The Negative Gain on Radiation Pattern, may I know what is the physical meaning?

Dear all,
Can anyone please help to clarify my doubt..

I have designed a patch antenna, attached file consists of the results (S11 and Radiation Pattern) of my simulation by HFSS.
The S11 have resonance frequency of 4GHz (Return Loss=23.47dB) and 5.5GHz (Return Loss=26.27dB). Impedance Bandwidth is ~8.8GHz.

I have a problem on interpreting the radiation pattern (I have done lots findings but still have some doubt:!.
1) I not sure the "gain" on radiation pattern is refer to Power gain or Directivity? The unit is in dBi.
2) I am getting negative "gain" on radiation pattern (E-field). I read from article is antenna Loss. What does it mean physically? Does it mean the antenna absorb power instead of radiating the power? May I know if this negative "gain" is a good things.
3) How about the positive gain? May I know what does it mean in physically?
4) I understand that dBi is used for rate the antenna ,what if the antenna is not isotropic (eg. is directional antenna) , do we still can use dBi as unit in radiation pattern?

Thank you so much. **broken link removed**
Lingling.

liling_03 said:

1) I not sure the "gain" on radiation pattern is refer to Power gain or Directivity? The unit is in dBi.

Click to expand...

In dBi means antenna gain in dB relative to isotropic radiator.

2) I am getting negative "gain" on radiation pattern (E-field). I read from article is antenna Loss. What does it mean physically? Does it mean the antenna absorb power instead of radiating the power? May I know if this negative "gain" is a good things.

Click to expand...

Negative in dBi means that in that direction the antenna has a gain less than the isotropic antenna.

3) How about the positive gain? May I know what does it mean in physically?

Click to expand...

That in that direction has more gain than the isotropic radiator.

4) I understand that dBi is used for rate the antenna ,what if the antenna is not isotropic (eg. is directional antenna) , do we still can use dBi as unit in radiation pattern?

Click to expand...

The reference antenna is isotropic. Your antenna (usually) is not.

Regards

Z

To add on, for point (1):

In HFSS, you can select directivity or gain for the report.