Multi Resonant Stacked Micro Strip Patch Antenna Designs for IMT, WLAN & WiMAX Applications

Transcription

1 Multi Resonant Stacked Micro Strip Patch Antenna Designs for IMT, WLAN & WiMAX Applications Tejinder Kaur Gill, Ekambir Sidhu Abstract: In this paper, stacked multi resonant slotted micro strip patch antennas (MPA) have been proposed which are suitable to be used for GSM, WLAN standard and WiMAX applications. The antennas have been designed using substrate of FR4 material. In the designed antennas, substrates having different thickness have been used. The performance of designed antenna has been observed by comparing without air gap between the stacks with same antenna having air gap of 0.8 mm between two stacks. It has been observed that air gap in stacking results in increase of antenna impedance bandwidth. The bottom stack of designed antenna has a radiating patch of circular shape and the patch on the upper stack is of rectangular shape. The antenna has a feed line which is connected to circular patch. The designed antennas have a defected ground structure in order to improve the antenna performance. The antenna performance has been measured in terms of antenna parameters such as impedance bandwidth, Return loss, antenna impedance, VSWR and Directivity. The designed antenna results have been simulated in CST Microwave Studio The practically designed antennas have been tested successfully by using Network analyzer E5071C. It has been observed that the practical results closely match with theoretical results. Index Terms Defected ground structure, Directivity, Micro strip patch antenna, Multi resonant air gap stacked antenna, Return loss (S11), VSWR. I. INTRODUCTION Microstrip antenna, also known as printed circuit antenna or patch antenna is suitable for conformal and low profile applications. The Microstrip Patch Antenna has advantage of low cost and weight, design flexibility and ease of installation [4]. The radiating elements together with feed line are photo etched on a thin dielectric sheet on a ground plane. The patch can be square, rectangular or circular in shape. However, MPA suffers from disadvantage that they have narrow bandwidth. Extensive research has been carried out to overcome the band width problem in recent years and many techniques have been suggested and implemented to achieve the desired wide band characteristics [2]-[3]. One of these techniques is stacked antennas, realizing dual frequency operation with two resonant frequencies separated by certain range [8]-[9]. Stacked patch antenna is a kind of microstrip antenna which consists of two printed antennas. The lower patch is called driven patch and another patch is parasitically coupled to driven patch. To produce broadband responses, the selection of the substrate of the first layer is very important.. Section II (Antenna Geometry) explains the geometry of antenna. The top view, bottom view and dimensions of substrate, patch, slots on the patch and ground plane are listed in section II. Section III (Results and Discussions) describes the simulated results obtained by using CST MWS (2010) which includes Return loss (S 11 ), Directivity, Gain at corresponding resonant frequencies, VSWR and Smith chart plots. Tejinder Kaur Gill, Department of Electronics & Communication Engineering, Punjabi University Patiala., India, Ekambir Sidhu, Department of Electronics and Communication Engineering, Punjabi University, Patiala, India, Section IV (Experimental verification) indicates the top and bottom view of practically designed antenna and describes practical results obtained by testing the practically designed antenna using E5071C ENA series Network Analyzer. 3577

