One of the leading causes of electronic equipment failure is from transient overvoltage. This is especially true for communication and wireless equipment which are at the same time both very susceptible to transient over voltages and exposure to a wide range of man-made and naturally occurring transient events. To protect sensitive RF/microwave electronics from any variety of external transients that can induce overvoltage, such as lightning, electromagnetic interference, acute component/device/system failure, and even solar weather, surge protection devices (SPDs), transient voltage surge suppressors (TVSSs), and lightning arrestors are commonly used. As exposed RF/microwave systems are often connected via coaxial cable assemblies, it’s essential to employ coaxial RF surge and lightning protectors, that can be installed in line with the coaxial interconnect.
This type of inline surge and lightning protection can be installed prior to any sensitive piece of equipment to provide protection from transient over voltages. It is important to note that there are several types of SDDs, TVSSs, and lightning arrestor technologies worth considering. The main types applicable to RF/microwave circuits are filter, gas tube, metal-oxide varistors (MOVs), and silicon avalanche suppression diodes (SASDs).
MOV & SASDs Based Coaxial RF Surge Protectors and Lightning Arrestors
Both MOV and SASDs are solid-state technology based SPDs. They also both have relatively similar performance, with a few exceptions. MOVs tend to exhibit higher large surge-current and energy rating, where SASDs tend to exhibit faster response times (several picoseconds compared to several nanoseconds for MOV devices). SASDs are also intrinsically unidirectional, which means that two SASDs in opposite directions are needed for alternating signals.
It is possible to achieve the benefits of both devices by incorporating both technologies into a single hybrid coaxial RF surge and lightning protector. This hybrid design provides the best performance aspects of both solid-state technology, and many hybrid protectors also include gas tube lightning arrestor technology. A drawback of this hybrid method is that there are some frequency limitations, and these modules usually only support a frequency range of operation under 3 GHz. Many of these hybrid surge protectors are DC-passing, which allows for DC power to be carried through the coaxial interconnect.
Filter-based Coaxial RF Surge Protectors and Lightning Arrestors
filter design coaxial RF surge protectors use surge filter designs that allow for typical RF signals to pass while suppressing overvoltage transients. Essentially, these components act as bandpass filters while also providing transient protection that is relatively fast. These filter based TVSSs are also ideal for multi-strike protection and are made to accommodate common wireless and cellular communication technologies (such as Wi-Fi and 3G, 4G, and 5G cellular). These types of surge protectors tend to also be DC blocking, which may be advantageous or undesirable depending on the application.
Gas Tube Based Coaxial RF Surge Protectors and Lightning Arrestors
Gas discharge tube (GDT) lightning arrestors are one of the most common types of lightning arrestors, as they are reliable. Gas tube coaxial RF surge and lightning protectors can divert a substantial amount of electrical energy and have relatively high operating power. Moreover, these devices can also be made to accommodate frequency range operation to several gigahertz, while providing DC-passing. A drawback to these lightning arrestors is that they often take microseconds of exposure to hundreds of volts for the gas within the tube to ionize and become conductive. This can leave more sensitive RF electronics unprotected for longer than they can survive, which is why GDTs are often paired with other forms of surge protection.