What are SMA Connectors?

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- everything RF

Sep 3, 2018

SMA Connectors are 50 Ohm RF Coaxial connectors that operate up to a 18 GHz. These connectors have screw type coupling mechanism which minimizes reflections and attenuation by ensuring uniform contact. SMA connectors are one of the most used RF connectors. They are used in a wide range of applications including antenna connections for most sub 6 GHz technologies like Wi-Fi and Bluetooth.

SMA Connector Gender & Mechanical Specifications:

SMA Male / Plug Connectors: In an SMA Male connector, the center pin is surrounded by a barrel with threads on the inside. SMA Male connectors are also known as SMA Plug connectors. They have a diameter of 0.312 in (7.9 mm) and have a hex nut which can be used to tighten or loosen a connection with a torque wretch.

SMA Female / Jack Connectors: In an SMA Female connector the center sleeve is surrounded by a barrel with threads on the outside. SMA Female connectors are also known as SMA Jack connectors. The connector has an outer thread length of 4.32 mm with the diameter of the thread area being: 6.34 mm.

Reverse Polarity SMA Connectors

Reverse Polarity SMA Connectors or RP-SMA are a variation of regular SMA Connectors with the interface gender reversed. So an RF-SMA Female connector will have the same external housing as a standard female SMA connector, with the threads on the outside, however the center receptacle will be replaced by a male pin. 

Similarly, for RP-SMA Male connectors will have the threads on the inside, but the center male pin will be replaced with a receptacle.

SMA Connector Geometry

SMA Connectors and most other RF connectors are available as straight SMA connectors or right angle SMA connectors. The geometry of the connector is chosen based on the circuit configuration. The Image below show the two SMA connector geometries.

SMA Connector Mounting Options

SMA Connectors have a number of different mounting configurations. The key mounting configurations include: Panel Mount (2-Hole and 4 Hold Flange) SMA Connectors, PCB Mount SMA Connectors, Edge Mount, Bulkhead Mount SMA Connectors, SMT SMA Connectors and Through Hole Mount.

SMA Connector Dielectric

The dielectric material in an SMA Connector acts like an insulator. The dielectric/insulator is between the inner and outor conductor of the SMA Connector. Air would be the ideal insulator, however we need some sort of material that will hold the center pin of the connector in place. SMA connectors usually use a polytetrafluoroethylene (PTFE) dielectric along the mating plane.

The dielectric used impacts the impedance of the SMA connector. And repeated connections can lead to ware and teare of the SMA connector causing the impedance of the connector to vary which increase the reflections and losses at the connection point and in the system. Due to this reason, most manufacturers specify the number of mating cycles.

SMA Connectory Body: SMA connectors usually have a Brass or Stainless Steel body. The Brass usually has a Nickel or Gold finish and the Stainless Steel body has a passivated or gold finish.

SMA Connector Center Contact: The center contact/pin of a SMA connector is usually made out of Brass or Copper and has a gold finish.

everything RF has listed complete catalogs of SMA Connectors from the leading manufacturers, you can narrow down on the list of SMA Connectors based on the specs explained above. Click here to find SMA Connectors from the leading manufacturers.

Did you know SMA Connectors, 3.5 mm and 2.92 mm Connectors are sort of compatible. Click here to read more about this.