AC sweep

The AC sweep feature is a frequency analysis of a periodic system. It uses the steady-state determination algorithm to compute the transfer function of a periodic system at different frequencies of a user-defined frequency sweep range. For each frequency, the following steps are performed:

• apply the (sinusoidal) AC sweep perturbation (see figure below to add this component in the circuit) to the periodic system,
• determine the steady-state operation of this perturbed system,
• compute the system response at this perturbation frequency.

Important

The AC sweep perturbation device must be in the top level circuit. If it is placed in a subcircuit, Simba will send an error.

The perturbation frequencies are defined by specifying:

• the frequency sweep range with the start and the end-frequency,
• the sweep type: linear or logarithmic,
• the start and the end-magnitude of the sinusoidal perturbation,
• the number of points within this range.

Once executed, the transfer function between the perturbation signal $S_p$ and the selected output variable $S_o$ is then available in the Results tab. The transfer function is computed such as: $20 \log\left( S_o / S_p\right)$

Important

The AC analysis on a range with low or very low frequencies should be carefully considered with the minimum time step which is set: it can lead to a very high number of points per period to be simulated for the steady state detection. For example, an analysis @10Hz with a minimum time step of 1e-10s could lead to an analysis of 1e9 points.

Python API

The AC Sweep is entirely accessible from the Python API to automate transfer function analysis.

AC Sweep Example

# Load modules
from aesim.simba import DesignExamples, ACSweep

# Load AC Sweep Design Example
buck_converter = DesignExamples.DCDC_Buck_Converter_ACSweep()

# Create the AC Sweep Test bench and assign the perturbation device
buck_converter_acsweep = ACSweep()
buck_converter_acsweep.Design = buck_converter;
buck_converter_acsweep.Device = buck_converter.Circuit.GetDeviceByName("Control")
buck_converter_acsweep.Fmin = 100;
buck_converter_acsweep.Fmax = 1E5;
buck_converter_acsweep.MagMin  = 0.03;
buck_converter_acsweep.MagMax  = 0.05;
buck_converter_acsweep.NumberOfPoints  = 41;

# Create and run the job
job = buck_converter_acsweep.NewJob();
status = job.Run();

# Retrieve Transfer Function
mag_sim = job.GetSignalByName('Rload - Voltage Magnitude').DataPoints
phase_sim = job.GetSignalByName('Rload - Voltage Angle').DataPoints