A fixed attenuator is a passive device comprised of resistors designed to create a voltage divider to reduce the signal without severely degrading the waveform.  An attenuator is essentially the opposite of an amplifier; where an amplifier is used to boost or amplify the signal, an attenuator is used to reduce the signal by resistive losses.

A fixed attenuator should have a wide and flat frequency response, as to behave the same across all frequencies for broadband signals. A fixed attenuator should match the system impedance, which is typically 50 ohms or 75 ohms. It should have a low Standing Wave Ratio (SWR) and be capable of attenuating between ranges of 0 - 60dB across the entire frequency band of interest. Fixed attenuators can be used for impedance matching, power dissipation and to take measurements of voltages that exceed the capability of the measurement equipment. By attenuating the signal first, the level can be brought within range of the measurement equipment.

A fixed attenuator is primarily comprised of resistors, which are passive linear devices. It can also be bi-directional, and is designed for both high or low power applications. Many fixed attenuators can be connected in line with standard connectors, such as SMA or BNC, enabling a seamless integration.