What are SMA Connectors?

By AJ Born | March 29, 2022

Meet the Connector: SMA coaxial RF connectors

SMA (Sub-Miniature version A) coaxial RF connectors were developed by Amphenol in the 1960s as a sub-miniature connector interface for RF cables with a screw-type coupling mechanism. Since then, many variants of the SMA series have evolved to meet the ever-changing requirements of the RF and microwave industry.

JAE end-launch type SMA connector

The connector has a characteristic 50 Ω impedance and was originally designed for use from DC (0 Hz) to 12 GHz. This has, however, been extended over time and variants designed to work at 18 GHz and 26.5 GHz are now available.

A standard-polarity SMA male connector has a 0.9 mm diameter center pin surrounded by a barrel with inside threads, and the standard SMA female connector has a center sleeve surrounded by a barrel with outside threads. The gender assignment corresponds to the innermost electrical component. The center pin is the same diameter as the center of RG402 Coax so that connections can be made without discontinuity. The pin is formed from the coax itself.

A reverse polarity RP-SMA, available in all styles, reverses the gender of the interface to allow for port identification and prevent the mating of incorrect antennas or devices to equipment. The pin and sleeve are swapped so that the male RP-SMA has a center sleeve surrounded by an inside-threaded barrel, and the female RP-SMA has a center pin and an outside-threaded barrel.

Cinch Connectivity’s SMA vertical launch coax connectors

SMA materials

Environmental demands dictate material selections for the manufacture of the connectors and surface plating. Use in harsh environments calls for IP68 versions of both popular standard SMA connectors and customer-specific bespoke designs.

SMA connectors usually have a brass or stainless-steel body. The finish is typically nickel or gold on SMA connectors, while the stainless-steel body has a passivated or gold finish. The center contact/pin of a SMA connector is usually made of brass or copper with a gold finish.

COAX Connectors’ SMA Reverse Polarity, Straight 3-Hole Flange-Mount PCB Jack is IP68-sealed un-mated with a black non-reflective nickel finish, gold-plated contact, and PCB solder body.

Design Notes

Mounting Configurations The key mounting configurations include panel mount (2-hole and 4-hole flange), PCB mount, edge mount, bulkhead mount, SM, and through-hole mount.

Characteristics 50 Ω impedance for use from DC (0 Hz) to 12 GHz, with variants available to work at 18 GHz and 26.5 GHz.

Materials The SMA connector body is typically either brass with a nickel or gold finish or stainless steel with a passivated or gold finish. The connector center contact/pin is most often brass or copper with a gold finish.

Markets, Sectors, Applications SMA connectors are used in telecom, medical, industrial, factory automation, and robotics markets. Applications include microwave systems, hand-held radio and mobile telephone antennas, Wi-Fi antenna systems and USB software-defined radio dongles, and radio astronomy, particularly at higher frequencies (5 GHz+).

Suppliers SMA connectors are available from a number of connector suppliers, including Amphenol RF, Bulgin, Cinch Connectivity, COAX Connectors, Hirose Electric, I-PEX, ITT Cannon, JAE, JPC Connectivity, SV Microwave, TE Connectivity, and Trexon.

Related products

  • RF connector
  • SMB connector
  • SMC connector
  • BNC connector
  • TNC connector
  • N connector
  • Coaxial cable
  • Optical fiber connector
  • MMCX connector
  • MCX connector

Learn more about RF coaxial connectors.

Visit the Preferred Supplier pages of the companies included in this article: Bulgin, Cinch Connectivity Solutions, COAX Connectors Ltd, Hirose Electric, I-PEX, ITT Cannon, JAE, JPC Connectivity, SV Microwave, TE Connectivity, and Trexon.

Like this article? Check out our other Meet the Connector, Wire & Cable and New Technology articles, our Datacom/Telecom Industry articles, and 2022 Article Archives.

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