A bandwidth enhancement technique for designing of microstrip planar antenna is presented for broadband wireless communication. By shifting the off-set fed radiating patch from the center of dielectric substrate it is seen that a 115.5% enhancement in the operating band can be achieved. The proposed planar antenna with bandwidth enhancement technique is prototyped and it is found that the designed antenna without etching any slot/slit/parasitic element can achieve a fractional bandwidth of 146% ranging from 2.96 to 19GHz. The antenna also achieved a good gain and exhibited stable omni-directional radiation patterns. The attractive features of the proposed planar antenna such as simple structure, less expensive, small size makes it very suitable for numerous wireless communications applications.
ACKNOWLEDGMENTThis work was supported by the Deanship of Scientific Research (DSR) at King AbdulAziz University, Jeddah, Saudi Arabia under grant no. 3-135-35-RG. It is also noted that in order to have an attractive appearance of the metal casing, the open slot embedded therein should be simple and narrow in its structure, which makes it a design challenge to achieve multiband operation for the antenna to meet practical applications. In this study, a multiband open-slot antenna with a sticker-like feed substrate for the GPS (global positioning system) operation at 1.575 GHz [12][13][14] and WLAN (wireless wide area network) operation in the 2.4 GHz (2400-2484 MHz), 5.2 GHz (5150-5350 MHz), and 5.8 GHz (5725-5875 MHz) bands [15][16][17][18] is presented for the metal-casing smartphone application. The sticker-like feed substrate in this study is a 0.4-mm-thick FR4 substrate with the microstrip feedline and circuit elements disposed thereon. Note that in this study, the metal casing is with a simple rectangular shape, and the applied sticker-like feed substrate is a rigid FR4 substrate, although it has a thin thickness of 0.4 mm only. For practical applications, a flexible printed-circuit board (PCB) can be applied as the sticker-like feed substrate. In this case, when the smartphone is with a smoothly curved metal casing, the flexible PCB can have the conformal capability to be attached onto the inner surface of the metal casing easily, so as to excite the open slot embedded therein to be an efficient radiator.In the proposed design, simply by attaching the sticker-like feed substrate onto a simple linear open slot embedded in the metal casing, the GPS/WLAN multiband operation can be obtained. The open slot has a small size of 1.5 mm in width and 23.5 mm in length and is spaced a short distance of 8 mm to the short edge of the metal casing, allowing it not to be covered by the display panel in the smartphone. With a narrow width, the open slot is also attractive to be embedded in the metal casing, so that the effects of its presence on the appearance of the smartphone can be decreased. The circuit elements include a shunt chip capacitor loaded across the open slot and a parallel chip capacitor added to the microstrip feedl...