# Designing and simulating a coax to double ridge waveguide using HFWorks for SOLIDWORKS

Article by Nadya Gary updated September 28, 2016

###### Article

Commonly used ridged waveguide (WG) are single and double ridged. The basic motivation for building ridged WGs is to lower the cutoff frequency of the fundamental TE10 mode without increasing the external dimensions. This is done by introducing a metallic ridge into a normal rectangular WG. An advantage of these WGs is that the ratio of the cutoff frequencies TE30/TE10 may exceed a factor of 15 depending upon the aspect ratio of the WG and the ridges. These cutoff frequency ratios have been worked out by analytical as well as numerical methods and can be found in the literature for a wide variety of ridged and rectangular WG geometry.

S parameters coupled to thermal analysis gives engineers an opportunity to investigate designs and scenarios to get the required geometry quickly, using a parameterization study. This article tackles this feature in EMS using a coax to double ridge waveguide as an example.

Figure 1: Coax to double ridged waveguide

Electromagnetic simulation with parameterization enables RF and microwave engineers to get an optimized geometry with the intended performance in one simulation. HFWorks, over the years, has made the task of the engineer easy by reducing the time to design and get the required optimized geometry thereby speeding up the overall design cycle.

This article outlines the workflow of designing a waveguide with SOLIDWORKS CAD and getting an optimized geometry with HFWorks. HFWorks is a full 3D electromagnetic simulator that is completely embedded inside SOLIDWORKS.

The waveguide in this study is a transition from coax to double ridge waveguide, and the main parameter which affects the resonance frequency of the structure is the depth of the coax pin.

The table below summarizes the different values of the depth of the coax pin that will be taken into account for the Parameterization study in HFWorks.

Depth of the pin of the coaxValue (mm)
Scenario 14
Scenario 26
Scenario 38
Scenario 410
Scenario 512

Table 1: shows the different depth of the coax pin to be simulated

### Selecting the model from demo viewer

HFWorks includes a Demo Viewer which is a large library containing a wide diversity of examples. In our case, the model is under the category S Parameters, Connectors and Transitions.

Figure 2: Selecting the model from the demo viewer

1. Can support multiple configurations of your design
2. Can study various geometry parameters and help you reach the optimized design quickly and efficiently.
3. Seamlessly integrated inside SOLIDWORKS thereby obviating the need to export/import geometry

### Simulation objective

The goal is to design, simulate and optimize the geometry of transition from coax to double ridge waveguide model.

Table 2 below, shows the different inputs for the simulation and the different properties.

SpecificationValue
Operating frequency6 to 7 GHz
Feed typeCoax feed
Impedance50 Ω
Convection coefficient10 W/(m^2.K)
Temperature300 K
Power400W

Table 2: Summarizes the properties of the structure

Figure 3, shows the Electrical Parameters simulation for different scenarios, the purpose of a parameterization study is to reduce time and optimize the geometry. In this plot, the S- parameter (S11) response to different depths of the pin of the coax are shown.

Figure 3: S11 for all the simulated scenarios

The total time to solve is 1 minute per configuration. It is a fraction of the time the user may need if they do not resort to simulation. Figure 3 shows the different results S11 for different configurations.

In 3D results we can see the field distributions, Electric field E and Magnetic field H, also temperature, temperature gradient and Heat flux.

Below is the electric field distribution at 6.7 GHz

Figure 4: Distribution of the electric field at 6.7 GHz

### Thermal results

In HFWorks, the S-parameter study can be coupled to thermal simulation. We can obtain the distribution of the temperature, temperature gradient and heat flux for all the configurations. Figure 5 and 6 represent respectively the flux lines of the temperature and the temperature gradient that exists in the structure, around the coax and the insulator.

Figure 5: the distribution of the temperature at 6.7 GHz

Figure 6: the distribution of the temperature gradient at 6.7 GHz

### Conclusion

HFWorks software package can be used to effectively calculate Electric and Magnetic field distributions, S Parameters and port fields. In this article, the design and optimization of Coax to double ridge waveguide was described.