Model Gallery

The Model Gallery features COMSOL Multiphysics model files from a wide variety of application areas including the electrical, mechanical, fluid, and chemical disciplines. You can download ready-to-use models and step-by-step instructions for building the model, and use these as a starting point for your own modeling work. Use the Quick Search to find models relevant to your area of expertise, and login or create a COMSOL Access account that is associated with a valid COMSOL license to download the model files.

Quarter-Wave Transformer

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 abrupt changes of the characteristic impedance along the transmission line. Similarly, the load impedance, Z(L), at the end of the transmission line must match its ...

Rat Race Coupler (180 Degree Ring Hybrid)

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 magic-T. The objective of this model is to compute the S-parameters and to observe the matching, isolation, and coupling around the operating frequency.

MRI Bird-Cage Coil

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 illustrates how thin sheets of metal can be modeled using impedance boundary conditions. It also illustrates the use of lumped ports to design simple RF circuit elements such ...

Circularly Polarized Antenna for the GPS Applications

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.

Sierpinski Fractal Monopole Antenna

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 and the calculated S-parameters shows good input matching at the higher order resonances.

Evanescent Mode Cylindrical Cavity Filter

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 modified by the addition of a metal box at either end representing a housing. Inside a dielectric substrate and a microstrip line coupled into the cavity. The ...

Thermal Drift in a Microwave Filter Cavity

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 must be eliminated with filters that have a rather narrow passband. Due to high power loads but also possibly from harsh environmental conditions (such as a ...

Waveguide Iris Bandpass Filter

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 elements which can be created by inserting a series of iris elements inside the waveguide. This model consists of a X-band waveguide WR-90 and symmetrical inductive ...

Beam Splitter

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 example, the thin metal layer is modeled using a transition boundary condition which reduces the memory requirements. Losses in the metal layer are also computed.

Magnetic Frill

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 situations, and one is the magnetic frill. This model shows the basic steps of defining a magnetic frill voltage generator for a dipole antenna, and it also compares ...

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