RF Connectors (Radio Frequency), also known as coax connectors, are used to transmit radio frequency signals by connecting transmission lines to various applications. RF connectors are primarily used with coaxial cables in devices such as television receivers, two-way radios, antenna WiFi devices, and various industrial & scientific measuring devices. In this blog, we will take a look at the most common types of RF connectors: BNC, SMA, SMB, N-type, and TNC.
Prior to understanding how RF connectors work, it is important to understand how coaxial cable works. To send radio frequencies, there must be a transmission line. Coaxial cables are the most common transmission line, as it keeps the transmitted signal between the inner and outer conductors. This means coaxial cables experience less loss of signal and can be used in close proximity to metal objects without interference.
Coaxial cables comprise four main parts: the outer jacket, metallic shield (outer conductor), dielectric insulator, and the central core (inner conductor). The space between the inner and outer conductors is the impedance. The impedance must be the same throughout the entire length of the cable to prevent signal reflection. When an RF connector is placed at the end of a coaxial cable, the impedance must match, or the signal will not be effectively transmitted. Now let’s take a look at the most common types of RF connectors.
BNC (Bayonet Neill-Concelman)
BNC connectors feature a secure and quick-fastening bayonet mechanism. These connectors are primarily used in coaxial cables in radio, television, RF electric equipment, test instruments, and video signals. Connectors of this type are usually available with either 50 or 75 ohms of impedance. The standard frequency limit is 4 GHz, but higher-quality versions can provide greater limits.
SMA (Sub-Miniature A)
SMA connectors are approximately half the size of BNC connectors and are used for RF connectivity between boards, microwave filters, attenuators, mixers, and oscillators. SMA connectors have a threaded coupling that provides a secure connection. They are available with an impedance of 50 ohms and a frequency limit of 18 GHz.
SMB (Sub-Miniature B)
SMB connectors are even smaller than SMA connectors and feature a snap-on fastening mechanism for rapid mating and unmating. SMB connectors are so small that they are often specifically used for inter-board or inter-assembly connections within equipment. Like BNC connectors, they are available in 50 or 75-ohm impedances and have a frequency limit of 4 GHz.
If you’re in need of a high-performance connector, N-Type connectors are ideal. These are used for broadcast & communications equipment, power transmitters, receivers, and general RF applications. N-Type connectors are available in 50 or 75-ohm impedance options and feature a threaded coupling mechanism to help them connect. Although their 11 GHz frequency limit is lower than that of SMA connectors, precise versions can perform at up to 18 GHz.
TNC (Threaded Neill Concelman)
The final type of coaxial connector is the Threaded Neill-Concelman, or TNC. This is a threaded version of the BNC connector with a 50-ohm impedance and a frequency limit of 11 GHz. In BNC connectors, the bayonet fastening often creates problems for the transmission of the signal. TNC connectors solve this issue and therefore are able to operate at higher frequencies than BNC connectors.
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