Reconfigurable multiband tapered slot antenna - Wiley Online Library

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RECONFIGURABLE MULTIBAND TAPERED SLOT ANTENNA Sahar Chagharvand,1 Mohamad R. Hamid,2 Muhammad R. Kamarudin,3 and Farid Ghanem3 1 Faculty of Electrical Engineering, UTM-MIMOS Centre of Excellence in Telecommunication Technology, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Malaysia 2 Faculty of Electrical Engineering, Wireless Communication Center, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor, Malaysia; Corresponding author: [email protected] 3 Center for Development of Advanced Technologies (CDTA), 16303, Algiers, Algeria Received 25 February 2015 ABSTRACT: In this article, a reconfigurable multiband tapered slot antenna is proposed. This antenna is able to support wideband, dualband, and triple-band operations. This is achieved by incorporating Tand C- shaped resonators that are used to integrate a filtering functionality to the antenna. The behavior of the antenna can be reconfigured by activating/deactivating the different resonators by means of PIN diode switches. By activating only the T-shaped resonator, a bandstop operation is obtained which results in a dual-band operation, while by coupling both T- and C-shaped resonators, a triple-band operation is achieved. By deactivating all of the resonators, a wideband operation is achieved. Results show, the frequency range of the wideband operation spans from 1.04 to 3.76 GHz. In the dual-band operation mode, the suppressed band is around 2.5 GHz. The operating frequency range of the triple-band operation is divided into low frequency (0.97–1.24 GHz), midfrequency (1.63–2.08 GHz), and high frequency (2.64–3.71 GHz) bands. To validate the proposed approach both simulated and measured C 2015 Wiley results are given and a good agreement is observed. V Periodicals, Inc. Microwave Opt Technol Lett 57:2182–2186, 2015; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.29295 Key words: slot antenna; wideband antenna; reconfigurable antenna

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1. INTRODUCTION

Recently, frequency-reconfigurable antennas have received much attention from the new development of communication systems. The upcoming wireless communication systems require wideband operations, which may cause some interference to the systems. Therefore, to counter this problem, multiband antennas can be used. Multiband antennas have the ability to reduce unwanted interference, allowing only a particular frequency to operate at a time. Various frequency reconfigurable multiband antennas, such as one with mechanical control [1] or electronic control [2], have been recently suggested. Most of wideband reconfigurable antennas proposed in the literature show wide to single narrowband only [3,4]. Only a few have designed wide to multiband reconfiguration [5]. The proposed Vivaldi antenna in [3] has the capability to switch between wideband, notch band, and narrowband modes. The operation in both wideband and narrowband due to different length locations to various ring slot pairs is shown in [4]. As demonstrated in [5], two C-slots are used on the patch elements to operate a single-feed reconfigurable wideband and multiband antenna on a planar structure. A reconfigurable wide slot antenna in [6] uses ideal switches for UWB and multiband communication applications. With integrated two stepped impedance stub-loaded SIRs, two notch bands are achieved. This article presents a new design of reconfigurable multiband tapered slot antenna (TSA). The proposed antenna has the capability to switch between wideband, dual-band, and tripleband modes. The reconfigurations are achieved by coupling the T- and C-shaped resonators. The T- and C-shaped resonators are designed to produce an appropriate Q-factor characteristic to achieve multiband operation. This antenna is potentially usable for wideband and multiband applications. 2. ANTENNA STRUCTURE

Figure 1 shows the proposed geometry of the reconfigurable multiband TSA. The antenna is a combination of an opening of V-shaped slot, a 50-X CPW line, T- and C-shaped resonators and four PIN diode switches. A TSA reported in [7] was made as a reference design of wideband operation. Detailed dimensions are shown in Table 1. The antenna is fabricated on FR4 structure with thickness (h) of 0.8 mm, dielectric constant (er) of 4.3 and loss tangent of 0.019. The original antenna without the resonators operates in a wideband mode and the operating band spans the frequencies

Figure 1 Geometry of proposed TSA. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 57, No. 9, September 2015

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TABLE 1 Parameters Values of Proposed Antenna Parameter Wt Wr Wx Ws W W1 W2 W3

