How does SIwave differ from HFSS?

SIwave and HFSS are both powerful tools used for electromagnetic simulations, but they have distinct differences in their applications and capabilities. 

1. Modeling Approach: HFSS performs a full 3D solution, which allows it to capture complex 3D effects, such as inductive spikes in via modeling, that SIwave might miss due to its simplified 3D model. This is evident in scenarios where HFSS regions in SIwave capture 3D effects that SIwave-only simulations do not.  

2. Frequency Range: SIwave is typically used for simulations in the frequency range from a few MHz up to several GHz, making it time-efficient and accurate within this range. For frequencies higher than several GHz, HFSS is the preferred tool due to its ability to handle high-frequency simulations more effectively.  

3. Simulation Efficiency: SIwave is known for its speed, especially when dealing with complex structures like boards with multiple layers and components. It is efficient for long transmission line structures. On the other hand, HFSS is renowned for its accuracy in extracting information about couplings at high frequencies and high-speed elements in arbitrary geometries.  

These differences highlight how each tool can be leveraged for specific types of electromagnetic problems, with SIwave excelling in speed and HFSS in detailed 3D accuracy.