A Brief History of QMAs
By David Zhou and Gregg Pollack, Anoison Electronics, LLC

The initial evolution of the coaxial connector was focused in two directions: 1) making them smaller, and 2) raising their operating frequencies. Today we have MMCX sized connectors (and smaller) and connectors that routinely work to 40 GHz (and higher). Recently, designers have turned their efforts to simplifying the mating procedures and making them more user friendly by eliminating the need for using a torque wrench during the assembly process. This has given rise to a new class of connectors, called “Quick Lock.”

The Quick Lock version of the SMA coaxial connector (commonly called QMA), was initially designed for use by the telecom industry. The original QMA connector design work was done by Huber+Suhner and Radiall, and in 2003 they were granted a joint U.S. patent (#6692286). Two years later, in 2005, they formed the Quick Lock Forum Alliance (QLF Alliance), which was later joined by Amphenol RF and Rosenberger. These latter two companies were granted QMA patent authorization by H+S and Radiall.

Connector technology is constantly evolving and advancing. In 2006, two German RF and Microwave connector manufacturers, Telegartner and IMS, jointly designed a new QMA type connector. They called it the “Quick Lock Standard” or QLS. The QLS is designed to offer up to 200 mating cycles, as compared with 100 for the QMA.

The two connectors in Figure 1 and Figure 2, the QMA and QLS, are intermatable, but not waterproof. This limits how and where these connectors can be used in some applications.
In the same year, 2006, Anoison Electronics released their version of the QMA, which was inherently designed to be waterproof to meet IP 68 standards. Their QMA is intermateable with both the QMA and QLS designs.

The following year, 2007, Huber+Suhner released their waterproof type QMA, which was intermateable with their previous design and meets the IP 68 standard.

In 2008, Amphenol RF introduced their version of the waterproof QMA.

Continuing the advancement of the QMA connector, Anoison Electronics recently released another QMA design, which is 100% backwardly compatible with all the existing QMAs. It has a similar locking mechanism to the QLF QMA, but with a different waterproof seal design. Anoison Electronics was awarded U.S. patent #7,553,185 B1 for this advanced design.

The designs represent the current state of the art in the evolution of the QMA type connector. All of them are intermateable and waterproof to IP 68, where noted. The QMA is an ongoing design process, and although it will never replace the SMA completely, it is gaining in popularity and achieving wider acceptance. This, in turn, is encouraging manufacturers to design better and more cost effective QMA style connectors.

The current “Quick Lock” connectors available are the previously discussed “QMA” type connectors and an offering of “N” type connectors. They are designated as “QN” by the QLF and as “HPQN” by Anoison Electronics. Unlike the QMAs, due to internal structure and performance differences, the two are not interemateable. As these “Quick Lock” connectors continue to evolve, it is anticipated that this concept will be applied to other series of threaded RF coaxial connectors.

Anoison Electronics, LLC
www.anoison.com
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