A balun can be modeled in AN-SOF using an equivalent generator, as the figure below shows. Since voltage sources admit an internal impedance, we can adjust its resistive part to match the antenna input resistance.

Learn more >

The Scilab script shown in this video, Isocontours script, is ready to use together with AN-SOF. It allows us to plot level curves or isocontours of a field pattern. The example shows the electric field pattern at the soil level just below an Inverted-V antenna.

Download Script >

Download Model >

Did you know that AN-SOF data can be exported to Excel?

It is important to be able to export data so we can write reports and share our progress with colleagues. Simulation results can be exported to CSV (Comma Separated Values) files, where data are saved in tabular format. CSV files can then be opened with a spreadsheet program, such as Microsoft Excel or Google Sheets.

We will find the “Export” button next to the following tables:

1. Select a wire in AN-SOF, go to Main menu > Results > List Currents. Move the slider to choose a segment and click on the Current on Segment button or Input List button (it is enabled if there is a source there). A table of current/input impedance vs. frequency will be shown.
2. Go to Main menu > Results > Power Budget/RCS to display the table of input power, radiated power, directivity, gain and efficiency.
3. The far-field can be tabulated as a function of the direction (far-field pattern) for a chosen frequency or as a function of frequency for a selected direction (theta,phi). Go to Main menu > Results > List Far-Field Pattern for the first option or Results > List Far-Field Spectrum for the second one.
4. Regarding the near field, we can say the same as in 3). Go to Main menu > Results > List Near E-Field (H-Field) Pattern or Results > List Near E-Field (H-Field) Spectrum.

Regarding plots, after plotting some result in AN-XY Chart, AN-Polar or AN-Smith, go to the main menu of any of these applications > File > Export to export a CSV file.

In addition, there is a Copy Plot (Ctrl+C) command in the Edit menu of these applications. This option is called Copy Workspace in the File menu of AN-SOF. It sends the graphic to the clipboard as a bitmap, which can then be pasted elsewhere (Ctrl+V), e.g. in Microsoft Word, Power Point or their Google-equivalents, in an image editor, in an email body, etc.

When creating an antenna model or a wire structure in the AN-SOF workspace, several crucial aspects must be considered to ensure the model’s validity. Particularly, when dealing with complex structures composed of numerous wires, the possibility of errors arises. However, AN-SOF provides three essential commands that can be executed in any order and whenever needed to aid in error detection within the model. These commands can be accessed by navigating to the AN-SOF main menu and selecting Tools, Fig. 1, where the following options are available:

Checking Individual Wires

The Check Individual Wires command performs a comprehensive assessment of three essential parameters associated with each wire individually. Wires with errors will be highlighted in red, while those with warnings will be highlighted in yellow. The parameters subjected to evaluation are illustrated in Fig. 2(a) and are as follows:

1. Segment Length / Shortest Wavelength (ΔL/λ_min): This parameter examines the ratio between each wire segment’s length, ΔL, and the shortest wavelength, λ_min, within the frequency sweep. It is essential to ensure that the segment length is sufficiently small compared to the shortest wavelength, representing the worst-case scenario. The criteria defining whether a wire is considered “OK,” “Warning,” or “Error” are as follows:

2. Cross-Section Size / Shortest Wavelength (d/λ_min): This parameter focuses on the wire’s cross-section diameter, d, relative to the shortest wavelength, λ_min, within the frequency sweep. If the wire’s cross-section is not circular, the equivalent radius is calculated to determine the diameter. The cross-section of each wire must be sufficiently small compared to the wavelength. The criteria for evaluating a wire’s status are as follows:

3. Thin-Wire Ratio (Segment Diameter / Length): This parameter is particularly relevant when increasing the segmentation in a given wire for purposes such as convergence analysis. As the segmentation increases, the segment lengths decrease, causing each segment to become “thicker” in the sense that its diameter, d, approaches its length, ΔL. AN-SOF provides two different Kernels for calculations: the default Exact Kernel, which allows precise calculations on very thick wires, and the Extended Kernel designed for wire segments with a diameter up to 3 times their length (d/ΔL = 3). If the Exact Kernel is not enabled in the Setup tab > Settings, the segment diameter-to-length ratio, d/ΔL, will be checked. This ratio is referred to as the “thin-wire ratio,” and the evaluation criteria are as follows:

Errors associated with a wire segment that is too long (ΔL/λ_min > 0.2) can be easily rectified by increasing the number of segments for the affected wire. However, it is crucial to enable the “Exact Kernel” option when significantly increasing the number of segments, as each segment becomes thicker. Only disable the Exact Kernel when prioritizing computational speed over accuracy.

For cases involving very thick wires (d/λ_min > 0.1), it is advisable to represent them using a cylinder composed of a grid of wires, instead of a single wire.

By conducting these individual wire checks, users can proactively identify and address any potential issues related to wire segment length, cross-section size, and thin-wire ratios within their antenna models, ensuring accurate and reliable simulation results.

Checking Wire Spacing

The Check Wire Spacing command plays a critical role in verifying that each wire within the model does not overlap with others, Fig. 2(b). The proximity between two wires is permitted as long as their radii allow it, without resulting in an actual overlap. Wires found to be in error due to overlapping will be highlighted in red, while those with warnings will be marked in yellow. In cases where multiple wires’ ends are connected at a common point, as Fig. 2(c) shows, overlaps may be detected and categorized as errors or warnings. However, it is important to note that such overlaps do not adversely affect the simulation calculations, as long as the limits specified in the previous evaluation items are adhered to.

