What Is An Sma Connector and Where are They Used

March 28, 2022 3 min read

SMA connectors (miniature version A) are semi-precision coaxial RF connectors developed in the 1960s as a minimal connector for coaxial cable with a screw-type approach mechanism. The connector has an impedance of 50 Ω, it is one of the connectors that work in the multi-megahertz range. The SMA was designed for use from DC (0 Hz) to 12 GHz, however this has been extended over time and as variants are available to 18 GHz and 26.5 GHz. [1] There are also mechanical connectors, such as the K connector, that operate up to 40 GHz. [2]The SMA connector is most commonly used in microwave, portable radio and mobile phone systems, and more recently with WiFi antenna systems and USB radio antenna software dongles. It is also commonly used in radio astronomy, particularly at higher frequencies (5 GHz+).

However, different variations of the SMA Connectors have been introduced over time that works over 12 hertz.

THE CONNECTOR

Interface dimensions for SMA connectors are listed in MIL-STD-348. [4] The SMA connector employs a 1/4-inch diameter threaded cylinder and 36 wires per inch. The male is equipped with a hex nut measuring 5/16 in. (0.3125 in. / 7.9 mm) on opposite faces, using the same wrench as a #6 SAE hex nut.

A standard polarity male SMA connector has a 0.9mm diameter central pin surrounded by a cylinder with internal threads, and a standard female SMA connector has a central sleeve surrounded by a cylinder with external threads. The central pin has the same diameter as the center of the RG402 coax so that connections can be made without discontinuity, forming the pin of the coax itself. As with most other connectors, the gender assignment corresponds to the innermost electrical component. There are also reverse polarity ("RP") SMA connectors in which the pin and sleeve are swapped so that the "male" RP-SMA has a central sleeve surrounded by an internal threaded cylinder and the "female" RP-SMA has a central pin and an externally threaded cylinder. See below for a more complete description.

SMA connectors are rated for up to 500 mating cycles, but this requirestightening the connector properly when connecting. A 5/16 inch torque wrench is required for this, set to 3-5 in·lbf (0.3 to 0.6 N·m) for brass and 7-10 in·lbf (0.8 to 1. 1 N · m) for stainless steel connectors. Flats are sometimes also provided on the cable side of the connector assembly, so a second wrench can be used toprevent it from twisting and damaging the cable joint. It is also advisable to inspect and clean loose debris from internal surfaces with compressed air or a gas mop can before docking. 

USAGE OF SMA CONNECTORS:

Are you wondering where the SMA connectors are used? The list of their usage in different areas is long. But most of the applications of SMA connectors are a bit old. Some of these usages include handheld radios and mobile telephone antennas.

But it doesn’t mean that the SMA connectors have gone obsolete. You can also find them inmicrowave systems, Wi-Fi antennas, and USB Dongles.

DESIGN OF THE CONNECTOR:

Like most connectors, SMA connectors have two separate parts termed male and female. The male SMA connector is 0.99 mm in diameter with a center pin. It is surrounded by a barrel with inside threads.

As opposed to it, the female side of the SMA connectors is based on the center sleeve surrounded by the barrel with outside threads.

With such a setting, both parts of the connectors complement each other and help form a connection.

SUMMING UP:

Available with multiple variations, SMA connectors have been in use since 1960. Even today, they are part of the setups which require multi-hertz management. Understanding them in a better way can ensure their proper usage and help you gain the best results.