As a microwave connector engineer, do you often struggle with the choice of SMA microwave connectors or 2.92mm microwave connectors? It may also be muttering, can the 3.5mm microwave connectors be directly connected to the SMA microwave connectors? Today we're going to talk about this topic. First of all, let's look at these microwave connectors:

SMA Microwave Connectors

SMA microwave connectors frequency coaxial connector was designed by Bendix and Omni-Spectra as OSM microwave connectors in the late 1950s. It was one of the most commonly used radiofrequency/microwave connectors at that time. Initially, SMA microwave connectors were designed for 0.141 semi-rigid coaxial cables and precision connectors for microwave applications in military industries, filled with PTFE media. Under the current conditions, SMA microwave connectors were quickly popularized because of their small size and high frequency (DC-18GHz for semi-hard cables and DC-12.4GHz for flexible cables). Even later developed millimeter microwave connectors (such as 3.5mm, 2.92mm) are considered to be mechanically compatible.

3.5mm Microwave Connectors

3.5mm microwave connectors is a microwave connector with 3.5mm inner diameter, 50_characteristic impedance, and 1/4-36UNS-2 inch thread. In the mid-1970s, Hewlett-Packard and Amhenol Inc. (mainly developed by HP and early manufactured by Amphenol Inc.) launched a 3.5mm microwave connector with a working frequency of 33 GHz, which was the earliest microwave radio frequency coaxial connector available in millimeter band. An obvious difference from SMA microwave connectors (including Southwest Microwave's "Super SMA") is that 3.5mm microwave connectors use air media.

The outer conductor of 3.5mm microwave connectors are thicker than SMA microwave connectors, and its mechanical strength is better than SMA microwave connectors. Therefore, not only the electrical performance is better than SMA microwave connectors, but also the mechanical durability and performance repeatability are higher than SMA microwave connectors, so it is more suitable for the testing industry.

2.92mm Microwave Connectors

2.92mm microwave connectors (some manufacturers call it 2.9mm or K-type microwave connectors, others call it SMK, KMC, WMP4 microwave connectors, etc.) is a microwave coaxial connector with outer conductor inner diameter of 2.92mm, the characteristic impedance of 50_and connecting mechanism of 1/4-36UNS-2 inch thread. Its structure is similar to 3.5mm microwave connector but smaller.

In 1983, senior engineer William Old Field of Wiltron Company developed a new type of 2.92 mm/K microwave connector (K connector is the trademark of Wiltron Company) based on summarizing and overcoming the previous millimeter microwave connectors. Its inner conductor diameter is 1.27 mm, which can be connected with SMA and 3.5 mm microwave connectors. 2.92mm microwave connectors have good electrical performance in the range of DC to 46GHz and can be mechanically compatible with SMA microwave connectors and 3.5mm microwave connectors. It is quickly recognized by manufacturers and has become one of the most widely used millimeter-wave connectors in the world.

See here, smart engineers can already analogize to 2.4mm microwave connectors, which is a connector with outer conductor inner diameter of 2.4mm, the impedance of 50 ohms and 1.85mm microwave connector with outer conductor inner diameter of 1.85mm and impedance of 50 ohms. Their inner diameter size is smaller, so their working frequency is higher. The nominal frequencies can reach 50 GHz and 67 GHz, respectively. These two connectors are mechanically compatible and can be interconnected, but bear in mind that they must not be interconnected with 2.92 mm, 3.5 mm or SMA microwave connectors, otherwise, they will directly cause the consequences of connector damage!

With the rapid development of millimeter-wave technology and high-speed communication technology, 1.85mm, 2.4mm, and 2.92mm microwave connectors are more and more widely used in military, aerospace, optoelectronics and other fields. More and more cases are combined with GPPO, GPO and other connectors, which will be described in the following articles.

At this point, you will also know the origin of the name of 1mm microwave connectors and its possible operating frequency, right?