Walking Antenna
Written by Adam Baddeley
SOTECH 2009 Volume: 7 Issue: 8 (October)
Can a Body-Worn Antenna Do the Job, or are the Demands of Price and Performance Irreconcilable?
Polishes Contingency Skills.
“The Army is spending a lot of money trying to come up with a body-worn antenna that has good technical performance. There are a lot of reasons in fundamental physics why that may be mission impossible,” explained Bruce G. Montgomery, president of Syntonics, an engineering technology company specializing in antenna technology. “Our [Handheld Tactical Antenna (HTA)-SINCGARS] antenna, for example, is a very simple antenna. It doesn’t try to be a great antenna, but it is good at what it does. I am beginning to suspect that this is a situation where there may be no perfect answer. Therefore, a good enough answer that is also inexpensive may be the way to go.”
Syntonics’ involvement in military antennae dates from 2002, as part of a SBIR project for USSOCOM for troops on board ships. Montgomery said, “We then found ourselves doing a lot of engineering development work for SOCOM, who have a combination of interesting problems and the budget to pay for the development of the answers.” Syntonics now has two principle product lines today based on that work, handheld tactical antennas—the self-evidently named HTA-TACSAT and HTA-SINCGARS—and the FORAX RF-over-fiber communications system.
The HTA-TACSAT derived from SOCOM’s requirement for high performance, extremely lightweight, very rugged UHF MILSATCOM (TACSAT) antenna. Originally developed in 2006 for use with manpack radios such as the AN/PRC-117 and the handheld AN/PRC-148 and -152, HTA-TACSAT is designed to be carried in a holster. When comms are required, the user takes it out of the holster, point it upwards, and a link is established within seconds.
Montgomery explained, “The heritage SATCOM antennas are relatively heavy, fragile and take a long time to set up and put away. SOCOM wanted something that weighed less, had a lower visual profile, and could be thrown across the room and still be OK. The HTA TACSAT is close to unbreakable. It can also be deployed almost silently and repackaged in a matter of seconds. All of those things are different from heritage antennas.” The antenna also has a very low profile and cross section, allowing it to easily blend in.
The HTA-TACSAT is distributed via direct sales as well as via two distributors using the GSA Advantage contract vehicle. The first export sales of HTA-TACSAT were made to the Royal Marines in 2007. The Polish and Portuguese militaries have also purchased units.
“We have just started shipping a second version of our TACSAT antenna, which has better technical performance. In the next year, we will begin to develop a vehicle-mounted SATCOM antenna that magnetically attaches to the roof of the vehicle for UHF TACSAT.” Syntonics’ next steps will also include the development of an antenna that can support both legacy TACSAT and the next generation Mobile
User Objective System (MUOS).
Whereas the HTA-TACSAT derived from government-sponsored work led by SOCOM, the vest-worn HTA-
SINCGARS came from the polar opposite direction. In late 2007, Montgomery received an e-mail from an Army sergeant stationed in Iraq, asking Syntonics to build a new antenna that would operate while threaded through the wearer’s MOLLE vest in a serpentine path. Initially, as Montgomery relates, the company was skeptical the design would work, but prototypes were ready when the sergeant stopped Bruce G. Montgomery by the company while on leave in February 2008.
Montgomery said, “We didn’t then understand why it worked or indeed if they would work at all, but we asked him to let us know if it did. About two weeks later, he sent a picture of himself standing in the streets of Baghdad, wearing the antenna and reporting it worked great.”
Syntonics then undertook a detailed analysis of the antenna design and took it to CECOM’s range for testing body-worn antennas at Fort Monmouth, in order to understand how it worked.
Montgomery explained what the design delivers. “This is a simple antenna. Is it only intended for shortrange communications such as a dismounted squads talking to each other or back to their vehicles—no more than 500 meters. However, it is at least equal to the issued metal tape antenna when it is all rolled up in a ball, wadded up and tied up with string, which is what everyone does with them anyway. It is an ugly antenna to an engineer, but for the soldier on the ground it works great.”
