You can accept the default settings and press the Start button to run the calculation. A progress bar appears at the bottom of the main window, displaying information about the calculations status:
This progress window disappears when the solver has successfully finished. During the simulation, the message window will display additional information:
Please note: If there are any warning or error messages during the simulation they will be written into the message window, as well.
Transient Solver Results
Congratulations, you have simulated the circular patch antenna using the transient solver! Lets review the results.
? 1D Results (Port Signals, S-Parameters)
First, observe the port signals. Open the 1D Results folder in the navigation tree and click on the Port signals folder.
Please note: It is possible to observe the progress of the results during the computation. In order to get the complete information, however, wait until the solver has finished.
This plot shows the incident and reflected wave amplitudes at the waveguide port versus time. The incident wave amplitude is called i1 (referring to the port name: 1) and the reflected wave amplitude is o1,1. As evident from the above time-signal plot, the patch antenna array has a strong resonance that leads to a slowly decreasing output signal.
A primary result for the antenna is the S11 parameter that will appear if you click on the 1D Results parameter:
|S| dB folder from the navigation tree. The following screenshot shows the reflection
It is possible to precisely determine the operational frequency for the patch antenna. Activate the axis marker by pressing the right mouse button and selecting the Show Axis Marker option from the context menu. Now you can move the marker to the S11 minimum and pinpoint a resonance frequency for the patch antenna of about 2.4 GHz.
The ripples that appear in the reflection parameters result from the time signal not sufficiently decaying (review again at the time signal plot). The amplitude of the ripples increases with the signal amplitude remaining at the end of the transient solver run. However, these ripples do not affect the location of the resonance frequency and therefore can be ignored for this example. More information about this type of numerical error is available in the Accuracy Considerations chapter.
? 2D and 3D Results (Port Modes and Farfield Monitors)
You should first inspect the port modes that can be easily displayed by opening the 2D/3D Results Port Modes
Port1 folder from the navigation tree. To visualize the electric field of the
fundamental port mode, click on the e1 folder. After properly rotating the view and tuning some settings in the plot properties dialog box, you should obtain a plot similar to the following picture (please refer to the Getting Started manual for more information on how to change the plots parameters):
The plot also shows some important properties of the coaxial mode such as TEM mode type, propagation constant and line impedance, etc.
In addition to the resonance frequency, the farfield is another important parameter in antenna design.
The farfield solution of the antenna device can be shown by selecting the corresponding monitor entry in the Farfields folder from the navigation tree. For example, the farfield at the frequency 2.4 GHz can be visualized by clicking on the Farfields directivity over the phi and theta angle:
farfield (f=2.4) [1] entry, showing the
Please note: You have the option to change the Results 5 degrees for a better angle accuracy of the plot.
As evident in the above figure, the maximum power is radiated in the positive z-direction. Note that there are several other options available to plot a farfield: the Polar plot, the Cartesian plot and the 2D plot.
? Accuracy Considerations
The transient S-parameter calculation is primarily affected by two sources of numerical inaccuracies:
1. Numerical truncation errors introduced by the finite simulation time interval. 2. Inaccuracies arising from the finite mesh resolution.
In the following section, we provide hints how to minimize these errors and achieve highly accurate results.
1. Numerical Truncation Errors Due to Finite Simulation Time Intervals
As a primary result, the transient solver calculates the time-varying field distribution that results from excitation with a Gaussian pulse at the input port. Thus the signals at ports are the fundamental results from which the S-parameters are derived using a Fourier Transform.
Even if the accuracy of the time signals is extremely high, numerical inaccuracies can be introduced by the Fourier Transform that assumes the time signals have completely decayed to zero at the end. If the latter is not the case, a ripple is introduced into the S-parameters that affects the accuracy of the results. The amplitude of the excitation signal at the end of the
Plot Properties
Step to