Studies of Triangular Slot Antenna for Dual-Band Antenna with Various Tuning Stub

In recent years, the introduction of new indoor communication wireless protocols such as Bluetooth, IEEE 802.11b, and wireless local area networks (WLANs) has led to enormous challenges with respect to antenna designs for wireless communications. The newer WLANs, however, have to provide high-speed wireless connectivity between PCs, laptops, and other equipment in corporate, public, and home environments. In practice, IEEE 802.11b is one of the WLANs, with frequency bands ranging from 2.4 to 2.484 GHz for the ISM band. HIPERLAN 2 was developed for the frequency band ranges of 5.15–5.35 GHz, 5.470–5.725 GHz, and 5.725–5.925 GHz. The required frequency for 5-GHz WLANs is 5.15–5.35 GHz / 5.725–5.825 GHz for the IEEE 802.11a. U-NII covers the frequency band of 5.725–5.825 GHz. In addition to individual approaches for 2.4 GHz and 5 GHz bands, triple-band antennas are necessary for many applications, driving a demand for them. For the WLAN, dualor triple-slot antennas have been proposed using a stair-shaped slot [1], a triangular slot [2], a rectangular slot [3], and a double-ring slot [4]. Compared with the regular patch antenna, the slot antenna fed by a microstip line has better characteristics, including a wider bandwidth, less conductor loss, and better isolation between the radiating element and feeding network. In particular, wide-slot antennas have an attractive property of providing a wide operating bandwidth, especially for those having a modified tuning stub, such as the rectangular stub [5]–[9]. However, although many microstrip-fed wide-slot antennas have been proposed for triple-band applications, studies on the triangular-slot antenna with various tuning stub for the triple band are rare. In this paper, we report a new design of microstrip printed triangular-slot antenna with various tuning stub for triple-band operation. The tuning stub is positioned within the slot region on the opposite side of the printed triangular slot. By choosing suitable parameters, we obtained a significantly enhanced triple-band impedance bandwidth. The results of the experiment that were conducted on the antenna’s impedance bandwidth, radiation pattern, and gain are discussed in detail in the succeeding section.