Wireless Local Area Network (WLAN) is now widely deployed in companies, public areas and home environments. This success is due to the very low cost of the equipments, the ease of installation and the low maintenance cost. However, with the multiplication of the number of access points and users, the capacity of wireless networks is becoming interference-limited rather than noise limited. The use of multi-sector antennas, comprising several narrow beams, can help to solve the interference issue while improving the wireless range or/and bit rate [1-5].Various multisectored antennas have been designed and produced in the recent past years based on an omnidirectional antenna by altering the environment [1-3] or the antenna feeding [4]. Another widespread technique consists in using a dedicated antenna for each sector [5-7], dividing the space into multiple sectors. Most of these solutions use a planar design while a volume antenna features significant advantages thanks to their ability to offer higher design flexibility and radiation pattern control (E and H planes). Following these considerations, a conceptually simple 3D multi-sector antenna based on an innovative layout of vertical Vivaldi-type antennas combined with an horizontal motherboard is introduced in this paper. This layout offers a great flexibility in parameters such as shape, position and dimensions of the Vivaldi antenna. Compared to planar antenna design, here the number of sectors as well as the gain of each beam can be chosen among a large set of values in order to fit to the shape and dimensions of the existing horizontal motherboard of the system.