Microwave Oven

This is a demonstration of the heating process in a microwave oven. The geometric dimensions and positioning of food stuffs in microwave ovens contribute significantly to the overall heating effectiveness.

The distributed heat source in a potato is computed in a stationary, frequency domain electromagnetic analysis followed by a transient heat transfer. The majority of the subdomain, boundary and solver settings are automatically defined through utilizing the pre-defined Microwave heating multiphysics coupling.

To save computational memory, symmetry is exploited by simulating only half of the problem, which requires a manipulation of the in-port descriptions. Furthermore, the permittivity, of the potato is included as a user-specified complex-valued expression.

As the model is large, an iterative solver using a pre-conditioner is utilized. The pre-conditioning process uses a hierarchical structure for solving the problem. This is based on the order of elements where solutions for higher-order elements use the solution from lower-order elements as their initial guess.

Three-port ferrite circulator

Microwave circulators are used to isolate microwave components to couple, for example, a transmitter and a receiver to a common antenna. They typically rely on the use of anisotropic materials, most commonly ferrites.

In this demonstration, a three-port circulator made from three rectangular waveguide sections is investigated, where a ferrite post is inserted at the center of the joint. To match the junction, identical dielectric tuning elements are inserted into each branch.

Here, the focus is on the modeling of the ferrite post and how to minimize reflections at the in-port by matching the junction by the proper choice of tuning elements. This is done by calculating the scattering parameters, or S-parameters, of the structure as a function of the permittivity of the tuning elements for the fundamental TE10 mode.

Thermal drift in a microwave filter

Microwave filters serve to suppress unwanted frequencies in the output of microwave transmitters. Amplifiers are in general nonlinear and produce harmonics that must be suppressed using one or several narrow bandpass filters on the output.

High frequency stability of such filters can be hard to achieve as microwave systems may be subject to thermal drift caused by high power loads or harsh environmental conditions like exposure to direct sunlight. Thus, system engineers need to estimate the drift of the bandpass frequency that arises due to thermal expansion of a filter.

This demonstration will model, firstly, the structural deformation of a microwave filter subjected to a range of temperatures. It will then map these solutions to the resulting deformed mesh in order to provide the actual geometric dimensions for the filter.

An electromagnetic analysis coupled to this deformed mesh application mode will then provide an answer to the extent of deviation from the optimal bandpass eigenfrequency for the filter. Two materials will then be compared in order to investigate the applicability for their use in environments of wide-ranging temperatures.

Balanced patch antenna for 6 ghz

Patch antennas are becoming more common in wireless equipment, like wireless LAN access points, cellular phones, and GPS handheld devices. Due to the complicated relationship between the geometry of the antenna and the electromagnetic fields, it is difficult to estimate the properties of a certain antenna shape. Engineers benefit greatly from simulating the geometries and operating conditions at early stages of the design process.

This demonstration will model the electromagnetic field and radiation pattern of such an antenna. While doing this, three significant features in COMSOL Multiphysics will be utilized:

• Perfectly Matched Layers (PMLs) – a technique for absorbing all outgoing EM waves so as to simulate infinite or open boundaries
• Far-field postprocessing – a way to calculate the electromagnetic field a long way from the source, although the model itself does not compute the field at this distance
• Interactive meshing – an ideal and easy way to manipulate your mesh so as to optimize it for each part or component, of the overall system, and reduce computational time and memory