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Tough Computers for Electrically Sensitive Environments

The increasing popularity of wireless in commercial and health environments has created EMC challenges for makers of mobile computing devices. WalkAbout Computers, one of the leaders in this emerging industry, has relied on Silent to rapidly resolve these technical hurdles.

WalkAbout's flagship product, the Hammerhead XRT, has been designed to stand up to rough and tumble places such as warehouses, airports, loading zones, construction sites as well as emergency medical teams (EMTs) where it is not uncommon for the XRT to be dropped or kicked about in the course of daily use. The XRT's rugged housing is so well designed that it can withstand several tons of pressure and absorb extreme shock without any damage or performance degradation. In real world applications this means users can depend upon reliable, seamless operation without data corruption. (Visit WalkAbout's website at www.walkabout-comp.com to see a video of a multi-ton truck rolling over the XRT).

The XRT features a CDMA modem which links to enterprise information systems for real-time processing of job orders, inventory, shipping and medical records. Users must have the freedom to move about, so radiated emissions and RF immunity requirements are very stringent. Emissions have to be extremely low in order to prevent disturbances in to environments with sensitive electronics. And the machine is expected to work flawlessly in harsh electromagnetic environments such as electrical power stations.

When Ron Valli, Senior Architect of Design and Development at WalkAbout, encountered radiated emissions beyond acceptable levels, he contacted Lee Hill and Randal Vaughn of Silent. The XRT had to comply with FCC and European Class B radiated emission requirements for shipment to the US and Europe. Due to the complex nature of FCC and European radio modem testing requirements, low RF emissions are essential for achieving regulatory compliance as well as ensuring robust wireless performance. No simple task for mobile PCs with 1 GHz clocks and CDMA modems that operate at frequencies up to 1900 MHz.

Randal and Lee reviewed the entire system design and imported the XRT design data into their PCB file viewer to get an interactive, real time picture of all signal and power layers. The source of the problem wasn'št immediately apparent, but after researching and using a CDMA test station in their debug lab, within a few hours Lee and Randal narrowed it down to issues associated with the modem design and features. They replaced the radio and ran anechoic chamber tests again but the problem still lingered. Further diagnostics led them to investigate the electrical characteristics of the modem's connector, integral shield, and physical attachment to the XRT. In one test, they discovered that the modem mounting holes were electrically floating from chassis, causing excessive emissions when linked to the base station. The solution: a new radio with different mounting characteristics.

Ron Valli has nothing but the highest praise for Lee and Randal. "In addition to being talented engineers, Lee and Randal are gentlemen. I was able to focus on my job while they worked collaboratively with my staff to solve a difficult problem at a crucial juncture. The XRT was shipped on time with a retrofit that was both cost-effective and manufacturable. "

As rugged PCs find their way into more and more commercial applications, Silent continues to advise WalkAbout on next generation design architectures. "With SILENT'S help, the future is not so rough and tumble after all", said Ron. "We have enlisted SILENT'S help for our next generation wireless platform." WalkAbout will continue to service these markets with the highest quality products and services that make personal communications in tough environments practical and affordable.

SILENT solves elusive RF problems at WalkAbout Computers.

Phone: (603) 578-1842   email: info@silent-solutions.com

Worldwide providers of EMC design, troubleshooting, and education services for the reduction of EMI and electrical noise