The HTA-SINCGARS generates an omni-directional pattern even though the serpentine antenna is on the back of the body, whether the soldier is standing, kneeling or flat on his stomach. There is also zero visual profile. Montgomery said, “People can put it on bomb disposal suits, go through windows and doors without the antenna catching, and nothing sticks up saying shoot me first.”
Its appeal was immediate. Montgomery said, “We loaned a couple to elite Navy units, and they bought a thousand. We have sold several thousand more of these just by word of mouth.”
L-3 FOR ISR
Delivering video feeds from five bands—C, L, S, Ku, UHF—from tactical UAVs down to the dismounted soldier is done today via L-3 Communications’ Rover technology.
“Rover is a kit that you have to stop and put together—a video link on the halt if you will,” explained James Diefenderfer, soldier ISR receiver business manager.
“The Army’s Land Warrior guys came to us and said they needed the Rover capability on their ensemble. We worked with them early on in their first deployment and showed them how they could integrate Rover into their system to take advantage of the video. What they did at that time was to have an OSRVT in the Stryker vehicles, capture video, and then retransmit still frames. That worked; they liked that, but it wasn’t real-time, and by understanding their needs was how we came up with the Soldier ISR Receiver [SIR].”
Taking the lessons learned, L-3 then embarked upon its own IR&D effort to develop a lighter, worn, always-on ISR receiver, which became the SIR. This has now been successfully integrated in the LW ensemble, and PEO Soldier has procured a number of systems for test and evaluation. Diefenderfer said, “They have determined that it is technology that they very much want, but how they deploy it is still up for discussion.”
The system has two elements: the modem, which weighs 0.65 pounds, measures 2.7 inches by 4.8 inches by 0.75 inches, and dissipates 5W; and the antenna, which weighs just 0.3 pounds and measures 1 inch by 4 inches by 0.5 inches. The system supports MPEG2/4, H.264 and MJPEG with a maximum throughput of 10.71 Mbps.
“With this device, the soldier can receive the video directly himself. Previously, as soon as they went around a building or corner, they would lose the communication link with the Stryker vehicle. That is why it is so important to outfit soldiers or leaders with SIRs to get the video feed directly"
Diefenderfer acknowledged that the antenna component is still the biggest challenge, something the company has addressed by working with a number of antenna partners. “How do you come up with an antenna that can be used in a dynamic environment taking into account the soldier’s head is in the way. You have UAVs that are flying around, and, as with other directional radios, the soldier can’t stop and realign his antenna; he is on the move all the time. I don’t expect that we have solved them all, but we are working on it.”
The SIR as currently configured is integrated into the LW ensemble so that the feed can be seen on the ensemble’s display and also draws from the system’s power. The company has also begun initial discussions with radio manufacturers on the possibility of integrating the SIR onto a handheld radio. Diefenderfer cautions however that while technically such a step would be feasible, it has yet to be reflected in customer requirements. He added, “The customer is currently satisfied with keeping video feeds separate from the local tactical network. As you might imagine, there are some things that happen within ISR video that you can’t put across the entire network. Not only could it not handle the bandwidth, but there are security and
CONOPS issues too.”
CONOPS issues too.”
Giving the SIR a technology readiness level (TRL) is not easy. Diefenderfer said, “There is no new technology in the SIR that hasn’t already been deployed and used in missions. It has just been repackaged in a different way. Clearly the technology is nine, but, as it is repackaged, SIR is probably a TRL 6.”
The current SIR has a single antenna that covers only the lower frequencies: C-, L- and S-band. Moving to a full CDL Ku-band capability has opened a discussion on whether to adopt a single antenna, or
two or more frequency-optimized antennas.
Diefenderfer commented, “A lot of that is down to how they employ it, where they want to put it on their kit, and the space that is available for the antenna. There are lots of integration efforts and questions still remaining. Right now however, our choice is to have a separate Ku-band antenna and then separate multi-band antenna.”
