## Documentation |

This model shows how to use harmonic balance to calculate the AC steady-state frequency response curve for an LC bandpass filter built using blocks from the SimRF™ Circuit Envelope library.

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The system consists of:

A Continuous Wave source and a series resistor, which model a voltage source with internal source impedance.

Inductor and Capacitor blocks configured to model a third-order Chebyshev filter with a center frequency of 2.4 GHz.

An Outport block acts as a voltage sensor, measuring the voltage across a load resistor.

The Configuration block, which sets up the circuit envelope simulation environment.

Type

`open_system('simrfV2_ac_analysis')`at the Command Window prompt.Double-click the block labeled 'Specify Frequency Values' to provide a vector of frequencies.

Double-click the block labeled 'Calculate Frequency Response' to execute a script,

`simrfV2_ac_analysis_callback`, that analyzes the model at the specified frequencies and plots the response.

**Configuring a Model for Harmonic Balance**

To configure a model with circuit envelope library blocks for harmonic balance:

In the Model Configuration parameters dialog box, set the

**Stop time**parameter to zero.Use a Continuous Wave block to drive the system.

Set the

**Carrier frequencies**parameter in the Continuous Wave, Outport blocks, and the**Fundamental Tones**parameter in the Configuration block to the same vector of frequencies.

Ludwig, Reinhold and Pavel Bretchko, *RF Circuit Design: Theory and Applications*. Prentice-Hall, 2000.

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