2 Section V (conclusion) explains both simulated theoretical results and practical results in terms of return loss at corresponding resonant frequencies and bandwidth, along with list of applications in which designed antenna can be used. II. ANTENNA GEOMETRY Fig.1shows the top view of the bottom stack of the antenna. The Fig1 shows circular slotted patch, excited by feedline of suitable width. Fig. 2 represents the top view of upper stack. Fig. 3 represents the bottom view of stacked antenna. The ground has been designed at the bottom of the lower stack which has been partially reduced. The antenna has been fabricated using FR4 as an substrate with dielectric constant of 4.4.The height of lower substrate is 1.57mm and that of upper substrate is 0.8mm.The feedline is designed in such a way that antenna will have 50 ohm resistance matched with the port impedance for maximum power transfer from port to patch. Fig. 4 shows the stacked air gap antenna with all the dimensions same except the air gap is present. The dimensions of substrate, patch, feed, slots cut on patch and ground are listed in Table. 1 NOTE: The dotted lines in Fig. 3 represent the projection of patch and feedline on ground. NOTE: The air gap of 0.8mm has been maintained by inserting a 0.8 mm FR4 sheet between the two stacks at their edges. This can be cleared from the Fig. 9 (c) Antenna Parameter Specification Length of substrate (Ls) 60mm Width of substrate (Ws) 60 mm Radius of lower patch (R1) 18.8mm Radius of circular slot (R2) 10.8mm Length of feed (Lp) 112mm Width of feed (Wp) 5.6mm Length (L1) 22mm Length (L2) 21mm Length (L3) 20mm Width (W1) 13.2mm Width (W2) 5.6mm Width (W3) 4mm Width (W4) 2mm Width (W5) 2mm Width (W6) 2mm Length of upper substrate (LUs) 60mm Width of upper substrate (WUs) 60mm Length of upper patch (LU1) 25mm Width of upper patch (WU1) 11.6mm Length of ground (Lg1) 12mm Width of ground (Wg4) 60mm Length of slot on ground (Lg5) 3mm Width of slot on ground (Wg5) 6.4mm Length (LU2) 30mm Width (WU1) 24.2mm Thickness of upper stack ( T1) 0.8mm Thickness of lower stack ( T2) 1.57mm Air gap (Ag) 0.8mm Fig. 2Top view of stacked antenna Fig. 1Top View of bottom stack of antenna TABLE 1. ANTENNA PARAMETERS 3578

3 It has been observed that the return loss is db at GHz, db at GHz, db at GHz, -20dB at GHz and db at 5.310GHz. The simulated bandwidth of the proposed antennas is GHz. Fig. 3Bottom View of stacked antenna Fig. 5Return loss of stacked MPA without air gap Fig. 6 Return loss of stacked MPA with air Gap Fig. 4 View of stacked antenna with air gap III. RESULTS AND DISCUSSIONS The designed stacked antenna have been simulated using CST Microwave Studio 2010 and the performance of the antenna has been analyzed in terms of return loss, VSWR, radiation pattern, directivity, impedance and gain. The experimental results have been also obtained using E5071C ENA series Network Analyzer and it has been concluded that the practical results closely matches with the simulated theoretical results. Fig. 5 represents the simulated results of return loss (S11) for designed stacked antenna without any air gap. It has been observed that the return loss is db at GHz, db at GHz, db at GHz and db at 5.047GHz. The simulated bandwidth of the proposed antennas is GHz. Fig. 6 represents the simulated results of return loss (S11) for designed stacked antenna without any air gap. The directivity of stacked antenna without air gap at resonant frequencies have been obtained and analyzed. Fig. 5(a), Fig. 5(b), Fig. 5(c) and Fig. 5(d) shows the 3D plot of directivity of slotted MPA at resonant frequencies of 1.7 GHz, 2.7 GHz, 3.4 GHz and 5.0 GHz, respectively. The directivity is dbi at 1.7 GHz, dbi at 2.7 GHz, d Bi a t 3. 4 G H z and dbi at 5.0 GHz. It has been observed that directivity is better for higher resonant frequencies than lower frequencies. Fig. 5(e), Fig. 5(f), Fig. 5(g), Fig. 5(h) illustrates the 3D plot of gain for slotted MPA at resonant frequencies of 1.7 GHz, 2.7 GHz, 3.4 GHz and 5.50 G H z respectively. The 3D plot shows that the gain is db at 1.7 GHz, db at 2.7 GHz, 4.290dB at 3.4 GHz and db at 4.307GHz. 3579

