RF Modeling Software for Optimizing Electromagnetics Devices

Designers of RF and microwave devices need to ensure that the electromagnetics simulations are reliable and robust. Traditional electromagnetic modeling lets you examine RF physics alone, but no real-world product operates under just one branch of physics. To see how other physics phenomena affect the design, you need multiphysics modeling, which allows you to extend the model to include effects such as temperature rise, structural deformations, and fluid flow.

With the RF Module expansion of the COMSOL Multiphysics® simulation platform, you can analyze RF designs in multiphysics scenarios, including microwave and RF heating, all within the same software environment.

Design for the Present and Future with the RF Module

Products, components, and devices can always be improved. With the RF Module, you can optimize designs by investigating effects such as electromagnetic wave propagation, microwave heating, and RF heating — ensuring that you create the best products possible and get ahead of others in your field.

In the fast-paced RF, microwave, and millimeter-wave industries, product development must keep up with advancements in technology. For example, antennas and RF front ends; including filters, couplers, power dividers, and impedance matching circuits; should be compatible with future developments, such as the 5G MIMO network, Internet of Things (IoT), and SatCom.

It is also important to evaluate RF interference and compatibility in wireless communication platforms for the seamless operation of your products for developing applications, including wearable devices, autonomous vehicles, and state-of-the-art microwave and RF products.

Ensure that your organization is ready to embrace these new technologies, and whatever comes next, with the COMSOL® software.

What You Get with the RF Module

When you expand COMSOL Multiphysics® with the RF Module, you can access features for specialized RF and microwave modeling, in addition to the core functionality of the COMSOL Multiphysics® software platform.

The RF Module includes tools for modeling:

  • Antennas
  • Far-field radiation patterns
  • Antenna gain and directivity
  • S-parameters
  • Input impedance
  • Phased arrays
  • Circuits
  • RFID
  • Biomedical devices
  • Microwave sintering and spectroscopy
  • Bandpass-filter type devices
  • Metamaterials and integrated plasmonics
  • Nanostructures
  • Millimeter-wave and terahertz radiation
  • Resonators and filters
  • Couplers and power dividers
  • Ferrimagnetic devices
  • Near-field communication
  • Bloch-Floquet periodic arrays and structures
  • SAR calculations
  • Microwave ovens
  • Scattering and cross radiation
  • Transmission lines
  • Microstrips
  • Coplanar waveguides
  • Substrate integrated waveguides (SIW)
  • Frequency tunable devices
  • RF MEMS
  • EMI/EMC

Multiphysics Couplings

Included in the RF Module:

  • Electromagnetic heating
  • Temperature-dependent material properties
  • Electromagnetic-field-dependent material properties
  • Strain- and stress-dependent material properties and deformed geometry

Accessible with additional modules:

  • Bioheating and biomedical therapy such as microwave ablation and millimeter-wave cancer tissue diagnosis
  • Performance impact due to thermal stress and mechanical deformation
  • Ferrites with magnetic field biasing
  • Piezoelectrically actuated tunable filters
  • Microwave plasma
  • Dielectrophoresis
  • Radiative heat losses
A COMSOL model for studying a transmission line Butler matrix beamforming network.

A Butler matrix beamforming network is designed using the Transmission Line interface in the RF Module. The results show the logarithmic norm of the electric field on the antenna elements at 30 GHz and the arithmetic phase progression on the beamforming network.

A COMSOL model for studying microwave absorption in an anechoic chamber. A biconical antenna, often used in EMI/EMC testing, is at the center of an anechoic chamber. The far-field radiation pattern and S-parameter in the model show that the walls' reflection is significantly reduced without distorting antenna performance.
A 1D plot of the S-parameters in an FSS model created with COMSOL Multiphysics and the RF Module. The S-parameters for a frequency-selective surface have been plotted in 1D to show the bandpass resonance for the design.
A 1D Smith plot of the S-parameters in an FSS model created with COMSOL Multiphysics and the RF Module. A Smith plot has been created to evaluate the reflectivity and transmittivity performance of the FSS model with different incident angles.
An example of modeling electromagnetic heating using RF software from COMSOL. An x-band waveguide bend contains a dielectric block made of temperature-dependent material properties. The model shows how the assembly heats up over time due to electromagnetic losses and finds the steady-state temperature.
A COMSOL Multiphysics model of a low-pass microwave filter on a PCB. The S-parameters of a low-pass microwave filter on a printed circuit board (PCB) are computed in this model. The model also considers the effect of mechanical deformation based on the placement and length of the stubs along the microstrip line.

RF Module Features and Functionality

Explore the features and functionality of the RF Module in more detail by expanding the sections below.

You can set up RF or microwave device designs by selecting predefined physics interfaces. These interfaces are packaged with features and functionality for a variety of specific modeling scenarios, so you can set up a model without first figuring out the complex Maxwell's equations that describe the physics.

Whether you need to investigate the electromagnetics of a simple RF device or couple other physical phenomena, such as heat transfer or structural mechanics, you can find what you need in the comprehensive selection of built-in physics interfaces.

