Waveguide terminations absorb energy and prevent RF signals from reflecting back from open-ended or unused waveguide ports. They are passive devices which dissipate radio frequency (RF) energy by producing heat energy. There are three main performance specifications to consider when selecting waveguide terminations. Frequency range is the range of frequencies over which devices waveguide terminations are designed to operate. Voltage standing wave ratio (VSWR), a unit-less ratio ranging from 1 to infinity, is a measure of the amount of reflected energy at the input of the device. Return loss is a measure of the match between system impedance and the impedance of waveguide terminations.

Selecting Waveguide Terminations

Selecting waveguide terminations requires an analysis of RF connector types. Choices include BMA, BMMA, Bayonet Neil-Concelman (BNC), Type C, Type F, Type G, and FME connectors. Waveguide terminations may also use the following connector types: miniature coaxial (MCX), micro-miniature coaxial (MMCX), MHV, Type N, QMA, or quarter wave stub (QWS). In addition, connector choices include subscription channel (SC), subminiature-A (SMA), subminiature-B (SMB), subminiature-C (SMC), and subminiature-P (SMP). Waveguide terminations that use SSMA, SSMB, TNC, Triax, Twinax, UHF, Mini-UHF, ZMA, 1.6 / 5.6, 7-16, or 1.0 / 2.3 connectors are also available. There are five metric connector styles: 1.85 mm, 2.4 mm, 2.92 mm, 3.5 mm, and 7 mm.

Differences

Waveguide terminations differ in terms of standards and certifications. Waveguide terminations that are destined for sale in Europe should comply with RoHS, ELV, and WEEE. Restriction of Hazardous Substances (RoHS) is a European Union (EU) directive that requires all manufacturers of electronic and electrical equipment sold in Europe to demonstrate that their products contain only minimal levels of specific hazardous substances.  End-of-Life Vehicles (ELV) requires manufacturers of automotive products to demonstrate that their products contain only minimal levels of mercury, cadmium and lead. Waste Electrical and Electronics Equipment (WEEE) is an EU directive designed to encourage the reuse, recycling and recovery of electrical and electronic equipment.

Guidelines and Certifications

Some waveguide terminations meet guidelines from the International Electrotechnical Commission (IEC), a global standards organization. Other waveguide terminations bear marks from the Canadian Standards Association (CSA) or Underwriters Laboratories (UL). CSA Marks that appear alone are used with products certified primarily for the Canadian market, to the applicable Canadian standards. CSA Marks that appear with the indicators “C” and “US” or “NRTL/C” are used with products certified for both the U.S. and Canadian markets, to the applicable U.S. and Canadian standards. Waveguide terminations that comply with U.S. Federal Communications Commission (FCC) guidelines are also available.


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