Antenna Software

Problem Description

Aperture antennas are constructed in many combinations of dielectric and metal walls. Ridges are often added to the design and feed pin position or waveguide feeds have to be optimised. To satisfy these requirements it is important to accurately model the currents on the entire structure. Accurate surface current representations can, in turn, be used to compute secondary parameters that are of interest to aperture antenna developers, e.g.:

• Transmission efficiency.
• Axial ratio.
• Far-field radiation patterns.
• Input impedance bandwidth.

FEKO's mesh generator is able to mesh the surfaces of aperture antennas with triangles for geometrically accurate representation of all surfaces. The Method of Moments (MoM) can solve for the surface current on each of these triangles and then use these currents for derivation of other important analysis and visualisation parameters.

Application Note: Analyzing A Pyramidal Horn Antenna With The MLFMM

Product Overview: FEKO Software

Problem Description

Mechanical design often determines the shape of microstrip antennas. Examples of such designs are:

• Mobile communication devices where ergonomics dictate the shape of the device.
• Aerospace designs such as aircraft fuselage or missile nosecones where aerodynamic drag considerations dictate the shape.
• The complexity of the modelling of microstrip antennas that conform to any given surface shape can be reduced by requiring that the shape aligns with the simulation coordinate system.

• General antenna performance, i.e. radiation patterns, antenna efficiency, input impedance bandwidths, etc..
• Optimisation of the antenna parameters in the presence of the body that the antenna is mounted on.

FEKO offers a range of solution options for the modelling of conformal antennas. These include:

• Planer Green's functions for infinite dielectric layers, which is applicable to antennas conforming to the simulation coordinate system.
• Modern techniques such as the Surface Equivalence Principle (SEP) for use with the Method of Moments (MoM) which allows the modelling of arbitrarily shaped antennas.
• Triangular surface meshing that enable simple modelling of conformal shapes.
• A CAD interface with powerful features for the modelling of conformal antenna models, e.g. lofting of curves to create surfaces, projection of points or lines onto surfaces, local coordinate systems.
• A variety of feed techniques for conformal antennas, e.g. probe feeds, stripline feeds, electromagnetically coupled feeds.
• Varying permitivity and loss parameter dielectric solids with conducters on top of or inside such solids.

Problem Description

Microstrip antennas have evolved from simple single substrate, square metallic area structures to highly complex designs incorporating multiple dielectric layers with widely varying electromagnetic properties and complex metallic shapes on different different dielectric layers that couple energy from one layer to the next. The fundamental design principles are highly complex and the influence of minor changes on antenna performance have to be properly investigated before building expensive prototypes. Some of the fundamentals that have to be evaluated by simulation include:

• Coupling efficiency between metallic layers.
• Near-field energy distribution.
• Far-field radiation patterns.
• Current distribution on metallic layers.
• Input impedance.

FEKO software Solution

Special planar Green's functions are applied to multilayered antennas, enabling the analysis of arbitrarily shaped and oriented metallic surfaces and wires. The metallic structures may even cross dielectric layer boundaries.

Various excitation options are available in the FEKO GUI:

• Voltage sources along wire segments between triangular patches.
• Edge ports at the end of a microstrip feed line.
• Coaxial feed approximation (vertical pin to ground).
• Impressed current source.
• Elementary electrical and magnetic dipoles.
• Plane waves.

Problem Description

The proliferation of communication devices that are required in modern automobiles, require automobile designers to include more and more antennas into their vehicle designs. Requirements include FM/AM antennas, TV antennas, etc. Aesthetically speaking, this is a problem that can only be overcome by including such antennas into vehicle designs in unobtrusive ways. A prominent modern development is to include these antennas into the windscreens of a vehicle. These windscreens include multiple layers of glass and wiring that form the antenna. As with other antenna designs, engineers require the ability to simulate new designs to evaluate many antenna operating characteristics, including:

• Efficiency
• Impedance bandwidth
• Far-field radiation characteristics

FEKO software Solution

• Boundaries of the dielectric interfaces between different layers of glass are accurately accounted for.
• Coupling between closely spaced antenna elements are taken into account.
• Finite size glass antennas can be integrated into a full car model.
• Curvature and rotation of the window is considered.

Product Overview: FEKO Software

Problem Description

Antennas often consist of arrays of contributing elements, either with direct feeds for each element or via indirect coupling. Designers are then forced to consider not only the characteristics of the individual elements, but also for the entire array. Depending on the complexity of the array such analyses can become computationally expensive or too large to solve.

The Method of Moments (MoM) based formulation of FEKO does not mesh or discretise the free-space region between array elements, resulting in a highly optimal use of computational resources. FEKO also provides the Multilevel Fast Multipole Method (MLFMM) as an accurate and highly efficient solution to very large problems.

Product Overview: FEKO Software

Problem Description

Reflector antennas are typically used when very high gain (e.g. satellite transmission or reception) or a very narrow main beam (e.g. secure communication) is required. Gain is improved and the main beam narrowed with increase in the reflector size. Large reflectors are, however, difficult to simulate as they become very large in terms of wavelength.

FEKO software is well suited to the numerical analysis of reflector antennas and provides the following accurate high frequency techniques as options for reflector simulation:

• Multilevel Fast Multipole Method (MLFMM).
• Physical Optics (PO).
• Users with limited computation resources or extremely large reflectors may use approximation techniques to perform their simulations:
• Domain decomposition where the feed antenna is simulated in isolation and the result used to replace the feed antenna with an equivalent source when the reflector is simulated.
• Uniform Theory of Diffraction (UTD) which places no restrictions on reflector size.

Problem Description

Wire antennas have been important tools in communication technologies since the birth of the industry. Their applications are extremely diverse, as are the physical designs that have evolved from wire. Examples of application and antenna type include:

• Two-way radio communication with HF whip antennas, monopoles, helix and dipole antennas.
• UHF and VHF television signal distribution with Yagi-Uda, log-periodic and grid antennas.
• GPS receivers with quadriflar helix antennas.

• Rapid simulation of wire antennas of a wide frequency band.
• Visualisation of radiation patterns of the antenna in isolation.
• Evaluation of basic antenna parameters, such as S-parameters, axial ratio and gain.
• EMC and efficiency studies for the wire antenna in the environment where it will be used.

FEKO is ideally suited to the simulation of wire antennas in isolation and also integrated in their operational environments. The FEKO kernel is based on the Method of Moments (MoM) technique which solves for the currents on wire structures and then uses these currents to derive secondary solution parameters such as radiation patterns and input impedance.

In the case of very large geometries in proximity to the wire antenna FEKO also provides MoM hybridisation with asymptotic high frequency techniques such as Physical Options (PO) and Uniform Theory of Diffraction (UTD).

Problem Description

The simulation of broadband antenna designs can be very time consuming because of the complexity of the antenna geometries and the time it takes to simulate each frequency point of interest. Axial ratio, input impedance and gain typically have to be characterised and optimised for maximal bandwidth, creating the necessity for a tool that can perform these functions in simulation before expensive prototypes are built.

FEKO is ideally suited to this application and includes the following features that may be applied to these problems:

• Method of Moments (MoM) based simulation engine that discretises only model elements where currents flow.
• A full-featured CAD GUI for easy construction or importing of complex antenna geometries and specification of solution requirements.
• A built-in optimiser for the optimisation of antenna characteristics over several goal functions.
• Adaptive Frequency Sampling (AFS) for the adaptive scanning of wide frequency bands, thereby limiting the number of frequency points that have to be simulated, while still accurately characterising model performance.