Cent. Eur. J. Eng. 3(4) 2014 281-286 DOI: 10.2478/s13531-013-0160-3 Central European Journal of Engineering Bandwidth optimization of compact microstrip antenna for PCS/DCS/bluetooth application Research Article Vinod Kumar Singh 1, Zakir Ali 2, Shahanaz Ayub 3, Ashutosh Kumar Singh 42 1 Department of Electronics Engineering, S.R. Group of Institutions, Jhansi, India 2 Department of Electronics Engineering, Bundelkhand University, Jhansi, India 3 Department of Electronics Engineering, Bundelkhand Institute of Engineering & Technology, Jhansi, India 4 Department of Electronics Engineering, Indian Institute of Information Technology, Allahabad, India Received 19 January 2014; accepted 17 March 2014 Abstract: A novel compact broadband microstrip patch antenna is presented for various wireless applications. The proposed antenna has been fabricated and the impedance bandwidth and radiation pattern are measured. The simulated and measured antenna characteristics along with radiation pattern and gain are presented. It is stated that the proposed designed antenna can completely cover the required band widths of Digital communication system (DCS 1.71-1.88 GHz), Personal communication system (PCS 1.85-1.88 GHz) and IEEE 802.11b/g (2.4-2.485 GHz) with satisfactory radiation characteristics. The Experimental result shows that the proposed antenna presents a bandwidth 60.25% covering the range of 1.431-2.665 GHz with the maximum radiation efficiency 90%. Keywords: Dual Slit Line Feed wide band patch Antenna, bandwidth gain efficiency VSWR Return Loss. Versita sp. z o.o. 1. Introduction Microstrip antennas (MSAs) are gaining popularity amongst the researchers due to its attractive features such as low profile, low cost, light weight, ease of fabrication and compatibility with microwave circuits[1, 2]. However, despite of these several advantages, the microstrip anten- E-mail: email@first.author.com nas suffers from some disadvantages of narrow bandwidth and low efficiency. Various researches have been made to increase the bandwidth of Microstrip antennas, which includes increase of the substrate thickness, the use of a low dielectric constant, slotted patch antennas, introducing the parasitic elements either in coplanar or stacked configuration, the use of various impedance matching and feeding techniques [3 8]. The dielectric constant of the substrate is closely related to the size and the bandwidth of the microstrip antenna. Low dielectric constant of the substrate produces larger bandwidth, while the high di- 281
Bandwidth optimization of compact microstrip antenna for PCS/DCS/bluetooth application electric constant of the substrate results in smaller size of antenna [12 15]. A trade-off relationship exists between antenna size and bandwidth. In the past few years researchers have tried various methods to enhance the bandwidth and it is observed that as the bandwidth is increased the efficiency and gain decreases. To obtain a larger bandwidth along with optimum gain and efficiency and maintaining the size of antenna is a major challenge to the researchers working with microstrip antennas these days. In the past decade many planar antenna had been designed to meet the requirement of mobile cellular communication systems. The most demanding these days are Global system for mobile communication system (GSM) ranging from 890 MHz to 960 MHz; Digital communication systems (DCS) ranging from 1710 MHz to 1880Hz. Personal Communication system (PCS) ranging from 1850 MHz to 1990 MHz; Universal Mobile telecommunication system (UMTS) ranging from 1920 MHz to 2170 MHz; and wireless local area network (WLAN) systems in the 2.4 GHz (2400-2484 MHz) bands. In this paper a dual wideband line feed microstrip antenna with compact size (40mm 60mm 1.6mm) is presented which gives a bandwidth of around 60.25% covering the range from 1.431 GHz to 2.665 GHz. The proposed antenna is suitable for various mobile cellular communication systems such as Digital communication system (DCS 1.71-1.88 GHz), Personal communication system (PCS 1.85-1.88 GHz), IEEE 802.11b/g or WLAN (2.4-2.484 GHz) applications. 