RF electromechanical switches are a key active device in many signal chains, including time-domain duplex communications and pulsed radar applications. Such switches can be as simple as a 3-port toggle switch, or single-pole double-throw, or more complicated such as double-pull switches or single-pole switches with more than 10 poles.
A main benefit of electromechanical switch technology is that they can be built using high-quality mechanical components and conductors that limit the insertion loss through the switch and can handle higher power levels compared to other switch technologies. However, electromechanical switches are not as fast as active switches (PIN diode or solid-state switches) or microelectromechanical machine (MEMS) switches.
Hence, RF electromechanical switches are better suited to some applications over others. Given the high isolation, low insertion loss, and high power handling of these types of RF switches, they are well suited to any application that requires optimising these parameters and can operate with switching times limited by the electromechanical relays. Moreover, electromechanical RF switches tend to be larger and heavier than other RF switch technologies and require more control signal power (actuating power) to switch. Therefore, electromechanical RF switches are more often packaged in coaxial or waveguide assemblies as opposed to surface mount or fully integrated options.
The metal-to-metal contact of these switches does allow for extremely high bandwidths, and the size of electromechanical switches can be a function of the frequency range of these devices. Though at very high frequencies the tolerances of machining the electromagnetic relays becomes infeasible and technologies such as MEMS or solid-state relays are more fitting. These metallic contacts also wear over time, and an electromagnetic RF relay is typically specified to operate along datasheet specification for a set amount of actuation cycles. The lifespan of these switches could range from hundreds of thousands of cycles to several million depending on the quality of the switch design and materials.
Depending on the design of the electromagnetic relay, such an RF switch may also have an extremely wide operating range compared to other switch technologies. Certain of these switch designs also conform to military standards for ruggedness and reliability, which makes electromagnetic switches better suited to high reliability (Hi-Rel) applications, such as military, land-mobile vehicle, aerospace, and naval.
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