VITA 67 provides the first coaxial-backplane standard for analog and RF I/O

The embedded computing industry serves markets where high-fidelity analog and RF signals are typical I/O requirements. The VITA 67 coaxial backplane standard (Analog/RF Interconnect, formerly 46.14) was developed in support of I/O of high-fidelity RF, video, and many other analog signals on the VPX (ANSI/VITA 46) backplane. Prior to the VITA 67 standard, no standard supported these requirements.

VITA 67 provides MTTR, cooling, and signal-fidelity advantages

The advantages of integrating coaxial connectivity on the backplane are significant and fall into several technical domains. The rear-panel coaxial interface enables the quick disconnect and replacement of a card, thus meeting crucial Mean-Time-To-Repair (MTTR) requirements for military systems. Consider a direction-finding system that has eight or more coherent channels and a supporting Local Oscillator (LO) distribution mechanism. In units with front-panel coaxial interfaces, it can take more than an hour to replace a broken card because of the need to disconnect and reconnect a complex rat’s nest of reference and LO cables. With a rear-panel coaxial interface, the card can be replaced within a minute. Moving connectors from the front panel is a must for conduction-cooling scenarios because front-panel I/O is disallowed. Finally, an unforeseen advantage discovered of some coaxial modules is they significantly improve channel-to-channel isolation.

The suggested connector for the 3U VITA 67.1 configuration is available from Tyco Electronics, which demonstrated much better channel-to-channel isolation than front-panel screw-on connectors. Laboratory testing has shown isolation among contacts of greater than 125 dB over the frequency range of 2 MHz to 40 GHz, with typical isolation of better than 140 dB during much of the tuning region. In comparison, the typical isolation provided by screw-on front-panel connectors is around 90 dB.

VITA 67 can be implemented with other VPX standards

The VITA 67 standard can be utilized in conjunction with other VPX standards. The attributes and benefits of the other VPX standards, such as ANSI/VITA 46, can coexist with VITA 67. For instance, the rich capability of ANSI/VITA 46 serial interconnects can be integrated with the VITA 67 standard, including GbE, 10 Gb, Fibre Channel, InfiniBand, Serial RapidIO, PCI Express, Advanced Switching Interconnect, and others. In many implementations, the VITA 67 standard will not impact the maximum serial bandwidth of ANSI/VITA 46 fabrics, since the coaxial connector position is strategically placed to enable the full capability of the defined ANSI/VITA 46 dot standards.

It is anticipated that there will be a variety of backplane configurations that include VITA 67 definitions, such as all the slots being VITA 67 coaxial slots, a combination of VITA 67 coaxial and ANSI/VITA 46 slots, or a combination of VITA 67 coaxial, VITA 66 optical, and ANSI/VITA 46 slots.

The end is near

The VITA 67.0 and VITA 67.1 standards recently passed their working group ballots. Some minor changes are being implemented, and it is anticipated that VITA 67.0 and 67.1 will be submitted for ANSI balloting by the end of 2010.

Robert Normoyle is a Senior Systems Architect at DRS Signal Solutions and Chairman of the VITA 67 working group. He can be contacted at