Why the feed side is open? (Slotted waveguide example)

Hi, I'm trying to simulate slotted waveguide antenna using the function 'waveguideSlotted' of antenna toolbox.

However, the example shows that the one face on the feed side is open (not blocked by PEC surface).

Anyone knows why this exmple was made in this way?

Answer 1

[Song-Hyun Ji]

The waveguideSlotted object creates a slotted waveguide antenna and the waveguide object is an open-ended rectangular waveguide. The waveguide object is often initialized as an open-ended rectangular waveguide for simplicity and convenience. The choice of an open-ended rectangular waveguide as a default is based on several practical considerations:

1. Common use case: Open-ended rectangular waveguides are one of the most commonly used waveguide configurations in practice. They are widely employed in various applications, including RF and microwave systems.
2. Ease of simulation: Open-ended rectangular waveguides are relatively straightforward to simulate and analyze, making them a good starting point for users who are new to waveguide simulations or antenna design.
3. Design flexibility: While an open-ended rectangular waveguide is used as a default, the Antenna Toolbox provides the flexibility to change various parameters, such as the dimensions and excitation method, to model other types of waveguides accurately.
4. Educational purposes: Choosing a commonly encountered waveguide type allows users to experiment with the Antenna Toolbox and understand waveguide behavior and antenna characteristics better.

It's important to note that the choice of an open-ended rectangular waveguide as a default does not limit the toolbox's capabilities. Users can customize the waveguide's parameters and excitation to simulate various other waveguide configurations according to their specific needs. The Antenna Toolbox aims to strike a balance between ease of use and versatility to cater to a broad range of users, from beginners to experienced antenna designers.

[Jaehoon Jeong]

Thank you very much for the reply!

I understand that it is better to have an open-ended waveguide for observing electromagnetic aspects inside a waveguide. However, I'm trying to simulate a slot array antenna, not just a waveguide. That is why I think the waveguide should not be open-ended. If the waveguide is fed with (or terminated with) a 50-ohm impedance at the open face, it would be fine, but the slotted waveguide antenna object is fed with a monopole inside the waveguide with an open-ended surface. I'm afraid it would result in an incorrect beam pattern for the slot array antenna.

Is there any way to block the waveguide and terminate it with specific impedance?

Thank you.

[Song-Hyun Ji]

I think you might be interested in this example "Analysis of Broad-wall Slotted Array Waveguide for High Frequency Applications" that shows how to analyze the performance of a slotted waveguide antenna. In waveguideSlotted, there is the 'ClosedWaveguide' property. About monopoleCylindrical, it also has the 'ClosedEnd' property to determine if the monopole top is closed with a cap or left open, specified as 0 or 1.

[Jaehoon Jeong]

Thank you so much! I have another question though it's not relevant to this post. I want to move the antenna object in cartesian coordinates, but 'translation' function did not work when I tried to translate the antenna. Can you please let me know how to do it?