Simulating Transmission Lines

Transmission line simulations are performed with the buttons located above the schematic. The buttons on the main control panel are for ideal filter response only and do not simulate the transmission line. The actual transmission line simulation may differ dramatically from the ideal filter due to the parasitics in the lines and the frequency aliasing effect due to finite length lines.

 

The following parasitics are accounted for to at least some degree in transmission line simulation:

• Finite line length

• Conductor resistivity

• Dielectric loss tangent

• End effect

• Joints, tees, and crosses

• Corners

• Hairpin cross coupling between the legs.

• Realizable widths and gaps of microstrips and striplines

• Microstrip dielectric constant error.

• Line thickness

 

Optimizing

Once a design is roughed out considering all of the parasitic effects listed above, it should be optimized. The optimization tool will attempt to force the passband response of the simulated filter to match the ideal pass band response of the filter.

 

Finalizing

Transmission lines simulations are component simulations only, and are not EMI based. To insure full accuracy, the design should be simulation with a good EM simulation tool, such as HFSS, prior to being finalized.