Flexible and Compact Spiral-Shaped Frequency ...

IETE Journal of Research

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Flexible and Compact Spiral-Shaped Frequency Reconfigurable Antenna for Wireless Applications Ashfaq Ahmad, Farzana Arshad, Syeda Iffat Naqvi, Yasar Amin, Hannu Tenhunen & Jonathan Loo To cite this article: Ashfaq Ahmad, Farzana Arshad, Syeda Iffat Naqvi, Yasar Amin, Hannu Tenhunen & Jonathan Loo (2018): Flexible and Compact Spiral-Shaped Frequency Reconfigurable Antenna for Wireless Applications, IETE Journal of Research To link to this article: https://doi.org/10.1080/03772063.2018.1477629

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IETE JOURNAL OF RESEARCH https://doi.org/10.1080/03772063.2018.1477629

Flexible and Compact Spiral-Shaped Frequency Reconfigurable Antenna for Wireless Applications Ashfaq Ahmad1 , Farzana Arshad1 , Syeda Iffat Naqvi1 , Yasar Amin2 , Hannu Tenhunen2,3 and Jonathan Loo4 1 ACTSENA Research Group, University of Engineering and Technology (UET), Taxila 47050, Pakistan; 2 iPack VINN Excellence Center, Royal Institute of Technology (KTH), Stockholm SE-16440, Sweden; 3 TUCS, University of Turku, Turku 20520, Finland; 4 Department of Computer

Science, School of Engineering and Information Sciences, Middlesex University, London, UK ABSTRACT

A flexible, spiral-shaped frequency reconfigurable antenna with a compact size (20 × 24 mm2 ) is presented. The proposed antenna has a low-profile planar structure and is able to operate at five different frequency bands, i.e., 4.19–4.48, 5.98–6.4, 3.42–4.0, 5.4–5.68, and 6.8–7.0 GHz. The multiband operation enables the antenna to cover aeronautical radio navigation, fixed satellite communication, WLAN, and WiMAX standards. A radiating element is backed R 5880 substrate with a thickness of 0.508 mm and dielectric constant of 2.2. The spiby Rogers ral shape is achieved by introducing different strips. Frequency reconfiguration is achieved by the incorporation of a lumped element in a strip, so that the antenna can switch between different resonances. To validate the performance of the antenna, the prototype of the design was fabricated and tested. Good acquiescent is seen between simulated and measured results. The proposed antenna operates efficiently with appreciable return loss, directivity, bandwidth, and peak gain.

1. INTRODUCTION Modern telecommunication systems extensively focus on developing the Internet and mobile devices. Such devices are able to operate on more than one application. Each application has its own operational band, i.e., wireless fidelity (Wi-Fi), Bluetooth, global positioning system, global system for mobile communication, and worldwide interoperability for microwave access (WiMAX). Being the most critical part of the communication system, antennas must be designed and deployed efficiently. So that optimal utilization of the available spectrum can be ensured. In this perspective, there are various antenna methodologies, simple antenna, multiband antenna, and reconfigurable antennas. Applications of these three types of antennas have their own merits and demerits. Better performance can be achieved by implanting more than one single band antennas in a device for different applications, but at the cost of size, complexity as well as coupling due to small space in between. To consolidate multiple services, multiband antenna is the best candidate that transmits and receives EM waves at multiple frequencies with optimum gain, directivity, and radiation efficiency.

© 2018 IETE

KEYWORDS

AMT fixed services; Flexible antenna; Reconfigurable; Satellite; WiMAX; WLAN

Currently, some approaches for the design of multiresonant antennas include integration of a metamaterial inspired split ring resonator [1] and insertion of slots [2] within the radiating elements. Defective ground planes [3] are also proposed to acquire the multiple frequency bands. However, they transmit all resonances irrespective of the end user requirement [4]. In other words, multiband antennas cannot be tuned at the desired frequency. Moreover, in the multiband antennas, the chance of jamming and unavailability of wireless services increases due to poor isolation between different operating frequency bands. To overcome these limitations, researchers have developed a possible solution, i.e., reconfigurable antennas. Reconfigurable antennas have great potential to mitigate the problems encountered in single band antennas and multiband antennas. There are various reconfigurable antennas such as polarization reconfigurable [5], frequency reconfigurable [6], and pattern reconfigurable [7]. Re-configurability essentially involves changing the current distribution within the radiating element and that can be realized by employing various switches such as PIN Diode [8], varactor diode [9], radio frequency micro-electro-mechanical system (RF-MEMS) switches

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ASHFAQ AHMAD ET AL.: FLEXIBLE AND COMPACT SPIRAL-SHAPED FREQUENCY RECONFIGURABLE ANTENNA

[10], variable capacitance switches [11], and lumped element [12]. A variety of re-configurable antennas with different switching techniques have been demonstrated.

higher fabrication cost. However, achieving multiband re-configurable antenna with minimum switching elements within a compact structure is still a challenge.

