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Microstrip feed can be considered as an extension of the patch and is easy to model. However, this limits the bandwidth due to increase in surface wave and spurious feed radiation. On the other hand, while using coaxial feed, the inner conductor is connected to the patch and the outer one is connected to ground. It has low spurious radiation but is difficult to model. It also may have some asymmetries due to which higher order modes are generated leading to cross polarization.