A Pi Pad attenuator is one in which the resistors are in a π configuration. The shunt resistors (R1) are connected to ground, while the series resistor (R2) is connected between them.
This forms a Pi Network.
Enter the desired value of attenuation and the characteristic impedance (default value is 50 ohm).
R1 = Zo [10dB/20 + 1] / [10dB/20 – 1]
R2 = Zo/2 [10dB/10 – 1] / [10dB/20]
where R1 is the shunt resistor and R2 is the series resistor. To build this attenuator you will need
- two shunt resistors – one at the input and the other at the output
- one series resistor
Note that it is assumed that both the source and load resistance are equal in this calculation.
 Pi Pad Attenuator on Wikipedia