A tri-band 35 × 53 mm2 (2.45, 3.50, and 5.20 GHz) frequency reconfigurable antenna using a lumped element is reported in Ullah et al. [12]. A novel 40 × 40 mm2 antenna is presented in [13] by introducing the switchable slots in the ground plane, the antenna can be switched between a narrow band, UWB, and dualband. A pervasive antenna of 90 × 50 mm2 is designed for industrial, scientific, and medical applications [14]. Small-size re-configurable antennas have also been reported in the literature. A compact tri-band frequency reconfigurable antenna with the size of 27 × 25 mm2 is presented in [15]. This slot antenna uses two pin diodes for frequency reconfiguration. The antenna proposed in [16] employs eight varactor diodes and covers only five operational bands. This design has a complex geometry because of the number of switches and biasing network, which further increases insertion loss and degrades antenna performances. However, most of the aforesaid designs are implemented on rigid substrates and merely a few designs are realized on flexible substrates. Antennas having rigid substrates are not suitable for conformal applications.

In this work a compact, flexible CPW fed spiral-shaped frequency reconfigurable antenna is proposed. The proposed antenna works on five different resonances with measurable gain and bandwidth depending on the status of a lumped element incorporated in the radiating patch.

Nowadays, because of their lightweight, low profile, and robustness bendable antenna have gained much attention. Still, deployment of such antennas in practical applications remains challenging. In conformal applications, the antenna cannot maintain its flat state. Different stretchable substrates have been reported in [17–21]. A 70 × 70 mm2 flexible crescent shape antenna with a high bandwidth of 7.1 GHz is proposed in [17]. Multi resonance antenna using Kapton polyamide is presented in Ahmed et al. [18] having bulky size of 70 × 70 mm2 . A paper-based 2.4-GHz antenna for WLAN applications is expounded in [19]. Using 44 × 40.2 mm2 flexible liquid crystal polymer dual frequency band rejection is successfully achieved at 5.25 and 5.775 GHz [20]. In [21] 60 × 63 mm2 UWB antenna is presented which uses cotton fabric as a substrate. The comparison has been made under bending and wet conditions. Above presented flexible antennas are not reconfigurable.

The work is organized as follows: Section 2 covers design and theory of proposed spiral-shaped antenna. Simulated and measured results are discussed in Section 3. Section 4 concludes the discussion.

2. ANTENNA DESIGN Figure 1 illustrates the configuration of the proposed R R design. The antenna uses a flexible Rogers RT/Duroid

Figure 1: Geometrical view of proposed design Table 1: Parameters of the proposed design Parameter

Different feeding techniques have been proposed, but coplanar waveguide (CPW) feeding is preferable as it reduces intricacy by placing an antenna patch and a ground plan on the same side of the substrate. A CPW feed flexible and reconfigurable T-shaped antenna for WLAN and WiMAX applications is presented in Saeed et al. [22]. This antenna has the low gain and

Ls L1 L2 L3 L4 L5 L6 L7 G

Size (mm)

Parameter

Size (mm)

24 15.8 8 1 11 7.5 2 1 0.55

Ws W1 W2 W3 W4 W5 W6 W7 Wt

20 5.3 1.8 3 4.6 3 8.8 13.7 1.52


5880 as a substrate. The dielectric constant and tangent loss of the substrate is 2.2 and 0.0009, respectively, with a thickness of 0.508 mm. The proposed antenna has a compact size of 20 × 24 mm2 . Focusing on the goal of impedance matching and measurable gain, the antenna consists of the spiral-shaped radiator. The antenna structure is designed to resonate at five different frequencies. Frequency agility is achieved using a lumped element switch in a 1-mm reserved slot. In order to achieve large

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bandwidth, better efficiencies and ease of integration, the CPW ground plane is used. The antenna is excited with a 1.5-mm wider CPW feed line having a characteristic impedance of 50 . Table 1 presents the optimized parameters of the proposed design. The effective resonating length for specific resonance frequency is calculated using transmission line theory [12]. Lr = 4fr

εr+1 2

c +

−0.5 εr−1 2 (1 + 12h/W)

,

where c is the speed of light, h is the thickness of the substrate, and r is the relative permittivity of the substrate.

