A Microstrip Meander Line Reconfigurable Antenna for Wireless Applications Avinash Kumar 1, Rajni 2 1 Dept. of Electronics and Communication Engineering, Shaheed Bhagat Singh State Technical Campus, Moga Road, Ferozepur, Punjab, 152004, India 2 Dept. of Electronics and Communication Engineering, Shaheed Bhagat Singh State Technical Campus, Moga Road, Ferozepur, Punjab, 152004, India Abstract In this work, we investigate a printed single-band classic meander line reconfigurable antenna with truncated patch and a back coupled square ground plane with the aim to accomplish frequency as well as pattern reconfigurability operation in 2-3 GHz frequency bands for climate radar framework, Wi-Fi gadgets and Direct-To- Home (DTH) satellite communication. To obtain a single-band with different radiation characteristics, a microstrip antenna has been designed with a classic meander line concept. The reconfigurability is achieved in terms of frequency and pattern by distributing antenna current through semiconductor devices such as p-i-n diodes and varactors. The antenna is printed on the FR-epoxy substrate having overall dimensions 19 mm 19 mm, dielectric constant 4.4 and thickness 1.6 mm. In the reported work, the reconfigurable antenna provides better impedance bandwidth of 100-240 MHz for 2-3 GHz operating frequency band. Keywords Reconfigurability, Bandwidth and Meander line. I. INTRODUCTION Nowadays, reconfigurable antennas are becoming more essential and vital component for portable applications. The usage of arrays of antennas for accomplishing distinctive radiation characteristics adds the complexities to the system. Since the compactness of wireless system is an essential variable, the utilization of numerous antennas is kept away through the acquaintance of reconfigurable antenna. This adequately diminishes the complexity of system without influencing the radiation qualities and gives the same outcome as arrays of antennas. The reconfiguration of an antenna is accomplished through intentionally changing its frequency, polarization, or radiation characteristics. This change is accomplished by several methods that redistribute the antenna current and alter the flow of electromagnetic fields of the radio wires [1]. The alteration in antenna current can be done by various techniques such as p-i-n diodes, varactors, radio frequency micro-electromechanical system (RF- MEMS) and liquid crystal materials. There are distinctive sorts of reconfigurable antennas relying upon the property need to be reconfigured, i.e. either in polarization, frequency, radiation design, and so on. The analysts are focusing more on frequency and polarization diversity antennas. A frequency reconfigurable antenna is preferred over others because it has capability to modify its characteristics in terms of polarization and radiation pattern. A frequency reconfigurable antennas utilizing p-i-n diodes have been discussed in [2-3]. The radiation pattern reconfigurable antenna also has the ability to expand its waves in broad and narrow pattern. A microstrip pattern reconfigurable antenna is proposed in [4] which exhibit the different radiation patterns in xz and yz plane. For achieving reconfigurability, the microstrip antennas are preferred due to their low-cost, low-profile and ease of fabrication. The microstrip antennas also suffer from various drawbacks such as narrow bandwidth, low gain and low efficiency. To improve the bandwidth of antenna, antenna developers have provided number of techniques like defected ground structure, metamaterial loading and fractal antennas etc. in [5-8]. The bandwidth of antenna can also be improved by decreasing the dielectric constant and by increasing the height of substrate, but these trends are limited by an inductive impedance offset that increase with thickness. In order to accomplish wide-band operation, it becomes necessary to reduce the antenna dimensions. The miniaturization in antenna size is done by various methods such as fractal technology, shorting pins and meander line. The meander line is preferred over all other techniques due to low-profile, ease of printing and low-cost. A long term evolution (LTE) applications based antenna is designed with different meander lines, are exhibited in [9]. In this paper, a classic meander line is investigated for a single band operation with wider bandwidth. The operation of classic meander line is changed by two p-i-n diodes which helps antenna to resonate at different frequencies. This paper is organized in six sections. Section I provides the overview of microstrip meander line reconfigurable antenna. Section II describes how the concept of classic meander line is formed. The geometry of antenna is explored in Section III. The results with parametric analysis are presented in Sections IV and V, followed by Section VI which concludes the topic. ISSN: 2231-5381 http://www.ijettjournal.org Page 144
