Figure 1: −3dB attenuator, during storage the female plug is protected with a rubber cap.
An attenuator is a passive component in high-frequency technology. It is practically a coaxial voltage divider made of resistors, which, however, must be specially frequency-compensated for high-frequency applications. Therefore, a frequency range is always specified for these components within which they guarantee their properties with acceptable tolerance.
The simplest attenuators are small components with a fixed attenuation value that can be plugged or screwed between the cable connector and the socket. The attenuators should always be mounted at the input socket of a measuring device, not at the input of the probe cable. So the inherent noise of the cable will be attenuated also.
More suitable for measurement purposes are (usually decadic) adjustable attenuators. The step sizes can vary: adjustable attenuators with step sizes between 0.1 and 10 dB are available on the market. Adjustment can still be done manually on older components. Modern measuring instruments use digitally adjustable attenuators. However, these require software control, which is usually handled by the following measuring device. The control is done either with a serial or via an Ethernet interface. Adjustable attenuators are required when measuring a receiver sensitivity in the radar.
Very precise attenuators are required when particularly high demands are made on the accuracy and repeatability of the set values. Such reference circuit assemblies belong to the standard equipment of calibration laboratories. They are very complex devices, which can be additionally equipped with digitally adjustable attenuators. Their setting is automatically taken into account when displaying measurement results.
Picture gallery of attenuators
Figure 2: Switchable
(Courtesy of Rohde & Schwarz)