Figure 2: Various stages of proposed antenna with corresponding S11

Figure 2 presents the designing steps to obtain the proposed spiral-shaped antenna and the corresponding S11 . Multiple strips are added in a spiral shape to yield the different operating modes. The effect of strips integration can be clearly seen in Figure 2. In the first step, the antenna consists of CPW and three strips. In this case, the electrical current path is shorter, which yield high frequency (6.8 GHz), with S11 < −15. In the second step, due to the addition of another slot, the electrical current path becomes large, and resonant frequency slightly moves toward the lower frequency (6.2 GHz) with S11 < −30. Similarly, due to the addition of another strip, overall radiating part increases, the resonance shift towards the lower frequency (3.73 GHz). The joint effect

Figure 3: Simulated current distribution. (a) 3.6 GHz, (b) 5.5 GHz, (c) 6.9 GHz, (d) 4.3 GHz, and (e) 6.22 GHz

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of strips allows the antenna to resonate at 5.6 and 6.9 GHz. To make the antenna reconfigurable a 1-mm slot is reserved for the switch.

Figure 3(a) depicts that at 3.6 GHz, the current is distributed in all strips except the uppermost one. The intensity of the current is higher around the central stripes,

The final proposed design, due to the integration of the switch and another strip also covers other resonances. When the switch is in OFF state, the antenna operates at 3.6, 5.56, and 6.9 GHz, while for ON condition the resonances shift to 4.33, 6.22, and 6.9 GHz. The multiband behavior of the antenna can be understood by analyzing the surface current distribution at the attained resonances, as shown in Figure 3(a)–(e). The current path obtained for different resonant frequencies can be readily identified in the illustrations.

Figure 6: Simulated and measured. (a) E-field and (b) H-field (SW ON) Table 2: Summarize results (SW ON) Frequency (GHz) Return loss (dB) Bandwidth (MHz) Gain (dBi) Directivity (dB) Efficiency (%age) VSWR

4.33 −24.9 281 2.55 3.44 81 1.12

6.22 −25.89 411 3.06 3.85 83 1.1

6.96 −31.04 147 2.65 3.73 80 1.05

Figure 4: Fabricated design. (a) Switch on and (b) switch off

Figure 5: Simulated and measured S11 of the proposed antenna (SW ON)

Figure 7: Simulated and measured S11 of the proposed antenna (SW OFF)


which resonate at 5.5 GHz, as shown in Figure 3(b). Similarly, in Figure 3(c) current is distributed in the shorter path, which gives rise to high frequency, i.e., 6.9 GHz. Figure 3(d) illustrates that other than lower and second strip all strips resonate, hence current follows the longer path, which stimulates a resonance at the lower frequency, i.e., 4.3 GHz. Figure 3(e) shows that only central strips do not resonate, due to this current distribution, 6.22 GHz frequency is achieved.

3. RESULTS AND DISCUSSION R The CST microwave studio is used to design and analyze the proposed antenna. To validate the performance

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of the design, the antenna is fabricated and tested R utilizing the vector network analyzer R&S ZVL13. Figure 4(a) and (b) illustrates the prototype of the fabricated antenna. All results are achieved due to different states of the switch, i.e., either ON or OFF.

3.1. Switch ON (Mode 1) The simulated and measured S11 in mode 1 is shown in Figure 5. In this mode, the antenna operates at three resonant frequencies 4.33, 6.22, and 6.9 GHz. The bandwidth of the first band is 6.72%, which is used for aeronautical radio navigation, while 6.88% and 1.4% bandwidth is achieved for the second and third band, respectively, supporting fixed satellite communication and WiMAX applications. The simulated and measured E-plane and H-plane of the antenna for the abovementioned three frequencies are shown in Figure 6. It can be observed that the shape of the radiation patterns in the E-plane, as well as in H-plane approaches to that of the monopole at all three resonances, which makes the design compatible for communication. The summarized results of mode 1 are presented in Table 2.

