A Low Profile Dual-Mode Reconfigurable Antenna Design Thennarasan Sabapathy, Muzammil Jusoh, R. Badlishah Ahmad and Muhammad Ramlee Kamarudin
Abstract A low profile dual-mode reconfigurable antenna design is introduced in this work. Two properties, namely frequency and radiation pattern are reconfigured using the proposed antenna. Parasitic patch array helps to produce the radiation pattern reconfiguration. Meanwhile, frequency reconfigurability is achieved with a resizable slot located at the back of the antenna. At frequency around 5.8 GHz, the antenna able to reconfigure the radiation pattern to three different directions with average peak gain of approximately 7dBi. Frequency reconfiguration is achieved at four different frequencies from 4.6 to 5.75 GHz.
1 Introduction A reconfigurable antenna is known as the antenna that has the capability to modify the antenna’s properties such as radiation pattern, polarization, or frequency/ bandwidth in some desirable fashion. Depends on the systems requirement the antenna is designed to alter any of the properties. Mainly, these types of antennas
T. Sabapathy (&) M. Jusoh R.B. Ahmad Embedded, Network and Advanced Computing (ENAC), School of Computer and Communication Engineering, Universiti Malaysia Perlis, Arau, Malaysia e-mail:
[email protected] M. Jusoh e-mail:
[email protected] R.B. Ahmad e-mail:
[email protected] M.R. Kamarudin Faculty of Electrical Engineering, Wireless Communication Centre (WCC), Universiti Teknologi Malaysia, Johor, Malaysia e-mail:
[email protected] © Springer International Publishing Switzerland 2015 H.A. Sulaiman et al. (eds.), Theory and Applications of Applied Electromagnetics, Lecture Notes in Electrical Engineering 344, DOI 10.1007/978-3-319-17269-9_26
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are reconfigured using the aid of RF switches. When an antenna is designed to change its frequency it is known as frequency reconfigurable antenna. Such antenna is capable of modifying the antenna’s frequency to certain operating bands which suit multiple applications in a single system. Such antenna can be useful for various applications such as Cognitive Radio (CR) or multi radio platforms [1]. Frequency reconfigurable antennas are also designed for UWB application [2] where the antenna is able to select the desired operating frequency within the UWB band based on the RF switches configuration. On the other hand, polarization reconfigurable antennas [3, 4] change their polarization to support wireless systems such Global Positioning System (GPS), Compass Navigation Satellite System (CNSS) and Wireless Fidelity (WiFi). Meanwhile, radiation pattern reconfigurable antenna is able to change its radiation pattern of the antenna where the direction of the peak antenna gain and/or the antenna beam-width could be changed according to the desired manner. In recent findings, two or more properties of the antenna were performed with reconfiguration. In work [5] a reconfigurable antenna known as multifunctional reconfigurable array (MRA) is proposed and this antenna can reconfigure all three properties (frequency, radiation pattern and polarization). Similar approach also used by work [6] to obtain multi-fucntions. However, the number switches and number of arrays required to design the antenna is the trade-off to obtain the multiple functions. Obviously, not many systems require all three types of reconfiguration in a single antenna. Reducing the reconfiguring capability of the antenna reduces the complexity and the size of the antenna. This work presents a reconfigurable antenna which has the conformal profile that can reconfigure two properties of the antenna, namely frequency and the radiation pattern. Frequency reconfiguration by this antenna is capable of increasing spectral density while the pattern reconfiguration able to improve the signal reception of the antenna at high operating frequency. The antenna consists of an active microstrip patch and two parasitic elements. Underneath the driven element, a slot is positioned on the ground plane. The variation of the slot size with the RF switches provides frequency reconfigurable functionality. The antenna is capable to reconfigure four different frequencies from 4.6 to 5.75 GHz using five switches (RF p-i-n diodes) placed in the slot. Meanwhile the parasitic elements which are adjacent to the driven element help to reconfigure the radiation pattern of the antenna at certain higher frequencies (5.6–5.8 GHz). The design of this work closely related to works [7, 8], where the principle of Yagi-Uda patch array antenna is adopted for pattern reconfiguration while slotted ground technique is deployed for frequency reconfiguration. The combination of these two methods in a single antenna design successfully performs the multi-mode reconfiguration. The size of the antenna is relatively small with a dimension of 32 × 76 mm. In what follows, Sect. 1 describes the details of the proposed antenna. Then, the results are presented, and the performances of the antenna are investigated.