Did You Know? An interface is a comprehensive package of modeling features that is tailored to a specific area of analysis.

Physics-based modeling interfaces in the RF Module:

  • Electromagnetic Waves, Frequency Domain
  • Electromagnetic Waves, Time Explicit
  • Electromagnetic Waves, Transient
  • Transmission Line
  • Electrical Circuits
  • Microwave Heating
The COMSOL software GUI showing predefined physics interfaces available with the RF Module.

RF heating in a waveguide is modeled using the Microwave Heating predefined interface available when adding the RF Module to the COMSOL Multiphysics® simulation platform.

Modeling electromagnetics problems calls for extensive options for boundary conditions and geometry settings. Therefore, you will find preset geometry capabilities in the RF Module, whether you are working in a 1D, 2D, or 3D domain.

Choose from a wide variety of detailed boundary conditions to describe metallic boundaries — including impedance boundaries and perfect electric and magnetic conductors — and radiating (absorbing) boundaries, such as scattering boundaries and perfectly matched layers. To reduce model size, the RF Module also supports the definition of periodic boundary conditions.

Did You Know?

You can reduce computational time and memory by using a Periodic, Perfectly Matched Layer, or Symmetry boundary condition.

The variety of boundary conditions covers a wide range of design scenarios, allowing you to model the geometry of ports, cables, devices, and other components and complex geometries.

Boundary conditions in the RF Module:

  • Surfaces
    • Perfect electrically conducting surfaces
    • Finite conductivity
    • Thin lossy boundaries
  • Symmetry
  • Periodic
  • Free space
    • Scattering (absorbing) boundaries
    • Perfectly matched layers (PMLs)
  • Elements
    • Capacitive
    • Inductive
    • Resistive
    • Complex impedance
  • Ports
    • Rectangular
    • Circular
    • Periodic
    • Coaxial
    • User defined
    • Numeric (mode matched)
    • Lumped
    • Two-port network systems
  • Cable terminations
  • Line currents
  • Point dipoles
 

Want to be in the driver’s seat of your simulation? With equation-based modeling, you can modify the governing equations directly within the software, further customizing the model for your own analyses.

For electromagnetics modeling problems, the RF Module relies on the finite element method, specifically the frequency domain form of the governing Maxwell’s equations. Modifying custom equations under the finite element method ensures that you are getting the results needed for a safe and reliable end product.

Did You Know? The finite element method is preferred in many cases over the finite difference method — specifically within multiphysics applications as well as for devices made up of complex geometries.

As an added benefit, by using an equation-based modeling approach and eliminating the need for fundamental coding, you can greatly increase the flexibility in what you can model and reduce the time it would take to set up simulations.

Equation-based modeling flexibility in the RF Module:

Did You Know? Equation-based modeling is the ability to access and modify the equations that govern the modeling interfaces to which they are applied.

  • 1D
    • Transmission line equations (can be projected to 2D or 3D applications)
  • 2D
    • In-plane, out-of-plane polarizations, or full three-component vector
    • Out-of-plane propagation
  • 2D axisymmetric
    • In-plane, out-of-plane (azimuthal) polarizations, or full three-component vector
    • Known azimuthal mode numbers
  • Field formulations:
    • Total wave (full field)
    • Background wave (scattered field)
  • 3D
    • Full-wave form of Maxwell's equations using vector edge (curl) elements
    • Material property relationships:
      • Dielectric media
      • Metallic media
      • Dispersive media
      • Lossy media
      • Anisotropic media
      • Gyrotropic media
      • Mixed media
  • Circuit (nondimensional) modeling with SPICE netlists
 

You have absolute control over your mesh in the RF Module. This is especially useful if the material properties vary during the simulation, such as for electromagnetic heating.

Using the COMSOL Multiphysics® physics-controlled meshing feature, you can easily resolve the wavelengths of electromagnetic phenomena for accurate solutions. Then, you can vary the amount of mesh elements used to solve the model for your desired level of accuracy.

Using a variety of meshing options, which can be automatic or manual, you can mesh dielectric domains and perfectly matched layers (PMLs), as well as periodic structures for RF models. Controlling the mesh ensures accurate simulation results.

Meshing features in the RF Module:

  • Tetrahedral
  • Triangular
  • Hexahedral
  • Prismatic
  • Rectangular
A screenshot of the COMSOL GUI for an EM simulation that uses PMLs and the physics-controlled mesh feature. A car geometry is meshed using the physics-controlled meshing feature. The car is enclosed in perfectly matched layers separated by an air domain in order to compute the far-field radiation pattern of the rear-windshield FM antenna.

You can use the numerical methods and solvers included in COMSOL Multiphysics® to compute the complex equations behind electromagnetics simulations — without sacrificing speed and accuracy. The well-thought-out default solvers built into the RF Module help you feel confident that your analysis is correct and the design is backed up by solid numerical solutions.

