Electromagnetic simulations
Electromagnetic simulations modeling and is the process of modeling and simulating the interaction of electromagnetic fields with different objects and surrounding environments. It basically involves the use of user-interactive computer programs to compute approximate solutions of Maxwell equations.
Maxwell Equations are a set of differential equations that form the basis of electromagnetism and electric circuits. These equations provide a mathematical model for electrical, optical, and radio technologies such as motors, wireless communication, radars, lenses, etc.
Analytical solutions of several real-world electromagnetic problems cannot be calculated. A complete solution includes solved Maxwell equations for a particular geometry. Since most real-world electromagnetic problems don’t have analytic solutions, numerical methods are used to find the solutions by solving the Maxwell equations. An Electromagnetic(EM) simulation calculates the Electric Field, Magnetic Field, Current Densities, Radiation patterns etc. of a particular arrangement/ simulation setup.
An electromagnetic Simulationsis different from a circuit simulation. A circuit simulation uses electronic models based on mathematical equations to solve a circuit. Circuit simulations are easy and preferred for low-frequency circuits. As the system analysis moves from low to higher frequencies, circuit-models become in-accurate and preferred solution to predict and analyse a system is only EM-simulation.
EM simulations are extensively used for design of antenna, wave-guides, radio-frequency equipment, high frequency circuits etc. EM-simulators are also used in design of Printed Circuit Boards (PCBs) and Integrated Circuits (ICs) where signal integrity and parasitic elements are crucial. There are many commercially available EM-solvers which perform EM-simulations on different designed structures and circuits. These solvers provide solution in the form s-parameters, radiation pattern, field pattern etc.
Why EM-simulations are required?
EM simulations predict the functioning of electric circuits. The solver calculates the solution by dividing the whole structure (to be simulated) into small parts called meshes and solves Maxwell Equations on each mesh separately. The simulator carefully solves the equations for every mesh. Boundary conditions are properly calculated and solved. These detailed calculations highlight every aspect of the circuit, hence highlighting important issues.
EM simulations are extensively in antenna design. Every antenna has its own characteristic radiation pattern, which can be visualized and optimised only by the help of EM-simulator. This practice not only saves time but actually reduces cost of production.
One of the versatile application of EM-solvers is signal-integrity analysis. PCBs or circuit boards that contain high speed signals usually emit part of the signal into the space around them in the form of noise. If two copper-tracks having high speed signals are in close proximity, the emitted noise induces interference called cross-talk which distorts the functioning of the overall system. Here EM simulations come handy by predicting and visualising the emissions. These visualisations are further used to optimise the design, hence saving cost of production.
EM simulators are also used in design of Waveguides. Waveguides are 3D transmission lines which propagate EM-waves with minimum losses. Such 3D structures can only be designed using EM-solvers/simulators.
Electromagnetic Simulators
As mentioned previously, EM-solvers are computer-software for performing EM-simulations. These software provide interactive environment to design different geometries to perform EM-simulations on them. A lot of EM-simulators are available. Some of these famous simulators will discussed below
- Ansys HFSS
HFSS or High Frequency Structure Simulator is famous EM-solver developed by ANSYS that uses Finite-Element-Method to perform EM-simulations. It was the first general purpose EM-Solver to solve arbitrary 3D EM field problems.
- CST Studio
It is a high performance 3D EM solver which is used for designing, analysing and optimising EM components and systems. It is developed by Dassault Systèmes. It is software that is highly appreciated in industry and academia.
- COMSOL Multiphysics
Just like HFSS, COMSOL is finite-element method EM solver that is used for various physics and engineering purposes. It is relatively a new software that can be integrated with software like MATLAB.
- Momentum
Momentum is an EM solver which is extensively used for 2D-planar structures. It is developed by Keysight systems, and is one of the best and most reliable software available. It uses Method of Moments to calculate the solution, making it different from other solvers in terms of algorithm.
EM-simulations can be time-consuming since the solver is continuously performing calculations on small meshes separately. The duration of simulation is directly proportional to the physical dimensions of the geometry-to-be-simulated. An average task can take up to few hours to a day depending upon the complexity.