What is an SMA connector? Because this connector is relatively small in our life and has a special name, few people know and understand it. Let’s learn about it today. The first puzzling thing about SMA connectors is the name. Let’s not worry about its function. First look at the photos. I believe we can have a general understanding. By comparison, we can first understand the difference between it and other connectors.

Sparkfun requires SMA type connectors on several circuit boards that require some 50 ohm impedance to connect to external antennas (Bluetooth, cellular, GPS, XBee and Nordic). However, some boards use SMA connectors of different gender and polarity. Therefore, we need to match different antennas according to the gender or polarity of RF connectors.

There are 4 different types of SMA connectors with gender combination, in which gender refers to the center pin and polarity refers to the rotation characteristics.

The last two connectors were designed to be used together, but there was a problem with this configuration, and the FCC began to move towards part 15 compliance. This means that all SMA RF connectors are changing gender (center pin). For those of us who need to pair the antenna with RF equipment, this is really annoying. The FCC’s gender change is to prevent home users from damaging RF devices when screwing the antenna (think of home WiFi). If all antennas are buses, the central connector cannot be damaged.

What is SMA antenna connector and what is its use

However, there is a polarity, all antennas, cables or anything are connected to a potential fixed object, using external nut or internal thread design and all fixed equipment. This is applicable to all sparkfun products. Therefore, all our antennas are SMA male or RP-SMA female. All of our plates were SMA women or RP-SMA men.

The only change in compliance with part 15 is the change of the center pin, which forms a “new” standard;. Reverse polarization SMA (RP-SMA). RP (reverse polarity) is named after its “thread gender” and has an opposite gender needle. (Figure 2 above). If the circuit board does not have a u.fl connector connected to the external antenna, the sparkfun RF board and antenna will use a combination of old (SMA) and new (RP-SMA):

Cellular and GPS (900 / 1700 / 1800MHz and 1.57542ghz, respectively) usually use the old standard. The antenna adopts SMA male type and the module adopts SMA female type. Any 2.4GHz (Bluetooth, ZigBee, WiFi and Nordic) communication usually uses the new standard. RP-SMA female is used on the antenna and RP-SMA female is used on the module. In fact, we ignore gender issues most of the time. If you have an RP-SMA board or module, you need to match the corresponding SMA and RP-SMA antenna. Just make sure to match the antenna frequency with the circuit board.

SMA antenna connector is also a kind of connector, but its special male and female interface makes us think it is very special. In fact, our parents should have seen this connector. In the 1980s and 1990s, the cable TV we watched at home was this interface. Of course, now our private family TV has long been replaced by wireless digital technology. So I haven’t seen much.

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