Image Credit: International Manufacturing Services, Inc.
Board mount electrical terminations are installed at the end of a bus or transmission line on a printed circuit board (PCB) to prevent signals from reflecting back. Sometimes called electrical terminators, these electrical devices are used to prevent electrical interference.
There are four basic types of electrical terminations: chip, coaxial, SCSI, and waveguide. Chip terminations have a form factor of an integrated circuit (IC) chip. They are manufactured using thin-film technology. Coaxial terminations terminate coaxial ports. SCSI terminations are electrical circuits placed at each end of a small computer system interface (SCSI) cable for impedance matching. Waveguide terminations are devices that terminate waveguide ports. Other unlisted or proprietary electrical terminations are also available.
Electrical terminations differ in terms of performance specifications. Power rating, voltage standing wave ratio (VSWR), and return loss are the most important performance specifications to consider.
Power rating is the maximum input rated power of the terminator.
VSWR, a unit-less 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 the adaptor or terminator and the impedance of the system.
RF connector type is an important parameter to consider when selecting electrical terminations. Selecting the right connector determines the compatibility of the electrical terminator to the circuit or system. Some choices include BMA, BMMA, BNC, Type C, Type F, FME, Type G, MCX, MHV, and MMCX.
Standards and Certifications
Standards and certifications are important to consider when selecting electrical terminations, as they provide assurances of quality, reliability, and safety. Many countries have expectations for electrical terminators to comply with certain requirements and directives. For instance, electrical terminations that are sold in the United States should comply with requirements from the Federal Communications Commission (FCC), or bear marks from Underwriters Laboratory (UL).