Lowpass Filter Design with CST Studio Suite 2023

In CST Studio Suite® 2023, we’ve again introduced many new and useful features for designing filters with our advanced tool called Filter Designer 3D.

In addition to the existing powerful Coupling Matrix synthesis for bandpass, bandstop and diplexer filters, one can now also get ladder circuits synthesized for lowpass and highpass responses. The user can place transmission zeros for out-of-band rejection, resulting in different circuit topologies; or select from the classical responses like Chebyshev or Butterworth.

An added bonus is that we also offer parameter extraction based on the simulated S-parameter response. This means that the built-in optimizers can directly utilize it as a goal function – similar to what is available with the coupling matrix.

Below a workflow is outlined, starting from the synthesis in Filter Designer 3D and ending with the optimized 3D model.

The recently introduced partial RLC solver can also be exploited in designing the equivalent lumped components. This may also help to determine the dispersive effects and thereby better control the out-of-band performance.

Here’s a few different examples:


CST Studio Suite Filter Designer 3D ​​​​​​​Electromagnetics