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Antenna Placement on Aircraft Platforms with FEKO and Antenna Magus

A dielectric patch antenna is designed to user specification with Antenna Magus and placed on an aircraft for simulation of various performance parameters with FEKO.

System integrators are often interested in the effects on performance of an antenna when it is mounted on an operational platform, but are not skilled at antenna design or electromagnetic simulation of antennas.  The combination of FEKO and Antenna Magus provide system integrators with a easy to use tool chain that can be used for various applications of antenna placement analysis:

  • Siting an antenna on a complex platform in a position where operational performance is optimal.
  • Calculation of the radiation pattens of the antenna, both in isolation and when mounted on the intended platform.
  • Determination of the coupling between antennas that are closely spaced on the platform (S21).

This white paper presents a possible information flow through Antenna Magus and FEKO to satisfy the requirements of communication system integrators.

 

Project Specification:

  • Antenna:
    • Low-profile microstrip patch antenna
    • Centre frequency: 4.3 GHz
    • Gain: 9 dBi
    • E-plane beam width:  88 °
    • H-plane beam width: 52 °
  • Mount the antenna on the lower fuselage of an aircraft platform
  • Calculate the antenna radiation pattern within this operating evironment
  • Calculate the coupling of this antenna with a monopole antenna (centre frequency 4.3 GHz) mounted on top of the fuselage

Antenna Design

The first step in the design process is to identify a suitable antenna topology.  Antenna Magus is used in "Find mode" to identify suitable candidates.

Search for "patch", "medium gain", "pin feed".
Antenna_Magus_find_mode.png
Searching for appropriate antennas in Antenna Magus

 

Once appropriate antennas have been short-listed, they can be interrogated via the Antenna Magus "info browser" to compare detailed information about the antennas in deciding which will be the best suited to the current requirements.

Antenna_Magus_infobrowser_views.png
Antenna Magus antenna information browser

 

The antennas that were considered in this case were either a triangular patch antenna or an elliptical ring patch antenna.  Both antennas satisfied the gain requirements.  A decision was made to select the triangular patch antenna for further work as its radiation pattern is closer to omni-directional than that of the elliptical ring patch.

Antenna_Magus_infobrowser_triangular_patch_antenna.png Antenna_Magus_infobrowser_elliptical_ring_patch_antenna.png
Triangular patch antenna Elliptical ring patch antenna
Antenna Magus antenna information browser

 

The next step of the process is to design the antenna in the Antenna Magus "design mode".  The antenna can be designed based on specification of the centre frequency and the substrate properties before performance is estimated.

Design process:
- Specify frequency as 4.3 GHz, free-space substrate (h = 2 mm)
- Estimate performance
- Tweak the centre frequency until resonance occurs at exactly 4.3 GHz
Antenna_Magus_design_tweaking.png
Tweaking designs in Antenna Magus

 

Having designed and tweaked an antenna in Antenna Magus and estimated its performance, prudent design methodology requires that the design be tested in a highly accurate 3D electromagnetic simulation software suite such as FEKO. The Antenna Magus design can easily be exported to FEKO, relying on the latest FEKO simulation functionality, to test the design in a rigorous analysis methodology.

In this case, FEKO confirms that the design results in the specified 4.3 GHz centre frequency and delivers 9.1 dBi gain.

CADFEKO_triangular_patch_antenna.png
CADFEKO model that was exported from Antenna Magus
POSTFEKO_triangular_patch_antenna_input_impedance.png POSTFEKO_triangular_patch_antenna_radiation_patterns.png
Input impedance presented in POSTFEKO Far-field gain presented in POSTFEKO

Antenna Placement

The triangular patch antenna that was designed in Antenna Magus and confirmed correct in FEKO is intended for use on an aircraft platform.  This aircraft can be imported into CADFEKO and the antenna simply mounted in the correct position.

FEKO_antenna_mounted.png
Antenna placement in CADFEKO, using the "align" tool

 

FEKO's Multilevel Fast Multipole Method (MLFMM) is a fast, full-wave, mathematically rigorous solution method that can be used to solve problems very accurately.  It can thus be used as a reference solution to test the results that were computed by the high frequency asymptotic simulation methods (e.g. Method of Moments-Physical Optics, MoM-PO).

POSTFEKO_3D_pattern_MLFMM.png POSTFEKO_3D_pattern_PO_coupled.png POSTFEKO_3D_pattern_PO_decoupled.png
MLFMM MoM-PO (coupled) MoM-PO (decoupled)
3D antenna gain patterns computed with different simulation methods in FEKO

3D gain patterns are a good way to evaluated installed antenna radiation patterns in a qualitative manner, but for detailed comparisons 2D plots remain the best.  2D comparisons of the radiation patterns computed with the different FEKO methods confirm that the MoM-PO is very accurate in front of the antenna, as is to be expected theoretically.

POSTFEKO_antennaplacement_2D_gain_comparison.jpg
Excellent agreement between MLFMM and MoM-PO

Different simulation methods have different areas of strength and weakness in application. The results shown here confirm that in front of a radiator, PO methods are highly accurate. As PO methods are asymptotic high frequency approximation methods, they will outperform full-wave solution methods in terms of simulation requirements.

Comparison of simulation requirements for different simulation methods in FEKO
(Antenna mounted on aircraft at 4.3 GHz)

MLFMM Coupled MoM - PO Decoupled MoM - PO Decoupled MoM - Large Element PO
Hardware Intel IA 64
12 CPUs
1.6 GHz
Intel Itanium 2
4 CPUs
1.5 GHz
Intel IA 64
12 CPUs
1.6 GHz
Intel IA 64
1 CPU
1.6 GHz
Runtime 2 hours 13 hours 1.7 hours 0.48 hours
Memory 36 GByte 24 GByte 6.6 GByte 0.026 GByte
# mesh triangles 1,832,217 1,731,743 1,731,743 29,812
# unknowns 2,747,102 2,597,414 2,597,414 44,759

 

Antenna Coupling Analysis

Coupling between different antennas that are mounted on the same platform can easily be modelled in FEKO by computing S-parameters between the two antenna ports.  For antenna coupling, only the MLFMM is a suitable simulation methods as it is the only method that accurately models mutual coupling and the shadow regions of a model.

CADFEKO_antenna_coupling_installation.png
CADFEKO model for a microstrip patch coupling to a monopole
antenna, both mounted on a fighter airframe

 

POSTFEKO_antenna_coupling_Sparameters.png
Coupling (S21) is very low between the microstrip patch and the monopole