Kicking a Radio's Tires
Written by Adam Baddeley
SOTECH 2010 Volume: 8 Issue: 5 (July)
ENSURING THAT VOICE, DATA AND VIDEO
COMMUNICATIONS REACH OPERATORS IN THE FIELD.
There are no shortcuts to a full MIL-STD, ruggedized military radio. Shock, vibration and extreme temperature swings must all be accounted for, as well as ensuring that devices can both operate in CBRN environments and survive the subsequent decontamination process. Equally, in achieving the required level of protection, the devices cannot grow to the point that they are so large, cumbersome and heavy that they meet ruggedization requirements, but in doing so, simply don’t meet the mission needs.
GD
For the dismounted soldier, Marine or airman, the next generation of communications technology is being delivering through the Joint Tactical Radio System (JTRS). General Dynamics C4 Systems is the prime for the handheld, manpack and small form fit (HMS) program within JTRS. The scope of HMS provides for the development of many different radios, all with the same common architecture, hardware and software.
This, according to Joe Miller, director JTRS Ground Domain at General Dynamics, has allowed new technology to be introduced. “It took very advanced technology to meet HMS requirements. As it turned out, this technology had not been applied to the military market before. The manufacturing volumes created by having one common design afforded us the ability to invest in the technology required to shrink the size down. We went out and hired engineers from the cellular industry. We took very standard, very mature cellular technology and applied it to a military problem in a way that has never been tried before.”
The two primary technologies are low temperature co-fired ceramics and high density interconnect. This allows the creation of three-dimensional circuits on either ceramic or other substrate. Miller said, “We took a board that was the size of a 3U board and we were able to get it down to the size of roughly a quarter.” This has had a key effect on thermal aspects of ruggedization. Miller explained, “When you shrink circuits down, you are now no longer driving signals across circuit boards and you are not dissipating power, so your battery life goes up and your thermal goes down.”
General Dynamics was able to take that technology and ‘stretch’ it, so that it covers a broader spectrum (2MHz-2.5GHz) than a cell phone, which typically doesn’t cover both narrow and wide band signals. Miller said, “It allows us to build a 5 watt radio that is less than nine cubic inches and weighs half a pound.”
To further advance thermal issues, General Dynamics has also introduced gallium nitride-based power amplifiers, which introduced efficiencies in the order of 60 percent, impacting both thermal issues and battery life.
Using commercial technology for a military application prompts the question of what additional work needs to be done to take to get it to a military standard. “It is not as difficult as you might think,” commented Miller. The biggest issue, he believes, is thermal, which can be addressed by the substitution of industrial grade parts that operate over a larger temperature range. The HMS radio creates additional thermal effects over cellular devices, operating at significantly higher power than a cell phone operating at 600mW.
Miller said, “There is a tremendous amount of effort that was applied to the thermal design. These radios operate significantly differently from their cellular counterparts, in that they are transmitting such high power and the waveforms that they run require very large signal processing elements. So the digital part of it actually burns up more power than the RF. Part of the design’s uniqueness is the thermal paths that we designed in the radios to pull the heat outside of the device and bring it down to the case.”
ITT
“We produce lot of SINCGARS [single channel ground and airborne radio systems]. SINCGARS has had very long lifetime, and for the most part what that is attributed to is the ability to meet those harsh environments,” asserted Jennifer Schoonover, director, SINCGARS Programs at ITT Electronic Systems. “That expertise is not SINCGARS only—it translates as we transition to more handhelds for the JTRS world and other handhelds such as SpearNet and SpearHead. Last time I looked at the JTRS specifications, they had the same environmental requirements as SINCGARS. A lot of the expertise on the government side rests with JTRS, but they certainly cut their teeth in the SINCGARS world.”
“A lot of it is based on many years of experimentation, trial and testing to the harsh environments that are imposed upon us: things like transit drop and loose cargo, simulating throwing a piece of equipment around the back of a truck and driving across rough terrain. We have a very mature mechanical engineering staff that pretty much can get it the first time around, based on the experience and knowledge.”
Schoonover said, “We have done some experimentation with different materials, trying to get some of the weight out. Each time we do it, we figure out what the pluses and minuses are for those materials. We look at plastics, magnesium and aluminum. We select all of our requirements when we manufacture the radio. We select based on their ability and a part to meet that requirement, and then test it to make sure that the final project continues to meet that thermal excursion. We have a series of tests we run every month to ensure that our processes and materials that we procure meet those requirements.”
Some argue that the drive to reduce weight and size can be contrary to achieving ruggedization requirements. Schoonover commented, “I don’t think the requirements clash. Small portable units, up to those deployed in vehicular installations, all meet the same requirement. They all have the same basic environmental and thermal requirement.”