2. Antenna design and layout The proposed line-fed wide band slit loaded antenna is depicted in Figure1. In this type of feed technique, a conducting strip is connected directly to the edge of the microstrip patch as shown in below Figure 1. The conducting strip is smaller in width as compared to the patch and this kind of feed arrangement has the advantage that the feed can be etched on the same substrate to provide a planar structure. Microstrip line feed is one of the easier methods to fabricate as it is a just conducting strip connecting to the patch and therefore can be consider as extension of patch. It is simple to model and easy to match by controlling the inset position. Since the current is low at the ends of a half-wave patch and increases in magnitude towards the center, the input impedance could be reduced if the patch was fed closer to the center [16]. The ground plane has the dimensions of Lg Wg and is printed on a substrate of thickness h = 1.6 mm and relative permittivity ε = 4.4. A 50 Ω microstrip feed line is employed to excite the proposed antenna having width of W 1 and Figure 1. Geometry of proposed antenna. Table 1. Designing parameters of proposed Antenna Parameters Value(mm) Lg 40 Wg 60 W 31 L 2 13.0 W 2 4.0 L 3 9 L 1 10.8 W 1 4.0 length L 1, respectively. The optimized design parameters of the proposed patch antenna are shown in table 1. The parallel slots are introduced on the patch with glass epoxy substrate provide bandwidth enhancement. The proposed radiating patch comprises slots symmetrically surrounding near the excitation probe pin so as to obtain good impedance bandwidth. Adding two more slots of same dimension of width W 2 and length L 3 on the patch eventually improve the overall impedance bandwidth and better impedance matching. The presences of two-slots restrict the patch currents as well as the two-slots on the patch reduce the size of the proposed patch The photograph of the designed antenna is shown in Figure 2. For an efficient radiator, a practical width that leads to 282
Vinod Kumar Singh, Zakir Ali, Shahanaz Ayub, Ashutosh Kumar Singh good radiation efficiencies is given by equation (1).For low frequencies the effective dielectric constant is essentially constant. At intermediate frequencies its values begin to monotonically increase and eventually approach the values of the dielectric constant of the substrate. The initial values (at low frequencies) of the effective dielectric constant are referred to as the static values, and they are given by equation (2). Because the dimensions of the patch are finite along the length and width, the fields at the edges of the patch undergo fringing. Due to the fringing effects, electrically the patch of the microstrip antenna looks greater than its physical dimensions. For the principal E -plane ( xy -plane),the dimensions of the patch along its length have been extended on each end by a distance l,which is a function of the effective dielectric constant ε reff and the width to height ratio ( W/h). A very popular and practical approximate relation for the normalized extension of the length is [9 11] c w = 2f (ε r + 1)/2 (1) ε reff = (ε r + 1) 2 + (ε r 1) [1 + 12 h 2 W ] 1 2 (2) Figure 2. Photograph of the proposed antenna l h =0.412 (ε ( reff +0.300) W +0.264) h (ε reff 0.258) ( (3) W +0.813) Since the length of the patch has been extended by l on each side; the effective length of the patch is now h L = 1 2fr ε reff µo ε o (4) Where, c = Velocity of Light ε r = is dielectric constant of the substrate f = antenna working frequency W = width of the patch L = Length of the patch h = height of substrate l = normalized extension of the length of the patch Figure 3. Return Loss of the proposed antenna Table 2. Measured & Simulated Bandwidth S. No. Simulated result Measured result (B.W)% (B.W)% 1. 