Hfss problem

[ruchak]

Hi, recently i designed a helical antenna array at 2.4GHzin which i took the sweep from 2GHz to 7GHz.
in this range i got the reflection coefficient around -15dB at 2.4GHz.
the graph started from -14 at 2GHz and then went further down to -15dB at 2.4GHz and at 4.1GHz its reflection coefficient went above -10dB.
to find out the nature of the graph below 2GHz and above 10GHz i increased the sweep from 0.5GHz to 10GHz.
When the results were out, i noticed that the whole graph between 2GHz and 7GHz had changed completely. (i.e. the values of reflection coeff. changed at those frequencies)
according to my expectations, the graph between 2 to 7GHz should have been same.
i dont know the reason.. can anybody figure out this problem as i want to include these results in my thesis.:sad:

 

[reidintransit]

what type of sweep are you using? if you increase bandwidth without increasing the number of sample points it may be interpolating different points (too few). If your solution setup->solution frequency changed, your mesh may have changed to be more or less accurate. try increasing the number of points in your sweeps.