TELECOMMUNICATION SYSTEMS INC. (TCS)
Jim Sprungle, vice president of government programs, TCS, contrasts the requirements for military and commercial ruggedization. “The big difference between commercial and military ruggedization is that products intended for military applications are designed to function while being subjected to conditions that exceed the most stringent environmental specifications and requirements, whereas commercial ruggedization ensures that we can count on reliable operation in the harshest surroundings in any foreseeable theater of operation, as applicable to the product’s mission objectives without the cost and lead times that traditional ‘MIL-SPEC’ designs entail.
“To accomplish this, we design and test for both extreme high and low temperatures, impact, shock and vibration, solar radiation, sand and dust, corrosive salt fog and various other conditions, which promotes an ultra high level of confidence that TCS equipment will operate during the most demanding situations to support mission-critical applications and to fulfill their battlefield roles. Commercial ruggedization is much the same as military in terms of designing for very similar environmental stresses and strains; however, we must also bear in mind that there is a fine balance between designing to meet the most extreme demands and the practicality of doing so with regard to value, performance and weight.”
TCS utilizes various analytical methodologies and employs the latest in state-of-theart software to fully engineer its products in a virtual computation environment before they ever let the “chips fly.” The company’s capabilities include designing in a fully 3-D modeling environment, structural substantiation using finite element analysis, dynamic motion simulation, and thermodynamic and airflow simulations using computation fluid dynamics.
“We want to ensure, for instance, that air is flowing properly over hot internal components removing heat, that when a certain mechanical component is actuated through its entire range there isn’t any interference, or when a certain external load is applied to one of our structures, the stress and strain is well within its limits. We design for all these factors and substantiate their performance upfront.”
To further validate much of their design work, TCS tests its product designs in their in-house testing lab and environmental chambers. “We have found with our gear that once it has been through our design, testing and environmental cycles at TCS with satisfactory results, we get very minimal warranty claims because our gear has really been hardened or test-driven, so it tends to operate without issues out in the field. “I think that we are starting to learn that the customer is willing to take gear that is perhaps slightly larger or a bit heavier as long as it works, and works well when they need it most. However, that is to also say that TCS engineering focuses on continual improvement, with the goal being smaller, lighter, more practical and intuitive man-packable secure communications equipment that is highly reliable in the most extreme conditions.”
HARRIS
“[Ruggedization] really brings in a number of key engineering disciplines from a packaging standpoint,” said Ed Maier, vice president and general manager of engineering and operations, Harris RF Communications. “It is really a systems design for ruggedness in, for example, material selection for the chassis and the main interfaces like keypads, speakers, the connectors and the circuit cards themselves.”
For Harris RF, MIL-STD-810F is the starting point for ruggedization, self evidently for U.S. programs, but also for international markets, said Pat Pendell, director of mechanical engineering and design services at Harris RF Communications. The U.S. MIL-STD “lays out 24 environmental conditions to be considered,” Pendell said. “You need to understand the precise user scenario, to be familiar with what that product is going to experience in the field. Our ruggedization is also designed for the global marketplace.”
“Through our extensive experience, we have developed design methods to exceed those standards,” Maier said. A major function of a rugged enclosure is to protect the high performance electronics from any environmental effects, Maier explained.
While a design may be perfect, Harris builds in additional checks and balances into the production process, Maier said, involving tests of the radio in conditions such as extreme temperatures or vibrations. The goal is to validate that the design is supportable in volume production. “We have systems to validate that the design can be built reliably and repeatedly in high quantities, and then within the production process itself we have a number of standard checkpoints. Every radio goes through a very extensive test and validation process.”
Harris’ work on size reduction is largely being enabled by work at the circuit level. According to Maier, “The things that are driving us in terms of size reduction really start at the circuit level, enabled by highly integrated circuits that allow us to include many more functions than in the past. We wrap the chassis and user interfaces around the circuitry. Although the radios are becoming much smaller, we must maintain a highly usable human-machine interface. We use technology such as connectors that are becoming much more dense and smaller, more functions on one switch, and just being clever by the way we use the chassis itself.”
Harris’ most recent development has the been the formal launch of new modules of the AN/PRC-117G, adding mission modules that add a second channel such as HF communications or ISR feeds to a standard PRC-117G manpack. Maier said, “These modules will be attached through an interface system that will be just as rugged as anything that you see on the base radio. We have some clever concepts for joining the base radio and its mission modules. They will be mechanically well-fastened and will use military grade connectors, which have been used successfully in military applications for years. The radio and modules clip together smartly.” ♦