At points where multiple wires are interconnected, AN-SOF ensures that Kirchhoff’s currents law is strictly enforced. This law states that the algebraic sum of currents meeting at a point must be zero. By fulfilling this requirement, AN-SOF effectively eliminates any errors that could potentially arise due to overlapping between wires.

In summary, the Check Wire Spacing command serves to identify and flag any instances of wire overlap, providing a visual indication of errors or warnings. Nevertheless, it is reassuring to know that such overlaps, particularly at points where multiple wires converge, do not compromise the accuracy of the calculations, as AN-SOF guarantees the fulfillment of Kirchhoff’s currents law at these interconnected points.

Deleting Duplicate Wires

The Delete Duplicate Wires command serves the crucial purpose of identifying and removing any duplicate wires present within the model. A duplicate wire is defined as one that completely overlaps another wire along its entire length. In the case of linear wires, mere coincidence of their endpoints is sufficient for them to be duplicates. Such duplicates are not permissible in a model because they lead to a singular matrix in the Method of Moments, analogous to repeating an equation in a system of linear equations. Running this command ensures the elimination of all duplicate wires from the model.

To ensure a robust and accurate simulation, it is considered a best practice to check specifically for duplicate wires before initiating any calculations.

In summary, we have explored crucial commands for detecting and correcting errors in AN-SOF antenna simulations. “Check Individual Wires” validates wire parameters, such as segment length, cross-section size, and thin-wire ratio, ensuring model integrity. “Check Wire Spacing” identifies overlaps between wires, essential for precise simulations. “Delete Duplicate Wires” eliminates redundancy, preventing singular matrices in calculations. By adopting these practices, users can achieve robust simulations, enhancing the accuracy and reliability of AN-SOF antenna models.

It is important to have control over the scales of the graphs for a better presentation and interpretation of the results. We can adjust the maximum and minimum values of the color bar in AN-3D Pattern to obtain increments in multiples of 5 or the value we want.

Go to the AN-3D Pattern main menu > Edit > Preferences and set the Max and Min values of the color scale.

From the far field point of view, the whole structure of an antenna and its surroundings is reduced to a single point at the origin (X,Y,Z) = (0,0,0). So the standard practice of superimposing the 3D radiation pattern to the antenna structure is just a means to facilitate the interpretation of the directional characteristics of an antenna.

For this reason, you can move the phase origin of the 3D radiation pattern to the desired point in order to get a better view of the antenna orientation versus its radiation pattern. Go to the Setup tab > Far Field > Origin and set the X0, Y0, Z0 coordinates of the radiation pattern center (see Section “4.3 Far-Fields” in AN-SOF user’s guide).

Wires can be imported into AN-SOF from another AN-SOF project, so wire structures of different projects can be merged in a single project.

When a project is saved, a file having extension .wre will also be saved. This file contains the geometrical description of the wires. To import wires to a project, go to File menu > Import Wires > AN-SOF Format and just find and select the .wre file that you want to import.

For instance, this feature allows us to analyze the electromagnetic response of an antenna and its supporting structure separately, and then to combine them in a new project to analyze the response of the whole structure.

We see that most of the time we are interested in calculating only the E-field in antenna projects when we are talking about the near field. For this reason, we have added an option to enable or disable the automatic calculation of the H-field when we click on the “Run ALL” (F10) button. Go to Tools > Preferences > Options tab.

If we are only interested in the near field and we don’t want to waste time calculating the far field, we can click on the “Run Currents and Near-Field” (F12) button.

In the “Simulate” menu we also have the options: “Run Far-Field”, “Run Near E-Field” and “Run Near H-Field” to calculate each field separately.

When it comes to simulations, there is always a trade-off between speed and accuracy. However, in the initial stages of antenna design, prioritizing speed is often crucial. To help you speed up your calculations in AN-SOF, here are some valuable tips:

1. Start with the minimum number of segments: Begin with 10 segments per wavelength. AN-SOF allows you to set the minimum recommended number of segments by entering “0” (zero) as the number of segments for any wire. In the case of a wire grid, use one segment per cell side if the electrical size of each cell is less than 10% of the wavelength.

2. Adjust the Quadrature Tolerance: Navigate to the Setup tab > Settings panel and set the Quadrature Tolerance between 5% and 10%. This parameter primarily affects simulations involving parallel wires that are very close to each other, approximately two wire radii apart.

3. Reduce the Interaction Distance: Go to the Setup tab > Settings and set the Interaction Distance to zero. This setting is relevant only for parallel wires that are in close proximity to one another.

4. Optimize spatial resolution for gain, directivity, and efficiency calculations: For calculating gain, directivity, and efficiency, a spatial resolution of 5 or 10 degrees in the far-field is usually sufficient. Access the Setup tab > Far-Field panel and set Theta Step to 5 degrees and Phi Step to 10 degrees.

5. Calculate only what you need: Instead of running unnecessary calculations, focus on what you really require. If you need currents and far-field data, click on Run Currents and Far-Field (F11). In the case of solely being interested in the input impedance, go to Run > Run Currents (Ctrl + R) in the main menu.

By implementing these strategies, you can significantly enhance simulation speed. In fact, the figure provided illustrates an example where the simulation runs more than three times faster, especially when setting the Interaction Distance to zero. You can find the “car.emm” project in the Examples folder, which is installed along with AN-SOF, or you can download the model by clicking on the button below.

Remember, finding the right balance between speed and accuracy is essential, and these tips will help you achieve faster simulations in AN-SOF Antenna Simulation Software.