Understanding and choosing GHz-range coaxial connectors and cable assemblies
Newer families for new applications Many industry-standard connector families are available which are more effective for higher frequency, more compact applications. Among the most popular are the SMA, SMB, SMP, MMX, and MMCX families, all with the standard 50 Ω RF impedance. Each offers a different combination of electrical and mechanical characteristics. In contrast to the 17 millimeter (mm) diameter of the BNC connector, these connectors have a much smaller diameter in the range of 5 mm. This article will look at a single connector member in each of these families. However, within each family, there are many members with nearly identical electrical specifications, but very different mechanical configurations and arrangements. These include printed circuit board (pc board) versions with a right angle body or a straight body, and with surface mount, through-hole, or end launch termination; rear-mounted bulkhead types; and panel mounted versions with solder cup, flat tab, or round post connection. There are also different arrangements for mating connectors that go on the end of the cable, such as straight and right angle variations. Having so many options within a given connector type is good for designers as it increases
Figure 2: Subminiature SMA series connectors use a threaded coupling for enhanced mechanical integrity in the face of intense vibration. (Image source: Würth Elektronik)
the likelihood that there is one available off-the-shelf that has a specific form factor that is well- suited to the product design and constraints. This means there will be little or no change required to the mechanical design priorities of the product. Now, a closer look at these five families: • SMA: Subminiature SMA series coaxial connectors are designed with threaded coupling technology to ensure high mechanical stability in the face of intense vibration (Figure 2). The connector’s captivated center contact and
insulator increase axial force and torque. The thick gold plating on the center contact contributes to enhanced electrical performance and up to 500 mating cycles. A good example of this type of connector is Würth Elektronik’s 60312242114510, a DC to 10 GHz SMA connector jack with a female socket (Figure 3). It is designed for board edge use and end launch orientation. This panel mount solder connector also comes with a front- side nut and lock washer to facilitate bulkhead (panel) attachment for additional rigidity in the end product.
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