Variable Attenuator

Model variable attenuator

• 

Libraries:
RF Blockset / Circuit Envelope / Elements

Description

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.

Simulate noise: on	Simulate noise: off

Examples

Vary Attenuation of Signal During Simulation

Use the Variable Attenuator block to attenuate a 20 dB constant signal. Use the Repeating Sequence Stair block as a Simulink control signal to vary the attenuation of the signal. In this model, the signal attenuation varies between 5 and 10 dB during simulation. To see the variation in attenuation, open and run the model.

• Open Model

Ports

Input

Att — Simulink control signal

scalar

Simulink control signal, specified as a scalar. This control signal is an Insertion Loss in dB.

Data Types: double

Parameters

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

on (default) | off

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

on (default) | off

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.

Version History

Introduced in R2016b

R2021b: Variable Attenuator block icon updated

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.