negative gain problem

sir i design a multiband microstrip H-shaped antenna using HFSS for DCS, WiMAX and WLAN application. I get three desired frequency which are 1.8268 GHz, 2.6352 GHz and 5.284 GHz. the gain at 1.8268 GHz is come negative -9 dBi GHz. How can correct the gain at this frequency.

Gain values in dB can be negative.
What gain do you expect?