I have been using HFSS to design an Antenna at 867Mhz.But the gain that i am getting is -4.9bd and directivity around the same.I have miniaturized the patch antenna.I have even physically implemented it with a reader and got 5 feet range for the tag in vertical and horizontal orinetation.But as the gain is negative im confused because i have not come across antennae with negative gain in DB.The dimensions of my antenna are 70mm X 70mm X 10mm
so they are less than 0.28(lambda) i have read some where that an electrically same antenna whose dimension is less than 0.28(lambda) will have negative gain.
Please help me out.Thanks.