4 Fig. 5(a) 3D plot of Directivity of stacked MPA without air gap at 1.7 GHz Fig. 5(e) 3D plot of Gain of stacked MPA without air gap at 1.7 GHz Fig. 5(b) 3D plot of Directivity of stacked MPA without air gap at 2.7 GHz Fig. 5(f) 3D plot of Gain of stacked MPA without air gap at 2.7 GHz Fig. 5(c) 3D plot of Directivity of stacked MPA without air gap at 3.4 GHz Fig. 5(g) 3D plot of Gain of stacked MPA without air gap at 3.4 GHz Fig. 5(d) 3D plot of Directivity of stacked MPA without air gap at 5.04 GHz. Fig. 5(h) 3D plot of Gain of stacked MPA without air gap at 5.0 GHz Similarly, the antenna with air gap has been designed and the directivity at resonant frequencies has been 3580

5 obtained and analyzed. Fig. 6 (a), Fig. 6(b), Fig. 6(c), Fig. 6(d), and Fig. 6(e) shows the 3D plot of directivity of slotted MPA at resonant frequencies of 1.8 GHz, 2.9 GHz, 3.2 GHz, 4.7 GHz and 5.3GHz respectively. The directivity is dbi at 1.8 GHz, dbi at 2.9 GHz, d Bi a t 3. 2 G H z, dbi at 4.7 GHz and dbi at 5.3 GHz. Fig. 6(f), Fig. 6(g), Fig. 6(h), Fig. 6(i) and Fig 6(j) illustrates the 3D plot of gain for slotted MPA w i t h a i r g a p at resonant frequencies 1.8 GHz, 2.9 GHz, 3.2 GHz, 4.7 GHz and 5.3 GHz respectively. The 3D plot shows that the gain is db at 1.8 GHz, db at 2.9 GHz, db at 3.2 GHz, db at 4.7 GHz and db at 5.3 GHz Fig. 6(c) 3D plot of Directivity of stacked MPA with air gap at 3.2 GHz Fig. 6(a) 3D plot of Directivity of stacked MPA with air gap at 1.8 GHz Fig. 6(d) 3D plot of Directivity of stacked MPA with air gap at 4.7 GHz Fig. 6(b) 3D plot of Directivity of stacked MPA with air gap at 2.9 GHz Fig. 6(e) 3D plot of Directivity of stacked MPA with air gap at 5.3 GHz 3581

6 Fig. 6(f) 3D plot of Gain of stacked MPA with air gap at 1.8 GHz Fig. 6(j) 3D plot of Gain of stacked MPA with air gap at 5.3 GHz Fig. 6(g) 3D plot of Gain of stacked MPA with air gap at 2.9 GHz Fig. 7(a) and Fig. 7(b) depicts the simulated VSWR plot for stacked MPA without air gap and with air gap respectively. The required value of VSWR should be less than 2. Fig. 7(a) shows that value of VSWR for stacked MPA without air gap is less than 2 in the operating frequency range of 1.57 GHz to 1.83 GHz, 2.5 GHz to 3.1 GHz, 4.2 GHz to 5.67 GHz. Fig. 7(b) shows that value of VSWR for stacked MPA with air gap is less than 2 in the operating frequency range of 1.64 GHz to GHz, 2.75 GHz to 3.46 GHz, 4.35 GHz to 6.03 GHz. Fig. 6(h) 3D plot of Gain of stacked MPA with air gap at 3.2 GHz Fig. 7(a) VSWR plot of stacked MPA without air gap Fig. 6(i) 3D plot of Gain of stacked MPA with air gap at 4.7GHz Fig. 7(b) VSWR plot of stacked MPA with air gap 3582

