Electronic Device Having Stacked-Patch Antenna with Floating Ground Via

An electronic device may be provided with an antenna module having a substrate. An antenna may be disposed on the substrate. The antenna may have a directly fed patch and parasitic patches. The antenna may be fed by a feed via. The parasitic patches may include a first layer of parasitic patches separated by a gap overlapping the directly fed patch. The parasitic patches may include an additional parasitic patch formed in a second layer. The additional parasitic patch may overlap the gap. A floating ground via may couple a center of the additional parasitic patch and a center of the directly fed patch to a landing pad in a ground layer. The landing pad may short the via to the ground layer at the radiating frequency of the antenna. The landing pad may be electrically floating at DC frequencies.