3.2. Switch OFF (Mode 2)

Figure 8: Simulated and measured. (a) E-field and (b) H-field (SW OFF) Table 3: Summarize results (SW OFF) Frequency (GHz) Return loss(dB) Bandwidth (MHz) Gain (dBi) Directivity (dB) Efficiency (%age) VSWR

3.6 −23.1 577 0.20 3.64 45.3 1.14

5.5 −24 285 2.24 3.56 73.7 1.12

6.96 −35.1 223 1.85 3.45 69.2 1.03

Both measured and simulated S11 in mode 2 is shown in Figure 7. In this mode, the antenna operates at three resonances including a repeated band of 6.9 GHz, which is already observed in mode 1. Operating bands are 3.6, 5.5, and 6.9 GHz. The first band has a bandwidth of 16% covering WLAN, while the second band has a bandwidth of 5% covering WiMAX applications. Simulated and measured E and H-plane for this state are presented in Figure 8. It can be observed that the shape of the radiation patterns in the E-plane as well as in H-plane approaches to that of the monopole at all three resonances. The summarized results of mode 2 are presented

Table 4: Comparison with previous work Characteristics

[22]

[15]

[23]

[24]

[25]

This work

Area (mm2 )

1829 0.1 PET 1 3 160,

675 0.8 RO4350 3 6 100,

400 0.8 FR4 3 3 210,

400 0.8 FR4 1 4 140,

2300 1.52 Taconic 5 6 250,

480 0.508 RT 5880 1 5 281,

180, 270

120, 280, 220, 100, 320

400, 580

280, 510, 1090

310, 300, 300, 260, 210

411, 147, 577, 285

Height (mm) Substrate Switches Resonances Bandwidth at different resonance bands (MHz)


6

in Table 3. Close agreement can be observed between measured and simulated results. The proposed design is compared with recently published work as shown in Table 4. In Saeed et al. [22], a single switch is used to change the antenna resonance frequency, but the design is bulky and bandwidth is narrow. Multi resonance antennas are presented in Han et al. [15], Borhani et al. [23], and Majid et al. [25], but at the cost of increased no of switches, large size, and narrow bandwidth. Similarly, a miniaturized reconfigurable antenna was presented in Kakhki et al. [24] with four resonances and the rigid substrate.

4. CONCLUSION A novel, compact, and flexible spiral-shaped frequency reconfigurable antenna is presented with detailed measured and simulated results. The spiral shape is designed to produce multiple resonances. Frequency reconfigurable behavior is achieved by incorporating a switch in the structure. The antenna operates at five different frequency bands, which are 3.6, 4.3, 5.5, 6.5, and 6.9 GHz with a bandwidth of 577, 281, 285, 411, and 223 MHz, respectively, which cover WLAN, aeronautical radio navigation, WiMAX, and satellite communication. The antenna is analyzed under the plane configurations. There is a close kindred attribute between simulated and measured results. With a compact size of 20 × 24 mm2 , the proposed antenna is viable for different wireless applications.

FUNDING

4. S. A. A. Shah, M. F. Khan, S. Ullah, A. Basir, U. Ali, and U. Naeem, “Design and measurement of planar monopole antennas for multi-band wireless applications,” IETE J. Res., Vol. 63, pp. 194–204, 2017. 5. K. M. Mak, H. W. Lai, K. M. Luk, and K. L. Ho, “Polarization reconfigurable circular patch antenna with a C-shaped,” IEEE Trans. Antennas Propag., Vol. 65, pp. 1388–92, 2017. 6. B. Bhellar and F. A. Tahir, “Frequency reconfigurable antenna for hand-held wireless devices,” IET Microwaves Antennas Propag., Vol. 9, pp. 1412–17, 2015. 7. M. S. Alam and A. M. Abbosh, “Wideband patternreconfigurable antenna using pair of radial radiators on truncated ground with switchable director and reflector,” IEEE Antennas Wirel. Propag. Lett., Vol. 16, pp. 24–8, 2017. 8. X. Zhang, M. Tian, A. Zhan, Z. Liu, and H. Liu, “A frequency reconfigurable antenna for multiband mobile handset applications,” Int. J. RF Microwave Comput. Aided Eng., Vol 27, no. 9, 2017. 9. Z. Mahlaoui, E. Antonino-Daviu, M. Ferrando-Bataller, H. Benchakroun, and A. Latif, “Frequency reconfigurable patch antenna with defected ground structure using varactor diodes,” in EEE conference on Antennas and Propagation (EUCAP), 2017, pp. 2217–20. 10. N. Kumar and Y. K. Singh, “RF-MEMS-based bandpassto-bandstop switchable single-and dual-band filters with variable FBW and reconfigurable selectivity,” IEEE Trans. Microwave Theory Tech., Vol. 65, no. 10, pp. 3824–37, 2017. 11. I. Rouissi, I. B. Trad, J. M. Floc’h, H. Rmili, and H. Trabelsi, “Frequency reconfigurable antenna using active capacitors,” in Microwave Symposium (MMS), IEEE 15th Mediterranean, 2015, pp. 1–4.

