RF Module Updates

For users of the RF Module, COMSOL Multiphysics® version 5.6 introduces a new physics interface analyzing radar cross sections (RCS) asymptotically, a study step that runs a port sweep faster, and new tutorial models addressing thermostructural effects in a 5G device, phased antenna arrays, and virtual EMI/EMC tests. Learn more about the news below.

Quickly Analyze the RCS of a Conductive Convex-Shaped Object

When the shape of a scattering object is convex, such as a sphere, you can use the new Electromagnetic Waves, Asymptotic Scattering interface to run quick studies of the far-field response of a 3D or 2D object to a given background field. The asymptotic scattering method will also give fast approximate answers for more general classes of objects. The physics interface sets up a surface electric background field for the far-field transformation, using the Stratton–Chu formula, performed in postprocessing. You can see this new interface used in the Fast Asymptotic RCS Analysis of a Conductive Sphere model.

A sphere with stripes in the heat camera color table with a partially transparent RCS pattern around it. Example of analyzing RCS The background field incident on the surface of a PEC sphere is plotted with the 3D RCS pattern that is partially transparent.

Solving for Fast Port Sweep

Use the new study step, Frequency Domain Source Sweep, to run a frequency domain study that is sweeping among ports and lumped ports calculating a full S-parameter matrix. The settings for this study step are similar to those for the Frequency Domain study step, and much simpler than the traditional port sweep, which requires a parametric sweep step. You can see this new feature in the H-Bend Waveguide 2D model.

Port Enhancement

The transverse electromagnetic (TEM) port type supporting the user-defined electric potential and ground boundaries is now available in 2D and 2D axisymmetric models. Also, numeric TEM impedance calculation is possible without defining the magnetic field integration line for the current. The port impedance is computed using the average power flow on the port boundary, and the voltage is calculated by the electric field line integration. Lastly, lumped port excitation can now be configured by input power.

Enhanced Usability of Eigenfrequency Study

The eigenfrequency study has been updated to reduce the number of modeling steps and enhance usability. After the eigenfrequency simulation, the eigenfrequencies and Q-factors are automatically evaluated and presented in a table.

Additional Parts from Signal Microwave

Four new edge-launch connectors are added in the RF part library, provided by Signal Microwave.

Four different connector geometry parts for RF modeling. Edge-launch connector parts Edge launch connector ELF110-001, ELF110-002, ELFT40-001, and ELFT40-002.

Polarization Plot Type

The Polarization plot type depicts the polarization state for the different diffraction orders seen in a periodic structure, such as a frequency-selective surface or metamaterial. It is used for default plots when periodic ports are included in the simulation, and can be added manually when postprocessing. You can see this new plot type used in the Hexagonal Grating (Wave Optics) model.

Polarization states plotted for three diffraction orders where the phases are shown in rainbow radians. Polarization plot example Polarization states for three diffraction orders in the Hexagonal Grating model.

Oblique Angle of Incidence for Scattering Boundary Condition in Mode Analysis

For mode analysis, the Scattering boundary condition can now use an oblique angle of incidence. That is, it can efficiently absorb waves with a wave vector composed of the mode's propagation constant directed tangentially to the boundary and a remaining normal component. This improves loss calculation in mode analyses for lossy waveguides. You can see this new feature in the Leaky Modes in a Microstructured Optical Fiber model.

Four 2D models of a microstructured optical fiber, visualizing different patterns in a rainbow color table for tangential electric field, tangential magnetic field, longitudinal electric field, and longitudinal magnetic field. Microstructured optical fiber model This graph shows the norm of the tangential and longitudinal electric and magnetic fields for one of the two degenerate HE11-like modes in a microstructured optical fiber.

Input Power to Control Gaussian Beam Amplitude

For Gaussian beam background fields and input fields to the Scattering and Matched boundary conditions, the amplitude of the beam can be specified by providing the input power. You can view this in the Self-Focusing model.

The electric field of a Gaussian beam modeled in a rainbow color table. Gaussian beam amplitude example The normalized electric field for a Gaussian beam propagation through a medium with an intensity-dependent refractive index. The higher intensity, the larger the refractive index becomes, and the tighter the beam is focused.

Reference Point Defined by a General Expression

The Reference Point subfeature to the Scattering and Matched boundary conditions can now be specified from a general vector expression. This makes it simpler to parameterize the propagation direction of input Gaussian beams for these boundary conditions.

A circle with a red, white, and blue striped pattern visualizing a Gaussian beam. Gaussian beam
A Gaussian beam propagating in an arbitrary direction toward the focal plane at the center of the circle.

Synchronization of Material Parameters Between Related Material Property Groups

The relative permittivity, refractive index, loss tangent, and dielectric loss material properties can synchronize the material parameters between groups. Thus, if a material is added and specified by the refractive index material property group, the Electric Displacement Field setting in the Wave Equation, Electric node can be any of the mentioned material models. If the required parameters are not directly available in the material, the parameters are created using a synchronization rule.

