SMA Connector Assembly Introduction
SMA connector assembly 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 connector assemblys come in many forms, male, female, straight, right angle, diaphragm accessories, etc., so that they can meet most requirements. Its ultra-small size also enables it to be used, even in relatively small electronic devices.
1. Introduction of SMA connector assembly
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 hexagonal shape and allows to be tightened with a wrench. Special torque wrenches can be used to tighten them to the correct tightness, so that a good connection can be achieved without over tightening.
The first SMA connector assembly is designed for 141 semi-rigid coaxial cables. The original SMA connector assembly can be called the smallest connector because the center of the coaxial cable forms the connected center pin, and there is no need to make a 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, while 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 a problem because the installation is usually fixed after initial assembly.
2. Performance of SMA connector assembly
The SMA connector assembly is designed to have a constant impedance of 50 ohms on the connector. SMA connector assemblys were originally designed and specified for operation up to 18 GHz, although some versions have a top-level frequency of 12.4 GHz and some versions are specified as 24 or 26.5 GHz. A higher upper frequency limit may require operation at a higher return loss.
In general, SMA connector assemblys have higher reflection coefficients than other connectors up to 24 GHz. This is due to the difficulty of accurately fixing the dielectric support, but despite this difficulty, some manufacturers have managed to appropriately overcome this problem and can specify 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 the cables accepted by SMA connector assemblys are very small, and their loss is naturally much greater than that of connectors, especially at the frequencies they may use.
3. Rated power of SMA connector assembly
In some cases, the power rating of SMA connector assemblys may be important. The key parameter to determine the average power processing capacity of the coaxial connector is that it can transfer high current and keep the heat rising 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 pad is together. A key area is the center contact, which must be formed correctly and fit together well. 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 connector assemblys vary greatly among manufacturers, but some figures show that some can process 500 Watts at 1GHz and drop to slightly lower than 200 Watts at 10 GHz. However, this is also the measured data, which may be actually higher.