Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.
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.
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).
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 radiation pattern.
The shape of a log-periodic antenna resembles that of a Yagi-Uda antenna, but is composed of a coplanar array to achieve a wider bandwidth. It is also known as a wideband or frequency-independent antenna.
All metallic parts are modeled using the perfect electric conductor (PEC) boundary conditions. The antenna is excited by a lumped port while a lumped element with a resistor is used to terminate the excitation.
Results show the impedance matching properties on a Smith plot as well as a far-field polar plot, which shows that the directionality of the radiation pattern varies slightly as frequency increases. A 3D far-field radiation pattern shows the same tendency. Also presented is the voltage-standing-wave-ratio (VSWR) of the antenna.
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 causes.
The increasing use of wireless equipment has also increased the amount of radiation energy to which human bodies are exposed. A common property that measures absorbed energy is the SAR value, (specific absorption rate) to determine the amount of radiation that human tissue absorbs.
The human head geometry is the same geometry (SAM Phantom) provided by IEEE, IEC and CENELEC from their standard specification of SAR value measurements. The original geometry was imported into COMSOL Multiphysics. In addition, the model samples some material parameters with a volumetric interpolation function that estimates the variation of tissue type inside the head.
This model studies how a human head absorbs a radiated wave from an antenna, and the temperature increase that this causes. This model requires the RF Module and the Heat Transfer Module.
Surface plasmon-based circuits are being used in applications such as plasmonic chips, light generation, and nanolithography. The Plasmonic Wire Grating Analyzer application computes the coefficients of refraction, specular reflection, and first-order diffraction as functions of the angle of incidence for a plasmonic wire grating on a dielectric substrate.
The model describes a unit cell of the grating, where Floquet boundary conditions define the periodicity. Postprocessing functionality allows you to expand the number of unit cells and extract the visualization into the third dimension.
Built into the app is the ability to sweep the incident angle of a plane wave from the normal angle to the grazing angle on the grating structure. The app also allows you to vary the radius of a wire as well as the periodicity or size of the unit cell. Further parameters that can be varied are the wavelength and orientation of the polarization.
The application presents results for the electric field norm for multiple grating periodicity for selected angles of incidence, the incident wave vector and wave vectors for all reflected and transmitted modes, and the reflectance and transmittance.
A large reflector can be modeled easily with the 2D axisymmetric formulation. In this model, the radius of the reflector is greater than 20 wavelengths and the reflector is illuminated by an axial feed circular horn antenna. The simulated far-field shows a high-gain sharp beam pattern.
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.
A signal integrity (SI) analysis gives an overview of the quality of an electrical signal transmitted through electrical circuits, such as high-speed interconnects, cables, and printed circuit boards. The quality of the received signal can be distorted by noise from outside the circuit, and can be degraded by impedance mismatch, insertion loss, and crosstalk. For this reason, EMC/EMI analyses are run to estimate the susceptibility of a device or a network to an undesired coupling.
In this tutorial model, we examine the crosstalk effect between two adjacent microstrip lines on a microwave substrate with a constant dielectric constant. Two pulses are applied to the device where a parametric sweep switches the frequency of the pulse during the simulation.
The simulation presents the time-domain reflectometry (TDR) response at the coupled ports, which shows increased distortion of the signals at higher frequency or data rates.
SMA connectors are popularly used on printed circuit boards (PCB) for testing. This model shows how to excite an SMA connector on a microwave substrate and how to terminate a grounded coplanar waveguide (GCPW) with 50 ohm using a lumped port and an air-bridge.
Microstrip patch antenna arrays are used in a number of industries as transceivers of radar and RF signals. This is a prime candidate for the 5G mobile network system.
The Slot-Coupled Microstrip Patch Antenna Array Synthesizer simulates a single slot-coupled microstrip patch antenna, fabricated on a multilayered low-temperature cofired ceramic (LTCC) substrate. When using this app, you will be able to simulate the far-field radiation pattern of the antenna array and its directivity. The far-field radiation pattern is approximated by multiplying the array factor and the single antenna radiation pattern to perform an efficient far-field analysis without simulating a complicated full-array model. You can also evaluate phased antenna array prototypes for 5G mobile networks with the default input frequency, 30 GHz.
You can do this by varying antenna properties such as the geometric dimension and substrate material.
An added feature of this app is the option to view it on either a narrow or a wide screen.
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.
