Software for Microwave and RF Design
Predicting Microwave and RF Designs Virtually
The RF Module is used by designers of RF and microwave devices to design antennas, waveguides, filters, circuits, cavities, and metamaterials. By quickly and accurately simulating electromagnetic wave propagation and resonant behavior, engineers are able to compute electromagnetic field distributions, transmission, reflection, impedance, Q-factors, S-parameters, and power dissipation. Simulation offers you the benefits of lower cost combined with the ability to evaluate and predict physical effects that are not directly measurable in experiments.
Compared to traditional electromagnetic modeling, you can also extend your model to include effects such as temperature rise, structural deformations, and fluid flow. Multiple physical effects can be coupled together and consequently affect all included physics during the simulation of an electromagnetic device.
Under the hood, the RF Module is based on the finite element method. Maxwell's equations are solved using the finite element method with numerically stable edge elements, also known as vector elements, in combination with state-of-the-art algorithms for preconditioning and iterative solutions of the resulting sparse equation systems. Both the iterative and direct solvers run in parallel on multicore computers. Cluster computing can be utilized by running frequency sweeps, which are distributed per frequency on multiple computers within a cluster for very fast computations or by solving large models with a direct solver using distributed memory (MPI).
- ANTENNA MODELING: A two-arm helical antenna example tutorial from the Model Library of the RF Module
- ELECTROMAGNETIC FIELD SIMULATION: The distributed heat source is computed in a stationary, frequency-domain electromagnetic analysis. This is followed by a transient heat transfer simulation showing how the heat redistributes in the foodstuff within the microwave oven.
- ELECTROMAGNETIC WAVES: Oblique TM wave incident on a gold wire grating. The unit cells of the periodic structure are shown as wires.
- MICROSTRIP ANTENNA DESIGN: The radiation pattern from a microstrip patch antenna is visualized with the fast far-field plots for 3D, 2D, and 3D cut planes.
Analysis Options for Electromagnetic Simulation
The RF Module simulates electromagnetic fields in 3D, 2D, and 2D axisymmetric, as well as transmission line equations in 1D, and circuit (non-dimensional) modeling with SPICE netlists. The 3D formulation is based on the full-wave form of Maxwell's equations using vector edge elements, and includes material property relationships for modeling dielectric, metallic, dispersive, lossy, anisotropic, gyrotropic, and mixed media. The 2D formulations can solve for both in-plane and out-of-plane polarizations simultaneously or separately, as well as for out-of-plane propagation. The 2D axisymmetric formulations can solve for both azimuthal and in-plane fields simultaneously or separately, and can solve for a known azimuthal mode number.
Both total-wave and background-wave formulations are available. The full-wave formulation solves for the total fields due to all included sources in the model, while the background-wave formulation assumes a known background field from an external source – a common approach for radar cross section and electromagnetic scattering models.
Boundary conditions are available for modeling perfect electrically conducting surfaces, surfaces of finite conductivity, and faces that can represent thin lossy boundaries within the model. Symmetry and periodic boundary conditions allow you to model a subset of your entire model space, and scattering boundary conditions and perfectly matched layers (PMLs) are used to model boundaries to free space. Various different excitation boundary conditions exist for modeling ports: rectangular, circular, periodic, coaxial, approximate lumped, user-defined, and precise numerically computed port excitations are available. You can include boundary conditions representing cable terminations as well as lumped capacitive, inductive, and resistive elements. Line currents and point dipoles are also available for quick prototyping.
Simulations can be set up as eigenvalue problems, frequency domain problems, or fully transient solutions. Eigenvalue problems can find the resonances and Q-factors of a structure, as well as the propagation constants and losses in waveguides. Frequency domain problems can compute the electromagnetic fields at a single frequency, or over a range of frequencies. Fast frequency sweeps, using the method of Padé approximants, can dramatically improve solution times when computing the behavior over a frequency range. Transient simulations are available for both the second order full-wave vectorial formulation as well the more memory-efficient first order discontinuous Galerkin formulation. Transient simulations are used for modeling of nonlinear materials, signal propagation and return time, as well as for modeling of very broad-band behavior.
The equations in all models developed in COMSOL Multiphysics can be completely coupled such that the electromagnetic fields can both affect and be affected by any other physics. In particular, a dedicated user interface for microwave heating expands simulation capabilities beyond traditional power deposition analysis, with features such as SAR calculations and precise temperature rise predictions. By solving for Maxwell's equations in the frequency-domain, and the heat transfer equation in the stationary or time-domain, it is possible to compute the rise in temperature over time, and compute the effects of varying material properties with temperature.
Extendable Results from Microwave and RF Simulations
The results of computations are presented using predefined plots of electric and magnetic fields, S-parameters, power flow, and losses. A fast postprocessing tool allows for quick generation of far-field radiation patterns. You can also display your results as plots of expressions that represent physical quantities you define freely, or as tabulated derived values obtained from the simulation. S-parameter matrices can be exported to the Touchstone format, and all data can be exported as tables, text files, raw data, and images.
The workflow is straightforward and can be described by the following steps: define the geometry by creating it using the COMSOL native tools or import a CAD model, select materials, select a suitable user interface and analysis type, define ports and boundary conditions, automatically create the finite element mesh, solve with optional mesh adaptation, visualize, and postprocess the results. All steps are executed from the COMSOL Desktop®. The solver selection step automatically uses default settings that are tuned for each specific RF interface but can also be user-configured.
Many Example Models for RF and Microwave Design
The RF Module Model Library describes the interfaces and their distinct features through tutorial and benchmark examples. The library includes models addressing antennas, ferrite devices, microwave heating phenomena, passive devices, scattering and radar cross-section (RCS) analysis, transmission lines and waveguides in RF and microwave engineering, tutorial models for education, and benchmark models for verification and validation of the RF interfaces.
