Lai, M.-I.M.-I.LaiSHYH-KANG JENG2020-06-112020-06-11200915361225https://scholars.lib.ntu.edu.tw/handle/123456789/499919https://www.scopus.com/inward/record.uri?eid=2-s2.0-77956195324&doi=10.1109%2fLAWP.2008.920266&partnerID=40&md5=ff089cbb4867ae34cb68b347475b9534In this letter, new slot antennas with an extended ground are proposed. They are easily built as internal antennas in a compact wireless device. Originated from λ/4 slot antennas, an additional vertical L-shaped metallic sheet as an extended ground and a main radiator is added to reduce the antenna size. The sheet is designed close to a ground plane, and its height can be chosen according to the available space of a given device. These features offer more design flexibility for antenna and mechanical engineers. In this letter, antennas for WLAN are designed and implemented as examples, and a four-element antenna design using the resultant antennas is demonstrated, showing that the multiple-antenna design occupies only a small region in the system board. With these design examples the proposed structures can be a promising solution for multiple-antenna systems in compact wireless devices. © 2009 IEEE.Slot antennaAntenna size; Design flexibility; Element antenna; Ground planes; Internal antennas; L-shaped; Mechanical engineers; Metallic sheets; Multiple antenna; Multiple antenna systems; Small region; System boards; Wireless devices; Antenna arrays; Antenna feeders; Antenna grounds; Broadcasting antennas; Design; Radio; Wireless local area networks (WLAN); Slot antennasjournal article10.1109/LAWP.2008.9202662-s2.0-77956195324