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gain and directivity of the patch is pretty much fixed and the peak radiation will appear at the top of the patch antenna. directivity is about 5 to 7dB for the patch antenna. how much do you want to improve?
I make 9dBi patch antennas (real dBi, not the directivity but gain with respect to isotropic; results are verified in controlled anechoic environment using Satimo tester) can even attempt to make 10dBi patch.