Picking the Pattern for a Stealth Antenna
F. De Vita, S. Di Marco, F. Costa and P. Turchi Altran, Italy
Stealth airplanes and ships avoid radar detection by optimizing the shape of surfaces to reflect away from the radar source or absorb its energy. Yet, if a ship or aircraft’s antenna for communication purposes is to operate properly, it cannot be completely covered up. This makes it one of the remaining components with a large radar cross section ...
Developing a New Microreactor for Organic Synthesis Using Microwave Heating
W. Lee, K. Jensen MIT, MA, USA
The chemical reactions used to generate solvents and certain pharmaceuticals rely on organic synthesis, a process of combining individual chemicals that can be accelerated through microwave heating. A microreactor system facilitates the direct, localized, and efficient temperature change necessary for successful synthesis. However, a uniform ...
Doubling Beam Intensity Unlocks Rare Opportunities for Discovery at Fermi National Accelerator Laboratory
M. A. Hassan, T. Khabiboulline, J. Reid Fermilab, IL, USA
Behind the discovery of the most fundamental and rare physical processes within our universe is powerful technology, such as the particle accelerators in use today at Fermilab. For over 40 years, one particle accelerator in particular, the Booster synchrotron, has been instrumental in providing high-intensity proton beams for particle physics ...
Nanoresonators Get New Tools for Their Characterization
J. Yang, M. Perrin, P. Lalanne CNRS, France
Nanoresonators, or optical nanoantennas, manage the concentration, radiation, and absorption of light at the nanometer scale and show stunning promise for future improvements to technology, such as sensors, computers, and other electronics. However, the ways that these devices scatter light and interact with their surrounding environment are not ...
Scattering of Electromagnetic Waves by Particles
S. Yushanov, J. Crompton, and K. C. Koppenhoefer, Altasim Technologies, OH, USA
When electromagnetic waves propagate through matter, they interact with inhomogeneities and particles that can locally disrupt the electron distribution, causing electromagnetic radiation and scattering. One mathematical model used to describe the scattering of electromagnetic waves is called Mie scattering, which provides a general solution ...
Analysis of Spiral Resonator Filters
S.P. Yushanov, J.S. Crompton, and K.C. Koppenhoeffer AltaSim Technologies
As the world becomes more digital, there is growing demand for advanced wireless systems. Increasingly high data rate transmission systems mean that components like microwave filters must fit into smaller and smaller spaces, and multiple filters need to be integrated into compact designs. Engineers are challenged to meet a filter's specific ...
MRI Tumor-Tracked Cancer Treatment
Gino Fallone and colleagues Cross Cancer Institute Edmonton, AB, Canada
Radiation therapy targeting in cancer treatment involves many uncertainties, including the movement of targeted sites due to breathing and the like. Magnetic resonance imaging (MRI) can accurately identify the location of a tumor in soft tissue, but unfortunately its magnetic field can interfere with radiation treatment delivered by a linear ...
Absorbed Radiation (SAR) in the Human Brain
Scientists use the SAR (specific absorption rate) to determine the amount of radiation that human tissue absorbs. This measurement is especially important for mobile telephones, which radiate close to the brain. The model studies how a human head absorbs a radiated wave from an antenna and the temperature increase that the absorbed radiation ...
This is a model of an RF waveguide bend with a dielectric block inside. There are electromagnetic losses in the block as well as on the waveguide walls which cause the assembly to heat up over time. The material properties of the block are functions of temperature. The transient thermal behavior, as well as the steady-state solution, are computed.
Plasmonic Wire Grating
A plane wave is incident on a wire grating on a dielectric substrate. Coefficients for refraction, specular reflection, and first order diffraction are all computed as functions of the angle of incidence. The model is set up for one unit cell of the grating, flanked by Floquet boundary conditions describing the periodicity. As applied, this ...
Corrugated Circular Horn Antenna
The excited TE mode from a circular waveguide passes through the corrugated inner surface of a circular horn antenna where TM mode is also generated. When combined, these two modes give lower cross-polarization at the antenna aperture than the excited TE mode. This example is designed using a 2D axisymmetric model.
The dipole antenna is one of the most straightforward antenna configurations. It can be realized with two thin metallic rods that have a sinusoidal voltage difference applied between them. The length of the rods is chosen such that they are quarter wavelength elements at the operating frequency. Such an antenna has a well known torus-like ...
Frequency Selective Surface, Periodic Complementary Split Ring Resonator
Frequency selective surfaces (FSS) are periodic structures with a bandpass or a bandstop frequency response. This model shows that only signals around the center frequency can pass through the periodic complimentary split ring resonator layer.
Circular Waveguide Filter
A circular waveguide filter is designed using a 2D axisymmetric model. Six annular rings added to the waveguide form circular cavities connected in series, and each cavity cutoff frequency is close to the center frequency of the filter. The simulated S-parameters show a bandpass frequency response.
Circularly Polarized Antenna for GPS Applications
One way to generate circular polarization from a microstrip patch antenna is to truncate the patch radiator. This model is tuned around the GPS frequency range. The axial ratios are calculated to show the degree of circular polarization.
Substrate Integrated Waveguide Leaky Wave Antenna
Substrate Integrated Waveguides (SIW) can be used in antenna applications. Leaky waves from a slot array on the top surface of the SIW in this model generate a beam in a certain direction that can be steered by choosing a different operating frequency.
Plasmonic Wire Grating
This application computes coefficients of refraction, specular reflection, and first order diffraction as functions of the angle of incidence for a wire grating on a dielectric substrate. The incident angle of a plane wave is swept from the normal angle to the grazing angle on the grating structure. The application also shows the electric field ...