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Thermal Drift in a Microwave Cavity Filter

Application ID: 692

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 cellular base station sitting in the sunshine in Phoenix), it is necessary to estimate the drift of the passband frequency due to thermal expansion.

It is easy to demonstrate that by using steel for the cylinder, a temperature-driven adjustment of the distance between the cylinder end and the brass box (where the adjustment screw is) can automatically compensate for most of the thermal drift.

This model is included as an example in the following products:

RF Module

The combination of COMSOL® products required to model your application depends on several factors and may include boundary conditions, material properties, physics interfaces, and part libraries. Particular functionality may be common to several products. To determine the right combination of products for your modeling needs, review the Specification Chart and make use of a free evaluation license. The COMSOL Sales and Support teams are available for answering any questions you may have regarding this.