Another resistive attenuator configuration that is a variant of the traditional symmetrical T-pad Attenuator is the Bridged-T Attenuator. The bridged-T attenuator, as its name suggests, has an additional resistive feature that forms a bridged network across the two series resistors of the standard T-pad.

A modified Pi attenuator can be thought of as a Bridged Tee (or Bridged-T) attenuator. When you need to reduce the signal level without altering the circuit's impedance, bridged Tee RF attenuators come in handy.

Our bridged-tee attenuator calculator (also known as a "bridged-T attenuator") is intended to assist you in determining the correct values for the resistors R1 and R2 as shown in the diagram below. Only the necessary attenuation in decibels (dB) and impedance in ohms are required.

Equations

Applications

A network of resistors makes up attenuators, particularly those used in RF applications. The signal from a source (transmitter) is weakened or "attenuated" by these passive circuits to a degree appropriate for the destination (receiver). Attenuating a signal is done not only to protect the receiving end circuit from harm but also to match the impedance between the source and the destination, which is necessary for optimum power transfer.

The pi network topology has been changed to create the bridged-tee attenuator. The ability to vary attenuation with only two resistors is an advantage of this network over other topologies (particularly the pi and the tee-pad). Furthermore, both R1 and R2 can use the entire spectrum of resistor values, while the resistances of a pi attenuator can never go below 50 ohms. The bridged-tee topology also has the advantage of matching impedances even at high attenuation values.