Coaxial terminations are electrical devices that connect to the ends of coaxial cables to prevent signals from reflecting back when they reach the end of the cable. They differ in terms of frequency range, power rating, voltage standing wave ratio (VSWR), return loss, and resistance.

Specifications

Voltage standing wave ratio (VSWR), a unitless ratio ranging from 1 to infinity, expresses the amount of reflected energy at the input of the device. A value of 1 indicates that all the energy passes through. Any other value indicates that a portion of the energy is reflected.

Return loss is a measure of the match between the impedance of coaxial terminations and the impedance of the system. With coaxial terminators, choices for electrical resistance include 50 and 75 ohms. 

Connectors

Coaxial terminations use various types of RF connectors. Common types include:

• BMA
• BMMA
• BNC
• Type C
• Type F
• Type G
• FME
• MCX
• MHV
• MMCX

Coaxial terminators with MMCX, Type N, QMA, QWS, SC, SMA, SMB, SMC, SSMA, SSMB, SMP, and TNC connectors are also available.

Some coaxial terminators use ZMA, 1.6 / 5.6, 7-16, or 1.0 / 2.3 coaxial connectors. Others use Triax, Twinax, UHF (PL259) or Mini-UHF connectors.

Metric-style coaxial connectors are measured in millimeters (mm) and include 1.85 mm, 2.4 mm, 2.92 mm, 3.5, and 7 mm.  

Certifications

Certifications are important to consider when selecting coaxial terminations. Products that are sold in Europe must comply with two major European Union (EU) directives:

• RoHS: Restriction of Hazardous Substances (RoHS) requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of the following hazardous substances: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyl and polybrominated diphenyl ether.
• WEEE: Waste Electrical and Electronics Equipment (WEEE) is a European Union (EU) directive designed to encourage the reuse, recycling and recovery of electrical and electronic equipment. 

Coaxial terminations that are sold in North American may bear marks from the Canadian Standards Association (CSA) and/or Underwriters Laboratories (UL).

In the United States, compliance with the Federal Communications Commission (FCC) standards is also important.

The American National Standards Institute (ANSI) represents the U.S. in the International Electrotechnical Commission (IEC), a global, non-profit organization that develops and maintains voluntary quality, safety, and performance standards for electrical devices such as coaxial terminations. 

References

Image Credits:

JFW Industries, Inc. | Anatech Electronics, Inc.  | RF Industries, Inc.