60.25 57.30 3. Results and discussions The resonant properties of the proposed antenna have been predicted and optimized using of a commercial software package IE3D Ver 12. It is measured by network analyzer. Figure 3 shows the simulated and measured results of the return loss of the proposed patch antenna which are very close to each other justifying the geometry and results. The two closely excited resonant frequencies at 1.88 GHz and at 2.18 GHz as shown in the 283
Bandwidth optimization of compact microstrip antenna for PCS/DCS/bluetooth application Table 3. Variation of W 2 for achieving maximum bandwidth Para Value F 1 F 2 BW meter (mm) (GHz) (GHz) (%) W 2 1 1.544 2.353 60.25 2 1.545 2.234 59.09 3 1.54 2.313 57.30 4 1.533 2.883 57.30 Table 4. Variation of L 1 for achieving maximum bandwidth Para Value F 1 F 2 BW meter (mm) (GHz) (GHz) (%) L 1 9.3 1.547 2.269 55.76 9.8 1.542 2.268 56.76 10.3 1.538 2.275 56.82 10.8 1.533 2.883 57.30 Figure 4. Return Loss Vs Frequency of the proposed antenna Figure 5. Return Loss Vs of Frequency figure gives the measure of the wideband characteristic of the patch antenna. The measured impedance bandwidth of 57.30 % (1.533-2.883GHz) is achieved at -10 db return loss (VSWR 2) while the simulated patch gives an impedance bandwidth of 60.25% (1.431-2.665GHz) 4. Bandwidth study of designed antenna 4.3. Case III : Effect of variation of L 2 The result of varying L 2 while keeping other parameter fixed is shown in figure 6 and summirised in Table 5. It is seen that increasing the length L 2 to 13mm gives the maximum bandwidth of 57.30% Figure 7 shows the efficiency of the proposed patch antenna. The figure indicates high antenna efficiency over the operational frequency and it is around an average of 90%.The peak gain of the proposed patch antenna at vari- 4.1. Case I: Effect of variation of W 2 : The width W2 of the antenna patch is varied and bandwidth of the antenna is studied, it is observed that maximum value of bandwidth is achieved at the optimum value of W2 =1mm as shown in figure 4 and summarized in table 3. 4.2. Case II: Effect of variation of L 1 : The righteous value of L 1 keeping other parameters constant is found to be 10.8 mm for achieving maximum impedance bandwidth of 57.30 % which is shown in figure 5 and depicted in Table 4. Figure 6. Return Loss Vs Frequency of proposed antenna 284
Vinod Kumar Singh, Zakir Ali, Shahanaz Ayub, Ashutosh Kumar Singh Table 5. Para Value F 1 F 2 BW meter (mm) (GHz) (GHz) (%) L 2 10 1.608 2.234 51.50 11 1.583 2.254 53.86 12 1.558 2.254 53.56 13 1.533 2.883 57.30 5. Conclusion The proposed antenna has been developed and designed and tested successfully. The simulated results demonstrate that it has a wide impedance bandwidth of 60.25% covering the range of 1.431-2.665GHz with the maximum radiation efficiency 90%, while the experimental impedance band width 57.30%(1.533-2.883 GHz) which are very close to each other defining the practical use of developed antenna. The maximum achievable gain of the antenna is 6.20 dbi.the developed line feed wide band compact microstrip antenna is suitable for DCS/PCS/ WLAN applications covering the range of (1.431 GHz to 2.665GHz). References Figure 7. Efficiency Vs frequency of the antenna ous frequencies is shown in Figure 8, the maximum achievable gain is 6.20 dbi at the frequency of 2.3 GHz and the gain is better compare to design reported in [17 21] Figure 8. Gain Vs frequency of the antenna [1] Balanis