This work was financially supported by Vinnova (The Swedish Governmental Agency for Innovation Systems) and University of Engineering and Technology, Taxila, Pakistan through the Vinn Excellence Centers program and ACTSENA research group funding, respectively.

12. S. Ullah, S. Hayat, A. Umar, U. Ali, F. A. Tahir, and J. A. Flint, “Design, fabrication and measurement of triple band frequency reconfigurable antennas for portable wireless communications,” AEU Int. J. Electron. Commun., Vol. 81, pp. 236–42, 2017.

REFERENCES

13. S. Shi, W.-P. Ding, and K. Luo, “A monopole antenna with dual-band reconfigurable circular polarization,” Prog. Electromagnet. Res. C, Vol. 55, pp. 35–42, 2014.

1. V. Rajeshkumar and S. Raghavan, “A compact metamaterial inspired triple band antenna for reconfigurable WLAN/WiMAX applications,” AEU Int. J. Electron. Commun., Vol. 69, pp. 274–80, 2015. 2. W. Liu, C. Wu, C. M., and N.-C. Chu, “A compact low-profile dual-band antenna for WLAN and WAVE applications,” AEU Int. J. Electron. Commun., Vol. 66, pp. 467–71, 2012. 3. A. K. Gautam, A. Bisht, and B. K. Kanaujia, “A wideband antenna with defected ground plane for WLAN/WiMAX applications,” AEU Int. J. Electron. Commun., Vol. 70, pp. 354–8, 2016.

14. H. Wang and M. Zheng, “An internal triple-band WLAN antenna,” IEEE Antennas Wirel. Propag. Lett., Vol. 10, pp. 569–72, 2011. 15. L. Han, C. Wang, X. Chen, and W. Zhang, “Compact frequency-reconfigurable slot antenna for wireless applications,” IEEE Antennas Wirel. Propag. Lett., Vol. 15, pp. 1795–8, 2016. 16. L. Ge, and K.-M. Luk, “Frequency-reconfigurable lowprofile circular monopolar patch antenna,” IEEE Trans. Antennas Propag., Vol. 62, pp. 3443–9, 2014.


17. M. O. Sallam, S. M. Kandil, Volski, V., Vandenbosch, G. A., and E. A. Soliman, “2.4/5 GHz WLAN crescent antenna on flexible substrate,” in IEEE Conference on Antennas and Propagation (EuCAP), 2016, pp. 1–3. 18. S. Ahmed, F. A. Tahir, A. Shamim, and H. M. Cheema, “A compact Kapton-based inkjet-printed multiband antenna for flexible wireless devices,” IEEE Antennas Wirel. Propag. Lett., Vol. 14, pp. 1802–5, 2015. 19. D. E. Anagnostou, A. A. Gheethan, A. K. Amert, and K. W. Whites, “A direct-write printed antenna on paper-based organic substrate for flexible displays and WLAN applications,” J. Disp. Technol., Vol. 6, pp. 558–64, 2010. 20. A. A. Gheethan and D. E. Anagnostou, “Dual band-reject UWB antenna with sharp rejection of narrow and closelyspaced bands,” IEEE Trans. Antennas Propag., Vol. 60, pp. 2071–6, 2012. 21. M. S. Shakhirul, M. Jusoh, A. Sahadah, C. M. Nor, and H. A. Rahim, “Embroidered wearable textile antenna

