Rules for Patch Antennas Use only air dielectric. This is caused by the wider beam width of the smaller patch. Mount patch higher not lower. The height of the patch above the groundplane should be approximately two percent of the width of the patch. With air dielectric a half wave square patch should be a minimum 0.01 wavelengths above the groundplane.
Lower heights result in higher Q and high currents resulting in higher losses.
Design for maximum bandwidth. The bandwidth of a patch antenna is direct function of it's height. The limiting factor is mutual H-plane coupling in a close spaced planner array. The higher the elements the greater the spacing required between elements. Minimum edge spacing for 20 dB isolation between elements is 0.12 wavelength for a height of 0.04 wavelength.