stacked patch antenna gain

hi all,
can any one plz help me that how can i increase the gain of a stacked patch antenna, as with stacked patch greater BW can be achieved but gain reduces. any parameters that can be used to control the gain.

thanks

What substrate are you using? I found that the dielectric losses of my stacked patches hammered the gain. The difference between a typical FR-4-type loss tangent of 0.02 and a better substrate at 0.002 yeilded more than a dB improvement for me at 2.4 GHz.