What is in this article?:
- Military Fights For Better Communications Links
- SDRs And More
Growing needs for faster communications are driving RF/microwave technologies in military communications systems.
SDRs And More
Software-defined radios (SDRs) have experienced increased use in military applications for secure communications, but these radios have also been embraced by a growing number of commercial customers, including for amateur (ham) radio use. Typically based on a personal computer (PC) in some form, an SDR typically employs spread-spectrum and ultrawideband techniques for security and to allow multiple radios to operate in the same location without interference. SDRs are also known as cognitive radios, where each radio measures available spectrum in an area and communicates that information to other SDRs within range.
JTRS has supported the use of SDR technology for military applications via the Software Communications Architecture (SCA) standard, which promotes the development of interoperable software modules based on accepted operating systems, to “define” the radios for different functions and applications. Commercial radio vendors also refer to the SCA for use in civilian radios for mass market applications. Although based on software to define their waveforms, SDRs still rely on increased functionality and affordability of the system-on-chip (SoC) devices within the radios, to provide microprocessor and digital-signal-processing (DSP) capabilities, for these radios to achieve wider-spread acceptance in commercial and military applications. It should be noted, however, that both variants of tactical radios and radios based on SDR technology have been gaining ground in public safety markets.
While these different radios support short-range communications, military customers still look to the skies (notably satellites) for longer-range communications. For example, Boeing and the US Air Force recently launched their sixth Wideband Global Satcom satellite, WGS-6, as part of the growing WGS communications network for the DoD and its international partners (Fig. 4). As Craig Cooning, Vice President and General Manager of Boeing Space & Intelligence Systems, notes, “The demand for wideband satellite communications continues to increase. WGS-6 and the additional WGS spacecraft yet to be launched will help to meet that need.” Earlier in the year, the firm launched WGS-5 as part of building this wideband military satcom system. The satellites provide secure X- and Ka-band communications using shaped and steerable spot beams that can be readily reconfigured.
Aside from launching military communications satellites, Boeing has been busy developing other electronic technologies for the military, such as high-energy lasers. Working as part of the DoD’s Robust Electric Laser Initiative (RELI) effort, Boeing recently demonstrated the latest capabilities of its Thin Disk Laser system, a solid-state laser system capable of better than 30 kW output power, or almost 30% more power than defined by RELI requirements (Fig. 5). Such directed-energy weapons can pinpoint a laser beam to destroy or disable a target with little or no collateral damage.
According to Michael Rinn, Vice President and Program Director for Boeing Directed Energy Systems, “In order to be truly viable as a weapons-class system, a laser must achieve high brightness while simultaneously remaining efficient at higher power. Our team has shown that we have the necessary power, the beam quality, and the efficiency to deliver such a system to the battlefield.” These demonstrations marked the first time the company has simultaneously achieved high beam quality at high power levels.
Back in space, Lockheed Martin, working with the US Navy’s Aegis Combat System, has completed its first live firing test to show that the system can defend beyond line of sight by integrating data from remote sensors to intercept a target. This was the first test at sea of the Naval Integrated Fire Control-Counter Air (NIFC-CA) capabilities of the Aegis system. By employing functionality known as Cooperative Engagement Capability (CEC) to interpret data from remote sensors, the Aegis system was able to launch a Standard Missile-6 (SM-6) missile from the USS Chancellorsville (CG-62) to intercept a target.
Jim Sheridan, Director of US Navy Aegis programs for Lockheed Martin, remarks: “The latest NIFC-CA test demonstrated how the Aegis Combat System has taken a significant step forward in increasing interoperability with remote systems to extend the distance that we can detect, analyze, and intercept targets.”The upgrades to Aegis systems on cruisers and destroyers are based on commercial-off-the-shelf (COTS) components to reduce costs.
Lockheed Martin has also been busy improving radar technology, thanks to $206 million in additional orders from the US Army for the AN/TPQ-53 (Q-53) long-range counterfire radar system. This radar system is designed to provide enhanced 360-deg. detection and protection from indirect fire. The company has so far delivered 32 systems to the US Army, with an additional 33 systems in production. This latest contract covers an additional 19 Q-53 systems. Mounted on a five-ton truck, the Q-53 can be rapidly deployed, automatically leveled, and remotely operated with a laptop computer or from a fully equipped climate-controlled command vehicle. The system provides 360-deg. capability to detect, classify, and track incoming motars, artillery, and rockets at distances to 20 km (to 60 km when operating in a 90-deg. search mode), is relatively easy to operate, and easy to transport.
In terms of future communications needs, US military researchers at the Defense Advanced Research Projects Agency (DARPA) are well aware of rapidly increasing requirements for handling more data at higher speeds, and are hoping to develop a military wireless data link that can transmit data at rates exceeding 100 Gb/s per radio channel. The research efforts are being conducted within the DARPA 100 Gb/s RF Backbone (100G) program. In support of this work, several contracts were recently awarded to Silvus Technologies and Trex Enterprises Corp. for work on the program. The contracts were awarded by the US Air Force Research Laboratory at Wright-Patterson Air Force Base on behalf of DARPA. The two companies join Applied Communication Sciences, already on the 100G program.
The goal of the 100G program is to establish an airborne communications link with the capabilities of the fastest ground-based fiber-optic communications systems, with the capabilities to operate effectively through clouds, rain, and fog. The companies will seek spectral efficiencies of better than 20 b/s/Hz for wireless data speeds of 100 Gb/s at ranges to 125 miles for air-to-air links and to 62 miles for air-to-ground links, assuming aircraft at about 60,000 ft. altitude.
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