RF attenuators are usually used to protect sensitive test and measurement equipment or circuits from high-level RF signals, but they can also be used to expand the range of RF power meters and amplifiers. In some cases, RF attenuators are also used between reflective elements to reduce the standing wave generated by reflection, otherwise, the standing wave will cause resonance between two such elements or devices. In addition, an impedance-matched RF attenuator can also improve the impedance matching between two mismatched nodes in the signal chain.
(1) Fixed optical attenuator provides a fixed attenuation value, such as 10 dB, 20 dB or more dB value.
(2) Voltage variable attenuator or voltage controlled attenuator, where the analogue voltage adjusts the attenuation level within a continuously variable range, for example, between 0 dB and 30 dB or between 0 dB and 60 dB.
(3) RF Digital attenuator, which establishes attenuation in corresponding steps from 0 dB to 32 or 64 dB through a multi-bit code. The controllable attenuator is a complement to the variable gain amplifier (VGA), which adjusts the signal to match the components in the chain. For VGAs that require additional flexibility in design, they can adjust gain and attenuation; inside the system, these are constructed by a variable attenuator (voltage or digital control) in series with a gain module.
RF attenuators are also available with a variety of structures, technologies and performance ranges. Some RF attenuators are compact enough to be installed on integrated circuits; some RF attenuators are larger and require internal or external thermal management systems. Therefore, the existence of high-power attenuators is necessary. Of course, the size and importance of the RF attenuator thermal management system depend on the attenuator technology, amount of attenuation, RF input signal power range and frequency range.