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on bending and wet performances for UWB reception,” Microwave Opt. Technol. Lett., Vol. 56, pp. 2158–63, 2014. 22. S. M. Saeed, C. A. Balanis, C. R. Birtcher, “Inkjetprinted flexible reconfigurable antenna for conformal WLAN/WiMAX wireless devices,” IEEE Antennas Wirel. Propag. Lett., Vol. 15, pp. 1979–82, 2016. 23. M. Borhani, P. Rezaei, and A. Valizade, “Design of a reconfigurable miniaturized microstrip antenna for switchable multiband systems,” IEEE Antennas Wirel. Propag. Lett., Vol. 15, pp. 822–5, 2016. 24. M. B. Kakhki, P. Rezaei, V. Sharbati, and M. M. Fakharian, “Small square reconfigurable antenna with switchable single/tri-band functions,” Radioengineering, Vol. 25, 2016, pp. 4. 25. H. A. Majid, M. K. A. Rahim, M. R. Hamid, and M. F. Ismail, “A compact frequency-reconfigurable narrowband microstrip slot antenna,” IEEE Antennas Wirel. Propag. Lett., Vol. 11, pp. 616–9, 2012.

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Authors Ashfaq Ahmad received his BSc degree in Telecommunication Engineering from UET Peshawar in 2016. He is doing his MSc in Telecommunication Engineering from UET Taxila. Currently, he is doing research on reconfigurable antennas. His research interests include planar antenna, millimeter wave antennas, multiband antennas, implanted antennas, specific absorption rate analysis and EBGs. Corresponding author. Email: [email protected] Farzana Arshad received her BSc and MSc degree in Software Engineering and Telecommunication Engineering from UET Taxila, Pakistan in the year 2006 and 2010, respectively. Currently, she is working towards her PhD degree in Telecommunication Engineering from UET Taxila. She is also a member of ACTSENA, research group. Her current research interests include low-profile multiband and reconfigurable antenna design. Email: [email protected] Syeda Iffat Naqvi received her BSc and MSc degree in Computer Engineering and Telecommunication Engineering from UET Taxila, Pakistan in the year 2006 and 2011, respectively. Currently, she is pursuing her degree of PhD in Telecommunication Engineering from (UET) Taxila. She is also a member of ACTSENA, research group. Her current research interests include RF and microwave antenna designing for cutting-edge wireless technologies. Syeda is a member of IEEE and ACES. Email: [email protected] Yasar Amin is Chairman and Associate Professor of Telecommunication Engineering Department, University of Engineering and Technology Taxila, Pakistan. He is founder of ACTSENA, Research Group at UET Taxila, Pakistan. He has done his BSc in Electrical Engineering in

2001 with specialization in Telecommunication and MSc in Electrical Engineering in 2003 with specialization in Systemon Chip Design from Royal Institute of Technology (KTH), Sweden. His PhD is in Electronic and Computer Systems from Royal Institute of Technology (KTH), Sweden, with research focus on printable green RFID antennas for embedded sensors, while has MBA in Innovation and Growth from Turku School of Economics, University of Turku, Finland. Email: [email protected] Hannu Tenhunen is Chair Professor of Electronic Systems at Royal Institute of Technology (KTH), Stockholm, Sweden. Tenhunen has held Professor positions as Full Professor, Invited Professor or Visiting, Honorary Professor in Finland (TUT, UTU), Sweden (KTH), USA (Cornel U), France (INPG), China (Fudan and Beijing Jiatong Universities), and Hong Kong (Chinese University of Hong Kong), and has an Honorary Doctorate from Tallinn Technical University. He has been Director of multiple national large scale research programs or being an Initiator and Director of national or European graduate schools. He as actively contributed on VLSI and SoC design in Finland and Sweden via creating new educational programs and research directions, most lately at European level as being the EU-level Education Director of the new European flagship initiative European Institute of Technology and Innovations (EIT), and its Knowledge and Innovation Community EIT ICT Labs. Email: [email protected] JONATHAN LOO a.k.a. KOK-KEONG LOO received his MSc degree in Electronics from the University of Hertfordshire, UK in 1998 and his PhD degree in Electronics and Communications from the same university in 2003. He leads a research team of 8 PhD students in the area of communication and networking. His research interest includes network architecture, communication protocols, network security, embedded systems, video coding and transmission, wireless communications, digital signal processing, and optical networks. He has successfully graduated 13 PhDs as Principle Supervisor and contributed over 150 publications in the aforementioned specialist areas. Email: [email protected]