Excitation Functions
 Simulation:
Sources and Loads SignalNew Excitation SignalSignal type
In the Excitation
Signal dialog, you may select from the following excitation
functions. Some of these functions are only available for low frequency
or CST MPHYSICS STUDIO solvers.
Overview
Common time functions
Gaussian
Rectangular
Sine Step
Smooth step
Double exponential
Impulse
User defined
Import
Low frequency
time functions
Sine
Heavyside step
Polynomial step
Exponential step
Constant
Trapezoidal
Gaussian
The stimulation is performed with a Gaussian pulse.
To define a Gaussian-shaped excitation function a frequency range (Fmin,
Fmax) must be specified.
This
signal type is relevant in particular for high frequency calculations
and is used there as default excitation function.
Gaussian
sine
This excitation function is similar to
the Gaussian pulse. However, it does not contain any DC part in its spectrum
if Fmin is greater than zero.
If results at relatively low frequency are of interest
choose the default Gaussian over this excitation function.
Rectangular
Enables
you to define a digital excitation. Use Ttotal, Trise, Thold and Tfall
to define the shape of the function. A step function can be obtained by
setting Trise and Tfall to zero.
Sine step
Enables you to define a sine step excitation. The
parameters Frequency and Phase specify the parameters of the modulation
with the sine function. The maximum Amplitude is reached after t=Trise.
Smooth step
Enables you to define a smooth step excitation,
whose amplitude grows from 0 (start) to 1 (end) amplitude. The parameters
Trise and Arise [%] specify the slope of the signal, in term of its rise
time and the amplitude (in per cent notation) rise interval. In the following
picture, for instance, Arise=80%, denoting a growth interval between 10%
- 90% value. The definition of the rise interval is always assumed symmetric
with respect to 50% value. In a similar way a rise interval between 20%
- 80% value is specified by Arise = 60%.
Double exponential
Enables you to define a double exponential excitation
using the following expression.
f (t) = A (exp (-t / B) - exp (-t / C))
A: Amplitude
B: Tfall
C: Trise
Impulse
Enables you to define an impulse excitation.
A highest required output frequency (Fmax) should
be specified to define the shape of this signal.
This signal is centred about zero. It starts at
t = -6.25 / Fmax and ends at 6.25 / Fmax. Outside this range, the signal
is zero.
User defined
The
edit button opens the VBA editor that lets you define an excitation function.
Please note that the total time of a user defined signal is always interpreted
in the unit seconds.
Example:
Option Explicit
Function ExcitationFunction(dtime
As Double) As Double
If ( dtime < 1.0e-9)
Then
ExcitationFunction = 1.0e9 * dtime
ElseIf ( dtime < 2.0e-9
) Then
ExcitationFunction = -1.0e9 * dtime + 2
Else
ExcitationFunction = 0
End If
End Function
Import
Enables you to import a two-column table from an
ASCII file which contains the time and signal data. Please note that the
data of an imported signal is always interpreted in the unit seconds.
Sine
Enables you to define a sine-shaped excitation.
The parameters Voffset and Frequency specify the vertical offset of the
sine function and the number of periods within one second (depending on
the predefined frequency unit setting), respectively. After Ttotal time
units the signal will fall to zero.
Heavyside step
Enables you to define a Heavyside step excitation.
The parameters Astart and Aend specify the amplitude values before and
after t=0. At t=0 the function value is Astart.
Polynomial step
Enables you to define a polynomial step excitation.
The parameters Astart and Aend specify the start and end amplitudes. The
end amplitude is reached after t=Trise.
Exponential step
Enables you to define a exponential step excitation.
The parameters Astart and Aend specify the start and end amplitudes. Cexp
is the exponential constant which determines the functions gradient. At
t=0 the gradient is: Cexp*(Aend-Astart)..
Constant
Yields the same constant value 1.0 for all time
steps. This signal is used as default in low frequency calculations. It
has no meaning for high frequency calculations.
Trapezoidal
The trapezoidal signal is a periodic function with
an offset and a trapezoidal pulse whose amplitude is scaleable.
The definition is very similar to the one of the
rectangular signal except that the offset and
the amplitude is available in addition.
See also
Excitation
Signal View, Excitation
Signal,
Excitation Signal
Library
HFSS视频教程
ADS视频教程
CST视频教程
Ansoft Designer 中文教程
|
淘宝官方店 
