What is SMA connector? Because this connector in our life is relatively niche, and the name is rather special, so know and understand the relatively few people, today we come together to understand the SMA connector first confusing is the name. Let’s not rush a its function, first look at the photo I believe we can have a general understanding, by comparing we can first understand the difference between it and other connectors.
SparkFun requires SMA type connectors on several boards that need some 50 ohm impedance to connect to external antennas (Bluetooth, cellular, GPS, XBee and Nordic). However, some boards use SMA connectors of different genders and polarities. Therefore, we need to match different antennas according to the gender or polarity of the RF connector.
There are four different types of SMA connectors using gender combinations, where gender refers to the center pin and polarity refers to the rotational characteristics.
The top two connectors are designed to be used together, but there is a problem with this configuration, and the FCC is starting to move toward Part 15 compliance. This means that all SMA RF connectors are changing gender (center pin). This is really annoying for those of us who need to pair antennas with RF devices. the FCC’s gender change is to prevent home users from damaging RF devices when screwing in antennas (think home WiFi). If all antennas are female, there is no way to damage the center connector.
However there is a polarity where all antennas, cables or anything is attached to a potentially fixed object using either an external nut or internal thread design and all fixed devices use to make the connection. This is applicable to all SparkFun products. So all of our antennas are SMA male or RP-SMA female. All of our boards are SMA female or RP-SMA male.
The only change to Part 15 compliance is the change in the center pin, which creates a “new” standard;. Reverse Polarized SMA (RP-SMA). RP (Reverse Polarity) is named after its “thread gender” and has a pin of the opposite gender. (Figure 2 above). If the board does not have an external antenna connected to the u.FL connector, the SparkFun RF board and antenna will use a combination of the old (SMA) and the new (RP-SMA).
Cellular and GPS (900/1700 / 1800MHz and 1.57542GHz respectively) usually use the old standard. SMA male type is used for antennas and SMA female type is used for modules. Any 2.4GHz (Bluetooth, ZigBee, WiFi and Nordic) pass usually uses the new standard. RP-SMA male is used on the antennas and RP-SMA female on the modules. in fact, we ignore the gender issue most of the time. If you have an RP-SMA board or module, you will need to match to the appropriate SMA and RP-SMA antennas, etc. Just make sure to match the antenna frequency to the board.
SMA antenna connector is also a kind of connector, just its special male and female interface, let us think he is very special. In fact, our parents should have seen this connector, in the 80s and 90s, we watch cable TV at home, it is all this interface, of course, now our private home TV has long been replaced by wireless digital technology. So have seen not much more
