If you ever visit the extravagant dome within St. Paul’s Cathedral in London, be careful what you say. As Lord Rayleigh discovered circa 1878, the vaulted structure exhibits an interesting acoustics phenomenon: Whispers from one part of the dome can be clearly heard in other areas. Rayleigh called the effect a “whispering gallery”. Surprisingly, you can observe a similar effect in another field of science entirely: light waves traveling in an optical ring resonator.

Circulators are a bit like traffic circles (also known as rotaries or roundabouts), where motion occurs in one direction only and each pathway doubles as an entrance and exit. In a circulator, however, the microwave signal always exits at the next available port. This characteristic makes circulators useful for applications that involve coupling transmitters and receivers to common antennas. To ensure that circulators function successfully, electrical engineers can study their designs with electromagnetics simulation.

In a previous blog post, we discussed the paraxial Gaussian beam formula. Today, we’ll talk about a more accurate formulation for Gaussian beams, available as of version 5.3a of the COMSOL® software. This formulation based on a plane wave expansion can handle nonparaxial Gaussian beams more accurately than the conventional paraxial formulation.

A thorough analysis of a loudspeaker driver is not limited to a frequency-domain study. Some desirable and undesirable (but nonetheless exciting) effects can only be caught by a nonlinear time-domain study. Here, we will discuss how system nonlinearities affect the generated sound and how to use the COMSOL Multiphysics® software to perform a nonlinear distortion analysis of a loudspeaker driver.

The Van Allen radiation belts consist of highly energetic charged particles that have become trapped in Earth’s magnetic field. These particles follow the shape of the field and give the belts a doughnut-like appearance. To study the behavior of the particles in the Van Allen belts, scientists can use the Particle Tracing Module, an add-on product to the COMSOL Multiphysics® software.

Electrically erasable programmable read-only memory (EEPROM) is a type of nonvolatile memory that enables users to repeatedly store and erase small amounts of data by applying a voltage pulse. EEPROM is often used as a storage medium in computers and mobile devices and has applications in devices like microcontrollers. To analyze the designs of EEPROM devices, engineers can turn to semiconductor simulation.

What do beer fermentation, soil analysis, and the production of dairy products have in common? They all involve the use of ion-sensitive field-effect transistors (ISFETs) for pH measurement. These sensors are small, efficient, and durable, which makes them suitable for food, environmental, and biomedical applications. However, ISFETs can experience drift and are sensitive to different temperatures, which limits their accuracy and stability. Using the COMSOL® software, engineers can accurately analyze ISFET designs and improve their performance.

Silicon planar devices, imaging sensors, and microprocessors often include a metal-oxide-silicon (MOS) capacitor. To ensure that these devices perform as expected in an application, engineers can accurately analyze their designs using simulation. With the Semiconductor Module, an add-on product to the COMSOL Multiphysics® software, there are multiple methods to do just that…

The greenhouse effect has made it necessary for scientists to develop combustion processes that minimize the accumulation of carbon dioxide in the atmosphere. Possible fuels in these processes include biomass and other biofuels, which recycle carbon within a short timescale. But there’s a downside: Combustion of these materials produces carbon and ash particles that must be removed from the exhaust. To improve particle filtration, researchers studied electrostatic filter designs using models that were validated by comparing them to experimental data.

One of the more common uses of the AC/DC Module, an add-on to the COMSOL Multiphysics® software, is for modeling conductors and other lossy materials in time-varying magnetic fields when there are significant induced currents. The appropriate modeling approach depends upon how quickly the magnetic fields vary over time. Here, we review the basics and describe various modeling techniques to use.