CST and HFSS are the commonly used tools for simulation. Most of the designers work on Antenna designs and RF/mmwave passives using these tools. Both are Full-wave EM tools.
CST is the most preferred tool die to it's accuracy.
CST stands for Computer Simulation Technology and is based on Finite Integration Method (FIT). CST integrates well with Dassault's SIMULIA/CATIA ecosystem.
HFSS stands for High Frequency Structural Simulator and is based on Finite Element Method (FEM). FEM is very accurate for resonant structures, filters, and problems with complex curved geometry and fine detail. Adaptive Meshing is the major advantage in HFSS compared to CST. The major advantage HFSS has is the integration with Ansys ecosystem. The community support for HFSS is good compared to CST, the academic integration is a big plus.
| Use case | Tool preferred - HFSS or CST? |
|---|---|
| Narrowband filters, resonant cavities, high-Q structures | HFSS |
| Broadband antennas, EMC/EMI, automotive radar | CST |
| PCB/package-level signal integrity | Both strong; HFSS very popular here |
| Very large/electrically large structures | CST (time-domain scales better) |
| Tight integration with Ansys ecosystem (Maxwell, Icepak, HFSS 3D Layout) | HFSS |
| Particle-in-cell, charged particle dynamics | CST has notable strength here |