I'm trying to simulate a 1 bit digitally coded meatsurface with 60*60 unit cells having two different dimensions which have a phase difference of 180 degrees between them. The structure is supposed to reflect at +30 degrees and it is also expected to reflect at -30 degrees since I'm using 1 bit coding as per the paper I'm referring to (I'm trying to simulate the paper). However, in farfield results I'm able to see another beam at 180 degrees below the pec ground and in polar plot it is showing that it is the main beam. I'm new to cst and I'm not sure why I'm seeing this beam. How do I remove the same?
I think you will find this is the forward scatter. The results show the power scattered by your structure. They do not show the field you illuminated it with (which would be a delta function in the forward direction). In the near field if you plotted the total field, with the incident field as well, your object will cast a shadow. For there to be a shadow, there must be power scattered into the shadow to cancel the illuminating field. This is forward scatter. For a flat reflecting plate the forward scatter is as big as the backscatter, and has the same lobe shape. For an opaque object the forward scatter is the largest lobe there can be (only for a flat plate can the backscatter be this big), so it's not surprising CST has labelled it your main lobe. As your reflected power is split between at least two lobes, these will be lower than the forward scatter.
The confusion you are experiencing is something that many beginners encounter as well. The undesired main beam is caused by the diffraction effect of the incident wave at the edge of the antenna. This phenomenon occurs only when the wave is irradiated as a plane wave. if you want to avoid this situation, you can use a horn or a patch antenna as the feed to project spherical waves onto the array.
- Badges
- Science topic
- Similar topics
- Computer Science and Engineering
- Computer Graphics and Animation
- 3D