Briged Tee Attenuator Calculator

What is attenuator?

An attenuator is a device used between the signal source and load to reduce the signal's power without appreciably distorting signal waveform, as well as the attenuator provides impedance matching between the input source and load. For example, the attenuator is used to lower the amplitude of the signal to the desired value to enable measurements or to protect the measuring device from signal levels that might damage it. The attenuator is also called a pad. The attenuator reduces the signal’s power by a fixed amount (called fixed attenuator) or variable amount (variable attenuator) or series of known switching steps.

Attenuators are usually passive devices that use the resistive network to attenuate the signal. The basic type of passive attenuators is L type, pi (π) type, and T type attenuators. Active type attenuators are also available.

What is Bridged Tee Attenuator?

A Bridged Tee attenuator is basically a Tee attenuator circuit with an additional resistance (R1) connected in series between the source and the load that forms a bridged network, thus it is called a bridged Tee attenuator. Tee type attenuator is a type of passive attenuator that uses a resistive network circuit that replicates the letter “T” (Tee). The bridged Tee attenuator can be considered as a combination of both pi (π) and “T” (Tee) type attenuator. In a bridge Tee attenuator circuit, the series resistors (R3 & R4) values are equal to the characteristic impedance of the circuit (Zo). i.e., R3=R4=Zo. These two resistor values are chosen such that they are equal to the source (Zs) and load impedance (ZL). i.e., R3=R4=Zo= Zs = ZL.

Thus, the values of R1 & R2 decide the attenuation level of the bridged Tee attenuator circuit.

The bridged Tee attenuator is suitable to connect between a signal source and load to reduce the signal power when the source impedance (ZS) and load impedance (ZL) are equal (i.e., ZS = ZL = ZO). Here, Zo represents the characteristic impedance of the bridged Tee attenuator.

The bridged Tee attenuators are ideal for use in radio, electronic circuits (for example, prevent the overloading of mixer or amplifier), communication, and transmission line applications to weaken a stronger signal that is suitable for the connected load.

How to calculate resistance of bridged tee attenuator?

The formula for calculating the value of resistor R1 & R2 of bridged Tee attenuator (shown below) for the required value of attenuation (in dB) and for the characteristic impedance (Zo = Zs =ZL Ω) is given below.

Here, Zo is the characteristic impedance of the bridged Tee attenuator, which is equal to the value of source (Zs) and load impedance (ZL).

• Where:
• R1 (Ω) = Value of series resistor between source and load in the bridged Tee attenuator
• R2 (Ω) = Value of shunt resistor in the bridged Tee attenuator
• Zo = Characteristic impedance of the bridged Tee attenuator (shown above) in Ω
• dB = Required attenuation level in dB (i.e., decibels)