Transient Simulation Task

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A transient task allows to analyze the behavior of a circuit for an arbitrary excitation in time domain. External ports are used to define excitations. Probes monitor voltages and currents inside the circuit during the simulation.

 

Within this dialog box you may specify excitations for the external ports contained in your design. You can either assign a standard excitation like a sine, pulse, etc. to a port or you can assign a bit sequence to obtain an eye-diagram. Furthermore, you can provide a termination by either a constant impedance or the frequency-dependent impedance of the connected block. The basic simulation settings like start time and time and number of time steps are also specified within this dialog box.

Simulation settings frame

You can specify the time interval and a sampling here.

Tmax: Specify the end time for the simulation here.

Note: If "CST MWS co-simulation" is switched on, the simulation may stop even before Tmax is reached. The EM/Circuit Co-Simulation makes use of the automatic steady state checking of CST MWS. Whenever the field energy in CST MWS drops below the accuracy level of the CST MWS time domain solver setting, the simulation automatically stops. For periodic time signals this behavior may not be desired. In this case you need to disable the steady state checking by selecting "No check" in the CST MWS time domain solver setting.

Samples: Specify the number of plot time steps for the given time interval or for a single pulse here. The default value of zero enables automatic sampling, which is the best setting in most cases. Note that this number specifies the time step for plots only. The simulation time step is set adaptively by the simulator.

Circuit Simulator frame

CST: Select this option to use CST's circuit simulator for the execution of this task.

CST MWS co-simulation: Select this option to perform a transient EM/circuit co-simulation with CST MICROWAVE STUDIO®.

Units frame

Local units: Enables local units for this task.

Units: Opens a unit definition dialog box to define local units. This button is only active if the Local units option is enabled.

Excitation settings frame

Port/Description: This list displays the excitations specified for the external ports. If an external port is not associated with an excitation, It will be considered as (complex) resistor with either fixed or frequency-dependent impedance during the simulation.

Signal...: Press this button to open the Excitation Signal dialog box where you can specify or modify the excitation for the selected external port.

Remove Excitation: Press this button to remove the specified excitation for the selected port.

Text box: This field displays the settings for the selected excitation.

Constant real valued impedances: Check this option to treat frequency dependent and/or complex reference impedances of external ports as constant, real values. The real part of the impedance values at the center frequencies will be used if this option is checked. This option only has an impact to ports that are not excited and only if the task does not contain any signal excitation. It helps to mimic the CST MWS behaviour where port impedances may be computed at a certain frequency, e.g. at the center frequency.

For excited ports this option has no impact: voltage and current sources do not have an impedance, for signal ports it is fixed to a constant real value.

S-Parameter Calculation frame

Calculate full S-Matrix: Option to calculate the full scattering matrix. If enabled, all ports are sequentially excited by a Gaussian pulse defined by the reference frequency range. All previously defined signals will not be used for this simulation sequence.

Note: Generally, S-Parameters describe the small signal behavior of a system. However, when calculating the S-Parameters by this option, it is not guaranteed that the simulation fulfills this small signal requirement. Especially for highly nonlinear circuits this may not be the case.

Reference Frequency Range frame

Fmin/Fmax: If Gaussian excitation signals are defined, this frequency range defines their frequency range if the Use reference Fmin/Fmax option is set for these signals.
If frequency depending results are normalized, it also specifies the frequency of a the Gaussian spectrum that is used for the normalization.

Eye diagram frame

Enable: Wraps all time signals to the eye-diagram time interval Twrap

Twrap: Eye-diagram time interval. Can only be set if eye diagrams are enabled.

Twrap start: Delays the eye diagram monitoring by this period of time.

OK

Stores the current settings and closes the dialog box.

Cancel

Closes this dialog box without performing any further action.

Apply

Stores the current settings (without closing the dialog box).

Specials

Shows the Solver Specials Dialog.

Help

Shows this help text.

 

See also

Simulation Task Overview, Time Integration, Frequency domain data normalization