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2 Antenna Design Figure 1 illustrates the physical structure of the proposed antenna. The antenna consists of three parallel patches on a full grounded Taconic dielectric substrate with a thickness of 1.6 mm and a dielectric constant (εr) of 2.2. The center rectangular patch has a width of W = 19 mm and length of L = 15.7 mm. This is the driven element (DE) of microstrip array where it is fed through a subminiature (SMA) probe from the back of the antenna. At the DE, the feed location, a is optimized to achieve a desired input impedance of 50 Ω. The size of the antenna is given by substrate width, Ws = 76 mm and substrate length, Ls = 32 mm. The parasitic elements (PEs) are named as PE1 and PE2 as shown in Fig. 1. The PEs are smaller than the DE where the width and length are denoted as W′ and L′. The optimized parasitic elements’ physical dimension is as follows: W′ = 0.9 × W mm, L′ = 0.998 × L mm. The gap between all elements is 2 mm. As shown in Fig. 1b
(a) Ws
W
W’
DE x O(0,0)
PE2
x
PE1
g
SR 1 SR 2 -27.5,-6 -20,-6
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SR 3
a
SR 4
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Feeding point
(b)
… … … … … … . . . SF 1
Ls
SF 9
16 mm
y
x
Fig. 1 Antenna structure. a Front and b Back
-z
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a slot with 18 × 1.5 mm2 is created for the purpose of frequency reconfiguration. In what follows, the deployment of the switches for reconfigurable properties of the antenna is described.
2.1 Reconfiguration Mechanism Radiation pattern and frequency can be reconfigured in a single antenna with the help of RF switches. The antenna consists of thirteen RF switches. Lumped element networks of the RF switch at ON state and OFF state are used to represent the switches in simulation. HPND-4005 PIN diode is adopted as the RF switches to control the reconfigurable mechanism of the antenna. According to the technical data sheet provided by the manufacturer [9], the HPND-4005 PIN diodes are simulated as 4.6-Ω resistor and 0.017-pF capacitor in the ON and OFF states respectively. The positioning of the diodes and radiation mechanism of each property are described in the following subsection. Radiation Pattern Four RF switches are required to perform the radiation pattern reconfiguration. As illustrated in Fig. 1a, SR1 to SR4 are placed at the parasitic elements. These switches mainly contribute the radiation pattern reconfiguration of the antenna. They connect the parasitic element to the ground plane underneath of the antenna. Switching ON the PIN diode connects the element to the ground plane while switching OFF the PIN diode disconnects the element from the ground plane. Switching the PIN diode ON directs the parasitic element to act as a reflector which will push the beam towards an opposite direction. On the other hand, switching the PIN diode OFF will make the parasitic element to act as director that will pull the beam. Overall, three sets of directive beam patterns can be obtained. The switching configuration and the direction for each pattern is tabulated in Table 1. Note that SF1 to SF9 are all ON when pattern reconfiguration is applied. Frequency At the back of the antenna, a slot is created on the ground plane. Resizing the effective length of the slot, reconfigure the resonant frequency of the antenna. SF1 to SF9 are placed across the slots to reconfigure the frequency of the antenna. When the switches are ON, the effective size of the slot is reduced, hence it reconfigure the frequency to higher resonant. The respective switching configuration for each resonant frequency is tabulated in Table 2. Note that only SR2 and SR3 are ON when frequency reconfiguration is applied. Table 1 Details of switches configuration for pattern reconfiguration
Configuration
SR1
SR2
SR3
SR4
Direction
P1 P2 F5
ON OFF OFF
OFF ON OFF
OFF ON OFF
OFF OFF ON
+x x = 0° −x
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Table 2 Details of switches configuration for frequency reconfiguration Configuration
SF1
SF2
SF3
SF4
SF5
SF6
SF7
SF8
SF9
F1 F2 F3 F4 F5
OFF OFF OFF OFF ON
OFF OFF OFF ON ON
OFF OFF ON ON ON
OFF ON ON ON ON
ON ON ON ON ON
OFF ON ON ON ON
OFF OFF ON ON ON
OFF OFF OFF ON ON
OFF OFF OFF OFF ON
3 Results and Analysis The proposed antenna designed and the results are analyzed. It can be seen from Fig. 2 that for pattern reconfiguration, the antenna is capable of directing its beam to three directions. An average peak gain of *8 dBi can be obtained for all three sets of beampatterns. For P1 and P3, a maximum tilt angle of 27° can be obtained. Meanwhile, the antenna also operates at a common frequency bandwidth from 5.678–5.949 GHz as can be noticed in Fig. 3. As one could expect, the resonant frequencies of P1 and P3 are similar. Meanwhile, for frequency reconfiguration, the antenna is able to achieve five sets of resonant frequencies. This result is presented in Fig. 4. The corresponding beam patters results are presented in Fig. 5. Table 3 summarizes the results by frequency reconfiguration. The S11 improves as the resonant frequency increases. It can be noticed that F4 and F5 are close thus it can be considered as single band.
