We Are Investigating Measurement And Simulation Results In Terms

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We are investigating measurement and simulation results in terms of various modulation schemes and bandwidths in one base station sector to adapt a load generator and WiMAX emulation scenario for more accurate predictions in urban areas. These predictions can support network operators’ management to scale their users. REFERENCES 1. IEEE Standard Std. 802.16-2004 and 802.16e-2005, IEEE standard for local and metropolitan area networks, IEEE Computer Society and IEEE Microwave Theory and Techniques Society, 2006. 2. G. Plitsis, Coverage prediction of new elements of systems beyond 3G: The IEEE 802.16 system as a case study, 58th Vehicular Technical Conference VTC, 2003. 3. V. Erceg et al., Channel models for fixed wireless applications, IEEE 802.16 Broadband Wireless Access Working Group, 2001. 4. V. Erceg, et al., An empirically based path loss model for wireless channels in suburban environments, IEEE J Selected Areas Commun 17 (1999), 1205–1211. 5. D.J. Cichon and T. Ku¨rner, Digital mobile radio towards future generation systems, COST 231 Final Report, 1999. 6. D. Har, H.H. Xia, and H.L. Bertoni, Path loss prediction models for microcells, IEEE Trans on Veh Technol 48 (1999), 1453–1462. 7. C.L. Hong, I.J. Wassell, G.E. Athanasiadou, S. Greaves, and M. Sellars, Wideband channel measurements and characterization for broadband wireless access, Twelfth International Conference on Antennas and Propagation (ICAP 2003), 2003, vol. 1, pp. 429 – 432. 8. C.L. Hong, I.J. Wassell, G.E. Athanasiadou, S. Greaves, and M. Sellars, Wideband tapped delay line channel model at 3.5 GHz for broadband fixed wireless access system as function of subscriber antenna height in suburban environment, Proceedings of the 2003 Joint Conference of the Fourth International Conference on Information, Communications and Signal Processing, 2003 and the Fourth Pacific Rim Conference on Multimedia, 2003, vol. 1, pp. 386390. 9. Airspan Networks Inc, www.airspan.com 10. Rohde&Schwarz, www.rohde-schwarz.de 11. Agilent Technologies, www.agilent.com 1. INTRODUCTION Digital Video Broadcasting-Handheld (DVB-H) is a new standard for delivering broadcast television to mobile terminals. The frequency band of 474 – 698 MHz has been specified for the operation of the DVB-H system. This 224-MHz bandwidth has been divided into 28 ultra high frequency (UHF) channels from UHF channel 21– 49 with a step of 8 MHz [1]. One of the major challenges in this UHF band is the design of terminal antennas which are required to be small in size while maintaining the performance as required by the specifications. The design of DVB-H terminal antennas has received considerable attention over the past few years. A DVB-H receiver antenna, consisting of a nonresonant coupling element, a chassis, and a matching circuit, has been studied in Ref. 2. A planar invert-F antenna (PIFA) and a folded-patch on a big ground plane have also been designed to operate in DVB-H UHF band in Ref. 3. However, the antenna performance of those antennas is very dependent on the ground plane or the chassis, as they act as the main radiators. A ground plane independent folded monopole antenna was proposed in our previous work [4], which is 106 mm, 13.5 mm, and 20 mm in length, width, and height, respectively. The antenna was operating at 610 MHz, with a ⫺6-dB return loss bandwidth of 30 MHz. It was operated with a tunable matching circuit to cover the entire DVB-H band. However, this design is still too large for commercial applications as the terminal size is shrinking with less available ground plane space. The antenna also suffers from a second resonance (750 MHz), which occurs within the DVB-H bandwidth. In this article, a dielectric-loaded monopole antenna is proposed to overcome these limitations presented in the previous folded monopole antenna. Its dimensions have been reduced to 60 mm, 13.5 mm, and 18 mm in length, width, and height, © 2007 Wiley Periodicals, Inc. STUDY OF A DIELECTRIC-LOADED FOLDED MONOPOLE ANTENNA AT UHF BAND FOR DVB-H TERMINALS Y. Gao, R. Kariyawasam, C. C. Chiau, X. Chen, Clive G. Parini Department of Electronic Engineering, Queen Mary University of London, London, E1 4NS, United Kingdom; Corresponding author: [email protected] Received 9 July 2007 ABSTRACT: This article presents a study on a dielectric-loaded folded monopole antenna operating at ultra high frequency band for Digital Video Broadcasting-Handheld terminals. It is an optimization of the folded monopole antenna in our previous work. The proposed antenna has a 43% reduction in volume when compared with the previous design. Because of the ground plane independency of the antenna, the proposed antenna can be mounted on any type of ground plate, thus improving the adaptability to different terminal designs. