Filters

A microwave filter blocks RF energy in some frequency bands (stop bands), while allowing energy in other bands to pass (pass bands).  Typical design criteria include the bandpass or bandstop location(s), the worst-case performance of the filter in each bandpass/bandstop, and how abruptly the filter transitions between bandpass and bandstop regions.

Both driven frequency and eigenmode solutions are commonly of interest in filter design.  Driven frequency calculations over the frequency band of interest are used to determine the performance of a complete filter.  Eigenmode analysis of the structure, or sections of the structure, are often useful in the design of a filter.

Microwave filters typically consist of a resonant structure linked with couplers to input and output ports.  Three-dimensional models that were created in an external CAD tool can be imported into Analyst simply by exporting the model from the CAD tool in a standard form (such as an ACIS .sat file), and then using geometry import functionality in Analyst.

Filter performance can be optimized automatically by Analyst using its embedded optimization capabilities.  For example, the optimizer has a built-in goal function for filters that allow the user to specify the band edge locations and the magnitude of the return loss within the band.  More complicated filters, e.g., those with multiple pass bands, can also be synthesized by creating custom goal functions in the Python language.