 | A 180° Ring Hybrid (Rat-Race Coupler) is a four-port network with 180° phase difference between two ports. It is cheaper to manufacture this type of microstrip line component compared to a wave guide 180° hybrid junction, so called... |
 | Electromagnetic heating is ideally suited for modeling in COMSOL Multiphysics. This model shows the area of hyperthermic oncology but the modeling issues and techniques are generally applicable to any problem involving electromagnetic... |
 | A model built with the RF Module can be connected to an electrical circuit equivalent, if there is some structure outside of the model space that you wish to approximate as a circuit equivalent. In this model, the 3D model of a coaxial... |
 | This is a model of a waveguide, a device used to conduct electromagnetic waves in the microwave range. The purpose is to calculate how well a TE10 wave propagates through a bend in a waveguide filled with a dielectric medium.
This is... |
 | Feeding a waveguide from a coaxial cable is a straightforward way to achieve electromagnetic waves inside a waveguide. Due to its small size and circular shape, the cable contributes significantly to the overall size of the problem. It is... |
 | Conical antennas are useful for many applications due to their broadband characteristics and relative simplicity.
In this example, we study the antenna impedance and radiation pattern as functions of frequency for a monoconical... |
 | In its simplest form, a magnetic dipole consists of a current carrying coil. Three such coils coupled together in an AC power circuit, constitute a radiating system. By changing the phases of the coils, you can alter the transmission... |
 | This is a model of an adapter for microwave propagation in the transition between a rectangular and an elliptical waveguide. Such waveguide adapters are designed to keep energy losses due to reflections at a minimum for the operating... |
 | Photonic crystal devices are periodic structures of alternating layers of materials with different refractive indices. Waveguides that are confined inside of a photonic crystal can have very sharp low-loss bends, which may enable an... |
 | The transmission speed of optical waveguides is superior to microwave waveguides, because optical devices have a much higher operating frequency than microwaves, enabling a far higher bandwidth.
This model is an example of a single... |
 | 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... |
 | Microwave filters are used to eliminate unwanted frequency components in the output from microwave transmitters. They are typically inserted between a power amplifier and an antenna. The amplifiers are nonlinear and produce harmonics that... |
 | Patch antennas are becoming more common in wireless equipment, like wireless LAN access points, cellular phones, and GPS handheld devices. The antennas are small in size and can be manufactured with simple and cost-effective techniques.... |
 | Laser systems are an important application area in modern electronics. There are several ways to generate a laser beam, but they all have one thing in common: the wavelength is determined by the stimulated emission, which depends on... |
 | Laser systems are an important application area in modern electronics. With nonlinear materials it is possible to generate harmonics that are a multiple of the frequency of the laser light.
This model shows how a second harmonic... |
 | A microwave circulator is a multiport device in which a wave incident on Port 1 is coupled only into Port 2; a wave incident on Port 2 is coupled only into Port 3; and so on. Circulators are used to isolate microwave components, for... |
 | In mode analysis it is usually the primary goal to find a propagation constant. This quantity is often, but not always, real valued; if the analysis involves some lossy part, such as a nonzero conductivity or an open boundary, the... |
 | Feeding antennas with proper signals can be difficult. The signal is often described as a voltage, and voltages are not well defined in electromagnetic wave formulations.
There are several tricks to model voltage generators in such... |
 | These examples show how to model a rectangular waveguide for microwaves in 2D and 3D. A single hollow waveguide can conduct two kinds of electromagnetic waves: transversal magnetic (TM) or transversal electric (TE) waves.
The models... |
 | This is a model of the heating process in a microwave oven. The distributed heat source is computed in a stationary, frequency domain electromagnetic analysis followed. This is followed by a transient heat transfer simulation showing how... |
 | A waveguide-type structure can be fabricated on a substrate by adding vias between the microstrip line and the ground plane. Such a device will behave as a high-pass filter and is attractive because it is easy to fabricate. A model is set... |
 | A Branch Line Coupler (Quadrature 90° Hybrid) is a four-port network device with a 90° phase difference between two coupled ports. The device can be used for a single antenna Transmitter/Receiver system or an I/Q signal... |
 | The microstrip patch antenna is used in a wide range of applications since it is easy to design and fabricate. The antenna is attractive due to its low-profile conformal design, relatively low cost and very narrow bandwidth.
It is... |
 | 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... |
 | A voltage generator feeds a microstrip on a circuit board using an interior lumped port boundary condition.