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 487– 490, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23111 Key words: DVB-H; folded monopole; UHF DOI 10.1002/mop Figure 1 (a) Configuration and (b) return loss results of the folded monopole antenna structure [4] MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 2, February 2008 487 curves are plotted in Figure 3(b). They agree reasonably well with each other. The prototype of the proposed antenna resonates at 690 MHz with a ⫺6-dB return loss bandwidth of 23 MHz. The measured second resonance with a dip to ⫺6 dB is around 1050 MHz (i.e., at least 390 MHz away from the main frequency, far away from the DVB-H and GMS 900 bands) as shown in Figure 3(b). The discrepancies between the measured and simulated values are because of the imperfections fabrication process. The proposed design has achieved an adequate bandwidth to cover an 8-MHz UFH channel. A tuning matching network can be used to sweep the frequency band of the antenna to cover the whole DVB-H frequency band which is commonly used [6-8]. The radiation patterns of the proposed antenna were also measured at 690 MHz in an anechoic chamber at QMUL. Figure 4 shows the measured radiation patterns of the proposed antenna in both YZ and XY planes. It is noted that the proposed antenna can receive both vertical and horizontal polarized signals. This is an advantage as signals arrive at the receiver usually are in the mixture of vertical and horizontal polarizations. 4. GROUND PLANE INDEPENDENCY OF THE ANTENNA Another prototype of the dielectric-loaded folded monopole antenna was fabricated as shown in Figure 5(a). The antenna was Figure 2 Configurations for the proposed antenna where a dielectric slab is loaded in the folded monopole up to the slot level only: (a) 3D view and (b) Top view. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] respectively. The ground plane independency of the antenna is further investigated. The hand effect on the antenna is also considered. 2. ANTENNA DESIGN The proposed dielectric-loaded folded monopole structure is based on our previous work [4], which operates at 610 MHz with a second resonance at 750 MHz, as shown in Figure 1. The antenna is placed 1 mm above the ground plate having dimensions of 134 mm ⫻ 80 mm. In the new design, the folded monopole is loaded with a dielectric slab of relative permittivity 4 up to the level of the slot as illustrated in Figure 2. This filling of the dielectric slab has resulted in a substantial reduction of the antenna size: the length being reduced from 106 to 60 mm and the height reduced from 20 to 18 mm, and also kept the second resonance out of the band. The feeding structure and ground plane of the proposed antenna are same as those used in the folded monopole as shown in Figure 1. It is fed by a 50-⍀ coaxial cable with the inner conductor directly connected to the folded plate. This folded plate is, in turn, connected to the ground plane via a shorting plate to make a balanced structure. 3. ANTENNA PERFORMANCE Computer-Aided Design (CAD) was carried out by using the Computer Simulation Technology (CST) Microwave Studio ® package, which utilizes the finite integral technique (FIT) for electromagnetic computation [5]. The antenna mounted on a flat ground plane was fabricated as shown in Figure 3(a). Its return loss was measured by a HP8720 vector network analyzer in the Antenna Measurement Laboratory at Queen Mary, University of London (QMUL). The simulated and measured return loss 488 Figure 3 (a) The prototype and (b) measured and simulated return loss of the proposed antenna on a flat ground plane. [Color figure can be viewed in the online issue, which is available at www.interscience. wiley.com] MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 2, February 2008 DOI 10.1002/mop measurement, the ground plane of the proposed antenna was held firmly in a pair of hands as shown in Figure 6(a), and the return loss variation was examined. It can be seen in Figure 6(b) that the antennas are only slightly detuned with the presence of users’ hands. It is noted that the main resonance has significantly increased to ⫺27 dB compared with the scenario without users’ hands where it is around ⫺11 dB. A slight increase in the bandwidth is also observed. Furthermore, it has been found that the second resonance is also enhanced and down shifted about 70 MHz. 6. CONCLUSIONS The dielectric-loaded folded monopole antenna proposed in this article has resulted in a substantial reduction in size. A reduction of 43% in volume has been achieved in this design when compared with the folded monopole antenna proposed in our pervious work. A ⫺6 dB return loss bandwidth of 23 MHz and dual-polarized characteristic makes the antenna highly acceptable for DVB-H operation. The dielectric-loaded folded monopole antenna also shows the adaptability to different terminal designs and greater resilient to human hands interactions. Figure 4 Measured copolar (⫺) and crosspolar (⫹) radiation patterns at 690 MHz for both (a) YZ and (b) XY planes. [Color figure can be viewed in the online issue, which is available at www.interscience. wiley.com] mounted on the flap edge (L-shape) of the ground plane. The return loss of this antenna was also measured and compared with that of the antenna mounted on a flat ground plane, as shown in Figure 5(b). It shows that the proposed antenna on both types of ground plane keeps almost the same return loss because of the balance structure, and therefore it has the adaptability to different terminal designs. 