New RF Connectors Advance Embedded Systems

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In recent years, the design of high-quality RF/microwave systems has experienced a significant transformation thanks to four pivotal advancements:

• the emergence of RFICs and monolithic microwave ICs (MMICs)
• the enhancement of design automation through EDA software
• the increased availability of advanced antennas
• the development of superior RF/microwave and data connectors.

At the forefront of these cutting-edge RF/microwave connectors are the VITA OpenVPX-specified devices, which have proven to be invaluable across a wide range of military and industrial applications, paving the way for more efficient and innovative communication systems.

The important Sensor Open Systems Architecture (SOSA) standard leverages the OpenVPX standard to define card profiles with specifications for features such as pinouts, networking capabilities, and serial interfaces. The SOSA Reference Architecture is specifically intended to support US DoD Command, Control, Communications, Computer, Intelligence, Surveillance, Reconnaissance, and Tracking (C4ISRT) systems development, but is very useful in many applications.

The VPX (VITA 46) specification was ratified in 2007 as the next-generation VME backplane. Then, in 2009, VITA introduced OpenVPX (VITA 65) to address interoperability issues. This brought profiles so that one manufacturer’s boards would always talk to another’s in a designated backplane/chassis setup. OpenVPX defined different "planes" in the specification (control, data, expansion, management, and utility planes) that grouped other signals/functions. Then, it defined the signal types in “pipe” classes, which include ultra-thin pipe (x1), thin pipe (x2), fat pipe (x4), and double fat pipe (x8) as the principal groups, as well as a couple of others.

SOSA requirements for 3U and 6U modules refer extensively to the VITA VPX standards. However, SOSA restricts good VPX primary slot profiles to a relatively small set of three 6U and six 3U profiles.

Meanwhile, the full VITA 65 OpenVPX standard provides dozens of 6U VPX and 3U VPX slot profiles with user-defined pins and, therefore, systems with unique backplanes designed to be used with specific modules. SOSA limits this individuality.

The SOSA standard also recognizes the need for excellent cooling methods so that power growth can be accommodated to support future processing needs. SOSA has defined a 1.00” slot pitch for conduction and liquid cooled modules to accommodate various cooling methods and a 1.5" pitch for air flow through modules.

While the SOSA approach establishes guidelines for military applications in command & control, communications, computers, cyber warfare, intelligence, surveillance, and reconnaissance (C5ISR), many civilian/commercial systems applications can benefit from this design philosophy. Aircraft and railroad control designs are sure-fire users, and factory industrial control systems will also help.

First, let's take a look at the four S’s of microwave connectors:

• SOSA - Sensor Open Systems Architecture
• SMP - miniature 50W plug-in RF coaxial connectors for applications up to 40GHz, with easy push-on connect
• SMPM - a smaller 50W coax interface with a frequency range of DC to 65GHz (Figure 1)
• SMPS - even smaller 50W coaxial connectors with a maximum frequency of 65GHz or 100GHz. These connectors are 45 percent smaller than the SMP connectors and 30 percent smaller than the SMPM.