8. K. Chung, S. Hong, and J. Choi, Ultrawide-band printed monopole antenna with band-notch filter, IET Microwave Antennas Propag 1 (2007), 518–522. 9. Ansoft High Frequency Structure Simulation (HFSS), ver. 10, Ansoft Corporation, 2005. V C 2010 Wiley Periodicals, Inc. FOLDED AND SLOTTED INTERNAL ANTENNA DESIGN FOR 3G IMT-2000 MOBILE HANDSETS Chan H. See, Raed A. Abd-Alhameed, Dawei Zhou, Khairun N. Ramli, N. J. McEwan, and P. S. Excell Mobile Satellite Communications Research Centre, Bradford University, Bradford, BD7 1DP, United Kingdom; Corresponding author: r.a.a.abd@bradford.ac.uk Received 4 October 2009 ABSTRACT: A four-sided folded, slotted and shorted rectangular patch antenna for 3G mobile handsets is described. The antenna provides a 17.65% bandwidth with S11 <10 dB from 1885 MHz to 2250 MHz, which completely encompasses the desired UMTS frequency band (1920–2170 MHz). The proposed antenna is minimized to a volume of 30 mm  30 mm  10 mm, in which the side length dimension is 0.2 wavelengths at the centre frequency 2045 MHz, whilst the height of the antenna above ground plane is about 1/15 wavelength. The experimental and simulated results on a finite ground plane show good agreement. The effect of varying key geometrical parameters of the proposed antenna is also discussed. V C 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1549–1553, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25271 Key words: shorted rectangular patch antenna; 3G; UMTS 1. INTRODUCTION Evolving mobile communication systems require increased bandwidth: for 3G UMTS it is 12.2% (1920–2170 MHz) [1, 2]. However, there is a constant requirement for smaller and lighter internal antennas, which are immune to damage and cause low specific absorption rate (SAR) [3–11]. Due to the limited vol- ume and the influence of the plastic case, the design of internal antennas is challenging. Bandwidth enhancement is a particular problem: the use of thicker substrates with low permittivity, multiple resonances, and optimized antenna geometry have fur- ther been proposed and investigated [2, 9, 12–14]. Alternatively, by implementing high permittivity substrate, shorting pins and altering the geometry of the internal antennas, the size can be minimized, but bandwidth may be reduced [3, 4, 15, 16]. In this article, a new four-side folded, slotted, and shorted rec- tangular patch antenna is introduced for 3G mobile handsets. It provides a bandwidth (|S11| 10 dB) of 17.65% (1885–2250 MHz), which completely covers the desired band. By fully utiliz- ing the limited projection area on the top edge of a ground plane of 40  100 mm, the proposed antenna can be minimized to a volume of 30 mm  30 mm  10 mm which is about 0.2 wavelengths, at the centre frequency, while the height from the antenna to the ground plane is about 0.07 wavelengths (10 mm). Altogether, the analysis of the antenna has been conducted using the CST com- mercial FIT (Finite Integration Technique) software package [17]. 2. ANTENNA DESIGN CONCEPT AND STRUCTURE The proposed antenna (Figs. 1 and 2) is very similar to that in Ref. 7 and 8, which was used as the starting point of this work. However, the proposed antenna must operate on a standard mo- bile handset ground plane, while the example in Ref. 7 works on an infinite ground. The proposed antenna is a four-folded edge and slotted rectangular antenna with dimensions of 30  30 mm, while the slot is of variable dimensions 2 mm  d1 and the variable height for the four-folded edge is h1. Figure 1(c) shows the location of the proposed antenna when mounted on a finite ground plane of size (40  d3  2) mm. As can be observed, the proposed antenna is located at d3-d2-30 mm from the top edge of the finite ground plane to prevent the user’s hand from causing deterioration of performance. The distance from the antenna to the ground plane was kept at around 10 mm. Since the impedance bandwidth is strongly related to the volume of the radiating patch, four folded edges are imple- mented in this design to broaden the bandwidth and increase the electrical length of the antenna for lower resonant mode imped- ance matching purposes. By pin-shorting the proposed antenna, its physical length is halved for a given operating frequency. It should be noted that the positions of the shorting pins (sp1 and sp2) are chosen for the reason of keeping the symmetrical struc- ture of the antenna, to some extent, so that the far field patterns will not be dissymmetrical. 3. PARAMETRIC STUDY RESULTS The fixed and variable parameters are listed in Table 1, where the variable parameters are considered as critical parameters for determining the lowest frequency of the operating bandwidth. In the present study, the variable parameters d1, d2, d3, h1, and r1 were initially set to be 25 mm, 65 mm, 100 mm, 6 mm, and 2 mm, respectively. The impedance bandwidth will be the main target to be opti- mized throughout the parametric study (defined at return loss S11 < 8 dB). Each simulation is run with only one parameter varied, while other parameters are held constant. Figure 2(a) illustrates the effect of the parameter d1 on the bandwidth. As can be seen, with d1 less than 5 mm, the desired UMTS band cannot be fully covered. However, with the increase of d1 from 5 mm to 6 mm, the degree of the impedance matching improves and fully covers the UMTS band. Figure 2(b) shows the influ- ence of the parameter d2 on the bandwidth. When the antenna is mounted closer to the top edge of the ground plane, d2 is increased from 65 mm to 70 mm, the impedance bandwidth decreases from 19.2% (1.88–2.28 GHz) to 16.4% (1.95– 2.3 GHz). The effect of the parameter d3 (which is identical to the length of the ground plane) is plotted against the bandwidth and is shown in Figure 2(c). By varying the d3 from 60 mm to Figure 1 Geometry of the proposed handset antenna: (a) top view, (b) bottom view, and (c) integration into a handset DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 52, No. 7, July 2010 1549