II. MEANDER LINE ANTENNA (MLA) The MLA is a type of microstrip antenna (MSA) that accomplishes the reduction in radio wire measurements by embedding the wire arrangement on dielectric substrate [10]. The meander line is shaped by an arrangement of succession of right angled twists as shown in Fig. 1 which are useful in diminishing the resonant length of the antenna. The discontinuity in angled susceptance for impedance matching is also reduced by the right angle bends [11]. The essential qualities of radio wires are shaped by number of right-angled twists and the radiation generally occurs from the vertical line of the array. The horizontal lines of meander line antenna are used as transmission lines. The spacing between meander lines permit the receiving wire to radiate in various frequency ranges and in addition narrow spacing gives more coupling which influences the antenna radiation attributes [12]. After each half wavelength or four half wavelength, the direction of current is changed. The number of turns of meander line delivers the wanted polarization when antenna transmits through curves. In other case, the presence of array grid restricts the spacing and the polarization of the radio wire. The MLA has drawback of low radiation efficiency and low data transfer speed. The number of flat and vertical lines helps to increase the efficiency and transmission capacity of the antenna [13]. In Fig. 1, w shows the width, L presents the length, h depicts the height and g mentions the gap between meander lines. Fig. 1 Classic meander line III. GEOMETRY OF PROPOSED ANTENNA A new microstrip reconfigurable antenna configuration is introduced with classic meander line concept for single frequency band applications. The key operation of Classic Meander Line Reconfigurable Antenna (CMLRA) is similar to microstrip truncated monopole patch antenna. The overall dimensions displayed in this antenna are 0.25 λ g 0.25 λ g, where λ g is the guided wavelength of the antenna and is 76 mm. The two switches, S 1 and S 2, are put on both meander lines to permit the antenna current through these lines. The reconfiguration of a radio wire is accomplished by utilizing these electrical switches to change the antenna setups. A 50 Ω lumped port is positioned at the edge of substrate for giving excitation to the antenna. The standard measurements of substrate and patch are described in [14-16]. The reported antenna is imprinted on FR-epoxy substrate with a dielectric constant 4.4 and thickness of 1.6 mm. The antenna comprises of a truncated monopole patch and ground plane which is imprinted on the substrate for microstrip feeding line. In this radio wire, a truncated patch is utilized whose length lies between 0.3 λ g < L < 0.5 λ g. The optimized gap between meander lines is considered as 1.5 mm and length (L) of meander line for each stair step is 9 mm. The structure and geometry of antenna are depicted in Fig. 2 and Table 1. Fig. 2 Geometry of CMLRA Table1. Geometry of CMLRA Parameters Dimensions (mm) Substrate (L, W) 19 Length of truncated patch (Lg, Ls) 6.75 Width of truncated patch (W3, W4) 3 Length of Meander line (L1, L2, L3, L4) Width of Meander line (W1,W2) 0.8 Gap between Meander line (g1, g2) 1 Height of Meander line (h1, h2) 1.8 The signal strip lengths, Ls and Lg, are acting as a normal microstrip transmission line. IV. RESULTS AND DISCUSSION In order to evaluate the performance of CMLRA, the designed antenna is numerically analysed with Finite Element Method (FEM) based High Frequency Structure Simulator (HFSS) to solve the electromagnetic fields in the solution region. After modeling the CMLRA, FEM meshes over the entire solution volume and solve for the far electric field throughout that volume. The maximum number of passes is considered as 20 and error tolerance as 2%. The mesh is improved adaptively with each pass and a full solution is carried out to meet the convergence criteria. 9 ISSN: 2231-5381 http://www.ijettjournal.org Page 145
