Axial ratio concerns on circular antennas. linearly polarized antennas doesnt need it. if u r designing circular patch antenna you need low axial ratio (0-4 or less more up to 6).
axial ratio is the measure of polarization characteristics of your antenna.
it should be infinity or very high for linear polarized antenna , 1 for circular polarized antenna and in between 1 and infinity for elliptically polarized antenna