Transmission line simulation

 

 
1. Description

This example illustrates a perfect transmission line (coaxial structure) with great performances from DC up to 60 GHz. The structure is simple: it is made up of PEC material along with Ultem 1000 material. The rest of the report provides further description of its composition and performances.


Figure 1: Perfect line 3D structure


 

 

Dimensions

The simulation can run faster if we make use of the symmetry of the model. Indeed, HFWorks needs only quarter of the model to be designed and the results will be even more efficient. The following figure shows different views of the line quarter's structure. All dimensions have been annotated.


The units are given in millimeter.

 

2. Simulation

The design and dimensions of the model have been optimized to a point where good performances were significantly responding to implications operating over as large as possible frequency band. Thus, the simulation is using the scattering parameter solver around from DC to millimeter wave frequencies, with one of the available frequency plans: Fast sweep or Discrete sweep. Fast sweep is faster to give results but its precision decrease as we move away from the center frequency.

The created finite element mesh must respond to a certain extent of accuracy to the curved shapes introduced in the design.


Figure 2: Mesh of the structure

3. Load/ Restraint

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

4. Results

The outputted results show we have good performances and that the line's performances are over a wide range of frequency from DC up 60 GHz with approximately zero insertion loss and a return loss better than 20 dB.


Figure 3: Insertion loss


Figure 4: Return loss

Using the 3D viewer of HFWorks, we can have a closer view on how things work in the inner part of the structure: we get to visualize the distribution of the electric field inside the structure for all tested frequencies.