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