feeds that information to the FAA, the Department of Homeland Security (DHS), and other government agencies.
Mike Leone, Chief Engineer, Radar Surveillance & Electronic Warfare Systems at Lockheed Martin MS2 Integrated Systems & Sensors, points to the military as the force behind many of radar's upgrades and developments: "In the radar industry, some say that every 30 years or so, there is an inflection point and a jump in radar technology. However, changes in US military operational needs over the last several decades have also driven the requirement for more advanced technology.For example, when the US Air Force Space Surveillance System was activated to detect and track space debris and objects in the early 1960s, it was intended to track about 20,000 objects put in low earth orbit by the only two countries in the space race.Today, with more than 70 countries in space, the old VHF Fence' is overwhelmed by hundreds of thousands of orbiting objects."
In response, Leone notes that Lockheed Martin is developing a new S-band radar as it competes for the Air Force's Space Fence program. This radar will provide organic detection, tracking, and accurate measurement of more than 200,000 space objects (including many smaller objects) to help protect our nation's space assets and missionsespecially from collisions. The first of as many as three Space Fence radar sites will be operational in 2017.
The nation's need to improve legacy radar systems has been moderated by today's economic pressures. "Over the next five years, due to budget cuts that have been requested by the President and Congress, the pre-planned product-improvement programs are the ones that are going to get a lot of attention," notes Michael Sarcione, Senior Principal Engineering Fellow at Raytheon Integrated Defense Systems. "You can't afford to swap out wholesale systems, so you'll end up upgrading those systems and giving them additional capabilities and modernizing them."
"The technologies that enable that to happen are going to be what we see evolving today, like gallium nitride (GaN)," states Sarcione. "For example, how do I get more power out of a given widget? How do I get more functionality within the RF circuitry? Silicon-germanium (SiGe) has been one enabling technology on both the commercial and defense sides, which allows you to do a lot of computer-like decision making and processing in the same component that has the RF devices and amplifiers. That's allowing us to reduce the size by integrating our processing functionality with our RF functionality."
Essentially, the radar market is now facing much of the same pressure as the consumer market. Government customers want more affordable solutions that are smaller, lighter-weight, and consume less power. Of course, they want design accomplished in a shorter time period as well. Yet these designs will still have to face the ruggedness and other requirements that are particular to the military. Aside from being a daunting challenge in terms of its contradictory requirements, this is a major change in how the military approaches design. It is being forced to go from building systems that would last the life of a platform to a "swap-out" approach like the consumer market.
Going forward, Sarcione notes that the government will be more inclined to take a modular open-systems approach (MOSA). Much as a printer, mouse, etc. are automatically plugged in and recognized with a personal computer (PC), a receiver exciter for a radar, for example, could be plugged in and automatically recognized by the signal data processor and phased array. Then all of the parts would automatically play together as they do with PCs. As the government moves toward procuring such product "boxes," it also wants to put them together itself. This new business model, which is beginning to take hold in some defense markets, is forcing contractors away from the traditional mission-systems-integration approach.
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Simultaneously meeting military performance requirements while adjusting to a new design cycle; improving size, weight, and power (SWAP); and adopting a swap-out approach seems nearly impossible. As Sarcione notes, the pressure does not end there. "On the functionality side, the adversaries of the military market domain are becoming more and more intelligent. The techniques and systems that they use have become more challenging, so we have to be sure that we stay ahead of that with how we counter it," he emphasizes.
"Some of the challenges are finding smaller objects further away in difficult environmentswhere they are in clutter from mountain rangesand finding them before they find us," Sarcione continues. "Typically, that requires higher-power apertures, more digital processing within those apertures within the sensor domain, and the ability to generate on-the-fly arbitrary waveforms. These requirements lead to the use of technologies like GaN to get more in a given aperture, digital beamforming in order to form more beams simultaneously and process that information nearly instantaneously, and the processors that go along with it."
By leveraging GaN, for example, Raytheon's transmit/receive (T/R) modules for the US Navy's Air and Missile Defense Radar (AMDR) program recently passed a significant developmental testing milestone. The modules exceeded Navy-specified requirements for extended measured performance. Even after 1000 hours of testing, they demonstrated no performance degradation. During the RF operating life testing, the modules demonstrated consistent power output across multiple frequency channels.
AMDR, which is still under open competition, provides a fitting example of how one radar system is juggling the different demands of today's program needs while keeping an eye toward the future. It fills a critical gap in the joint forces' integrated air and missile defense capability, as it enables effective missile defenses to be deployed in a flexible manner wherever needed. The radar suite consists of an S-band radar, X-band radar, and radar suite controller. The system is fully scalable, enabling the radar to be sized according to mission need and to be installed on ships of varying size as necessary. Thanks to its digital beamforming capability, the radar can perform multiple, simultaneous missionsmaking it both affordable and operationally effective.
Digital approaches are becoming more widespread in radar systems. Recently, for example, Northrop Grumman and CEA Technologies Pty, Ltd. demonstrated the CEAFAR phased-array sensor system. CEAFAR is an active, S-band, multi-function, phased-array radar that is fully scalable in frequency, size, and power based on the number and type of tiles in each face. This fully digital radar system incorporates advanced digital beamforming. It also is user-configurable, depending on operational and technical requirements. Each of the sensor elements can be individually tuned and adjusted. In addition, the lightweight system requires relatively modest cooling and power.
This active-electronically-scanned-array (AESA), multi-function radar is suitable for naval vessels as small as offshore patrol craft and as large as destroyers and cruisers. It can be fitted to both new-build and in-service vessels that need enhanced capabilities or an extended lifespan. The self-contained Dual Face Demonstration unit consists of two CEAFAR faces, which only require power and an Ethernet connection to control the system (see figure). The Dual Face Demonstration unit was developed in support of the CEA Technologies phased-array radar system, which was recently fitted to the Royal Australian Navy's (RAN's) ANZAC Class Frigate HMAS Perth as part of the ANZAC Class Anti-Ship Missile Defense (ASMD) Upgrade Program. This program included the installation of six CEAFAR S-band AESA radar faces and four CEAMOUNT X-band active phased-array illumination faceseach providing full 360-deg. radar coverage.
From affordability and scalability to 360-deg. awareness and power management, these radar developments exemplify newer radar systems. By using advanced networking capabilities, modern radar systems can take advantage of enormous computer processing power to fuse data, share resources, and even offload tasks when necessary. With this intelligence, radar systems will be able to accurately sift through the growing number of RF emissions in various environments. Armed with advances in digital and process technologies, modern radar systems are smaller, lighter, and more efficient than ever. Going forward, they will increasingly achieve measurement capabilities that were never before thought possible.