Coaxial cable rf type connectors

Coaxial cable rf connectors

Coaxial cable connectors, often called RF connectors are in widespread use. Wherever radio frequency or RF connections need to be made there is the possibility of using coaxial connectors. Where signals reach frequencies above a few million Hertz, these coaxial connectors need to be used. The need for their use arises because it is necessary to transfer radio frequency, RF, energy from one place to another using a transmission line. The most convenient and hence the most commonly used form of transmission line is coaxial cable which consists of two concentric conductors, an inner conductor and an outer conductor, often called the screen. Between these two conductors there is an insulating dielectric.

Coaxial cable has a number of properties, one of which is the characteristic impedance. In order that the maximum power transfer takes place from the source to the load, the characteristic impedances of both should match. Thus the characteristic impedance of a feeder is of great importance. Any mismatch will result in power being reflected back towards the source.

It is also important that RF coaxial cable connectors have characteristic impedance that matches that of the cable. If not, a discontinuity is introduced and losses may result.

There is a variety of connectors that are used for RF applications. Impedance, frequency range, power handling, physical size and a number of other parameters including cost will determine the best type for a given applications. Some of the most popular styles are:

BNC Connectors

The BNC coax connector is widely used in professional circles being used on most oscilloscopes and many other laboratory instruments, although it is widely used for many other RF applications. The BNC connector has a bayonet fixing to prevent accidental disconnection while being easy to disconnect when necessary. This RF connector was developed in the late 1940s and it gains its name from a combination of the fact that it has a bayonet fixing and from the names of the designers, the letters BNC standing for Bayonet Neill Concelman. In fact the BNC connector is essentially a miniature version of the C connector which was a bayonet version of the N-type connector.

C Type Connectors

Invented by and named for Amphenol engineer Carl Concelman it is used in industrial, and military and aerospace applications. The C Type series connector is a weatherproof medium size series. The series features a coupling two-stud bayonet lock. It has a constant 50 ohm impedance and performs up to 11 GHz.

HN Connector

HN-Type connectors are medium sized, weatherproof units designed for high voltage applications. These connectors feature captivated contact design which prevents contact recession under extreme temperatures and mechanical stresses. HN connectors are capable of handling up to 5,000 volts, making them ideal for use in high power industrial applications from DC to 4 GHz. This type of connector is used in high voltage test equipment and radiation detection equipment.

MHV connectors

MHV (Miniature High Voltage) connectors are bayonet locking interconnects used for high voltage applications up to 5000 volts. They are similar in size to, but not designed to mate with the BNC interface. MHV connectors conform to MIL-STD-348 and offer a quick-connect functionality that is used where transmission of high voltage is required. This type of connector is used in transmission lines, X-Ray equipment and high voltage power supplies.

N Type Connectors

The N-type connector is a high performance RF coaxial connector used in many RF applications. This coax connector was designed by Paul Neill of Bell Laboratories, and it gained its name from the first letter of his surname.The N-type coaxial connector is used for many radio frequency applications including broadcast and communications equipment where its power handling capability enables it to be used for medium power transmitters, however it is also used for many receivers and general RF applications.

SC connectors

The SC-Type connector series is a medium size, 50 ohm series; with performance up to 11 GHz. The SC-Type connectors are manufactured to meet MIL-C-39012 category D, specification sheets 35 through 43. The series meets all of the mechanical and electrical requirements of the Limited Co-ordination Specification (LC Spec.) as generated by the U.S. Air Force. They are used in instrumentation and test and measurement equipment as well as in military applications.

SMA Connectors

This sub-miniature RF and microwave coaxial cable connector takes its name from the words Sub-Miniature A connector. It finds many applications for providing connectivity for RF assemblies within equipment. It is often used for providing RF connectivity between boards, and many microwave components including filters, attenuators, mixers and oscillators, use SMA connectors. The connectors have a threaded outer coupling interface that has a hexagonal shape, allowing it to be tightened with a spanner. The SMA connector was originally designed for use with 141 semi-rigid coax cable. However its use extended to other flexible cables, and connectors with centre pins were introduced.

TNC Connectors

The TNC connector is very similar to the BNC connector. The main difference is that it has a screw fitting instead of the bayonet one. The TNC connector was developed originally to overcome problems during vibration. As the bayonet fixing moved slightly there were small changes to the resistance of the connections and this introduced noise. To solve the problem a screw fixing was used and the TNC coax cable connector gains its name from the words Threaded Neill Concelman. Like the BNC connector, the TNC connector has constant impedance, and in view of the threaded connection, its frequency limit can be extended. Most TNC connectors are specified to 11 GHz, and some may be able to operate to 18 GHz.

UHF Connectors

The UHF connector, also sometimes known as the Amphenol coaxial connector was designed in the 1930s by a designer in the Amphenol Company for use in the radio industry. The plug may be referred to as a PL259 coaxial connector, and the socket as an SO239 connector. These are their original military part numbers. These coaxial connectors have a threaded coupling, and this prevents them from being removed accidentally. It also enables them to be tightened sufficiently to enable a good low resistance connection to be made between the two halves.