Attenuators

An attenuator is a passive device that reduces the amplitude of a signal without significantly distorting its waveform, by dissipating part of the power as heat. Attenuators are used to control signal levels, protect equipment from overload, and improve impedance matching across a wide range of systems in RF, microwave, optical, and audio domains.

Electrical attenuators are typically resistor networks designed to present a specified impedance (often 50 ohms) to the source and load. They can be fixed or adjustable. Fixed models use networks such as a Pi-pad or a T-pad to achieve a chosen attenuation, while adjustable devices provide a controllable attenuation value (step or continuous). Important specifications include the attenuation value (in dB), insertion loss, input/output impedance, power handling, and frequency range. At high frequencies, parasitics and connector quality become significant, and good return loss or VSWR is sought.

Optical attenuators reduce light intensity in fiber optic or free-space links. Fixed optical attenuators employ absorbing materials or neutral density filters to provide a defined attenuation in dB, while variable or tunable attenuators allow adjustment of optical power. They are used for link budgeting, receiver protection, and calibration of optical receivers.

Common considerations across domains include maintaining a constant impedance, managing heat dissipation, and ensuring stability over temperature and time. Attenuators may introduce noise or nonlinearities if operated outside specified ranges, so adherence to power and frequency specs is important. Connectors and form factors vary by application, with RF/microwave devices using coaxial interfaces and optical devices specified for single- or multi-mode fibers.