The model calculates the microstrip impedance and compares two terminations; a numerical port using boundary-mode analysis, and... |
 | A plane TE-polarized electromagnetic wave is incident on a gold nanoparticle on a dielectric substrate. The absorption and scattering cross sections of the particle are computed for a few different polar and azimuthal angles of... |
 | This is an example of a Fabry-Perot cavity, the simplest optical resonator structure. It is a classical problem in optics and photonics. Two methods are shown for computing the Q-factor. The losses in this model are purely via radiation... |
 | An evanescent mode cavity filter can be realized by adding a structure inside of the cavity. This structure changes the resonant frequency lower than the dominant mode of the unfilled cavity. A piezo actuator is used to control the size... |
 | A bird-cage coil is used in Magnetic Resonance Imaging (MRI) applications as a receiving antenna.
This particular coil would sit around limbs and be used to scan a leg or arm.
The COMSOL Multiphysics with RF Module model... |
 | Microstrip filters can be fabricated directly on a printed circuit board (PCB) with a microstrip line going from the input to the output. Along the microstrip line there are a number of stubs of certain lengths and widths. The design of... |
 | The impedance of an antenna is an important parameter that determines how it behaves in transmitter circuits. Impedance matching and low reactive components are important to get reliable operation, which can be achieved either by proper... |
 | The optimization of components with respect to geometrical design parameters is a common task in microwave engineering. In this model the reflection coefficient of a waveguide structure is minimized, and the sensitivities of the real and... |
 | A dielectric resonator placed near a radiating element can be used to increase directivity and gain. Here, a block of quartz dielectric, with additional passive metallic antenna elements, is placed above a slot antenna.
The fields in... |
 | An Electromagnetic Band Gap (EBG) structure can be used to increase the isolation between antennas close to each other. The decoupling effect is not only a function of frequency but also polarization and coupling-plane... |
 | This model demonstrates the calculation of the scattering of a plane wave of light off of a gold nanosphere. The scattering is computed for the optical frequency range, over which gold can be modeled as a material with negative... |
 | A conductive diaphragm, an iris, placed transverse to a waveguide aperture causes a discontinuity and generates shunt reactance. Bandpass frequency response can be achieved from cascaded cavity resonators combined with these reactive... |
 | A Biconical antenna is a type of wideband antenna with omni-directional radiation pattern in the H-plane similar to a dipole antenna. A coaxial feed is connected to the radiators using two 90 degree bent arms.
The model shows that the... |
 | A tapered slot antenna, also known as a Vivaldi antenna, is useful for wide band applications. Here, an exponential function is used for the taper profile. The objective of this model is to compute the far-field pattern and to compute the... |
 | Coplanar waveguide (CPW) bandpass filters can be realized using interdigital capacitors (IDCs) and short-circuited stub inductors (SSIs). Such a filter can readily be implemented on a GaAs wafer.
This presented model is very compact in... |
 | Some conventional three-port power dividers are resistive power dividers and T-junction power dividers. Such dividers are either lossy or not matched to the system reference impedance at all ports. In addition, isolation between two... |
 | RF coils are important in numerous applications ranging from wireless technology to MRI scanning equipment. This introductory tutorial model demonstrates how to find the fundamental resonance frequency of an RF coil as well as how to... |
 | The transmission of a TE10 wave through a 90 degree bend in a waveguide is modeled. |
 | The marine controlled source electromagnetics method (CSEM) for oil prospecting has emerged as a promising technique during recent years. This model demonstrates
one variant of it. It uses a mobile horizontal 1 Hz electric dipole antenna... |
 | This model describes how to define periodic boundary conditions in the 3D Electromagnetic Waves physics interface. It calculates a tilted plane wave incident into a cube using a periodic boundary condition with Floquet periodicity. |
 | This tutorial model demonstrates the use of a background field in an electromagnetic scattering problem. Although this example is a boat hit by a radar, this same technique can be used in any situation where an isolated object meets... |
 | 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... |
 | A classic benchmark example in computational electromagnetics is to find the resonant frequency and Q-factor of a cavity with lossy walls. Here, models of rectangular, cylindrical, and spherical cavities are shown to be in agreement with... |
 | 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... |
 | A lossy ferrite circulator at 3GHz is modeled. Geometrical design parameters are varied to match the impedance for minimal reflection of the fundamental TE10 rectangular waveguide mode. |
 | A classic benchmark problem in computational electromagnetics is to solve for the radar cross section (RCS) of a sphere in free space illuminated by a plane wave. This model solves for the RCS of a metallic sphere that has a very high... |
 | It is possible to realize a narrowband bandpass filter using cascaded microstrip coupled lines. In this example, a design composed of cascaded microstrip lines, each approximately a half wave length in size at the resonant frequency, is... |
 | An evanescent-mode cavity filter is resonant at a frequency lower than its original fundamental mode frequency. Evanescent mode resonance can be realized by creating a discontinuity or reactance inside the cavity.
