Fest3D is a software tool capable of analyzing complex passive microwave components based on waveguide and coaxial cavity technology in very short computational times with high accuracy compared to mode-matching methods. This suite offers all the capabilities needed for the design of passive components such as optimization and tolerance analysis. Moreover, Fest3D advanced synthesis tools can be used to design bandpass, dual-mode and lowpass filters from user specifications.

Fest3D is based on the integral equation technique efficiently solved by the Method of Moments. Additionally, the Boundary Integral-Resonant Mode Expansion (BI-RME) method is employed for extracting the modal chart of complex waveguides with arbitrary cross-section. The successful combination of such methods ensures a high degree of accuracy and a reduction in the computational resources required (in terms of CPU time and memory).

Fest3D is an optional part of CST Studio Suite and is also available as a stand-alone offering.

Fest3D component analysis

The Fest3D analysis method is based on a multimode equivalent network representation of waveguide junctions. Each element in the complete circuit is solved with the best available method, ensuring both efficiency and accuracy. On this basis, Fest3D is able to simulate complex passive devices in extremely short times (of the order of seconds or a few minutes), whereas general purpose software (based on segmentation techniques such as finite elements or finite differences) can take hours for the same calculations.

On top of that, unlike traditional mode-matching techniques, the electromagnetic algorithms employed in Fest3D minimize the problems of relative convergence, leading to confidence in the results. Furthermore, the employed integral equation technique extracts part of the frequency dependent computations, resulting in a very low computational time per frequency point when compared to standard mode-matching techniques. This benefit is more evident when high accuracy is required and therefore a large amount of electromagnetic modes is required to analyze the component.

Some of the components that can be analyzed with Fest3D are:

  • Filters (Comb-line, Inter-digital, waffle-iron, dual-mode, band-stop, etc.)
  • Multiplexers (Diplexers, OMUXs, etc.)
  • Couplers
  • Polarizers
  • OMTs
Fest3D component design

Fest3D includes the possibility to automatically design several types of components from user specifications. Currently, the user can synthesize dual-mode filters, band-pass filters, low-pass filters and rectangular tapers.

During the synthesis stage, full-wave simulations are performed in order to consider the impact of non-propagating waveguide modes. Thanks to this and to the particular algorithms employed in each case, the synthesis process provides very good responses with respect to the user specifications without the need for post-optimization.

In addition to the automatic design generation of specific components, Fest3D has an optimization tool for the refinement of the component’s geometrical parameters in order to get the final desired response. Several optimization algorithms are included in the tool (Simplex, Powell and Gradient). The progress of the optimization can be monitored in real time, as well as stopped, reconfigured and resumed from the Graphical User Interface at any time.

With Fest3D users can easily perform sensitivity analysis of the final design. They can choose which geometrical parameter/s to modify and the deviation of each one can be set separately.