An electronic device may have peripheral conductive housing structures divided into first and second segments. First and second antennas may be formed from the segments and may be fed using a flexible printed circuit structure. The structure may include a first substrate attached to the first segment, a second substrate soldered to the first substrate and attached to the second segment, and a third substrate soldered to the second substrate. Third and fourth antennas may be formed on the first substrate whereas fifth and sixth antennas are be formed on the second substrate. The second substrate may be folded and may have a lateral area oriented perpendicular to the third, fourth, fifth, and sixth antennas. Modularly forming the structure in this way may maximize the flexibility with which the structure can accommodate other components, thereby minimizing the space consumption associated with mounting and feeding the antennas without sacrificing wireless performance.