Value (mm) 166.2 103.14 6.9 2 7.8 22 63.5 13.2

Parameter Lt Ls L1 L2 L3 L4 g

Value (mm) 141 17 24.5 5.7 10 19 0.9

from 1.04 to 3.76 GHz. However, the insertion of the C- and T-shaped resonators at the edge of the tapered slot does affect the antenna radiating properties and the control of this perturbation mechanism allows the control of the antenna operation. Some simulations have been performed to analyze the electromagnetic waves traveling along the edge of CPW lines

containing the C- and T-shaped resonators, as depicted in Figure 2. This modelization does not include the effect of the tapering, however, quantitatively; it does allow to understand what is happening. Figure 2(a) shows the insertion loss in a CPW line with integrated T-shaped resonators and Figure 2(b) the C-shaped resonators. As it can be seen from both Figures 2(a) and [2](b), the two resonator shapes act like traps to frequencies proportional to their lengths and prevent the corresponding electromagnetic waves from traveling along the edges of the CPW lines. However, the effect of the slots can be deactivated by shortcircuiting the access to the slots which can be done using switches. In this case, the electromagnetic waves travel normally, through the CPW as if the slots are not present. This is shown in Figure 2(c). In the simulations, the electrical length of the C- and T-shaped resonators is set to 0.5ks and 1.85ks at 1.5 and 2.5 GHz, respectively. The wavelength ks is calculated using Eq. (1) [8]. The physical length of the resonators is 40 mm and 70 mm, respectively.

Figure 2 S-parameters of (a) Longer T-shaped, (b) C-shaped, and (c) Both T- and C-shaped slots are closed. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

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Figure 5 Simulated and measured reflection coefficient magnitudes of wideband. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

Figure 3 The current distributions of proposed antenna at wideband operation (a) at 2.5 GHz and (b) at 1.5 GHz. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com] TABLE 2 Different States of the Switches and Corresponding Bands Bands Switches S1 S2 S3 S4

Wide

Dual

Triple

ON ON ON ON

OFF OFF ON ON

OFF OFF OFF OFF

ks ¼ k0

rffiffiffiffiffiffiffiffiffiffi 2 er 11

where ko is the free space wavelength and er is the relative permittivity. It is well-known that in tapered slot lines, the high frequency electromagnetic waves are radiated from the narrow region of

(1)

Figure 4 Photograph of the proposed TSA. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

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Figure 6 Simulated and measured reflection coefficient magnitudes of dual-band. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

Figure 7 Simulated and measured reflection coefficient magnitudes of triple-band. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]


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Figure 8 Simulated and measured radiation patterns at 2 GHz, (a) wideband, (b) dual-band, and (c) triple-band. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com]

the taper while the low frequency ones are radiated from the wider region. Thus, the T-shaped resonators used to suppress frequencies around 2.5 GHz band are placed in the bottom of the V-shaped slot. The optimum positions of the resonators are determined by placing them in a high concentration current area of their own resonating current. This is to provide good band stop operation at the desired band. Some desired set of frequencies can be obtained according to the k/4 wavelength and k/2 wavelength resonator lengths. Moreover, the resonator placement toward V-shaped slot may also be adjusted with different Q-factor. Current distributions of wideband operation at 1.5 and

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2.5 GHz are shown in Figure 3. As can be seen in Figure 3(a), the current at 2.5 GHz is highly concentrated, where the Tshaped resonator is positioned. The switches used to activate/deactivate the resonators are PIN diodes, model BAR50-02V. Their effect has been included in the antenna simulations by including their S-parameters provided by the constructor. As these diodes are used in the ground plane, then there is a need to cut the ground plane to separate the two ports of the diode and be able to bias them. The DC separation slot used here are of 0.3 mm width. However, to maintain an RF continuity of the ground plane, capacitors are


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TABLE 3 Measured Gain of the Proposed Antenna Gain (dBi)

f1

f2

f3

Wideband Dual-band Triple-band

4.31 3.21 2.26

7 3 4.54

5.63 6 6.95

used to bridge the separation. On the other side, to isolate the biasing part, inductors are used as RF chokes to let the DC voltage pass to the antenna and switch on and off the PIN diodes, while preventing the RF signal to flow into the DC part. The antenna performances have been simulated using the CST Microwave Design software tool [9]. As described previously, when all the switches are in on-state, the different slot resonators are deactivated and the electromagnetic waves flow normally, through the entire antenna tapered slot to be radiated to the free space. In this case, the antenna exhibits a wideband operation as a normal wideband TSA. When the switches S1 and S2 are turned off, it becomes possible to the electromagnetic waves to access the Tshaped slots and be trapped there which results in the frequencies around 2.5 GHz to be suppressed. Consequently, the antenna exhibits a dual-band operation. Finally, when all the four switches S1–S4 are turned off, then the frequencies around 1.5 and 2.5 GHz are suppressed as the corresponding electromagnetic waves are trapped in both the T- and C-shaped resonators. In this case, a triple-band operation is obtained. The different switch configurations are the corresponding operating mode are summarized in Table 2. The gain at 1.1 GHz (f1) in triple-band operation is reduced compare with wideband operation due to the change in current distribution and attributed to losses within the PIN diode switch. 3. RESULTS AND DISCUSSION