5. HAND EFFECT ON THE ANTENNA Normally, the ground plate of the antenna is always in contact with the hands of users that may alter the performance of the antenna [9]. Therefore it is important to assess the performance of the proposed antenna with the presence of users’ hands. In the second DOI 10.1002/mop Figure 5 (a) The prototype and (b) the measured return loss results of the proposed antenna mounted on a L-shape ground plane. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley. com] MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 2, February 2008 489 PRINTED UWB PELLET-SHAPE MICROSTRIP-FED MONOPOLAR ANTENNA FOR 3.1 TO 17 GHz C. H. Chan, T. K. Lee, and W. S. Chan Department of Electronic Engineering, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong SAR, People’s Republic of China; Corresponding author: [email protected] Received 15 July 2007 ABSTRACT: A printed pellet-shape microstrip-fed monopolar antenna is proposed for portable UWB devices. An impedance bandwidth of 138.3% within the frequency range of 3.1 –17 GHz for S11 ⬍ ⫺10 dB is achieved. Positive gain and constant group delay are obtained with omnidirectional radiation pattern. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 490 – 494, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop. 23128 Key words: UWB antenna; broadband antenna; antenna 1. INTRODUCTION Figure 6 (a) The prototype of the proposed antenna held by hands and (b) return loss under hand effect. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com] REFERENCES 1. G. Faria, J.A. Henriksson, E. Stare, and P. Talmola, DVB-H: Digital broadcast services to handheld devices, Proc IEEE, 94 (2006), 194-209. 2. J. Holopainen, Antenna for handheld DVB terminals, Master Thesis, Helsinki University of Technology, Finland, 2005. 3. F. Perssson and M. Wideheim, Design of antennas for handheld DVB-H terminals, Master Thesis, Lund University, Lund, January 2006. 4. Y. Gao, C.C. Chiau, and X. Chen, Design of a folded half loop antenna for handheld DVB-H terminals, In: IET Seminar on RF for DVB-H/ DMB Mobile Broadcast: Handset and Infrastructure Challenges, 2006, pp. 91–105, . 5. Computer Simulation Technology (CST), User Manual 6, CST Microwave Studio, Germany, 2006. 6. C. Goldsmith, J. Randall, S. Eshelman, T.H. Lin, D. Denniston, S. Chen, and B. Norvell, Characteristics of micromachined switches at microwave frequencies, IEEE Microwave Theory Tech Symp Dig 2 (1996), 1141-1144. 7. S. Pacheco, L.P.B. Katehi, and C.T. Nguyen, Design of low actuation RF MEMS Switch, IEEE Microwave Theory Tech Symp Dig 1 (2000), 165-170. 8. S. Pacheco, L.P.B. Katehi, and C.T. Nguyen, High-isolation CPW MEMS shunt switches, Part 2: Design, IEEE Trans Microwave Theory Tech 48 (2000), 1053-1056. 9. L.-C. Kuo and H.-R. Chuang, Design of a 900/1800 MHz dual-band loop antenna mounted on a handset considering the human hand and head effects, IEEE Antennas Propag Soc Int Symp 3 (2003), 701-704. © 2007 Wiley Periodicals, Inc. 490 With the rapid development of technology, the demand for wireless communications is continuously increasing. Many portable devices are increasingly using wireless rather than wire for the transmission and reception of data. However, there is a big limitation in the available data rate for the technologies currently available in the market, within the assigned usable frequency bands. For the presently available technologies, the data rate is limited by narrow bandwidth of the front-ends. On the other hand, because of the limited resources available in the already crowded spectrum, bands are allocated for particular applications. However, the assigned usable frequency band is usually very narrow, which is not favorable for high data rate applications. Therefore, a new application of an old technology named Ultra-WideBand (UWB), which is unlicensed, was proposed to solve this problem. This standard was released by the FCC in 2002 and occupies the frequency range from 3.1 to 10.6 GHz [1]. One of the crucial components for this technology is the ultra-wide band antenna. More recently, many works on these small antennas have shown a requirement of wide impedance bandwidth. As shown in earlier studies, the shapes of these resonators can be rectangular, circular, half knight’s helm, and triangular in shape [2– 6]. However, their bandwidths are only 114.3% within the frequency range of 3.1–11 GHz, which may not be sufficient for future communication systems especially with the ever-increasing demands on user bandwidth [7, 8]. It was also shown that the group delay of the ultra-wide band antenna could be of concern [5]. In our work, the return loss, radiation pattern, gain and group delay of the proposed pellet-shape monopolar antenna are studied experimentally. In addition to the enhanced bandwidth, the proposed antenna has demonstrated positive gain and flat group delay from 3.1–17 GHz. 2. ANTENNA DESIGN The geometry of the printed pellet-shape monopolar antenna with the dimensions of 43.5 mm ⫻ 32 mm is shown in Figure 1. The antenna is fabricated on a wangling substrate, which has a thickness of 1.5 mm and a dielectric constant of 2.65. On the front side of the antenna, it has both vertical and horizontal symmetry with a pellet-shape and a height (L) of 24 mm and width of 23 mm. The height and width of the microstrip feed MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 50, No. 2, February 2008 DOI 10.1002/mop