Practical RF Handbook, 4th Edition

15

Attenuators and equalizers

Attenuators, or pads as they are often called, are networks which simulate a lossy transmission line, so that the signal at the output is smaller than at the input, but not changed in any other way. Like a transmission line, they are designed to have a specific characteristic impedance, commonly 50Ω and like a good transmission line their frequency characteristic is flat. Unlike a length of lossy line though, they provide no delay; the path length through an attenuator is ideally zero. A pad exhibiting a resistive impedance R₀ at both its input and its output can be realized with three resistors connected in either a ‘Tee’ or a π configuration (see Figure 15.1), which gives design formulae expressed in two different ...