Learning Forum

[vivekparimi]

I am currently simulating a Hertzian dipole antenna that is resting on a substrate. I try simulating in two ways.

1. I have the current source (1A) at the midpoint of the antenna feeding two PEC boxes.
2. I have the current source vertically feeding the antenna at one end of the antenna

In both cases I expect the radiation pattern to look identical. However, the radiation pattern in the second scenario is tilted w.r.t to the axis. What is the reason for this?

Images of the setups and the corresponding radiation patterns have been added.

[Praneeth]

Please note that by default the tool assumes that your antenna center is located at the origin point of co-ordinate system (CS).
For you case, you need to define a new origin at the mid point of the antenna using local CS.
And use this CS while defining the infinite far field sphere.
All the very best Praneeth.

[vivekparimi]

In the setup I have used so far, both the coordinate systems have their origin at the mid point of the antenna. It is only the current excitation location that is changed. Does the excitation need to be at the origin for the infinite far field set up?
Thanks.

Best Vivek

[Praneeth]

Please give a try and see.
All the very best Praneeth.

[vivekparimi]

For the second scenario I tried to have the Infinite sphere defined with a coordinate system centered at the current source but saw no difference to the radiation pattern. Just to add more details, I am simulating at 500 GHz with a 200nm gold dipole. The substrate has a dielectric constant of 12.96 (GaAs) and I am using radiation boundary conditions.
I even tried doing this simulation with the structure in vacuum and there was still a slight tilt when the feed was vertically oriented at one end of the antenna as opposed to a central feed. Is it possible that the current source itself is radiating?

Best Vivek