Coaxial SMA Connector

What is an RF connector?

An RF connector is an electrical connector that works with radio frequencies set in the multi-megahertz range. These connectors are usually used with coaxial cables and are designed to keep their shielding. Mechanically, RF connectors use a fastening mechanism to allow a low ohmic electric contact, whilst sparing the gold surface. This allows more than 1000 reconnections and a reduction of the insertion force.

What is an SMA connector?

SMA connector, or SubMiniature version A connector, is a coaxial RF connector that was developed as a minimal connector interface for coaxial cables with a screw type coupling mechanism. It has a 50 Ω impedance, and presents exceptional electrical performance from DC to 18 GHz.

SMA Connector Design

  1. An SMA connector is composed of a 0.250×36 thread.
    • The male is fitted with a .312 inch hex nut that should be properly torqued with a 5/16 inch wrench, 3-5 in for brass, and 7-10 in for stainless steel connectors.

  2. SMA connectors are rated with 500 mating cycles.
    • It uses a polytetrafluoroethylene (PTFE) dielectric that comes in contact in the mating plane.
    • The outer shell of the male or plug connector contains an inside thread and an inner pin that often causes confusion. In SMA, the male connector refers to the “plug”, whereas the female connector refers to the “socket”.

Reverse Polarity SMA

Reverse Polarity SMA, or RP-SMA and RSMA, is a commercial variation of the SMA connector specification, where it reverses the male and female interfaces. It features the same external housing as a standard SMA plug connector. However, its internal pin is replaced with a female inner pin. In order to avoid confusion with the terms “male” and “female” with reverse connectors, these terms should be replaced with the terms “plug” and “jack” respectively.

RP-SMA connectors are predominantly used by Wi-Fi equipment manufacturers in compliance with specific local regulations. The term reverse polarity may be confusing to non-Wi-Fi engineers as the reverse of polarity may be thought to refer to electromagnetic polarity instead of the reversal of the gender interfaces.