A. Classic Meander Line Reconfigurable Antenna (CMLRA) The p-i-n diodes are utilized as switches for changing the condition of frequencies and radiation pattern of CMLRA. Without broadening the dimensions, these switches permit the antenna to accomplish the diverse antenna characteristics. In this antenna, the combination of series resistance and series inductance is utilized to permit the diode to work in forward condition. For reverse bias condition, the series resistance and series inductance are utilized with shunt capacitance. The CMLRA is analysed for following two states: a. State1 Fig. 4 (a) Radiation pattern in xz and yz plane of CMLRA in In state 1, switch S 1 is forward bias and S 2 is reverse bias. For this arrangement, the proposed antenna resonates at frequency 2.46 GHz with return loss of - 16.5 db and the antenna changes its radiation pattern in terms of xz and yz plane. The CMLRA works on 2-3 GHz frequency band for Bluetooth and direct-tohome (DTH) satellite applications as depicted in Fig. 3 and bandwidth up to 150 MHz is obtained. b. State2 In state 2, switch S 1 is reverse bias and S 2 is forward bias, then antenna resonates at different frequencies such as 2.53 GHz with return loss of -12.8 db and the antenna alters its radiation pattern in terms of xz and yz plane with bandwidth of 110 MHz shown in Fig. 3. Fig. 4 (b) Radiation pattern in xz and yz plane of CMLRA in Fig. 5 Simulated VSWR of CMLRA in state 1 and state 2. Fig. 3 Simulated return loss of CMLRA. with various radiation designs in xz and yz plane in Figs. 4 (a) and 4 (b) respectively and achievable VSWR of 2:1 depicted in Fig. 5. V. PARAMETRIC STUDY A. By changing the gap between meander lines In order to do parametric study, the space between the meander lines is varied as 1.0 mm and 0.8 mm and all other parameters of antenna remain unchanged. It is apparent from Figs. 6 (a) and 6 (b) that the decrease in the space between classic meander lines results in shifting the frequencies to higher frequency side. The meander line length is controlled by means of p-i-n diode switch. ISSN: 2231-5381 http://www.ijettjournal.org Page 146
Fig. 6 (a) Simulated return loss of CMLRA in state 1. Fig. 6 (b) Simulated return loss of CMLRA in state 2. a. State 1: When switch S 1 is forward bias and S 2 is reverse bias, the antenna resonates at 2.54 (with gap (g) = 1 mm) and 2.62 GHz (with gap (g) = 0.8 mm) with return loss of -17 db and -21 db respectively as displayed in Fig. 6 (a). b. State 2: When switch S 1 is reverse bias and S 2 is forward bias then antenna resonant at 2.64 (with gap (g) = 1 mm) and 2.73 GHz (with gap (g) = 0.8 mm) with return loss of -12 and -16 db respectively as depicted in Fig. 6 (b) and the bandwidth of 200 MHz and 150 MHz are obtained for state 1 and state 2 with various radiation designs in xz and yz plane in Figs. 6 (c) and 6 (d) in state 1 and state 2 Fig. 6 (d) Radiation pattern in xz and yz plane of CMLRA in B. By changing the length of meander line The reduction in length of meander lines effect the antenna performances in terms of frequencies and reflection coefficient. In this case, the length of meander lines is changed. The initial length of meander line is 9 mm and it reduced to 8 mm or 7 mm. The reduction in length to every stair-step of meander line is 1.0 mm and 2.0 mm whereas gap between lines remain unchanged. Due to reduction in meander lines, antenna resonates at higher frequencies. The alteration in frequencies is achieved by after execution of p-i-n diodes shown in Fig. 7 (a) and 7 (b) Fig. 7 (a) Simulated return loss of CMLRA in state 1. Fig. 7 (b) Simulated return loss of CMLRA in state 2. Fig. 6 (c) Radiation pattern in xz and yz plane of CMLRA in a. State 1: When switch S 1 is forward bias and S 2 is reverse bias, the antenna resonates at 2.72 (with length (L) = 8 mm) and 2.82 GHz (with length (L) = 7 mm) return loss of -28 db and -33 db respectively as presented in Fig. 7 (a). b. State 2: When switch S 1 is reverse bias and S 2 is forward bias, the antenna resonant at 2.75 GHz (with ISSN: 2231-5381 http://www.ijettjournal.org Page 147