7 Fig. 8(a) and Fig. 8(b) indicates Smith chart plot for slotted MPA without air gap and Smith chart plot for slotted MPA with air gap. The Smith Chart plot indicates the variation in impedance of antenna with frequency. The value of impedance should lie near 50 ohms in order to perfectly match the port with the antenna. The antenna impedance for both designed slotted MPA antenna without air gap and with air gap is 50 Ω. db at 1.81 GHz, at 2.9 GHz, at 3.25 GHz, dB and db at GHz and GHz, respectively. The bandwidth obtained from practical results of designed MPA is 3.042GHz. Fig. 9(a) Top view of designed stacked MPA Fig. 8(a) Smith chart plot of stacked MPA without air gap Fig. 9(b) Bottom view of designed stacked MPA Fig. 8(b) Smith chart plot of stacked MPA with air gap IV.EXPERIMENTAL VERIFICATION The proposed antenna has been physically designed and the top and bottom view of practically designed antenna are shown in Fig. 9(a) and Fig. 9(b), respectively. The Fig. 9(c) represents the air gap between two stacks. The designs are tested using E5071C ENA series Network Analyzer. The practically analyzed results of slotted MPA are shown in Fig. 10(a) and Fig. 10(b). It has been observed from Fig. 10(a) that the practical results of designed MPA without any air gap have return loss of db at 1.79 GHz, db and db at 2.78 GHz and 5.10 GHz respectively. The bandwidth obtained from practical results of designed MPA is 2.57 GHz. Similarly it has been observed from Fig. 10(b) that the practical results of designed MPA with air gap have return loss of Fig. 9(c) View of air gap of stacked microstrip antenna with air gap 3583

8 from 1.51 GHz to 5.63 GHz and the designed stacked antenna with air gap has practical results with bandwidth from 1.62 GHz to 6.18 GHz. The designed antenna w i t h o u t a i r g a p is suitable to be used for IMT only (2.69 GHz to 3.57 GHz, GHz to 5.63 GHz) and the antenna with air gap is suitable for GSM (1.62 GHz to 1.98 GHz), WLAN standard (4.37 GHz to 6.18 GHz) and WiMAX (3.4 GHz to 3.69 GHz, 5.25 GHz to 5.85 GHz) applications [1]. CONCLUSION TABLE: Fig. 10(a) Experimental result of MPA without air gap PARAMETERS WITHOUT AIR GAP WITH AIR GAP Bandwidth Between 1.5 Between 1.63 Range GHz to 5.7 GHz to (Theoretically) GHz GHz Bandwidth Range (Practically) Between 1.51 GHz to 5.63 GHz Between 1.62 GHz to 6.18 GHz VSWR Less than 2 Less than 2 Impedance (ohm) APPLICATION IMT only GSM, WLAN,WiMax REFERENCES Fig. 10(b) Experimental result of MPA with air gap V. CONCLUSION From the above discussion, it can be concluded that the stacked microstrip patch antenna without air gap has bandwidth of GHz with operating frequency range between 1.5GHz to 5.7 GHz.The VSWR for stacked microstrip patch antenna without air gap is less than 2 in the operating frequency range of 1.5 GHz to 5.7 GHz. For the stacked microstrip antenna with air gap of 0.8mm, it can be concluded that bandwidth is GHz with operating frequency range between 1.63 to GHz. The VSWR for stacked microstrip patch antenna is less than 2 in an operating frequency range between 1.63GHz to GHz. The simulated results of the designed stacked antenna closely match with practical results. It has been observed that the practical results obtained from designed stacked MPA without air gap has bandwidth of 2.57 GHz having frequency range [1] olume5/ijece-v5n1p104.pdf. [2] J. R James., Hall P.S. and Wood C. Microstrip antenna theory and design IEE Electromagnetic wave, Series 12 London, Peter Peregrinus1989. [3] K.C Gupta. Recent advance in microstrip antenna. Micro wave Journal, vol-27, pp.50-67, [4] J. l BahI & Bharta P., Microstrip Antennas, Massachusetts (USA) Artech House, [5] Neha Ahuja, Study and investigations on various micro strip patch antennas for wireless applications /1783/1/thesis.pdf. [6] =http%3a%2f%2fieeexplore.ieee.org%2fstamp %2Fstamp.jsp%3Ftp%3D%26arnumber%3D %26userType%3Dinst&denyReason=134& arnumber= &productsmatched=null&use rtype=inst [7]

9 [8] S.A Long & Walton M.D, A Dual-frequency circular-disc antenna, IEEE Trans. Antenna & Propag (USA), AP-27, and pp , [9] T.M Au and K M Luk, Effect of parasitic element on the characteristics of microstrip antenna, IEEE Trans Antenna & Propagation (USA) 39,pp , [10] AB2-4.pdf. [11] ds. 3585