Model variable attenuator
RF Blockset / Circuit Envelope / Elements
The Variable Attenuator block attenuates the signal power by a given factor known as Insertion Loss in dB. Using the Variable Attenuator block, you can vary the attenuation of the input Simulink® signal during simulation. Commonly, the block matches the impedance of the RF circuit at the input and output ports. You can use attenuators to dampen the power of the incoming signal to protect RF circuits.
Variable Attenuator block mask icons are dynamic and show the current state of the applied noise parameter. This table shows you how the icons on this block vary based on the state of the Simulate noise parameter on the block.
Att— Simulink control signal
Simulink control signal, specified as a scalar. This control signal is an Insertion Loss in dB.
Minimum attenuation (dB)— Lowest value for insertion loss or attenuation
0.001(default) | scalar
Lowest value of insertion loss or attenuation to apply to the signal, specified as a scalar in dB.
Maximum attenuation (dB)— Highest value of insertion loss or attenuation
1000(default) | scalar
Highest value of insertion loss or attenuation to apply to the signal, specified as a scalar in dB.
Input impedance (Ohm)— Input impedance
50(default) | scalar
Input impedance of the attenuator, specified as a scalar in ohms.
Output impedance (Ohm)— Output impedance
50(default) | scalar
Output impedance of the attenuator, specified as a scalar in ohms.
Simulate noise— Simulate thermal noise
Select this parameter to simulate thermal noise in the attenuator. You must select Simulate noise in the Configuration block.
This parameter inserts a current noise source with the single-sided power density of 4 kT/R A2/Hz, where:
T is the value of the Temperature parameter in the Configuration block. Units are in degrees Kelvin.
k is the Boltzmann constant.
Ground and hide negative terminals— Ground RF circuit terminals
Select this parameter to ground and hide the negative terminals. To expose the negative terminals, clear this parameter. By exposing these terminals, you can connect them to other parts of your model.
Behavior changed in R2021b
Starting in R2021b, the Variable Attenuator block icon is now updated. The block icons are now dynamic and show the current state of the noise parameter.
When you open a model created before R2021b containing a Variable Attenuator block, the software replaces the block icon with the R2021b version.