Learning Forum

[fparveen]

Hello,

Can anyone help me understand how the antenna parameter- Front to Back ratio is calculated in HFSS? Is it the ratio of the E-fields, i.e. ratio of voltages? Or it is the ratio of powers?

There are two options available for plotting: dB10 and dB20. Does this mean that, the FBR is calculated as the ration of voltages, as there is the dB20 option available?

Thanks.

[Praneeth]

Please go through "Front to back ratio" topic in the HFSS help document to get detailed information about it.
All the very best.

[fparveen]

Hello In the HFSS help document the following definition is provided-
"Front-to-back-ratio is one value for the entire far field setup (and is an unambiguous single quantity for a given setup) and is maximum rETotal (equivalently directivity) as the front value, then the rETotal from the opposite direction and use the ratio of front to back values, without log."

So what does it mean? Does it mean that, HFSS takes the ratio of rETotal? or directivity?
rETotal and directivity are not same. If it is the ratio of rETotal, then I need to take dB20, if it is the ratio of directivity then I need dB10, to get the db value.

I plotted the rETotal vs freq plot for my antenna, and found the followings:
maximum rETotal (at theta = 100 deg, phi = 100 deg) = 11.9191
rETotal at the opposite direction (at theta = 280 deg, phi = 100 deg) = 3.7313
So, the ratio of rETotal = 11.9191/3.7313 = 3.194
But, the FBR vs freq plot in HFSS shows 10.204 .
This value is obtained when I take the square, i.e. 11.9191^2 / 3.7313^2 = 10.204

This means that the HFSS is calculating the FBR as the ratio of rETotal^2 (or ratio of directivity).
Then, why does the help document say that it is the ratio of rETotal? Also, why is the db20 option available then?

Thanks.