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Simulation of a Transmission Line

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This example illustrates a perfect transmission line (coaxial structure) with great performance from DC up to 60 GHz.. The structure is made up of PEC material along with Ultem 1000 material. The structure inherits the shape of a coaxial transmission line with few differences: it is made up of PEC material and Ultem 1000 material. further description of its composition and performances is found in the next sections. 

Perfect line 3D structure
Figure 1 - Perfect line 3D structure

Perfect line 3D structure




The simulation can run faster if we profit from the symmetry of the model. Indeed, HFWorks needs only quarter of the model to be designed : It is always useful to use symmetry whenever the model allows to do so. The following figure shows the dimensions of the line quarter's structure. All dimensions have been annotated and given in millimeter.

the dimensions of the line quarter's structure



The design and dimensions of the model have been optimized to a point where good performance was observed.  The simulation is using the Scattering Parameter solver from DC to millimeter wave frequencies with Fast sweep or Discrete sweep. The created Finite Element mesh must respond to a certain extent of accuracy on the eddy areas of curved bodies.

Mesh of the structure

Figure 2 - Mesh of the structure

Load/ Restraint

The propagation of waves is considered in TEM mode: We assign signal boundary condition to  the outer surface of the RF signal carrier i.e. the lateral face of  the extruded cylindrical cut . The lateral revolution (cylindrical) shapes of the structure are treated as perfect electric conductors.


The output results show that we have excellent performance over a wide range of frequency from DC up to 60 GHz : approximately  zero insertion loss and a return loss better than 20 dB.

Insertion loss

Figure 3 - Insertion loss

Return loss

Figure 4 - Return loss


Using the 3D viewer of HFWorks, we can have a closer view on the inner field distribution of the structure.

Inner distribution of electric field at 40 GHz

Figure 5 - Inner distribution of electric field at 40 GHz