Tee Attenuator Calculator

What is Tee Attenuator?

Tee type attenuator is a type of passive attenuator that uses non-inductive resistive network circuit that replicates the letter "T" (Tee). This attenuator configuration can be considered as a “Y” configuration.

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 of 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 Tee type attenuators are ideal for use in radio, electronic circuits, communication, and transmission line applications to weaken a stronger signal and to provide impedance matching.

The Tee type attenuator circuit is an unbalanced circuit. In an unbalanced circuit/configuration, the impedance of two transmission lines (up & bottom) does not have equal impedance with respect to ground, and the bottom line is grounded/earthed (see below left fig). The unbalanced attenuator is suitable to connect with an unbalanced transmission line, such as a coaxial cable that feeds the load.

However, the Tee attenuator can be converted to a balanced circuit by placing half the series resistances on both the top and bottom line (return path) and ground the shunt resistor's middle. Such a balanced circuit has two transmission lines with equal impedances along their lengths with respect to ground. The balanced attenuator is suitable to connect with a balanced transmission line, such as a twisted-pair cable that feeds the load.

Symmetrical Tee attenuator:

As we know, the Tee type attenuator is an unbalanced circuit, and it acts as a symmetrical attenuator when both the series resistor's values are equal to each other (i.e., R1 = R1). The symmetrical attenuator has the same value of the characteristic impedance (Zo = V/I) at the input, and output sides, allowing for its input and output terminals to be transposed with each other.

The symmetrical Tee type attenuator is ideal to connect between a signal source and load to reduce the signal's power when the source impedance (ZS) and load impedance (ZL) is equal (i.e., ZS = ZL = Zo).

Unsymmetrical Tee attenuator:

The unbalanced Tee type attenuator act as an unsymmetrical attenuator when both the series resistors values are unequal to each other (i.e., R2≠ R3). The unsymmetrical Tee type attenuator is suitable for insertion between the source and load impedance (ZS ≠ ZL) to reduce signal power level as well as for providing impedance matching between source and load. The unsymmetrical Tee attenuator is also called “taper pad attenuator”.

Note: Balanced Tee attenuator (also called “H” pad) is a symmetrical pi attenuator. Thus, balanced Tee type attenuator is also 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 balanced Tee attenuator.

How to calculate the resistance value of Tee type unbalanced symmetrical attenuator?

This calculator is used to calculate the value of resistor R1 & R2 of Tee type unbalanced symmetrical attenuator (shown below) for the required value of attenuation (in dB)and for matching impedance/characteristic impedance (Zo = Zs =ZL Ω). Here, Zo is the characteristic impedance of Tee type symmetrical attenuator, which is equal to the value of source (Zs) and load impedance (ZL).

The following formula is used to calculate the value of resistor R1 & R2 of Tee type symmetrical attenuator (shown above) for the desired value of attenuation (dB) and matching impedance/characteristic impedance (Zo Ω).

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