To validate experimentally the proposed approach to achieve the described frequency reconfiguration, a prototype has been fabricated and its photograph is shown in Figure 4. The S11 has been measured in the different modes and the obtained results have been compared with the simulated results and shown in Figures 5–7 which are corresponding to the wideband, dual-band, and triple-band mode, respectively. From Figure 5, it can be noted that the frequency range of the wideband operation extents from 1.04 to 3.75 GHz. From Figure 6, the dual-band mode is well-observed and frequencies around 2.5 GHz are attenuated. From Figure 7, the magnitude of the S11 parameter shows clearly the triple-band operation; the lowest band corresponds to frequencies between 0.97 and 1.24 GHz, the mid frequency band is 1.63–2.08 GHz, and the upper-band correspond to high frequency (2.64–3.71 GHz) bands. The three bands cover actually the LTE, UMTS, and WiMAX applications. In all three modes, a good agreement between the measured and simulated S11 results can be observed. A little dissimilarity is observed due to the fabrication tolerance and switch losses. To examine the effect of the frequency reconfiguration on the radiation properties of the antenna, simulated and measured radiation patterns at 2 GHz in the E- (x-y) and H- (y-z) plane are shown in Figure 8. It is observed that over the entire operating frequency, the antenna has nearly similar radiation patterns. The measured gains in wideband and triple-band modes at f1 5 1.1, f2 5 2, f3 5 3.2 GHz, and dual-band mode at f1 5 1.1, f3 5 3.2 GHz is shown in Table 3.

triple-band modes. The triple-band is able to cover the LTE, UMTS, and WiMAX applications. Studies from measured and simulated results show that the proposed TSA can be used for wideband and multiband applications. ACKNOWLEDGMENT

This work was supported by UNIVERSITI TEKNOLOGI MALAYSIA, GRANT REFERENCE NUMBER: Q. J13000. 2523. 04H83. REFERENCES 1. P. Lotfi, M. Azarmanesh, and S. Soltani, Rotatable dual-band notched UWB/triple-band WLAN reconfigurable antenna, IEEE Antennas Propag Lett 12 (2013), 104–107. 2. T. Wu, H. Bai, P. Li, and X. W. Shi, A simple planar monopole UWB slot antenna with dual independently and reconfigurable band-notched characteristics, Int J RF and Microwave Comput Aided Eng (2014), 1–7. 3. M.R. Hamid, P. Gardner, P.S. Hall, and F. Ghanem, Multimode vivaldi antenna, Electron Lett 46 (2010), 1424–1425. 4. T.L. Yim, S.K.A. Rahim, and R. Dewan, Reconfigurable wideband and narrowband tapered slot vivaldi antenna with ring slot pairs, J Electromagn Waves Appl 27 (2013), 276–287. 5. H.F. Abutarboush, R. Nilavalan, S.W. Cheung, K.M. Nasr, T. Peter, D. Budimir, and H.A. Raweshidy, A reconfigurable wideband and multiband antenna using dual patch elements for compact wireless devices, IEEE Trans Antennas Propag 60 (2012), 36–43. 6. H. Kim and C.W. Jung, A reconfigurable wide slot antenna integrated with sirs for UWB/multiband communication applications, Microwave Opt Technol Lett 55 (2013), 52–55. 7. H. Kim and C.W. Jung, Ultra-wideband endfire directional tapered slot antenna using CPW to wide-slot transition, Electron Lett 46 (2010), 1183–1185. 8. K.C. Gupta, Microstrip lines and slotlines, Artech House, Norwood, MA, 2nd ed., 1996. 9. CST. Microwave studio based on the finite integration technique, Computer Simulation Technology, Wellesley Hills, MA, 2013. C 2015 Wiley Periodicals, Inc. V

HIGH POWER CLADDING-PUMPED L-BAND EDFA WITH A DOUBLE-PASS CONFIGURATION Yizhen Wei,1,2 Feihong Chen,2 Xuefang Zhou,1 Miao Hu,1 and Qiliang Li1 1 College of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018, China; Corresponding author: [email protected] 2 Centre for Optical and Electromagnetic Research, Zhejiang University, Hangzhou 310058, China Received 27 February 2015 ABSTRACT: A high power broadband cladding-pumped erbium-doped fiber amplifier (EDFA) in the long-wavelength band (L-band) is proposed and experimentally demonstrated. The L-band EDFA presented here is based on a double-pass (DP) configuration, and employs commercially available double-cladding fiber. An output power over 2 W and an operation wavelength range from 1570 to 1620 nm have been achieved using clad pumping technique in the DP scheme. Compared with the single-pass structure, obvious improvements on power conversion efficiency and signal gain are obtained while the deterioration of C 2015 Wiley Periodicals, Inc. Microwave noise figure is also observed. V Opt Technol Lett 57:2186–2189, 2015; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.29294

4. CONCLUSION

Reconfigurable multiband TSA has been proposed. The proposed antenna is capable to operate in wideband, dual-band, and

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Key words: erbium-doped fiber amplifier; L-band; high power; doublepass; cladding-pumped


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