length (L) = 8 mm) and 2.9 GHz (with length (L) = 7 mm) with return loss of -20 db and -16 db respectively as demonstrated in Fig. 7 (b). The bandwidth of 240 MHz and 200 MHz are achieved for state 1 and state 2 with different radiation pattern designs in xz and yz plane in Figs. 7 (c) and 7 (d) in state 1 and state 2 Fig. 7 (c) Radiation pattern in xz and yz plane of CMLRA in Fig. 7 (d) Radiation pattern in xz and yz plane of CMLRA in VI. CONCLUSION A compact and reconfigurable antenna is presented in this work for single-band frequency operations. The antenna is fabricated on FR-epoxy substrate with the dimensions of 19 mm 19 mm. A classic meander line is printed on substrate which exhibits the two resonant frequencies with the help of p-i-n diodes. By changing the gap between the classic meander lines, the reflection coefficient, VSWR and radiation characteristics of the antenna are improved. With the change in length of the classic meander lines, the operating frequency of antenna can also be changed. The radiation pattern of the meander line antenna is appropriate for wireless devices such as mobile phones and other communicating devices. [3] R. J. Chitra and V. Nagaranjan, Frequency reconfigurable antenna using p-i-n diodes, National Conferences on Communication system, Kanpur, 2014, pp. 1-4. [4] S. Raman and P. Mohanan, Microstrip-fed pattern and polarization reconfigurable compact truncated monopole antenna, IEEE Trans. Antenna and Wireless Propagation Letters, vol. 12, 2013. [5] Gurpreet Singh, Rajni, Ranjit Singh Momi, Microstrip patch antenna with defected ground structure for bandwidth enhancement, International Journal of Computer Applications, vol. 73, pp. 14-18, 2013. [6] Simarpreet Kaur, Rajni and Anupma Marwaha, Fractal Antennas: A Novel Miniaturization Technique for Next Generation Networks, International Journal of Engineering Trends and Technology (IJETT), vol. 9, No. 15, Mar 2014. [7] Simarpreet Kaur, Rajni, Gurwinder Singh, On the bandwidth enhancement of modified star triangular Fractal Antenna", In Proceedings of International Conference on Recent cognizance in wireless communication & image processing (ICRCWIP), 16-17 th Jan. 2015, pp 703-710. [8] Rajni, Anupma Marwaha, "CSC-SR structure loaded electrically small planar antenna", The Applied COMPUTATIONAL Electromagnetics Society Journal, vol. 31, no. 5, pp. 591-598, May 2016. [9] Lothari Popatlal Nitin and Thakre Pandurang Nikhil, Design of meander line monopole patch antenna for LTE applications, International Journal of Applied Engineering Research, vol. 8, no. 19, 2013. [10] Kumar Sandeep and Tripathi Kumar Subodh, Design of microstrip square patch antenna for improved bandwidth and directive gain, International Journal of Engineering Research and Applications, vol.2, pp. 441-444, 2012. [11] A. Khaleghi, Dual-band meander line antenna for WLAN communication, IEEE Trans. on Antenna and Propagation, vol. 1, pp. 1004-1008, 2007. [12] Y. Saito, T. Fukusako, Low-profile and electrically small meander line antenna using a capacitive feed structure, IEEE trans. Antenna and Wireless Propagation Letters, vol.11, pp. 1281-1284, 2012. [13] Tondare Shivshanker, Meander line antenna with artificial magnetic conductor, International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol. 3, pp. 8936-8943, 2014. [14] Nhi T. Pham, Gye-An Lee, Franco De Flaviis, Minimized dual-band coupled line meander antenna for system-in-apackage applications, IEEE Trans. Antenna and Propagation, vol.2, pp. 1451-1454, 2004. [15] Inder Bahl, Lumped elements for RF and microwave circuits, Ar. Tech House Inc., 2003, pp. 430. [16] Constantine A. Balanis, Antenna theory analysis and design, A John Wiley & Sons inc., publication, 3rd Edition, 2005, pp. 817-820. REFERENCES [1] Christos G. Christodoulou, Steven A. Lane, Scott R. Erwin, Youssef Twak, Reconfigurable Antenna for Wireless and Space Application, Proc. IEEE, vol. 100, no. 7, pp. 2250-2261, July 2012. [2] Fakharian M. Mohammad, Rezaei Pejman, Orouji A. and Ali, Reconfigurable multiband extended U-slot antenna with switchable polarization for wireless applications, IEEE Antenna and Propagation Magazine, vol. 57, pp. 1-9, 2015. ISSN: 2231-5381 http://www.ijettjournal.org Page 148