A closeup view of the COMSOL Multiphysics version 5.6 UI with the material settings shown for RO4003C laminates. Material settings The RO4003C™ Laminates material is specified by the provided real part of the relative permittivity, epsilonPrim, and the frequency interpolation function for the dissipation factor, tanDelta. In this example, the Wave Equation, Electric feature requests the complex relative permittivity as the material parameter. Thus, that parameter is synchronized from the two available material parameters, as seen in the last row in the Material Contents table.

Wide Support for Eigenfrequency Analysis

The Eigenfrequency study is now supported for most of the AC/DC Module interfaces: Electric Currents, Electric Currents in Shells, Electric Currents in Layered Shells, Electrical Circuit, Electrostatics, and Magnetic Fields. In addition to supporting full-wave cavity mode analysis in the Magnetic Fields interface, it is possible to run eigenfrequency analyses with models involving electrical circuits. The eigenfrequency support is primarily developed for the AC/DC Module, but other modules that provide one of the affected physics interfaces will benefit from it too.

The COMSOL Multiphysics version 5.6 UI showing the Model Builder, Global Evaluation settings with the Data and Expressions sections expanded, and a probe plot for the eigenfrequency analysis of an RLC circuit. Eigenfrequency analysis example The resonance peak of a simple RLC circuit. The eigenfrequency and Q-factor are analyzed and compared to analytically determined values.

New and Enhanced Functionality for the Electrical Circuit Interface

For Time Dependent studies, the Electrical Circuit interface has been equipped with an "event-based" Switch feature. This allows you to model the "instantaneous" on-off switching of certain connections in the circuit. The switch can be current controlled, voltage controlled, or controlled by user-defined Boolean expressions.

Furthermore, Parameterized Subcircuit Definitions are added. Together with the Subcircuit Instance, these allow you to create your own building blocks containing smaller circuits, and use multiple parameterized variants of those in your larger circuit. Finally, the state, event, and solver machinery has been improved, especially the transient modeling of nonlinear (semiconductor) devices, which has become more robust.

The circuit improvements are primarily developed for the AC/DC Module, but other modules that provide access to the Electrical Circuit interface will benefit too. You can view the new functionality in these updated models:

New Curl Shape Function

The Nédélec finite element of the second kind is now available. This element type, or shape function, has full polynomial orders in all directions for each field component. This can give a solution to certain finite element problems for lower shape orders, or with coarser meshes, and it can also make the resulting fields look smoother in postprocessing. You can see this new functionality in the Orbital Angular Momentum Beam model.

A rainbow phase plot of an orbital angular momentum beam. Demonstrating the new curl shape function An orbital angular momentum beam. The use of the new curl shape function makes the phase plot look smoother.

Updated Tutorial Models Showing Useful Postprocessing Functionality

Several tutorial models in the RF Module Application Libraries have been updated to introduce useful postprocessing features.

Item Functionality Model
Compute beam width Half power beam width calculation in a radiation pattern plot dipole_antenna
Transparency subfeature Partial transparency separately applied on each plot dipole_antenna
Graph Marker subfeature Maximum and minimum point cylinder_orientation
Touchstone export Touchstone export using the saved solution coupled_line_filter
Two y-axes Multiple plots with two y-axes scaled separately branch_line_coupler

New Tutorial Models

COMSOL Multiphysics® version 5.6 brings several new tutorial models to the RF Module.

Thermostructural Effect of a Cavity Filter

A partially transparent model of a cavity filter for 5G applications visualizing structural changes due to heating. Cavity filter model Multiphysics analysis of a cascaded cavity filter operating in the millimeter-wave 5G band with temperature-induced structural changes. The electric field z-component on the cavity walls as well as the arrow plot of the electric field are shown. The cavity body is finished by partially transparent colors.

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Basic Emission and Immunity Analysis of a Circuit Board

A circuit board model shown in a partially transparent box. Circuit board model Mockup circuit board with an ABS enclosure finished by incomplete conductive walls. Some of the conductive walls are not included to show the interior clearly. The surrounding air domain is not shown in this figure.

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Fast Asymptotic Radar Cross-Section Analysis of a Conductive Sphere

A sphere with stripes in the heat camera color table, RCS, and background electric field. RCS analysis model The z-component of the background electric field and dB-scaled bistatic radar cross section are visualized.

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Modeling of a Phased Array Antenna

A model of a phased array antenna with the electric field norm and far-field radiation pattern shown in a rainbow color table. Phased array antenna model The electric field norm and dB-scaled far-field radiation pattern are plotted when the arithmetic phase progression is set to have the maximum radiation toward 30 degrees tilted from the normal axis.

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