Selection Factors for SMA Connectors

The selection of SMA RF connectors mainly includes the following five factors:

1. The interface mechanism type

The connection mechanism of connectors not only provides the convenient and rapid connection or separation of coaxial transmission lines, but also provides stable electrical performance and environmental protection devices. A non-torsional connection mechanism should be selected when there is not enough space to rotate the connecting nut in use. In addition, non-torsional connection mechanism is also very helpful for the frame connectors.

2. The electrical performance

A. Characteristic impedance: The military electrical connector should match the impedance of the transmission system and the cable, otherwise the system performance will be degraded;

B. Voltage resistance: The maximum voltage resistance value of the connector shall meet the voltage resistance requirements used by the system;

In general, in broadband applications, some beneficial broadband impedance matching characteristics should be sacrificed to obtain the required high voltage ratings.

C. The maximum work efficiency.

3. The cable connection method and cable type

A. Cable connection: There are two connection methods of connector cables: 1. It is common to weld the center conductor and standardize the tightness of braided wires. This method is specially suitable for occasions without special installation tools, and on- site maintenance can be carried out easily; 2. The clamping method of welding the center conductor and crimping braided layers has become a common approach today due to the high efficiency of the pressure welding, reliable terminating performance and good consistency.

B. Cable type: Suitable connectors should be selected according to the characteristics of all kinds of cables (such as flexible cables, semi-rigid cables, corrugated conductor insulation cables and foam plastic insulation cables). Cables with small outer diameter should be matched with small connectors(such as, small circular connector).

4. Terminating modes

Mil spec RF connectors can be used for RF coaxial cables, printed wiring boards, machine frame drawer-type functional components and their connection interfaces.

5. Materials and coatings

The outer shell and inner conductor are mainly brass, beryllium copper and tin bronze, and the insulating material is mainly tetrafluoroethylene.

The center conductor is usually silver or gold plated, and the housing is nickel or silver plated. The outer conductors of SMB, SMB, SSMB, SMC are all gold-plated.

RF coaxial connectors are used to transmit RF energy with a frequency range of 18GHz or higher. The basic structure includes:

Positive and negative neutral contacts, external interface materials and the outermost contact. The outer part functions as the outer shielding layer of the cable: signal transmission and shield earthing.