Introduction to CST MWS
EKT 341
By
Dr Soh Ping Jack
Muhammad Ezanuddin bin Abdul Aziz
Cheor Wai Loon
Universiti Malaysia Perlis (UniMAP)
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Introduction to CST MWS
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Why 3D electromagnetic simulation
tools are needed?
3D simulation methods
CST MWS – Simulation example
Summary
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Why 3D electromagnetic
simulation tools are needed?
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Radiating electric & magnetic fields are described
by Maxwell´s equations
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Analytical calculation by solving the
Maxwell´s equations
> exact or approximation
Analytical equations are derived for simple
antenna structures
> dipole, monopole, microstrip antennas
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Why 3D electromagnetic simulation tools are needed?
Present-day antennas are not simple structures
> Complex antenna shapes
> Dielectric material (phone covers, antenna radome)
> User close to antenna –> absorption
 Exact solutions do not exist
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Solution is approximated by using computational
electromagnetic tools
• Numerical solution for the Maxwell´s equations
• Do not give exact solution, accuracy depends on the
calculation capacity
• Arbitrary antenna shapes and materials can be solved
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Why 3D electromagnetic simulation tools
are needed?
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User / environment / phone material influence on antenna
performance
 Specific Absorption Rate (SAR) [W/kg]
 Hearing Aid Compatibility (HAC)
 Optimized antenna solution for every situation
• Location
• Size
• Form
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Why 3D electromagnetic simulation tools are
needed?
Solution is visualized for the designer
• Impedance matching
• Radiation properties
• Surface currents
• SAR
Prototype manufacturing and measurement rounds
are replaced by simulations
 Speeds up the design flow
Final goal is an efficient antenna for a specific application
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3D simulation methods
Excitation signal in a certain location of the 3-dimensional
space.
• This is typically antenna feed assuming 50Ω impedance
• Can be also plane wave e.g. In radar cross section
simulations
Structure is surrounded by boundaries
• Open, electric, magnetic
• Antenna simulations are typically made with open
boundaries -> radiation goes through boundary -> far field
approximations are based on the power through boundary
Time or frequency domain calculation is made for the
excitation
• Idea is to calculate wave propagation in simulated
structure
• When steady-state situation is met -> solver stopped
• Criteria can be e.g. The energy of back-reflected signal
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3D simulation methods
Mesh
 Simulated structure is meshed =
divided in small subdomains (cubes)
or triangular parts
 Mesh type depends on the solver type
(time or frequency domain)
 Mesh is dense in critical points
• Surface of the conductors
• Feed area
• Small details
• High permittivity material
• High loss material
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3D simulation methods
Method of Moments, MoM
• Full wave solution of Maxwell's integral equations in the
frequency domain.
• Well suited for models including conductive materials only.
One famous simulator is IE3D by Zeland
Finite Element Method, FEM
• Frequency domain calculation, ideal for low loss and
resonance –type structures. Commercial simulator HFSS by
Ansoft
Finite Difference Time Domain, FDTD
• Time domain simulation, good for broadband antennas.
Commercial simulators SEMCAD-X by Speag and MWS by
CST.
Nowadays trend is toward simulation tools with different solvers
for different simulation problems !!!
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CST MWS
Computer Simulation Technology CST
• Several products for 3D simulation
• Microwave Studio is for electromagnetic high
frequency problems
• FDTD method -> large simulations are relatively
fast
• Not ideal for high Q resonators
• Lately included also frequency domain solver
• Widely used by antenna manufacturer and academia
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References
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http://cst-simulation.blogspot.com/
http://www.cst.com/content/products/mws/overview.a
spx.
Swanson D.G., Hoefer W. J. R. “Microwave circuit
modeling using electromagnetic field simulation
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Question and answer?