Introducing Antenna Magus
Presenter
Location
Date
Overview
• What is Antenna Magus?
• The design problem
• An Antenna Magus Demo
– Find
– Design
– Export
• Arrays, tools and “Adding your own” antenna
• Highlighting some recent extensions
• Ensuring quality of models and designs
• A closer look at some synthesis approaches
What is Antenna Magus?
Antenna Magus is the first antenna design tool of its kind.
Antenna Magus allows antenna engineers to
find + learn about + design
many antennas, and
export models
of designed antennas to EM simulation tools like FEKO
Engineers may also
add their own
antennas to the database
The design problem
Antenna Design Antenna Analysis
The process of creating
an arrangement to
achieve a desired effect
• Antenna Magus aids in
antenna design
Take a given arrangement and predict its effect
• Analysis is part of the design process
Frequency
Gain
Frequency
Gain
Lengths
Angles Lengths
Angles
The faces of Antenna Magus
Find Design
Performance Export Array Synthesis
Libraries Tools Add your Own
Info
Demo…
Find
Design
Learn
Export
Prototype
Stages in array design
Layout assuming isotropic elements
Replace isotropic elements with real element pattern
(in isolation)
Calculate mutual coupling between elements
Compensate element patterns for coupling effects
Feed network design etc.
Example
• Choose a concentric
circular layout, with
main bean steering
and side lobe control
Layout, distribution and Isotropic
pattern result
Choose microstrip patch as element
Synthesized pattern
• This array can now
either be taken to
the next design step
(mutual coupling
effects)
• Or its pattern
exported as a source
(or load) in another
simulation
Toolbox
Chart tracing
Gain from an
aperture
Radar equation Gain/BW
Pattern
calculator
Friis equation
Aperture
distribution
Toolbox: Example
Gain/BW
Custom antennas in Antenna Magus
Information and documents
Designs
FEKO models
Performance data
Use your antenna in Magus
Custom antennas in Antenna Magus
• Document and store antenna designs
• Collaborate and share information and models
• Work with your antennas inside the Antenna Magus
workflow
Version 1.0 - 68
Version 2.0 - 113
Version 3.0 - 148
Version 4.0 - 200
Recent extensions…
Recent extensions…
• Pre-optimised designs for specific applications (e.g. WLAN)
• Instant performance estimation for certain designs
• Any general 3D radiation pattern may be used to represent the elements in an array synthesis (various file formats supported).
• The total number of antennas in each search group is indicated in the find mode.
Recent extensions…
• IEEE Axial ratio in dB (handedness not included) can be plotted
• 2D and 3D Plots of co- and cross-polarised gain based on the Ludwig III method.
• Many additional export options
– 3D Pattern files -> VSS format, CSV format, IEEE1979 format
– Array layouts -> XML format
• Additional sampling options when exporting 2D data
Ensuring quality of Models and Designs
• Simulation models are first
tested against published results
• Validation criteria are set e.g.
S11 < -15dB, fc < +- 5% etc.
• Validation sets are created
(between 50-250 per group
depending on the number of
objectives) and simulated.
Sample designs
Generate models
Run simulations
Compare results to
expectation
Validating designs and simulation models
• Result tables are created that are scrutinised by the engineer
• Failures are investigated
– modelling problem
– design problem.
• If the same failures occur for different solvers or techniques it usually points to a design error or invalid constraint.
• Failures unique to a technique usually points to a model error or shortcoming
Over the whole design range:
The designs algorithms work
The models are correctly
parameterised
The meshing is correct
The best techniques are used
The basic output requests are
correct
Different solvers and techniques
agree
Etc…
Synthesis of parabolic reflector antennas
A ‘basic’ reflector: The focus-fed parabolic
• Let’s take look at one design with these inputs:
– Frequency
– Gain (G)
– Sidelobe level (SLL)
– Feed beamwidth (FBW)
– Edge taper (ET)
– Feed distribution efficiency (FDE)
The focus-fed parabolic antenna
• The design process
• Consider aperture efficiencies.
• Consider aperture distribution shape.
• Blockage ratio is calculated and used to determine and compensate for overall efficiency.
• The design assumes an ideal pattern-excitation (i.e. no horn) but feed-blockage is compensated for and can be adjusted in the analysis.
