SMA Connector
The SMA type RF coaxial connector was designed by Bendix and Omni-Spectra as an OSM connector in the late 1950s. It was one of the most commonly used RF/microwave connectors at that time. Initially, SMA connectors were designed for 0.141’’ semi-rigid coaxial cables, as well as precision connectors for microwave applications in the military industry, filled with PTFE dielectric. Under the conditions at that time, due to the small size of the SMA connector, it can work at a higher frequency (the frequency range of mating the semi-rigid cable is DC~18GHz; the frequency range of mating the flexible cable is DC~12.4GHz), and it is very fast expanding. Even the later developed millimeter wave connectors (such as 3.5mm, 2.92mm) also consider the issue of mechanical compatibility.


Picture quoted from https://en.wikipedia.org/wiki/SMA_connector

3.5mm Connectors
The 3.5mm connector is a connector with the outer conductor inner diameter of 3.5mm, a characteristic impedance of 50Ω, and a connection mechanism of 1/4-36UNS-2 inch threads. In the mid-1970s, Hewlett-Packard and Amphenol (mainly developed by HP, and the early production was carried out in Amphenol) launched a 3.5mm connector with a working frequency up to 33GHz. This is the earliest RF coaxial connector that can be used in the millimeter wave band. One obvious difference with SMA connectors (including Southwest Microwave's "Super SMA") is that 3.5mm uses air medium.
The outer conductor of the 3.5mm connector is thicker than the SMA connector, and its mechanical strength is much better than that of the SMA connector. Therefore, not only the electrical performance is better than the SMA connector, but also the mechanical durability and performance repeatability are higher than the SMA connector, so it is more suitable for applications in the testing industry.


2.92mm connector
2.92mm connector (some manufacturers call this connector 2.9mm or K-type connector, and some manufacturers call it SMK, KMC, WMP4 connector, etc.). The inner diameter of the outer conductor is 2.92mm, the characteristic impedance is 50Ω, and the connection structure is mated with 1/4-36UNS-2 inch threads. Its structure is similar to 3.5mm connector, but smaller.