SMA Connector Overview

SMA Coaxial Connectors, or just SMAs, are one of the most common coaxial connector types used throughout the RF, microwave, and even millimeter-wave (mmW) industries. SMA stands for subminiature version A and was developed in the 1960s. The interface dimensions and other aspects of the SMA connector are detailed in MIL-STD-348 and was originally designed for 12 GHz. However, this has changed and most common SMAs that meet the standard achieve mode-free operation to 18 GHz. There are also some high precision SMAs that reach 26.5 GHz operation.

SMA connectors are very commonly used in portable and some laboratory test equipment, as they are relatively compact and easy to handle without being too small to reliably operate. Though SMA connectors are designed to be torqued to a precise setting depending on the housing material used, in the field it is possible to achieve good performance with SMAs just from hand torquing.

As the power handling capability of a coaxial connector is directly related to size, SMA connectors are not suited to high power operation, but for low-to-medial power. This is why these connectors are very common for many telecommunications applications and for low-power interconnects within assemblies. Many test and measurement applications below 18 GHz use SMAs as they are common enough to be more affordable than other cable standards and are relatively compact. The ubiquitous use of SMAs also means there is a wide variety of types and styles to choose from.

It is important to note though, that SMA connectors are semi-precision and not high precision, like the 3.5mm, 2.92mm, and k counterparts. SMA connectors have a solid dielectric, typically PTFE, while 2.92mm and 3.5mm connectors have an air dielectric. These connectors have the same interface dimensions and can be interconnected, though it is likely that the 3.5mm and 2.92mm connectors may be damaged during connector cycling.

SMA connectors are typically rated to 500 mating cycles, though there are some SMA connectors that are manufactured for higher levels of reliability. Like most common coaxial connectors, SMA connectors are typically found as “standard polarity”. This means that the connector with the interface threads internal to the housing also contains the center pin and is denoted as the “male” connector. The female connector of standard polarity SMAs has the threads on the outside of the connector housing and a receptacle inside the housing and is denoted as female. There are reverse polarity SMA connectors, often used for WI-FI routers and other consumer equipment and has the center pin and receptacle in the opposite housing gender as the standard polarity connectors.

SMA connectors can be found in virtually all form factors of coaxial cables, from the variety designed to be connected to a coaxial cable, to reusable compression tight end board connectors, to bulkhead connectors, to adapters, to connectors with a variety of different bend radii. For most applications below 18 GHz, within the low power range, and not requiring the highest precision, SMA connectors are the go-to connector for many applications.