This letter presents a microstrip-fed antenna that is compact, low profile, and planar. The antenna is suitable for UPCS (1.85-1.99 GHz) and UWB applications. The antenna occupies an area of 20 Â 40 mm 2 . The antenna exhibits dual frequency bands at 1.8-2 GHz and 3. 825-8.177 GHz with good radiation pattern characteristics.
496MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 54, No. 2, February 2012 DOI 10.1002/mopThe antenna radiation pattern is almost as the radiation pattern of a monopole antenna, and the gain remains nearly constant within UPCS and UWB bands. antennas (PIFA) were frequently used in designing mobile phone antennas [5, 6]. Although PIFA has been known for its small radiator size, and multiband operations; it uses large ground plane, and is not suitable for wideband functionality.In this article, we present a new planar antenna design that contributes to the wireless applications. The antenna operates over the frequency bands UPCS (1.85-1.99 GHz) and . The antenna features a small size of 40 Â 20 cm 2 , and is printed on both side of a PCB whose thickness and permittivity are 1.5 and 4.4 mm, respectively. Ansoft HFSS software, which is a full-wave electromagnetic field simulation package, is used as a design tool.
ANTENNA DESIGN AND EXPERIMENTAL RESULTSThe geometry of the antenna is depicted in Figure 1, where As it is seen, the ground metallization is removed underneath the radiator, so that the antenna is considered a monopole antenna. Monopole antennas have attractive features such as wide impedance bandwidth, omnidirectional radiation pattern, low cost, ease of construction, compact structure of a two metallic layer, no soldering point, and easy integration with MMICs [7][8][9]. The simulated bandwidths for VSWR 2 are 1.916-2.07 GHz and 3.62-7 GHz, whereas the measured bandwidths are 1.8-2 GHz and 3.825-8.177 GHz as shown in Figure 2. The current distribution on the top radiating patch at 2.0 GHz gives us a theoretical explanation of the UPCS resonance as shown in Figure 3.It can be noticed that UPCS path marks the high density current path at 2.0 GHz; the length of the UPCS path represents the length required to achieve a resonance at 2.0 GHz and follows the following set of equations [10]:where f r ¼ 2.0 GHz, e r ¼ 4.4, h (the height of the substrate) ¼ 1.5 mm, and w, the width of the radiating strips of UPCS path ¼ 3 mm. The ground plane plays an important role in matching the feed line to the radiating patch. Therefore, the effect of varying the length, L g , is shown in Figure 4. It is seen that the UPCS band is not affected by varying L g , whereas the widest UWB spectrum is achieved at L g ¼ 10 mm. The peak gain is almost constant over the UPCS band and varies from 3.92 to 4.3 dBi, yet it slightly varies over the UWB spectrum from 2.5 to 3.7 dBi as exhibited in Figures 5(a) and 5(b). The radiation pattern is nearly omnidirectional at 1.9 and 4 GHz as shown in Figures 6 and 7, respectively. The radiation patterns at U ¼ 0 and 90 at 6 GHz are shown in Figure 8.
CONCLUSIONA no...