Also, there is a little mismatch between simulated and measured results.This might be due to other unknown parasitic effects that are not considered in the simulation. As the soldering on the PCB is not done with a machine, positional errors might give rise to the discrepancy. The measured radiation pattern (normal- ized) at different frequencies is given in the Figures 10(a) and 10(b). 3. CONCLUSION The aim of this work is to design a wide band antenna structure as simple as possible while having multiband applications. This letter presents a novel structure where complementary slots in the ground plane are used to achieve wide band characteristic. The key contribution of this article is the conversion of separate bands to a single wide band using complementary slots. The slotted antenna structure with and without complementary slots are examined using simulation and experimental results and the idea has been verified. Furthermore, the inclusion of comple- mentary slots in the ground plane causing conversion of multi- band to wide band does not affect other characteristics of the antenna. Thus, the proposed concept can be used for achieving improved band width where narrow band antenna becomes a major limitation in the compact antenna structure. REFERENCES 1. J. Anguera, Fractal and broad-band techniques on miniature, multi-frequency, and high-directivity microstrip patch antennas, Ph.D. Dissertation, Universitat Politmecnica of Catalunya, Barcelona, Spain, 2003. 2. J.C. Anguera, C. Puente, C. Borja, and J. Soler, Dual frequency broadband stacked microstrip antenna using a reactive loading and a fractal-shaped radiating edge, IEEE Antennas Wireless Propag Lett 6 (2007), 309–312. 3. J. Anguera, C. Puente, C. Borja, N. Delbene, and J. Soler, Dual fre- quency broadband stacked microstrip patch antenna, IEEE Antennas Wireless Propag Lett 2 (2003), 36–39. 4. J. Anguera, G. Font, C. Puente, C. Borja, and J. Soler, Multi-fre- quency microstrip patch antenna using multiple stacked elements, IEEE Microwave Wireless Compon Lett 13 (2003), 123–124. 5. S.C. Pan and K.L. Wong, Dual-frequency triangular microstrip antenna with a shorting pin, IEEE Trans Antennas Propag 45 (1997), 1889–1891. 6. C. Picher, J. Anguera, A. Cabedo, C. Puente, and S. Kahng, Multi- band handset antenna using slots on the ground plane considerations to facilitate the integration of the feeding transmission line, Prog Electromagn Res 7 (2009), 95–109. 7. A. Cabedo, J. Anguera, C. Picher, M. Ribo and C. Puente, Multi- band handset antenna combining a PIFA, slots, and ground plane modes, IEEE Trans Antennas Propag 57 (2009), 2526–2533. 8. W. Kwak, S.O. Park, and J.S. Kim, A folded planar inverted-F antenna for GSM/DCS/bluetooth Triple-band application, IEEE Antennas Wireless Propag Lett 5 (2006), 18–21. 9. R.A. Bhatti, Y.S. Shin, N. Nguyen, and S. Park, Design of novel multiband planar inverted-F antenna for mobile terminals, In: Inter- national Workshop on Antenna Technology: Small Antennas and Novel Materials, iWAT, Chiba, Japan, 2008, pp. 530–533. 10. X. Zhang and A. Salo, Design of novel wideband planar inverted-F antenna for mobile application, In: Progress in Electromagnetics Research Symposium, PIERS, Beijing, China, 2009, pp. 1191–1195 11. C.L Tang, C.W. Chiou, and K.L. Wong, Broadband dual-frequency V- shape patch antenna, Microwave Opt Technol Lett 25 (2000), 121–123. 12. K.M. Luk, C.H. Lai, and K.F. Lee, Wideband L-probe-fed patch antenna with dual band operation for GSM/PCS base stations, Elec- tron Lett 35 (1999), 1123–1124. 13. R. Hossa, A. Byndas, and M.E. Bialkowski, Improvement of com- pact terminal antenna performance by incorporating open end slots in ground plane, IEEE Microwave Wireless Compon Lett 14 (2004), 283–285. 14. M.F. Abedin and M. Ali, Modifying the ground plane and its effect on planar inverted-F antennas (PIFAs) for mobile phone handsets, IEEE Antennas Wireless Propag Lett 2 (2003), 226–229. 15. R.A. Sainati, CAD of micro strip antenna for wireless applications, Artech House, Inc, Norwood, MA, 1994. V C 2016 Wiley Periodicals, Inc. AN ULTRAWIDEBAND ANTENNA FOR PORTABLE MIMO TERMINALS Zamir Wani and Dinesh Kumar Vishwakarma Indian Institute of Information Technology, Design and Manufacturing Jabalpur, Madhya Pradesh 482005, India; Corresponding author: zamir.wani@iiitdmj.ac.in Received 20 May 2015 ABSTRACT: A compact printed ultrawideband (UWB) antenna system used to combat multipath fading has been proposed and investigated. The antenna consisting of two shovel-shaped monopole antenna elements (AE) on a low loss substrate with dimensions 35 3 30 mm 2 can be used for multi-input-multi-output (MIMO)/diversity applications. Both the monopole antennas are fed with microstrip lines, matched to 50 X lines at each port. To reduce the mutual coupling, two F-shaped ground stubs are added to the ground plane and rectangular slots have been made to ensure proper impedance matching. Measured and simulated results show that the antenna system covers most of UWB with isolation greater than 22 dB. A low value of measured envelops correlation coefficient less than 0.005 is achieved throughout the entire band of interest (3.1– 10.6 GHz). The proposed antenna satisfies all the requirements of an MIMO antenna used for UWB, thus is a potential candidate for MIMO/ diversity applications in UWB communication. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:51–56, 2016; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.29498 Key words: diversity; envelope correlation coefficient; ground stub; iso- lation; multiple-input-multiple-output; ultrawideband 1. INTRODUCTION Multiple-input-multiple-output (MIMO) is a multiplexing tech- nique, uses number of antennas both at transmitter and receiver which can enhance the channel throughput without any increase in bandwidth or power. Using multiple antennas with different radia- tion properties can reduce the effect of multipath fading [1–3]. Ultrawideband (UWB) communication uses the unlicensed band (3.1–10.6 GHz) and has inherit advantages, such as, high data rate, low power, and easy fabrication [4]. UWB communica- tion can be used to set up personal area network for controlling different devices like printers, digital cameras, and computers [5]. The combination of UWB communication and MIMO tech- nology is an interesting research direction. Various MIMO/ diversity antennas for UWB have been proposed [6–15]. It is very challenging to increase the isolation between the antenna elements in a small space. Various methods to enhance the iso- lation between antennas have been proposed. High isolation can be achieved by making slots in the ground plane or adding stubs to ground plane [13,14]. Dual polarization can also be used to increase the isolation between the antenna elements [15]. The diversity antennas proposed in [7–9], were not compact and are not suitable for portable devices. In [6], a tree like structure has been proposed to enhance the isolation (S12 < 216 dB) and had smallest size of 35 3 40 5 1400 mm 2 . DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 58, No. 1, January 2016 51