Cascade-Connected Attenuators

Two or more calibrated attenuators are often connected in series (cascade) in order to obtain a desired reduction in power level. The total attenuation of the combination is usually obtained by adding the attenuation of each unit. In general, this will not give the correct result because of reflections due to mismatch at the attenuator junctions. It is shown how the correct value of attenuation can be obtained in terms of reflection coefficient measurements at the attenuator junctions. A nomogram of mismatch error for two cascade-connected attenuators is given.