The basic model was... |
 | A cascaded cavity filter provides much better bandpass filter performance compared to a single cavity. Out-of-band rejection improves dramatically using a cascaded design.
This model uses three rectangular cavity filters coupled via... |
 | An antenna array is a group of radiating elements. By controlling the phase and magnitude of the input signal assigned to each antenna element and the number of array elements, the radiation pattern can be steered in a desired direction... |
 | A radome minimizes losses and improves radiation characteristics of an antenna through its design. The structure can be optimized to minimize the transmission loss and also designed to improve radiation characteristics including antenna... |
 | An antenna balun blocks undesirable currents on the outside of a cable. A quarter-wave coaxial balun (1:1) is one of the easiest designs: it works as a transformer and makes the input impedance from the inner conductor to the outer... |
 | A spiral slot antenna provides a conformal design and can be used for communication, sensing, tracking, positioning, and many applications in different microwave frequency bands due to its wide-band frequency response. This model shows... |
 | A planar dielectric slab waveguide demonstrates the principles behind any kind of dielectric waveguide such as a ridge waveguide or a step index fiber. This model solves for the effective index of a dielectric slab waveguide, as well as... |
 | Simulation of Maxwell’s equations in the time domain is useful if the objective of the analysis is to observe a transient phenomenon, to find the time it takes a signal to propagate, or if the materials being modeled are non-linear with... |
 | The coaxial cable (coax) is one of the most ubiquitous transmission line structures. It is composed of a central circular conductor, surrounded by an annular dielectric, and shielded by an outer conductor. This model computes the electric... |
 | A beam splitter is used to split a beam of light in two. One way of making a splitter is to deposit a thin layer of metal between two glass prisms. The beam is slightly attenuated within the layer, and split into two paths. In this... |
 | A parallel wire transmission line is composed of two conducting wires in a dielectric such as air. The fields around such a transmission line are not directly confined by the conductors, and extend to infinity, although they drop off in... |
 | A plane electromagnetic wave propagating through free space is incident at an angle upon an infinite dielectric medium. This model computes the reflection and transmission coefficients and compares to the Fresnel equations. |
 | It is possible to engineer the structure of materials such that both the permittivity and permeability are negative. Such materials are realized by engineering a periodic structure with features comparable in scale to the wavelength. It... |
 | Transmission lines are used when the frequency of the electromagnetic signals is so high that the wave nature of the signals must be taken into account. A consequence of the wave nature is that the signals are reflected if there are... |
 | A Gaussian electromagnetic wave is incident on a dense array of very thin wires (or rods). The distance between the rods and, thus, also the rod diameter is much smaller than the wavelength. Under these circumstances, the rod array does... |
 | A fractal is a mathematical form showing self-repeating patterns. By virtue of its geometrical properties, a fractal structure can generate multiple resonances in RF applications. This antenna model uses a 3rd order Sierpinski triangle... |
 | This is a variant on the heat transfer model library model "RF Cancer Therapy" which includes a damage integral calculation to estimate the extent of cancer necrosis. The damage integral is based on an energy-absorption method rather... |
 | A helical antenna has two major modes. One is normal mode and the other is axial mode. When the helical antenna is operating at the normal mode, its far-field radiation pattern is similar to the torus shaped pattern of a classic dipole... |
 | This example demonstrates how to set up a spatially varying dielectric distribution, such as might be engineered with a metamaterial. Here, a convex lens shape is defined via a known deformation of a rectangular domain. The dielectric... |
 | This model of a circular waveguide demonstrates how to use ports with numerical solution of the port modes. It illustrates how to align the polarization of degenerate port modes and in particular how to model and excite the TE11 mode of... |
 | A bowtie antenna patterned on a dielectric substrate is optimized by changing the length of the arms and the flare angle to reduce the magnitude of S11, the reflection coefficient. The two geometric dimensions that are used as design... |
 | Modeling in the RF, microwave, millimeter wave and terahertz regimes requires modeling the propagation of electromagnetic waves in and around structures that can be metallic, dielectric, gyromagnetic, or even metamaterials with engineered... |
