Worrying about Intellectual Property? Combine Measurements with FEKO Simulations

Numerical modelling of electromagnetic (EM) phenomena is maturing quickly due to ease of use, intuitive simulation codes and powerful hardware solutions. By taking advantages from the synergies between EM simulations and measurements, the industry can make earlier decisions on important device and platform features, as well as reduce the number of prototypes. In this article on simulations versus measurements, we concluded that in complex real-world problems, EM simulations should be seen as a complement to measurements.

Measurements can also be used in EM simulations together with model decomposition in FEKO. Model decomposition uses equivalent sources for complex sources and receivers in order to solve large and complicated antenna placement and Electromagnetic Compatibility (EMC) studies in platforms easier and quicker. We recently showed a use case related to EMC and Electronic Control Units (ECUs) in vehicles. The user can import into FEKO the measured or simulated near fields around an ECU and use model decomposition to create an equivalent source for such ECU. The equivalent source is then used for a high level EMC simulation in the vehicle.

OEMs who integrate antennas in different kinds of platforms, like aircraft, vehicles, ships and satellites are also interested in combining measurements with simulations. However, there are some challenges. Typically, antenna suppliers are reluctant to share their antennas’ CAD data with OEMs in order to protect the Intellectual Property (IP) of their antenna designs. As a result, an OEM who wants to do antenna placement or coupling analysis can typically consider the following alternative approaches:

• Create a CAD model of an equivalent (or similar) antenna
• Get the simulated fields of the antenna from the supplier also using FEKO, and then import such fields into FEKO (simulated fields in other formats can also be imported into FEKO)
• If one antenna is available legally, such unit may be disassembled to create a CAD model from it
• Import antenna measured data into FEKO, and create an equivalent source for such antenna

With respect to importing antenna measured data into FEKO, FEKO can also import data from Microwave Vision Group (MVG) antenna measurement systems using Insight. Insight is a software tool from MVG to compute the equivalent current distribution (EQC) from the near or far field of the measured antenna. By using the equivalent currents generated by Insight, FEKO creates an equivalent source for the antenna.

Figure 1: Monocone antenna (MVG SMC220) working at 3.3 GHz and 5.8 GHz mounted on a ground plane in an off center position.

Fig.1 shows a monocone antenna from MVG mounted on a rectangular ground plane, which was one of the test cases used to validate the approach of using measured data from MVG within FEKO simulations. The results from the full measurement (complete setup including the monocone antenna and rectangular ground plane) were compared to the full simulation (full-wave simulation for the antenna and ground plane) and the simulation using the equivalent model (including ground plane and equivalent source generated from the measured data).

The comparative antenna gain patterns at 3.3 GHz and 5.8 GHz are shown in Fig. 2. A very nice agreement is shown when comparing the combined approach (using FEKO simulations with MVG measurements) to both, the full FEKO simulations and the full MVG measurements.

Figure 2: Comparative antenna gain patterns for monocone antenna (MVG SMC220) at 3.3 GHz and 5.8 GHz.

By using model decomposition in FEKO, simulation times and required memories can also be decreased. For the test case on Fig.1, when using an equivalent source and comparing to the full simulation, simulation times could be reduced by a factor between 5.8 and 25, and memory could be decreased too between 2.6 and 9.6 times without compromising accuracy.

Another test case that was used to validate this approach is a monopole antenna on a space plane mockup, as shown in Fig.3. In this case, full simulations were compared to the equivalent model and the correlation between both was also outstanding.

Figure 3: Monopole antenna (MVG SM600) working at 7.5 GHz and 15 GHz mounted on the roof of a space plane mockup (being the plane 25λ long at the highest frequency). Screen shots from FEKO – Full simulation, left, and equivalent model, right.

The combination of measurements with simulations in FEKO represents an alternative solution for antenna manufacturers to share data with OEMs without exposing their IP. Also, thanks to model decomposition with equivalent sources, complex antenna placement and EMC studies in platforms can be conducted easier and quicker.

This article also appears on the Altair HyperWorks Insider.