Fig. 2 Beam patterns by pattern reconfiguration at 5.8 GHz frequency
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Fig. 3 Reflection coefficient by pattern reconfiguration
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Fig. 4 Resonant frequencies by frequency reconfiguration
Reflection Coefficient, S11 (dB)
Frequency (GHz)
0 -5 -10 -15 -20
F1 F2 F3 F4 F5
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4
5 Frequency (GHz)
Fig. 5 Beam patterns by frequency reconfiguration
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Table 3 Resonant frequencies, bandwidth and the associated antenna gain for by frequency reconfiguration Frequency
Resonant frequency (GHz)
Bandwidth (%)
Peak gain (dBi)
F1 F2 F3 F4 F5
4.624 5.208 5.544 5.721 5.764
5.7 6.0 5.9 6.0 6.1
4.5 6.2 7.0 7.8 8.0
Thus effectively the frequency reconfiguration produces four frequency bands. The beam pattern results show that the peak gain of the antenna increases as the resonant frequency increases while the back lobe level decreases.
4 Conclusion A dual-mode reconfigurable microstrip patch antenna is developed for pattern reconfiguration and frequency reconfiguration application. Parasitic arrays are adopted for pattern reconfiguration while slot underneath of the antenna is used for frequency reconfiguration. The proposed antenna is able to steer the beam to three directions (−27°, 0°, +27°) with an average peak gain of *8 dBi. On the other hand, it can reconfigure up to four effective frequency bands from 4.624 to 5.764 GHz. The reconfigurability is obtained by switching the PIN diodes. The results show that the proposed antenna is potentially suitable for multiple applications such as frequency scanning and direction finding using a single platform. Acknowledgments The authors would like to thank Research University Grant UTM (Vote 05H34 and 00M21), Ministry of Higher Education, Universiti Teknologi Malaysia (UTM) and Universiti Malaysia Perlis (UniMAP) for their support and encouragement.
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5. Yuan, X., Li, Z., Rodrigo, D., Mopidevi, H.S., Kaynar, O., Jofre, L., Cetiner, B.A.: A parasitic layer-based reconfigurable antenna design by multi-objective optimization. IEEE Trans. Antenna Propag. 60, 2690–2701 (2012) 6. Rodrigo, D., Cetiner, B.A., Jofre, L.: Frequency, radiation pattern and polarization reconfigurable antenna using a parasitic pixel layer. IEEE Trans. Antenna Propag. 1–1 (2014) 7. Sabapathy, T., Jamlos, M.F.B., Ahmad, R.B., Jusoh, M., Jais, M.I., Kamarudin, M.R.: Electronically reconfigurable beam steering antenna using embedded RF pin based parasitic arrays (Erppa). Prog. Electromagn. Res. 140, 241–261 (2013) 8. Majid, H.A., Abdul Rahim, M.K., Hamid, M.R., Murad, N.A., Ismail, M.F.: Frequencyreconfigurable microstrip patch-slot antenna. IEEE Antenna Wirel. Propag. Lett. 12, 218–220 (2013) 9. HPND-4005 beam lead PIN diode, Datasheet, edited. Avago Technologies, San Jose, CA (2006)
