Microstrip Low Pass Filter

S-Parameter EM/Circuit Co-Simulations

 

 

 

General Description

 

The low pass' characteristics are optimized according to the goals described below. Therefore, six parameters describing the lines' width and the stubs' length are taken into consideration.

After the optimization, a final 3D simulation is performed to validate the analytical results.

 

Model Description

 

Standard microstrip blocks and clone blocks are used to build up this model. The substrate properties are defined by a reference block that all of them refer to. The following filter optimization goals for the stop band and the pass band are used:

 

Goal

Frequency range

|S21| > -0.8 dB

0 to 4 GHz

|S21| < -30 dB

5 to 7 GHz

 

The parameters' allowed variation ranges are chosen quite wide. The Optimizer may change the parameters L1 - L3 from 3 to 10, the parameters W1 - W3 from 1 to 2.5. Nevertheless, this 'brute force' optimization with the simplex algorithm by Nelder and Mead just takes around one minute on a 3.2 GHz PC. Note that there is a user-defined result plot that compares the transmissions before and after the optimization.

To validate the optimized results a simulation project is setup that performs a full 3D simulation.