As for conventional patches, the increase in the horizontal size W produces a gain enhancement. Depending on the position of the tag on the body, and on the available space, it is possible to increase that dimension in order to achieve better radiation performance. The length L of the patch is chosen approximately equal to λ/4 , where is the effective wavelength in the dielectric substrate. While the size of the slot’s central gap is mainly fixed by the microchip packaging and by the eventual sensing electronics, different shape-factors and positions may be instead considered for the matching slot.