Introduction to MIL-PRF-39012 and MIL-STD-348 Coaxial Connectors
To enable interoperability amongst RF systems, the military and industry rely on standardized dimensions and types of coaxial connectors. The two major standards that define coaxial connectors for the US military are MIL-STD-348 and MIL-PRF-39012. MIL-STD-348 provides the dimensions for control of the standard interfaces, while MIL-PRF-39012 defines the, detail specifications, materials, quality conformance, qualification, and verification for coaxial connectors. As a greater number of industries and applications adopt Hi-Rel coaxial cable assemblies, both MIL-PRF-39012 and MIL-STD-348 are becoming increasingly valuable in manufacturing and sourcing coaxial cable connectors and adapters. Hi-Rel coaxial connectors are used with virtually all RF devices and assemblies that require RF transmission line interconnect, other than waveguide. This includes common assemblies, such as amplifiers, transceivers, filters, antennas, mixers, attenuators, combiners/splitters, couplers, and many other devices and components.
MIL-PRF-39012 can be compared to MIL-DTL-17 for coaxial cables, as they both involve visual, mechanical, and electrical testing in several stages to uphold quality standards. This standard also requires that manufacturing facilities and processes meet quality standards and that the parts covered by the specification can be listed on the Qualified Products List (QPL). Coaxial connectors and adapters that meet MIL-PRF-39012 are well suited to military, and non-military use for a wide range of Hi-Rel applications, including radar, RF instrumentation and test equipment, transceivers, ruggedized RF/microwave assemblies, SATCOM ground equipment, indoor/outdoor antennas, transportation, and aerospace RF/microwave assemblies.
Materials used for MIL-PRF-39012 qualified connectors are specified in referenced industrial standards, listed in the following table.
|Steel||ASTM A484/A484M, ASTM A582/A582M|
|Brass||ASTM B16/B16M, ASTM B36/B36M, ASTM B121/B121M, ASTM B455|
|Phosphor bronze||ASTM B139/B139M|
|Soft copper||ASTM B152/B152M|
|Copper||ASTM B88, ASTM B124/B124M|
|Copper-Beryllium||ASTM B194, ASTM B196/B196M, ASTM B197/B197M|
|PTFE fluorocarbon||ASTM D4894, ASTM D4895|
|FEP fluorocarbon||ASTM D2116|
A key aspect of MIL-PRF-39012 connectors is that the center pin for qualified connectors must be gold-plated to a standardized depth, adhesion quality, and finish. The gold plating on the captivated contacts ensures a minimized insertion loss and consistent electrical contact over time and exposure to the environment.
The types of connectors specified in MIL-PRF-39012 include the following:
MIL-DTL-348 specifies the United States standard interfaces for RF coaxial connectors, which are universally accepted by all US military services. Hence, these connectors are very commonly used in, and outside of military applications, even if the application doesn’t specifically require the use of this standard. The benefit is that MIL-DTL-348 brings interoperability of coaxial connectors, as well as a basis for Hi-Rel design and construction of these components.
MIL-STD-348 includes the RF connectors and adapters referenced in other MIL-SPEC documents: