RF Module

Software for Microwave and RF Design

RF Module

VEHICLE ANTENNA AND EMI/EMC: This example simulates a printed FM antenna on a car windshield. The 3D far-field radiation pattern is visualized. The upper half of the space is truncated with a perfectly matched layer to model an infinite air space. The electric field intensity on a cable harness is also studied.

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.

View screenshot »

Solver Technology

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).

View screenshot »


Additional images:

  • COSITE INTERFERENCE: Antenna crosstalk, or cosite interference, on a single large platform can be analyzed by S-parameter analysis of different configurations of a receiving antenna installed on an airplane fuselage. This model simulates interference between two identical antennas at a very high frequency (VHF). COSITE INTERFERENCE: Antenna crosstalk, or cosite interference, on a single large platform can be analyzed by S-parameter analysis of different configurations of a receiving antenna installed on an airplane fuselage. This model simulates interference between two identical antennas at a very high frequency (VHF).
  • ANTENNA MEASUREMENT: Pyramidal absorbers with radiation-absorbent material (RAM) are commonly used in anechoic chambers for electromagnetic wave measurements. Here, microwave absorption is modeled using a lossy material to imitate the electromagnetic properties of conductive, carbon-loaded foam. ANTENNA MEASUREMENT: Pyramidal absorbers with radiation-absorbent material (RAM) are commonly used in anechoic chambers for electromagnetic wave measurements. Here, microwave absorption is modeled using a lossy material to imitate the electromagnetic properties of conductive, carbon-loaded foam.
  • BIOMEDICAL ENGINEERING: This model uses a low-power, 35-GHz Ka-band millimeter wave and its reflectivity to moisture for noninvasive cancer diagnosis. It detects abnormalities in terms of S-parameters at the tumor locations. An analysis of the fraction of necrotic tissue is also performed. BIOMEDICAL ENGINEERING: This model uses a low-power, 35-GHz Ka-band millimeter wave and its reflectivity to moisture for noninvasive cancer diagnosis. It detects abnormalities in terms of S-parameters at the tumor locations. An analysis of the fraction of necrotic tissue is also performed.
  • POWER DIVIDER / COUPLER: A Wilkinson power divider is a three-port lossless device that outperforms T-junction and resistive dividers. This simulation includes a 100-Ω resistor modeled via a lumped element feature and computes S-parameters, which show good input matching and a -3 dB evenly split output. POWER DIVIDER / COUPLER: A Wilkinson power divider is a three-port lossless device that outperforms T-junction and resistive dividers. This simulation includes a 100-Ω resistor modeled via a lumped element feature and computes S-parameters, which show good input matching and a -3 dB evenly split output.
  • TUNABLE DEVICE: In this tunable device simulation, resonant frequency is controlled by the capacitance inside of the evanescent mode cavity filter. The capacitance is tunable by a piezoelectric actuator. TUNABLE DEVICE: In this tunable device simulation, resonant frequency is controlled by the capacitance inside of the evanescent mode cavity filter. The capacitance is tunable by a piezoelectric actuator.
  • WIDEBAND ANTENNA: A tapered slot antenna, also known as a Vivaldi antenna, is useful for wide-band applications. The taper profile can be easily configured by an exponential function. This model shows the radiation pattern from the antenna visualized with a fast 3D far-field plot. WIDEBAND ANTENNA: A tapered slot antenna, also known as a Vivaldi antenna, is useful for wide-band applications. The taper profile can be easily configured by an exponential function. This model shows the radiation pattern from the antenna visualized with a fast 3D far-field plot.

Analysis Options for Electromagnetic Simulation

GOVERNING EQUATIONS

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.

FIELD FORMULATIONS

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

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.

SOLUTION TYPES

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.

MULTIPHYSICS COUPLINGS

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.

View screenshot »

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.

View screenshot »

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.

View screenshot »

Scattering of Electromagnetic Waves by Particles

Doubling Beam Intensity Unlocks Rare Opportunities for Discovery at Fermi National Accelerator Laboratory

Nanoresonators Get New Tools for Their Characterization

Developing a New Microreactor for Organic Synthesis Using Microwave Heating

Analysis of Spiral Resonator Filters

Picking the Pattern for a Stealth Antenna

MRI Tumor-Tracked Cancer Treatment

RF Heating

Plasmonic Wire Grating

Absorbed Radiation (SAR) in the Human Brain

Dipole Antenna

Frequency Selective Surface, Periodic Complementary Split Ring Resonator

Corrugated Circular Horn Antenna

Hexagonal Grating (RF)

Circular Waveguide Filter

Circularly Polarized Antenna for GPS Applications

Second Harmonic Generation of a Gaussian Beam