C. A., Antenna Theory, Analysis and Design John Wiley & Sons New York 1997 [2] Kumar Girish, Ray K.P., Broadband Microstrip antennas, Norwood: Artech House 2003. [3] Balanis C. A., Advanced Engineering Electromagnetics, John Wiley & Sons, New York, 1989. [4] Deshmukh A.A., Kadam Ameya, Ray K. P., Broadband Proximity Fed Modified E-shaped Microstrip Antenna, Proc. IEEE, Vol. 978-1, 2011.4. [5] Islam M. T., Shakib M. N., Misran N., Broadband E-H shaped microstrip patch antenna for wireless systems, Progress In Electromagnetics Research, PIER 98, pp. 163-173, 2009. [6] Srivastava Stuti, Singh Vinod Kumar, Bow-Tie Shaped Printed Antenna for UMTS/WLAN/WiMAX applications, Journal of Environmental Science, Computer Science and Engineering & Technology (ISSN: 2278 179X), Vol.3.No.1, 0261-0268, December 2013. [7] Ansari J. A., Singh P., Dubey S. K., H-Shaped stacked patch Antenna for Dual Band Operation, Progress In Electromagnetics Research B, Vol. 5, 291-302, 2008. [8] Pathak Rajeev Shankar, Singh Vinod Kumar, Ayub Shahanaz, Dual band Microstrip Antenna for GPS/ WLAN/WiMax Applications, International Journal of Emerging Trends in Engineering and Development(ISSN:2249-6149),Issue2 Vol.7,pp154-159,November 2012. [9] Ansari, J. A., Ram R. B., Broadband stacked U-slot microstrip patch antenna, Progress In Electromagnetic Research Letters, Vol. 4, 17-24, 2008. [10] Hammerstad E.O., Equations for Microstrip Circuit Design, Proc. Fifth European Micro-wave Conf., pp. 268-272, September 1975. [11] Bahl I. J., Bhartia P., Microstrip Antennas, Artech 285
Bandwidth optimization of compact microstrip antenna for PCS/DCS/bluetooth application House, Dedham, MA, 1980. [12] Kulkarni Nagraj, Mulgi S. N., Satnoor S. K., Design and Development of Triple Band Tunable Microstrip Antenna, Microwave and Optical Technology Letters Vol. 54, No. 3, pp 614-617March 2012. [13] Veysi Mehdi, Kamyab Manouchehr, Jafargholi Amir, Single-Feed Dual-Band Dual-Linearly Polarized Proximity-Coupled Patch Antenna, IEEE Antennas and Propagation Magazine, Vol. 53, No.1, February 2011. [14] Alkanhal M. A. S., Composite Compact Triple-Band Microstrip Antennas, Progress In Electromagnetics Research, PIER 93, 221-236, 2009. [15] Singh Vinod K., Ali Zakir, Singh Ashutosh Kumar, Dual wideband stacked patch antenna for WiMax and WLAN application, Proc. IEEE-CICN- 2011, Print ISBN: 978-1-4577-2033-8 pp- 315-318. Gwalior, India. [16] Singh Vinod K., Ali Zakir, Design of Compact Triple Band Microstrip Antenna for Wireless Communication, International Journal of Electronics and Communication Engineering. ISSN 0974-2166 Volume 3, Number 1 (2010), pp. 323-330. [17] Ghalibafany J., Attari A. R., A new Dual-Band Microstrip Antenna with U-Shaped slot, Progress In Electromagnetics Research C, Vol. 12, 215-223, 2010. [18] Mishra A., Singh P., Yadav N. P., Ansari J. A., Compact Shorted Microstrip patch Antenna for Dual Band Operation, Progress In Electromagnetics Research C, Vol. 9, 171-182, 2009. [19] Singh Vinod Kumar, Ali Zakir, Singh A. K., Ayub Shahanaz,Dual band triangular slotted stacked microstrip antenna for wireless applications, Central European Journal of Engineering (CEJE), Springer ISSN: 1896 1541Volume 3, Issue 2, pp 221-225 June, 2013. [20] Singh Vinod Kumar, Ali Zakir, Ayub Shahanaz, Ashutosh Kumar Singh, A wide band Compact Microstrip Antenna for GPS/DCS/PCS/WLAN Applications, a book chapter in the book entitled "Intelligent Computing, Networking, and Informatics", (Book ISBN: 978-81-322-1664-3) Chapter 113, pp: 183-204,Springer. [21] Singh A. K., Kabeer R.A., Singh Vinod. K., Ali Z., Performance Analysis of First Iteration Koch Curve Fractal Log Periodic Antenna of Varying Angles, Central European Journal of Engineering (CEJE), Springer ISSN: 1896-1541Volume 3, Issue 1, pp 51-57 March 2013. 286