The focus-fed parabolic antenna
G SLL FDE FBW ET
D
F/D ADE
EFF
F
P
BR
Gain = 39.7 (40) dBi
SLL = -20.05 (-20) dB
Real horn-feed Blockage adjusted
Choosing design inputs and outputs
• There are many feasible combinations of inputs that could be the basis for a design!
• A careful choice needs to be made of the most useful combinations
• Design approaches for each combination allow for flexible usage in practical situations
Synthesis of parabolic reflector antennas
A ‘complex’ dual reflector: The Cassegrain
The Cassegrain reflector
• Design for gain (38 dBi) at a specific frequency
• There are many viable designs to achieve the required performance. The choice between these designs rests on external factors and implications.
• flexible input options allow case-specific factors to be considered.
Synthesis with simple dependencies
• Consider a simple pin fed rectangular patch
• Closed form solution based on transmission line theory and simple slot current model for radiation resistances.
• Model is not 100% accurate, but works well enough to provide a first order design for a wide range of inputs.
An antenna with simple dependencies
• Strong relationship between pin location and input impedance allows adjustment of the pin inset to adjust the impedance
• Only a moderate effect on other performance properties like resonant frequency.
• The design approach is robust and works!
– Frequency -> patch dimensions
– Impedance -> pin position
– Etc.
An antenna with complex dependencies
• Consider the aperture coupled patch
• This patch has several independent parameters that all have dependent effects.
• Some first order effects of modifying a parameter are well known, BUT secondary effects are considerable.
• E.g. Increasing aperture size reduces the radiating resistance… AND the resonant frequency!
• It is extremely complex to create a robust algorithmic design for this antenna!
Synthesis with complex dependencies
• Circuit models separate the problem into separate components: microstrip line + slot + patch ; Each have complicated design equations, or require iterative optimisation to resolve.
• Quantities must be derived from physical parameters. E.g. simple slot current model used for the pin fed patch falls apart with the much thicker substrates that are used in the aperture coupled patch.
• Derivation of the coupling from the feed-line to the patch through the slot, is formidably complex!
• Empirical and analytic relations between circuit model quantities and physical parameters only applicable to very specific combinations of material parameters. E.g. for er ranges of 2.1-2.3.
• Not good enough to base a general design on!
M. Himdi et al., “Analysis of aperture-coupled microstrip
antenna using cavity model”, Electronics Letters, v25, n6,
1989, pp. 215 – 216
D. M. Pozar, “Microstrip antenna aperture-coupled to a
microstripline”, Electronics Letters, v21 n2, 1985 pp. 49 – 50.
Multidimensional regression:
Some drawbacks
Radial basis function (RBF) regression
Input 1
Input
2
7 3
1
7 0.07
3 0.4
8 0.53
1 0.1
8
Known
designs Required
value
Weighting values
based on
distances to
known designs
Design
space
A practical application of RBF’s
Step 1: Determine limits of input values that can be designed for.
Step 2: Choose a sparse set of design points in the chosen space. Complete a satisfactory design for each of those points.
Step 3: Choose a random design point inside the design space.
Step 4: Apply the radial basis function interpolation using all of the available designs. Evaluate this design.
Step 5:If the design does not meet specification, adjust the design till it is satisfactory and add it to the design set.
Repeat step 3-5 until the interpolation always yields satisfactory designs
• During the design testing process the design space can continually be adjusted
• Great emphasis must be placed on the accuracy of the computational models used to analyse design points.
• What about frequency?
– As an added dimension it increases the sample space.
– Normalizing by frequency could lead to Non-unique ‘best-designs’ solutions for non-frequency-scalable structures.
• You need a good validation/testing system to coordinate the simulations and designs!
Known/tested designs
Choose ‘random’
design point
Test RBF-based design
quality
Improve design
Add to known designs
Select bounded design space
New designs are acceptable
A practical application of RBF’s
• The aperture coupled patch requires 40 or 50 known design points in a large 5D design space!
Input quantity Minimum Maximum
Operating frequency 500 MHz 20 GHz
Top substrate relative permittivity 1 4.4
Top substrate thickness 0.15 mm 90 mm
Bottom substrate relative permittivity 1.8 13
Bottom substrate thickness 0.127 mm 24 mm
Thank you
More information:
www.feko.info/antennamagus
Contact information for local distributors:
(FEKO distribution network)
http://www.feko.info/about-us/contacts