Directivity of antenna less than 1

[Nesrine_Cadence]

Im simulating a helical antenna on HFSS, every thing is ok i verified the geometry, the port the boundaries etc. i found a directivty value of the antenna less than one??? this is weird can anyone help me please??

 

[anilkrpandey]

There must be some issue in design setup ( like absorbing boundary conditions) otherwise directivity is always greater than or equal to 1 (0 dB), antenna gain can be less than 1 (0 dB).