PHARAD FINDS SOLUTION
In 2004, Pharad, LLC was developing JTRS vehicle antennas for the U.S. Army CERDEC, when the Army began looking at wearable antennas for the Future Force Warrior Program. “It sounded like an interesting antenna challenge, so we posed the problem to our antenna engineering team to see what kinds of radiator solutions they could develop,” explained Austin Farnham, president of Pharad. “We decided to involve a materials company to see if we could develop an optimal solution when our antenna engineers were allowed to consider a variety of material properties. With their material scientists and our antenna engineers, we think we came up with a robust wearable antenna development process that results in high performance body worn antennas.”
It turns out that there was not just one antenna style that would work for all RF communications applications. “This is an extremely challenging problem,” said Rod Waterhouse, vice president of antenna development at Pharad. “There is not one magical solution that fits all applications; our antenna designers needed to be flexible, like the materials themselves. I believe the solutions we have created are near optimal and provide a viable technical solution.” Pharad has been awarded several patents covering their wearable antennas and has subsequently developed a large variety of wearable antenna products for applications ranging from voice communications to video and data transmission systems. The end results are small, thin flexible patches that can be worn under clothing or on tactical soldier/marine gear.
Pharad offers a variety of mounting options such as covert undergarment carriers or MOLLE pouches for tactical gear for those customers that do not directly integrate the wearable antennas into their own mounting systems.
Pharad’s team also had to consider the safety aspects of having radiators close to the body. The Pharad engineers performed a great deal of modeling and simulation, followed by SAR (specific absorption of radiation) testing. They have found that for the antennas subjected to SAR testing, their modeling matched closely. The Pharad antennas have been designed to comply with the IEEE (FCC) exposure limits for occupational/controlled RF exposure environments.
AMTI: POWER UP
The premise of AMTI’s Alpha 320KT solution is to provide a 20W lightweight amplifier with a relocatable, multi-band antenna, enabling handheld tactical radios to have the transmission performance of a manpack radio, but at half the weight. It has been sold widely for the past three years to the SOF community in the U.S. and internationally. Following JITC certification in 2008, it began to gain traction among conventional forces.
One of the reasons a kit was designed was to provide an unambiguous, turnkey solution that soldiers could clearly understand and implement in the field. Kirk Traber, communications product manager, said, “We supply the amplifier, amplifier mounting device, RF cable from the radio to the amplifier and power cable. Then we also supply an RF cable to go from the antenna port on the amplifier to the antenna relocation device along with a 20-watt multi-band antenna. All the end-user has to do is install the RF cable from the radio to amp, connect the battery cable, install the antenna directly to the amp or use the antenna RF cable and relocation device, turn the amp on and ensure the radio is set to 5W, and now they have a 20W system.
“One of the rules of good transmission is a clear and unobstructed antenna,” Traber continued. “When many soldiers put their radio and/or amplifier on their person, the antenna is right up against
their body. That causes a lot of voltage standing wave ratio [VSWR], or ‘vizoir,’ which is just bad for transmission. The absorption rate [caused by the body] usually knocks the transmission down by about 10-14 db. If your handheld radio is putting out 5W at minus 10 db, you are effectively only putting out 0.5W. What we have tried to do with our antenna relocation device to is to allow guys to transmit a little better because it is designed to clip onto the shoulder portion of their backpacks to raise the antenna and take it away from the body so that VSWR is minimized and allow for a better radiation pattern to transmit more effectively.”
Transmission is not just a function of the antenna; power output is largely a function of the power amplifier. The PA of the Alpha 320KT is a 20W power amplifier that covers the frequency range from 30-512 MHz. It works by taking the RF signal from a user-supplied radio such as an MBITR, AN/PRC-152, or similar radio operating in the 30-512 frequency range. It takes the 5W output from the radio and automatically detects the frequency and the mode of operation—AM or FM—and then amplifies the signal to 20W.
“The main reason we designed the kit is that it allows operators that want to utilize this small amplifier to lighten their load. The Alpha 320 only requires one battery to operate it, whereas other
designs require two,” Traber said.
