subminiature A (SMA)
The coaxially constructed SMA (Subminiature A) connector is a microwave connector developed by Bendix Scintilla Corp. and is used in RF and microwave applications because of its robustness.
SMA connectors have threaded closures and therefore high RF tightness, but the reflection coe fficient is higher than other RF connectors. The SMA connector comes in two versions: standard and reverse. In the standard version, the plug has a coupling nut with an internal thread and a pin, and the SMA socket forms the counterpart with the external thread and the calyx. In the reverse version, reverse plug has a calyx and reverse socket has a pin.
The standard SMA connector is designed for frequencies up to 12.4 GHz. High-quality ones can be used with most high- frequency cables up to 18 GHz, and specially designed versions are suitable for frequencies up to 24 GHz and even for cutoff frequencies up to 34 GHz, but with reduced values for VSWR and return loss. The latter is above 40 dB for the standard version in the frequency range up to 8 GHz and above 30 dB up to 18 GHz.
With careful handling, SMA connectors can withstand several hundred mating cycles without significant degradation of transmission characteristics.
There are so-called precision SMA connectors that are mechanically compatible with SMA connectors; these connectors are known as 2.92-mm connectors, 3.5-mm connectors, and WSMA connectors.
The WSMA connector is a precision SMA connector made by Wiltron, which can be used for precision measurements. It has good transmission characteristics up to 33 GHz and is very similar to the 3.5 mm connector.