flows are more dominant around of the meander-line slit embed- ded at radiating patch [13, 14]. The proposed antenna with final design was built and tested. The measured and simulated return loss characteristics of the proposed antenna are shown in Figure 5. The fabricated antenna has frequency bands of 2.01–2.67 GHz, 3.25–3.75 GHz, and 5–6 GHz which are suitable for 2.4/5.2/ 5.8 GHz WLAN and 2.5/3.5/5.5 GHz WiMAX applications. Figure 6 illustrates the measured radiation patterns, including the copolarization and cross-polarization, in the H-plane (x-z plane) and E-plane (y-z plane). It can be seen that the radiation patterns in x-z plane are nearly omnidirectional for the three fre- quencies [15–17]. This antenna element can be arrayed for use in MIMO appli- cations. The performance of an antenna array suitable for MIMO applications is based on various parameters such as mutual coupling and radiation pattern. Based on the four possi- ble configurations that any two such monopole antennas can be arranged beside each other. Figure 8 shows the relevant simu- lated S-parameters. In each case, the spacing between array ele- ments is set at 15 mm (k/10 of the lowest frequency band) [9, 10]. From Figure 7 results, it can be seen that the array struc- tures of Figures 7(c) and 7(d), in which the antenna elements are orthogonal, show lower mutual coupling than those struc- tures in which the elements are parallel. For such orthogonal elements, the pattern of each element lies on a plane. 4. CONCLUSION A new small monopole antenna with triple-band performance for WLAN/WiMAX applications is presented. The operating frequen- cies of the proposed antenna are 2.4/3.5/5.5 GHz, which covers WLAN and WiMAX systems. To generate a triple-band perform- ance for the proposed antenna, we use two meander-line slits in the ground plane and radiating patch, respectively. Two-element arrays of such antennas in four different configurations for MIMO applica- tions are analyzed. Simulated and experimental results show that the proposed antenna could be a good candidate for MIMO application. ACKNOWLEDGMENT The authors are thankful to Microwave Technology (MWT) Company staff for their beneficial and professional help (www. microwave-technology.com). REFERENCES 1. G.J. Foschini and M.J. Gans, On limits of wireless communications in a fading environment when using multiple antennas, Wireless Pers Commun 6 (1998), 311–335. 2. K.L. Wong, Compact and broadband microstrip antennas, Wiley Press, New York, NY, 2002. 3. A. Sen and N. Chattoraj, Dual-frequency microstrip antenna for wireless applications and effect on fraud, Electr Electron Eng 2 (2012), 78–81. 4. V. Deepu, R.K. Raj, M. Joseph, M.N. Suma, and P. Mohanan, Com- pact asymmetric coplanar strip fed monopole antenna for multiband applications, IEEE Trans Antennas Propag 55 (2007), 2351–2357. 5. N. 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Ojaroudi, A novel design of triple-band monop- ole antenna for multi-input multi-output communication, Microwave Opt Technol Lett 55 (2013), 1258–1262. 11. Ansoft, Ansoft High Frequency Structure Simulation (HFSS), Ver. 13, Ansoft Corporation, 2010. 12. N. Ojaroudi, Design of ultra-wideband monopole antenna with enhanced bandwidth, In: 21st Telecommunications Forum, TELFOR 2013, Belgrade, Serbia, November, 2013, pp. 1043–1046. 13. N. Ojaroudi, A new design of koch fractal slot antenna for ultra- wideband applications, In: 21st Telecommunications Forum, TEL- FOR 2013, Belgrade, Serbia, November, 2013, pp. 1051–1054. 14. N. Ojaroudi, Compact UWB monopole antenna with enhanced band- width using rotated L-shaped slots and parasitic structures, Micro- wave Opt Technol Lett 56 (2014), 175–178. 15. N. Ojaroudi, S. Amiri, and F. Geran, A novel design of reconfigura- ble monopole antenna for UWB applications, Appl Comput Electro- magn Soc J 28 (2013), 633–639. 16. N. Ojaroudi, Application of protruded strip resonators to design an UWB slot antenna with WLAN band-notched characteristic, Prog Electromagn Res C 47 (2014), 111–117. 17. N. Ojaroudi, Microstrip monopole antenna with dual band-stop function for UWB applications, Microwave Opt Technol Lett 56 (2014), 818–822. VC 2014 Wiley Periodicals, Inc. MICROWAVE DIELECTRIC MEASUREMENTS OF FIBROUS CATALYST USING TRANSMISSION LINE TECHNIQUE IN THE FREQUENCY RANGE OF 1–4 GHz Adam Aboutaleb, 1 George Chi-Tangyie, 2 Katherine Huddersman, 2 and Chris H Oxley 1 1 Faculty of Computing Sciences and Engineering, De Montfort University, Leicester LE2 7DR, United Kingdom; Corresponding author: aaboutaleb@dmu.ac.uk 2 Faculty of Health and Life Sciences, De Montfort University, Leicester LE2 7GZ, United Kingdom Received 9 March 2014 ABSTRACT: Materials performance at microwave frequencies has gen- erated a wide interest in recent years for commercial and industrial pur- poses. However, the interaction between microwave energy and iron compounds is an area where further characterization work is required. The article presents a novel optimized analytical-numerical method for conversion of smoothed transmission scattering (S 21 ) parameters to com- plex permittivity. The measurement method was validated and subse- quently used to characterize the dielectric properties of modified polyacrylonitrile catalyst powder incorporating ligated iron cations. The result is compared to other published iron catalyst materials measured in the same frequency range of 1 to 4 GHz. VC 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2671–2676, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.28674 Key words: dielectric measurement; transmission line technique; New- ton Raphson iterative method; polyacrylonitrile catalyst dielectric properties 1. INTRODUCTION Microwave applications have significantly increased over the past years and it is expected that they will continue to increase DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 56, No. 11, November 2014 2671