Size is relative. But almost all aspects of military electronic technologies are looking to get smaller, lighter, and more power efficient as well as faster and smarter. The 6U and 3U form factors used by VME systems for decades remain the form factor for standards such as VPX, VXS, and CompactPCI.
Other standards-based solutions such as AdvancedTCA and MicroTCA are found in the military and avionics environment because of the importance of communication. For example, the RadiSys Promentum C2 AdvancedTCA Server is designed to bring communication to the front line (see “Rugged Communications,” p. xx).
Systems like the Promentum C2 AdvancedTCA Server are ruggedized. However, they normally don’t compete with their more rugged cousins in deeply embedded systems where extreme shock, vibration, and temperature ranges are encountered. Still, the extremes are much wider than most industrial environments.
AdvancedTCA systems tend to be rather large. 3U systems are much smaller but still substantial in size. Even smaller form factors are needed in many applications such as small unmanned aerial vehicles (UAVs) and small unmanned ground vehicles (SUGVs). Until now, most of these solutions have included custom-built electronics.
This often meant custom cases as well as custom boards. Developers would reuse their own designs, and there was rarely commonality beyond a project or organization. Computers-on-modules (COMs) are popular in this environment, allowing developers to move much of the hard processor design work to the COM boards. Unfortunately, tying the COM boards into a conduction cooling system isn’t always easy.
This trend toward smaller systems isn’t unique to military and avionic environments. Compact industrial applications have a range of standard or de facto standard solutions (see “Rugged Stacks,” p. xx). Many of these solutions wind up in military and avionic applications that are in harsh environments but not necessarily at the extremes. In some cases, this is because the underlying boards are Class 2 while hardier solutions are Class 3.
The Air Transport Rack (ATR) is standard fare. An ARINC 404A 1 Short ATR is 257.05 by 320.5 by 269.88 mm, and a 1 Long ATR is 257.05 by 498.3 by 269.88 mm. There are smaller and larger ATR versions as well. These days, they’re often filled with VPX boards like Pentek’s 5300 series of VPX Software Radio boards (Fig. 1). The OpenVPX standard has made VPX board utilization even easier by providing standard backplane and system configurations (see “OpenVPX Accelerates Military Time-To-Market,” June 17, p. 33).
Smaller tends to be better if a designer can create a solution within other design constraints. This leads to more compact ATRs like Curtiss Wright Controls Embedded Computing’s MPMC-5931. It’s smaller than a 1/2 Short ATR, which is essentially half the size of a conventional ATR (Fig. 2). What used to fit into a full-size ATR box can now fit into an MPMC-5931. Of course, this means that even more can fit into a smaller package.
Rugged, Compact proposals
Three companies look to fill the low-end void where custom implementations currently reign. Themis, PCI-Systems, and Curtiss Wright Controls Embedded Computing have submitted competing proposals to the VITA Standards Organization that are related to the popular VPX standard, which utilizes high-speed serial fabrics on the backplane (see the table).
In all cases, the boards are smaller and the power limitations of the system are lower, but that’s what the designs call for. They all provide a substantial reduction in volume (Fig. 3). The proposed standards all mirror the VPX backplane in some fashion. In some cases, though, the connectors differ from the MultiGig RT-2 connectors found on standard VPX boards (Fig. 4).
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