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.
In 1983, Wiltron’s William.Old.Field senior engineer developed a new type of 2.92mm/K type connector based on the summary and customer service of the millimeter wave connectors previously introduced (the K type connector is a trademark of Wiltron’s formula ), the inner conductor diameter is 1.27mm, which can be inserted into SMA and 3.5mm connectors. The 2.92mm connector has good electrical performance in the frequency range of DC~46GHz, and is mechanically compatible with SMA connectors and 3.5mm connectors. It is quickly recognized by the majority of manufacturers and has become one of the most widely connectors used millimeter wave in the world. 


2.4mm connector
The 2.4mm connector is a connector with an outer conductor inner diameter of 2.4mm and impedance of 50Ω. The operating frequency can reach 50GHz
2.4mm connectors are mechanically compatible with 1.85mm connectors and can be interconnected, but they cannot be mated with 2.92mm, 3.5mm or SMA connectors.


1.85mm connector
The 1.85mm connector is a connector with an outer conductor inner diameter of 1.85mm and an impedance of 50Ω. The operating frequency can reach 67GHz, and it can be mechanically compatible with 2.4mm connectors.