SMA connector is a widely used semi precision subminiature RF and microwave connector, especially suitable for RF connection in electronic systems with frequencies up to 18 GHz or even higher. SMA connectors have many forms, male, female, straight, right angle, diaphragm fittings, etc., which can meet most requirements. Its ultra small size also allows it to be used, even in relatively small electronic devices.
1、 Introduction to SMA connector
SMA is usually used to provide RF connection between circuit boards. Many microwave components include filters, attenuators, mixers and oscillators. The connector has a threaded external connection interface, which has a hexagon shape and can be tightened with a wrench. They can be tightened to the correct tightness using a special torque wrench, so that a good connection can be achieved without over tightening.
The first SMA connector is designed for 141 semi-rigid coaxial cable. The original SMA connector can be called the smallest connector, because the center of the coaxial cable forms the center pin of the connection, and there is no need to transition between the coaxial center conductor and the center pin of the special connector.
Its advantage is that the cable dielectric is directly connected to the interface without air gap, and its disadvantage is that only a limited number of connection/disconnection cycles can be carried out. However, for applications using semi-rigid coaxial cables, this is unlikely to be an issue, as the installation is usually fixed after initial assembly.
2、 Performance of SMA connector
The SMA connector is designed to have a constant impedance of 50 ohms on the connector. SMA connectors were originally designed and designated for work up to 18 GHz, although some versions have a top frequency of 12.4 GHz and some versions have been designated as 24 or 26.5 GHz. Higher upper frequency limits may require operation with higher return loss.
In general, SMA connectors have higher reflectance than other connectors up to 24 GHz. This is due to the difficulty in accurately fixing the dielectric support, but despite this difficulty, some manufacturers have managed to properly overcome this problem and are able to designate their connectors for 26.5GHz operation.
For flexible cables, the frequency limit is usually determined by the cable rather than the connector. This is because SMA connectors accept very small cables, and their losses are naturally far greater than those of connectors, especially in the frequency they may use.
3、 Rated power of SMA connector
In some cases, the rating of the SMA connector may be important. The key parameter to determine the average power handling capacity of the mating shaft connector is that it can transmit high current and keep the heat rise to a moderate temperature.
The heating effect is mainly caused by the contact resistance, which is a function of the contact surface area and the way the contact pads are together. A key area is the center contact, which must be properly formed and well fitted together. It should also be noted that the average rated power decreases with frequency because the resistance loss increases with frequency.
The power processing data of SMA connectors vary greatly among manufacturers, but some figures show that some can process 500 watts at 1GHz and drop to slightly less than 200 watts at 10GHz. However, this is also the measured data, which may be actually higher.
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Post time: Dec-30-2022