Coaxial connectors are composed of an insulated, central conducting wire wrapped in another cylindrical conductor (the shield).  The cable is usually wrapped in another insulating layer and an outer protective layer. Coaxial cables and coaxial connectors have the capacity to carry vast quantities of information. They are commonly referred to as 'coax' connectors and are used to transmit radio frequency (RF) signals in applications such as high-speed data and CATV applications.

Coaxial connectors can able be used as mini power connectors for attaching extra-low voltage devices such as consumer electronics to external electricity. The primary use of these plug is as a DC connector on the cable that comes from an external power supply. Generally, most coaxial power plugs are considered to be female and most coaxial power jacks are considered to be male. The sizes and shapes of connectors do not consistently correspond to the same power specifications across manufacturers and models. Use of the wrong power supply may cause severe equipment damage or even fire.

The most common connectors for home video installations are F-style or N-style connectors. Type F connectors have a screw-type coupling and a frequency range up to 1.5GHz. Type N connectors include an integrated gasket to protect against environmental ingress and create an air gap between the center and the outer conductor. The frequency range is 11GHz and while it primary has an impedance of 50Ω, 75Ω versions are also available for CATV.

The gender, cable orientation, and plating material are important properties used to distinguish and select a coax cable.

Gender

A coaxial connector can be male or female in gender.

Male - Male connectors or plugs are often referred to as header or free connectors. In coaxial RF connectors, the plug is normally the movable portion and is usually attached to a cable or removable sub-assembly.

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Female - Female connectors are connecting devices into which plugs are inserted to make circuit connections.

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Plating Material 

Coaxial connectors are most commonly plated in copper, gold, nickel, or silver.

• Copper - Copper is a common metal that is reddish in color. This metal is often used due to its ability to conduct electricity and it plates easily with other metals. Copper is very ductile and easily polished. The benefits of copper plating are that  it is an excellent heat conductor, easily polished, and very malleable.
• Silver - Silver is an economical choice for plating. It is an excellent conductor of heat and electricity. It is easy to solder and it is very ductile with high lubricity, which is beneficial for bearing surfaces and anti-galling applications.
• Nickel- Nickel is used for wear resistance, hardness, lubricity, and magnetic purposes. It is smooth and dull grey in appearance; however bright nickel is available and commonly used in decorative applications. Nickel is highly resistant to corrosion and tarnish making it a good plating option.
• Gold- Gold is commonly used in electronics and aerospace applications. Gold is the third best conductor of electricity (behind silver and copper). It is extremely ductile and has the best corrosion protection. Gold also conducts heat well and is easy to solder.

Geometry 

In terms of device geometry, coaxial connectors are either straight or right-angled. The geometry of the connector is based on the system in which it needs to fit.

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Another important specification is to determine the size of the cable. The most common types of coaxial cables are RG-6 and RG-59. RG stands for "Radio Guide" and the number corresponds to the diameter (e.x. 59 means .059) and internal characteristics of the cable, including the amount of shielding and the cable's attenuation, which refers to how much signal loss there is per length of cable.

Types of Coaxial Connectors

There are many different types of coaxial connectors. Many products use lettered or numbered designations. Lettered connectors include BMA, BMMA, BNC, BNC, DVI, FME, MCX, MMCX, MHV, RCA, SC, SMA, SSMA SMB, SSMB, SMP, TNC, UHF, XLR and ZNA connectors. Numbered devices include 1.6 / 5.6, 7-16, and 1.0 / 2.3 connectors.

A detailed chart of types of coaxial connectors can be found on How to Select RF and Microwave Connectors.

Termination Options

Terminals are devices designed to terminate a conductor to be affixed usually to a post, stud, chassis, other conductor, or the like in order to establish electrical connection. Coaxial connectors differ in terms of termination. 

Screws, screw-ons, or lugs are easy to use. They are less secure and small air pockets can be trapped in the connection, affecting signal quality.

Tabs are quick-connect terminal options.

Cage clampsdo not require special tools or very much preparation. It has a high degree of mechanical security and low installation cost. Cage clamps fit standard wires with a cross section 0.14 to 2.5mm².

Crimpingis the physical compression (deformation) of a contact wire barrel around a conductor to make an electrical and mechanical connection to the conductor. There are two parts to crimp style terminators: a ring (or crimp) and a terminator. Crimps are more difficult to install but they can attain the greatest lengths and best connections when used correctly.

Wire wrappingis done using a special tool to wrap a solid-stripped or unstripped wire around a terminal post containing a series of sharp edges.

Insulation displacement connectors (IDC) slice through the cable insulation to make a connection. Electrical connection is made when an insulated conductor is forced into a restrictive slot in the connection part of a contact, during which time the insulation is displaced and the bare wire engages the sides of the slot. IDC are mass termination connectors for flat cables with contacts that displace the conductor insulation to complete termination. They eliminate the need to strip insulation.

Through-hole technology(THT) mounts components on a printed circuit board (PCB) by inserting component leads through holes in the board and then soldering. In pin termination, components are mounted on PCBs without soldering.

PCB solder or solder pin termination makes an electrical connection by soldering wires or pins onto a printed circuit board (PCB).

Solder cup termination creates a connection by soldering the connector onto the mounting location to terminate the electrical connection.

Performance

Performance specifications for coaxial connectors include:

• Impedance - In terms of impedance, the nominal resistance is usually 50 or 75 ohms.
• Frequency range - Frequency range is the range of frequencies over which coaxial connectors are designed to function.
• Voltage rating - Voltage rating is the maximum operating voltage.
• Contact resistance - Contact resistance is the measurement of electrical resistance of mated contacts when assembled in a connector under typical service use.
• Insulation resistance - Insulation resistance is the electric resistance between two conductors separated by an insulating material.
• Voltage standing wave ratio (VSWR)- Voltage standing wave ratio (VSWR) is a unit-less ratio ranging from 1 to infinity, expressing the amount of reflected energy at the input of the device. A value of one indicates that all the energy will pass through, while any other value indicates that a portion of the energy will be reflected.
• Operating temperature -  Operating temperature is the full required range of ambient temperature in which the connector will properly function.    

Resources

Metal Finishes

How to Connect Coaxial Cable Connectors

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