COMSOL Multiphysics^® 6.4 Release Highlights

For users of the RF Module, COMSOL Multiphysics^® version 6.4 introduces simplified transmission line modeling, a new feature for streamlined metamaterial design, and enhanced far-field functionality for optimization and polarization analysis. Learn about these updates and more below.

Improved Transmission Line Modeling

The new Transmission Line, Parameters interface replaces a complex multiphysics setup with simplified configurations. It computes the series resistance, series inductance, shunt conductance, and shunt capacitance per unit length, as well as the characteristic impedance and propagation constant for two-conductor transmission lines. The computation is performed in the frequency domain using 2D modeling and is demonstrated in the Transmission Line Parameters of a Coaxial Cable tutorial model.

Multiconductor configurations are now supported in the Transmission Line interface through multiple dependent variables. Distributed element parameters are defined as square matrices sized according to the number of conductors. In addition, series and shunt element features are now supported, providing improved modeling flexibility.

A coaxial cable modeled using the Transmission Line, Parameters interface. The model extracts the transmission line parameters and computes the electric potential, electric field, and magnetic flux density.

Periodic Structure for Streamlined Metamaterial Modeling

To streamline the modeling of periodic and metamaterial structures, the new Periodic Structure feature, available in the Electromagnetic Waves, Frequency Domain interface, provides default Periodic Port and Floquet Periodic Condition features. The tutorial models Fresnel Equations (RF) and Frequency Selective Surface, Periodic Complementary Split Ring Resonator showcase this new addition.

The Frequency Selective Surface, Complementary Ring Resonator tutorial model has been revamped to use the new Periodic Structure feature.

Enhanced Far-Field Functionality

Far-field functions are now available for optimization, enabling shape optimization studies that enhance antenna gain. The new Optimizing the Front End of a Conical Horn Lens Antenna tutorial model demonstrates this capability. Additionally, new variables, EfarLHCP and EfarRHCP, have been introduced to compute left-handed and right-handed circular polarization components in far-field analyses.

Far-field radiation in the presence of a substrate can also be analyzed using the new Far-Field Domain, Inhomogeneous feature. This new feature supports far-field computation for structures consisting of a superstrate (air) and a homogeneous dielectric substrate, as shown in the Embedded Scatterer on a Substrate tutorial model.

Far-field functions are accessed in the settings of the Shape Optimization study via the Replace Expression button in the Objective Function section.

The animation demonstrates how the optimization process modifies the original lens geometry to achieve a gain-enhanced version.

New Variables for Calculation of Coupling Between Different Source and Destination Boundaries

To simplify the analysis of, for instance, coupling between guided waves and free-space waves (and vice versa), new variables for outcoupling efficiency (i.e., the ratio between the integrated output power and the input power) have been defined. The variables are accumulated hierarchically, making it easy to analyze coupling to both small and large features and boundaries. Similarly, there is a hierarchy of variables to account for the integrated loss due to absorption. Variables for both the power loss and the loss normalized to the input power are available. This functionality is primarily demonstrated in the Modeling a Scatterer Near an Optical Waveguide model but can also be seen in the following tutorial models:

• grating_coupler (new)
• sesam_laser_heating (new)
• mach_zehnder_modulator
• optical_ring_resonator

A waveguide with a scatterer (shown as a pillar). The light scattered backward, forward, and to the sides is accounted for by the new outcoupling variables.

Updated Polarization Plot and Results Improvements

In the Polarization plot, there is a new option for normalizing the polarization ellipses to the largest diffraction efficiency. As a result, the size of the ellipse represents the diffraction efficiency. Furthermore, there are new plot options that indicate the area for propagating diffraction orders. The updated Polarization plot is shown in the Hexagonal Grating (Wave Optics) and Hexagonal Plasmonic Color Filter tutorial models.

The Cross Section Calculation feature now provides multiple options for modeling the scattering, absorption, and extinction cross sections: a default plot or global evaluation, which are demonstrated in the Optical Scattering off a Gold Nanosphere model and the Scatterer on Substrate tutorial models, respectively.

Global Evaluation nodes, such as reflectances, transmittances, and diffraction efficiencies, have been wrapped in Evaluation Group nodes, enabling automatic updates of the table data after repeated simulations. This functionality is demonstrated in the Waveguide S-Bend tutorial model, where reflectance, transmittance, and loss are evaluated.

The Polarization plot for the Hexagonal Grating (Wave Optics) tutorial model, showing the polarization ellipses normalized to the largest diffraction efficiency and the curve encircling the area for propagating diffraction orders.

New Tutorial Models

COMSOL Multiphysics^® version 6.4 brings several new tutorial models to the RF Module.

Optimizing the Front End of a Conical Horn Lens Antenna

A parameterized lens geometry is optimized into a more effective lens shape, improving realized gain. Shape optimization removes the need for explicit parameterization and achieves comparable or better performance in a fraction of the time required for multiple parametric sweeps.

Application Library Title:
conical_horn_lens_antenna_shape_optimization
Download from the Application Gallery

Microstrip Patch Antenna Surrogate Model

This example model trains a deep neural network (DNN) surrogate model to rapidly evaluate the performance of a microstrip patch antenna as a function of four design parameters: patch length, tuning stub length, substrate dielectric constant, and frequency. The surrogate model enables fast performance estimation without requiring full electromagnetic simulations. Asymptotic waveform evaluation of computed S-parameters is also used for efficient frequency-response analysis.

Application Library Title:
microstrip_patch_antenna_surrogate
Download from the Application Gallery

Embedded Scatterer on a Substrate

A plane transverse-electric (TE) polarized electromagnetic wave is incident on a metallic sphere embedded in a substrate. Far-field variables are computed for several elevation angles of incidence.

Application Library Title:
embedded_scatterer_on_substrate
Download from the Application Gallery

MRI Implant Heating

This tutorial model shows RF-induced heating of a passive conductive polyaxial screw implant inserted into the C3–C5 vertebrae and surrounded by a jelly phantom that mimics human tissue. The phantom geometry and material properties follow the ASTM F2182-19e2 standard.

Application Library Title:
mri_implant_heating
Download from the Application Gallery

Efficient Modeling of a Spherical Radome

This model demonstrates an efficient approach for simulating a thin, spherical radome using a 2D axisymmetric formulation with cubic discretization. Using higher-order elements on a coarse mesh reduces computational cost while maintaining accuracy.

Application Library Title:
radome_spherical
Download from the Application Gallery