Feko Simulation Models for Anten’it Prototype Antennas
Altair EmployeeAntennas are fundamental components of wireless communication systems, enabling the transmission and reception of electromagnetic waves. The design and fabrication of antennas are critical for achieving optimal performance in terms of radiation pattern, gain, bandwidth, efficiency, etc.
Simulation is an important tool to design and optimize antennas. A new design should be tested with a manufactured prototype of antenna. Many strategies like 3D printing, PCB prototyping, wire bending and shaping or metal machining are known. An interesting alternative for antenna prototyping is to build the antenna with re-usable connectable blocks. Such a concept is realized in the Anten’it Antenna Design and Prototyping Kit [1]. The kit offers multiple rectangular bricks with metallic and dielectric material properties.
Complex antennas can be assembled from these simple bricks. Different brick types are available:
- Metal Cells to build the antenna
- Ground planes
- Absorber Cells
- Dielectric Cells with 3 different material types
- Coaxial Connectors to feed the antenna
To construct a horn antenna, multiple metal cells, a ground plane, and a connector are required. These components, or 'building blocks,' come together to create the antenna structure, allowing for customization and modular assembly.
The combination of simulation and measurement with these prototype models is very well suited for understanding and testing antenna technology. At the same time, you can compare and evaluate different complex models of an antenna. For example, the small cylindrical connectors on each brick make the CAD data of the antenna more complex and a simulation mesh considering these details need much more mesh elements.
In this article we show different modelling strategies using Altair® Feko® [2] to simulate different antennas from the Anten’it Antenna Design and Prototyping kit.
Pyramidal Horn Antenna
The kit contains building instructions and datasheet documents of a standard gain pyramidal horn antenna (001A-WR159-2-6-FM26-12 in Anten’it) for the frequency range 3.7 GHz – 7.5 GHz. With CAD export from Anten’it, a simulation model can be set up. The connector is modeled with dielectric material (eps_r = 2.02, tand = 0.00022). For this horn antenna geometry different modelling strategies can be chosen:
- Complex Model: Union imported geometry and mesh directly
- Simplified Model: Remove all internal and external connection elements before meshing
- Very simplified Model: Replace volume structure with surface structure and replace staircase flair with flat surface flair.
The first complex model is easy to create without any preprocessing. But the price regarding the model size is very high. At 5 GHz the horn antenna model consists of more than 180.000 triangle elements and the computing effort becomes extremely high and needs HPC resources. Therefore, it is recommended to simplify the model before meshing: First remove all internal faces inside metallic regions. Also, the external connection cylinders can be removed in this frequency band, because at the highest frequency of 7.5 GHz, the cylinder diameter of 2.5 mm corresponds to lambda / 16. This simplification gives a model with 18.435 triangle elements that can be handled using classical Method of Moments (MoM) on a notebook.
One can even go one step forward and build a surface model instead of a volume model of the antenna. This model is even leaner with around 3.000 triangle elements and very fast to simulate. Another advantage is that it can be easily parametrized to do a parameter analysis or optimization as will be shown in the second chapter of this article.
Let us compare the simulation results for all 3 models at f = 5 GHz: The 3D antenna pattern for all 3 models shows the same principal pattern shape. Note that the current distribution looks different for the very simplified model, because the outer wall and the inner wall coincide.
In the cartesian graphs the absolute values of the antenna gain pattern in E-plane and H-plane are compared for the 3 simulation models with measurement results:
The simplified model results (solid lines) correlate very well with the results in measurement and with the complex antenna model. Only on the back side of the antenna (|theta| > 90°) the curve levels show some differences. The gain in main beam direction (theta = 0°) is for the very simplified model around 1 dB lower.
Also, S11 shows the same behavior in measurement and simulation. The complex model is simulated only at 5 GHz (orange dot), where the result matches well to the simplified model and the measurement.
Conclusion of these results: The best trade-off between simulation effort and accuracy can be realized with the simplified model. You can download the model here.
Antenna Design Exploration and Optimization
Even if the highly simplified model does not exactly represent the antenna prototype, it is very useful for understanding and optimizing the design. The simple horn shape built from a cuboid and a flare can be easily parametrized which is very useful for design exploration and optimization. Here the cuboid height CH, the flare height FH and the two inclination angles alpha_x and alpha_y are used to investigate different designs.
The Design Exploration is performed by coupling Altair Feko with Altair HyperStudy [3]. Variant 0 represents prototype geometry. With the in HyperStudy integrated GRSM optimizer the design can be optimized for arbitrary goal functions. In this case two alternative designs are generated by optimization: For variant 1 the gain in main direction theta = 0° is maximized. Especially in the lower part of the frequency band the gain has increased by more than 1.5 dB (Compare blue curve with green curve of original design). Variant 2 (red curve) represents a design with optimized half power beam width (HPBW). With HPBW = 49.12° it is similar to the original design, but more than 10° larger as for the design with highest gain. You can download the parametrized model of the horn antenna here.
Inverted F-Antenna
As a second example we investigate the inverted-F antenna (011A-IFA-7-10 in Anten’it). The IFA is designed for the frequency range 1.5 GHz – 1.56 GHz with omnidirectional gain. Like in the previous example we clean the CAD data: The cylinder elements on the ground surface are removed in the simulation model to reduce the computational costs.
The excitation is realized with a waveguide coaxial port. The model consists of 10.236 triangles and needs 2.4 GB memory. The solution on a laptop with 1 CPU using 6 cores took 4.5 minutes. In simulation model the resonance appears at 1.5 GHz and matches well with the measurement results.
Also, the antenna pattern has the same shape in simulation and measurement at f = 1.5 GHz.
You can download the antenna model here.
Hopefully these examples show how the combination of Anteni’it prototype antennas and numerical antenna simulation with Altair Feko help to design, build and validate antenna concepts. Order the Anten’it prototypes and download the simulation models to do your own investigations!
References:
- [1] Anten’it:
- [2] Altair Feko:
- [3] Altair HyperStudy: