# Introduction to CST MWS EKT 341 By Dr

Introduction to CST MWS EKT 341 By Dr Soh Ping Jack Muhammad Ezanuddin bin Abdul Aziz Cheor Wai Loon Universiti Malaysia Perlis (Uni. MAP)

O U T L I N E Introduction to CST MWS Why 3 D electromagnetic simulation tools are needed? • 3 D simulation methods • CST MWS – Simulation example • Summary •

I N T R O D U C T I O N Why 3 D electromagnetic simulation tools are needed? � Radiating electric & magnetic fields are described by Maxwell´s equations Analytical calculation by solving the Maxwell´s equations > exact or approximation � Analytical equations are derived for simple antenna structures > dipole, monopole, microstrip antennas �

I N T R O D U C T I O N Why 3 D 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 Ø Exact solutions do not exist � 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 �

I N T R O D U C T I O N Why 3 D electromagnetic simulation tools are needed? User / environment / phone material influence on antenna performance q Specific Absorption Rate (SAR) [W/kg] q Hearing Aid Compatibility (HAC) q Optimized antenna solution for every situation • Location • Size • Form q

I N T R O D U C T I O N Why 3 D 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 Ø Speeds up the design flow Final goal is an efficient antenna for a specific application

I N T R O D U C T I O N 3 D 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

I N T R O D U C T I O N 3 D simulation methods Mesh q Simulated structure is meshed = divided in small subdomains (cubes) or triangular parts q Mesh type depends on the solver type (time or frequency domain) q Mesh is dense in critical points • Surface of the conductors • Feed area • Small details • High permittivity material • High loss material

I N T R O D U C T I O N 3 D simulation methods Method of Moments, Mo. M • Full wave solution of Maxwell's integral equations in the frequency domain. • Well suited for models including conductive materials only. One famous simulator is IE 3 D 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 !!!

I N T R O D U C T I O N CST MWS Computer Simulation Technology CST • Several products for 3 D 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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R E F E R E N C E S References � 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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