New Directions in Hfss for Designing Microwave Devices

Developed by Ansoft in 1990, the High Frequency Structure Simulator (HFSS) has become the simulator of choice for the electromagnetics design of complex threedimensional microwave devices. HFSS has been used to design thousands of microwave devices more quickly and reliably than is possible with prototypes alone. This broad use has generated considerable user feedback and customer requests for the software to address new simulation capabilities and directions. Two of the most requested features for Ansoft HFSS are the ability to model the resonance and quality factor of microwave cavities as well as a more broadband fast sweep capability. Another requested feature is the ability to model active devices and phasedarray antennas through fields linked by values at two different boundaries. Development of higher accuracy mesh truncation procedures for modeling radiation from antennas, more powerful geometry modeling using precise solids and faster, more complete graphics tools for postprocessing also have been requested. Version 6 sets a new direction for HFSS in these high impact areas. A new graphical user interface streamlines model creation, simulation and postprocessing. Adaptive LanczosPade sweep (ALPS), a new fast frequency sweep technology, provides a more broadband and reliable fast sweep capability than was available in earlier versions. The ALPS fast sweep capability coupled with a new field calculator allows microwave cavity resonances and quality factors to be determined precisely. The linked boundary condition (LBC), which allows active devices and periodic structures to be modeled, has been added and open boundaries can be modeled more accurately by perfectly matched layers (PML) that mimic free space to a remarkable degree. In addition, the software’s geometry entry and postprocessing capabilities have been completely revamped to allow users greater flexibility and freedom in entering geometry and displaying results. This article highlights two application areas that can be solved for the first time using Ansoft HFSS version 6. The new ALPS fast frequency sweep algorithm and the new field calculator can be used to compute closed-cavity resonant frequencies and quality factors, respectively. Also, large phased-array antennas can be simulated using the simulator’s new PML and LBC features.