Military systems represent extreme environments for COTS electronic equipment. Many systems involve multiple enclosures, often from different suppliers. Equipment layout, the selection of racks, whether isolation is used, and how the electronics are “housed” can vary widely. There are no standards regarding maximum allowable shock and vibration levels. Design factors are often based on estimates of equipment fragility and expected loads, both of which can be uncertain.

VPX is like a three act play. Act one was the launching of a new high density platform for critical embedded computing applications. Leveraging the wildly popular VMEbus in 3U and 6U Eurocard formats, VPX added the capability of using high speed serial switch fabric technologies such as Ethernet, PCI Express, serial RapidIO, and others, that can be configured in various backplane topologies. VPX also greatly increased the number of backplane pins to handle more data traffic and user I/O making it more effective for today’s applications.

The OpenVPX Industry Working Group, a 28-company team founded by Mercury Computer Systems, collaborated with a common goal and accelerated the completion of a system architecture specification for open system COTS suppliers and integrators to specify, design, and build multi-vendor interoperable solutions.

VPX systems offer tremendous performance for the Mil/Aero market, including naval, airborne, and ground-based computing systems. The architecture provides an unprecedented combination of bandwidth, user IO, and rugged design, in both a 3U and 6U Eurocard format. The new OpenVPX initiative has opened up new definitions for VPX system interoperability, including defined module profiles, slot profiles, backplane & chassis configurations, secondary expansion fabrics and control planes, and higher speed fabric options.

Before the advent of OpenVPX, designers of embedded systems took advantage of the extreme connectivity offered by VPX (VITA 46), but were faced with a virtually unlimited number of possible implementations. Specific choices for the control and data channel assignments for each slot, the backplane connectivity, and serial fabrics were often made somewhat arbitrarily to suit the particular needs of the current system. Although following the general framework of VITA 46, each system tended to be so unique that the boards and backplanes designed for one system were seldom usable in other systems, even from the same vendor.

Systems engineering is not about developing electronics, mechanical, or software designs. Systems engineering is really about four things:

DC is not always DC. When systems are developed to operate on DC power, the DC electrical environment will have noise and may experience other disturbances. This article will explore considerations for generating low frequency disturbances (glitches, sags, surges, spikes) that occur in the 100 microsecond and longer region with bandwidths of 10 kHz or less. In contrast, noise, which is outside of the scope of this article, can be low frequency (like 50/60 Hz hum) but becomes a challenge to generate in range from kHz, to MHz or up to the GHz range.