“This doesn’t eliminate the need for large manpack radios altogether, but for those individuals that have the option of carrying a handheld radio and an amplifier versus a 17- to 19-pound manpack radio, they can cut their weight by less than half. Our amplifier is only 24 ounces, and the whole kit is 3 pounds. When you add a 2.25-pound battery and a 37-ounce radio, you are still less than half the weight of
most manpack radios.”
The amplifier allows the user to switch between various power settings between 20W and 7W using a keypad. According to Traber, “The primary reason for this is RF and power management. Users don’t always need to transmit at 20W to get back to their command post or C2 node. The other reason is for compliant DAMA operation.”
One of the key features between the Alpha 320KT kit and its competitor, Traber argued, is AMTI’s use of filters across the full frequency spectrum of 30-512 MHz. He commented, “The filtering we provide with our amplifier suppresses those harmonics that were not conducive
to good communications.”
to good communications.”
The Alpha 320 amplifier was successfully tested by JITC in 2008 and has also gone through certification to MIL-STD-810F and MILSTD-461E.
The kit also has applications for public safety, homeland security and police enforcement. Traber said, “We didn’t want to design our kit solely for just military use. We designed it for anybody to utilize in those frequency ranges because in times of national emergencies, radio towers have been lost and are unable to transit in their normal frequency ranges. Now they can come back and use our small amplifier with their existing handheld radios and still communicate.
QINETIQ INTEGRATION
QinetiQ North America’s Technology Solutions Group has done extensive work in developing wearable electronics solutions, namely the integration of electrical and optical conductors into fabrics that become part of the soldier ensemble itself, in terms of power, data cabling as well as the antenna. This work originated with a number of SBIR contracts, undertaken by the former Foster-Miller’ and dating from 2000, in support of both CERDEC and the Natick Soldier Center Brian Farrell, Group Director, Integrated and intelligent solutions,
QinetiQ North America Technology Solutions Group said, “We do lot spectrum of 30-512 MHz. He commented,
“The filtering we provide with our amplifier suppresses those harmonics that were not conducive to good communications.”
The Alpha 320 amplifier was successfully tested by JITC in 2008 and has also gone through certification to MIL-STD-810F and MILSTD-461E.
The kit also has applications for public safety, homeland security and police enforcement. Traber said, “We didn’t want to design our kit solely for just military use. We designed it for anybody to utilize in those frequency ranges because in times of national emergencies, radio towers have been lost and are unable to transit in their normal frequency ranges. Now they can come back and use our small amplifier with their existing handheld radios and still communicate.
QINETIQ INTEGRATION
QinetiQ North America’s Technology Solutions Group has done extensive work in developing wearable electronics solutions, namely the integration of electrical and optical conductors into fabrics that become part of the soldier ensemble itself, in terms of power, data cabling as well as the antenna. This work originated with a number of SBIR contracts, undertaken by the former Foster-Miller’ and dating from 2000, in support of both
CERDEC and the Natick Soldier Center.
Brian Farrell, Group Director, Integrated and intelligent solutions, QinetiQ North America Technology Solutions Group said, “We do lot of work in wearable electronics. We work with a number of different customers, providing novel materials and design rules to implement power and data cables and antennas using conductive textiles. Some of the antennas that we have done have been specifically integrated into shoulder guards.”
QinetiQ’s work also supports company-led efforts in this area such as BAE Systems and Megawave, with Farrell noting a solution constructed for BAE Systems which gave, he said, “excellent omnidirectional coverage.” He continued, “The antennas are made up from conductive and dielectric materials. Where you would have ceramic or print circuit boards in a more conventional implementation, we use textiles which are also the dielectric material and we also have conductive textiles that we would use for the radiating element—ground planes etc. They would be integrated into the ensemble itself. It might be a GPS antenna in a soldier patch but we have also done some work with communications antennae that take up a larger area of real estate on the ensemble itself.”
The company is currently working at General Dynamics EDGE facility, providing vendor agnostic wearable electronics, which are currently in the final stages of qualification to support the Ground Soldier Ensemble and other programs. ♦