Sma Connector
Connector design
Connector design
The SMA connector consists of a 0.250x36 thread. The male is equipped with a .312inch (7.925mm) hex nut.
The outer shell of the male or plug connector has an inside thread and an inner pin, which can be confusing. In conventional SMA, the terms "male" and "female" refer exclusively to the inner pin or socket of the connectors. The male connector is also commonly referred to as a "plug", whereas the female connector is also known as a "socket" or "jack".
The SMA connector uses a polytetrafluoroethylene (PTFE) dielectric which will contact along the mating plane. Variability in the construction and the mating of the connectors limit the repeatability of the connector impedance. For that reason, an SMA connector is not a good choice for metrological applications.
It is important that the nut be properly torqued with a 5/16inch wrench, 3-5 inlbf (0.3 to 0.6 Nm) for brass, and 7-10 inlbf (0.81.1 Nm) for stainless steel connectors. When turning the nut, it is very important that the remainder of the connector does not rotate, otherwise premature wear of the connector will result. Furthermore, the connector should be carefully inspected before each use, and any debris cleaned with compressed air. When properly handled, an SMA connector should remain within specified performance through 500 mating cycles.
Variations
The SMA connector is typically rated for mode-free operation from DC to 18GHz, though some proprietary versions are rated to 26.5GHz. For performance above this, SMA-like connectors are used. These are the 3.5mm connector, rated to 34GHz, and the 2.92mm (also known as 2.9mm), good up to 46GHz. These connectors keep the same outside thread as the SMA, so they can all be cross-mated, however they use an air dielectric, with the center conductors appropriately scaled. However, the life of the precision connector will be reduced, and can be easily damaged when mating with low-grade SMA connectors.
Beyond 46GHz, the 2.4mm, 1.85mm and the 1mm connector exist. These are similar to the SMA connector, but with the geometries incompatibly scaled. These have mode-free operation to 50, 65, and 110GHz respectively.
Figure 2) Proprietary male RP-SMA jack connector: RP-SMA jack with male contact
Reverse polarity SMA
Reverse polarity SMA (RP-SMA or RSMA) is a proprietary variation of the SMA connector specification which reverses the gender of the interface, as shown in Figures 1 and 2.
There is much confusion surrounding the correct terminology to describe Reverse Polarity connectors. This stems from the general use of "male" and "female" in common parlance, compared to the more specialized use of "plug" and "jack" within the industry. This is not an issue in straight connectors, but becomes a problem when the association of "plug" with "male" and "jack" with "female" becomes broken.
Where "SMA male" and "SMA plug" are equivalent, "reverse SMA male" and "reverse SMA plug" are NOT the same thing.
The RP-SMA plug connector has the same external housing as a standard or conventional SMA plug connector, which consists of an outer shell with the thread on the inside; however, the internal prong or pin is replaced by a receptacle or female inner pin.
Similarly, an RP-SMA male has a pin like a conventional male, but is housed in a jack (or socket) rather than a standard plug connector. The RP-SMA female connector keeps the female receptacle, but is housed in a plug casing.
Male Pin
Female Receptacle
Inner Thread
(outer nut)
SMA Plug / SMA Male
Reverse SMA Plug / Reverse SMA Male
Outer Thread
Reverse SMA Jack (socket) / Reverse SMA Female
SMA Jack (socket) / SMA Female
RP-SMA connectors are widely used by Wi-Fi equipment manufacturers to comply with specific local regulations {Section 15.203 Antenna requirement}, e.g. the FCC, which are designed to make it difficult for consumers to connect antennas with gain and thereby breach compliance.
The term "reverse polarity" might appear confusing to some non-WiFi RF engineers, as polarity elsewhere in RF literature can refer to the electromagnetic polarity, not to a change of gender (in this case replacing the prong for a receptacle and vice-versa).
See also
SMB connector
SMC connector
TNC connector, also has RP-TNC version used for Wi-Fi
References
Radio-frequency connectors. Part 15: R.F. coaxial connectors with inner diameter of outer conductor 4.13 mm (0.163 in) with screw coupling Characteristic impedance 50 ohms (Type SMA). International Standard IEC 60169-15, 1979.
CECC 22110/111
Connectors, plug, electrical, radio frequency. Military specification sheet MIL-C-39012.
47 C.F.R. Section 15.203 Antenna requirements.
External links
RF Connectors from WA1MBA
Coaxial SMA Connectors from CMPTER
Wikimedia Commons has media related to: Connectors
vde
RF connectors (coaxial)
APC-7 BNC C F FME Hirose U.FL IPX Motorola MCX MMCX N QLS QMA/QN RCA SMA SMB SMC Twin-lead TNC TV aerial plug UHF / Mini-UHF
Variations and alternate names: 2.9 mm (SMA) 7 mm Triax / Triaxial Twin BNC / Twinax (BNC) IPEX MHF AMC (UFL) SnapN RP-TNC RP-SMA
Old or seldom used: EIA GR LEMO 00 Musa
See also: Radio frequency Radio spectrum Audio and video connectors Audio and video interfaces and connectors
Categories: Coaxial connectors
by: gaga
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