What is the meaning of the negative theta degree?

- April 19, 2024 at 10:32 am
  
  DRG
  Subscriber
  
  Greetings! I'm currently working on an antenna project.
  As you might be aware, typically theta degrees range from 0 to 180 degrees.
  However, the antenna gain analysis in HFSS is displaying gain values for negative theta degrees.
  Initially, I assumed that negative theta values didn't hold significant information, possibly indicating symmetry.
  But upon plotting the gain values, I noticed a slight asymmetry around the theta=0 point, as shown in the figure below.
  I'm curious if anyone could shed some light on the significance of negative theta values?
- April 22, 2024 at 11:04 am
  
  Jason.k
  Ansys Employee
  
  Hello DRG,
  
  Thank you for reaching out to Ansys Learning Forum.
  
  Theta is the angle from Z axis. Negative theta values provide information (related to Elevation) for angles from 180 to 360 or in other words for the other "half" Elevation plane.
  Extracting data from 0 to180 degrees (for theta) does not provide any information for the whole Elevation Antenna behavior, but only for half of the Elevation plane.
  In order to extract information for the whole Elevation plane, you need to scan theta from 0 to 360 (or from -180 to 180 degrees). For both options, you will get same results (as the Theta scan plane is equal to 360 degrees) which means that the extracted information is related to the whole Elevation plane.
  
  Best regards,
  Jason.