No matter what your simulation goal is, you can select a study type and manipulate all its associated settings, including for eigenvalue, frequency-domain, and fully transient analyses. Based on your unique simulation needs, the RF Module offers a method to solve your problem.

Numerical methods in the RF Module:

  • FEM
    • Frequency domain
    • Implicit time domain
    • Vector/edge elements of order 1, 2, or 3 that adapt to the curvature of CAD surfaces
  • Discontinuous Galerkin (dG), explicit time domain
  • Transmission line equation, frequency domain
  • Model order reduction (MOR) techniques
    • Asymptotic waveform evaluation (AWE) method
    • Frequency domain modal method

Study types in the RF Module:

  • Eigenfrequency
    • Resonance frequencies and Q-factors of a structure
    • Propagation constants and losses in waveguides
  • Frequency Domain
    • Compute behavior over frequency range
  • Fully Transient
    • Nonlinear materials
    • Signal propagation and return time
    • Very broad-band behavior
    • Time-domain reflectometry (TDR)
A screenshot showing a Wilkinson power divider model that uses the Frequency Domain study type in the RF Module. A Wilkinson power divider's electric field norm is modeled using the Frequency Domain study type. The study settings have been configured for a particular frequency range.

Present simulation results to colleagues, customers, and decision makers in an appealing way, including complex visualizations for S-parameter matrices, far-field radiation patterns, and Smith plots. From eye-catching color scales to straightforward plots of derived values, you can show off results that are both captivating and easy to understand. No matter what your simulation helps you discover, this functionality will get your team on board for the next steps in the development process. This data can also be exported for further postprocessing in other tools.

Did You Know? The finite element method is preferred in many cases over the finite difference method — specifically within multiphysics applications as well as for devices made up of complex geometries.

Postprocessing features in the RF Module:

  • S-parameter matrices
  • Far-field radiation patterns
  • Antenna gain
  • Axial ratio
  • User-defined expression plots
  • Derived variables and user-defined functions and variables
  • Radar cross sections
  • Smith plots
 

Think of the time and energy you would be able to devote to new projects if you did not have to run repetitious simulation tests for other people on your team. With the Application Builder, built into COMSOL Multiphysics®, you can build simulation apps that further simplify the simulation workflow by enabling you to restrict the inputs and control the outputs of your model so that your colleagues can run their own analyses.

With apps, you can easily change a design parameter, such as gain or frequency in an antenna, and test it as many times as you need without having to rerun the entire simulation. You can use apps to run your own tests more quickly or distribute apps to other members of your team to run their own tests, further freeing up your time and resources for other projects.

The process is simple:

  1. Transform your complex RF model into a simple user interface (an app)
  2. Customize the app to your needs by selecting inputs and outputs for the app users
  3. Use the COMSOL Server™ product to catalogue apps and make them accessible to other team members
  4. Enable your team to run their own design analyses without further assistance

You can expand the capabilities of simulation throughout your team, organization, classroom, or customer base by building and using simulation apps.

A custom simulation app for analyzing plasmonic wire grating, built with COMSOL Multiphysics. An example of a simulation app made for analyzing a plasmonic wire grating on a dielectric substrate. The app computes the coefficients of refraction, specular reflection, and first-order diffraction as functions of the angle of incidence.
A custom simulation app for studying a microstrip array patch antenna, built with COMSOL Multiphysics. An example of an app made for simulating microstrip patch antenna arrays. The app visualizes the far-field radiation pattern of the antenna array and its directivity. App users can also evaluate phased antenna array prototypes for 5G mobile networks.

Develop Microwave and Millimeter-Wave Circuits, Antennas, and Metamaterials for the Real World

In order for RF products, devices, and components to safely operate in the real world, the simulated designs need to be viable. You can analyze how multiple physics affect RF designs by using the COMSOL Multiphysics® software and the specialized add-on RF Module.

Most of the RF components, devices, and products you design are affected by some other branch of physics, whether it be heat transfer, plasma, or structural mechanics, to name a few. For the most accurate study possible, you need to be able to simultaneously examine a variety of these effects. You can couple all of the necessary physical effects in the same modeling environment with the RF Module expansion of COMSOL Multiphysics®, thus streamlining your research.

Is there another specific physics area affecting your end-product that you need to investigate? You can mix and match the RF Module with any add-on module or LiveLink™ product from the product suite, all of which seamlessly integrate with the core COMSOL Multiphysics® software platform. This means that your modeling workflow remains the same regardless of the application area or physics you are modeling.

A multiphysics model of a dielectric probe coupling heat transfer and RF physics. A conical dielectric probe used for skin cancer diagnosis is modeled by coupling heat transfer and RF physics. 2D axisymmetry allows for a quick analysis of the circular waveguide at the dominant mode and the probe and its radiation characteristics.
A multiphysics model of a tunable cavity coupling RF physics and MEMS. A tunable evanescent mode cavity filter is modeled by coupling MEMS and RF physics. The model shows how the structural mechanics of a piezoelectric actuator control the resonant frequency inside the cavity filter.

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