ABSTRACT A Compact low profile MIMO Diversity antenna system with multiple feeds with a size of 105mm*61.5mm is proposed. Multiple feeds are used to provide maximum power to antenna elements so that signal can propagate a long distance. The proposed antenna is achieving multiple frequencies, i.e. 2.5 GHz, 3.21 GHz, 4.22GHz, 4.68GHz, 6.5GHz, 6.74 GHz, 7 GHz and 8.35  GHz. Measured S-parameters show the isolation is -23.715 db. The maximum achievable bandwidth is 1.32 GHz (1320 MHz). This antenna can be applicable at Wimax, WLAN, LTE and Satellite Bands

Ehsan Muhammad Wasif Nisar

Muhammad Wasif Nisar

Ullan Munir

Waqas Ahmad

Waqas Anwar

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J. Basic. Appl. Sci. Res., 1(9)1084-1088, 2011 
© 2011, TextRoad Publication 
ISSN 2090-424X 
Journal of Basic and Applied  
Scientific Research 
www.textroad.com 
 
 
*Corresponding Author: Muhammad Wasif Nisar, COMSATS Institute of Information Technology, Wah Cantt. 47040, 
Pakistan. Email: wasifnisar@comsats.edu.pk 
 
 
Low Profile MIMO Diversity Antenna with Multiple Feed 
 
Waqas Ahmad, Muhammad Wasif Nisar, Ehsan Ullan Munir, Waqas Anwar 
 
COMSATS Institute of Information Technology, Wah Cantt. 47040, Pakistan. 
COMSATS Institute of Information Technology, Abbottabad,Pakistan 
 
 
 
ABSTRACT 
 
A Compact low profile MIMO Diversity antenna system with multiple feeds with a size of 
105mm*61.5mm is proposed. Multiple feeds are used to provide maximum power to antenna 
elements so that signal can propagate a long distance. The proposed antenna is achieving multiple 
frequencies, i.e. 2.5 GHz, 3.21 GHz, 4.22GHz, 4.68GHz, 6.5GHz, 6.74 GHz, 7 GHz and 8.35 GHz. 
Measured S-parameters show the isolation is -23.715 db. The maximum achievable bandwidth is 
1.32 GHz (1320 MHz). This antenna can be applicable at Wimax, WLAN, LTE and Satellite Bands.  
KEY WORDS: Multiple-input multiple-output (MIMO), multi feed, circular-slots, diversity. 
 
1. INTRODUCTION 
 
MULTIPLE-INPUT–MULTIPLE-OUTPUT (MIMO) wireless communication systems uses 
multiple antenna elements at both the transmit and receive sides to improve capacity gain as compared to 
the usual single-input–single-output (SISO) systems [1]. 
In [2] they have designed a multiband MIMO antenna using a band stop matching circuit. This 
antenna is applicable at next generation mobile applications. At LTE band antenna has the isolation of 
approximately 15 dB and 20 dB at the upper bands.  
In [3] a compact Microstrip patch antenna operating at tri-bands is being proposed. The proposed 
antenna operates at 2.7 GHz, 3.2 GHz and 5.3 GHz. The antenna has two U-shaped slots and a small 
ground plane in order to have better performance. The achieved return losses are -18.5 dB, -14.5 dB and -
19 respectively. 
  In [4] they have presented a single layer, feed, multi frequency, compact rectangular microstrip 
patch antenna. In order to reduce resonant frequencies they have used the mechanism of cutting rectangular 
slots at the edges with adding two small circles inside the patch in order to improve the return loss. By 
cutting the edges the antenna size has been reduced to 64%. 
In [5] they have presented the design of LMDS antenna. They have used aperture coupled method 
in order to enlarge the band of patch. They have also tried to minimize the fringing effect across the band 
patch.  Due to which both the antenna efficiency and frequency bandwidth are increased.  
In [6] they have presented a dual-polarized shorted bowtie antenna included with a cross dipole. 
The dipole is used to get same radiation patterns in order to balance high back radiations which are 
produced due to shorted patches. The proposed antenna is designed to operate on DCS, PCS, and 3G 
mobile communication systems working between 1.71 and 2.17 GHz. 
  In [7] a wideband planar diversity antenna for mobile terminal is presented. The antenna is operate 
able on UMTS and WLAN bands and has corresponding bandwidth of  1.904–2.504 GHz including UMTS 
(1.920–2.170 GHz) and 2.4 GHz WLAN (2.400–2.484 GHz) bands. The mutual coupling effect of the 
antenna has also been reduced.  
In [8] a new approach using directive antenna for designing MIMO arrays is presented. The main 
emphasize in this work is on reducing the mutual coupling. In this work a MIMO array of printed Yagi 
antennas with integrated balun is presented. The end-fire radiation mechanism of the Yagi is exploited to 
obtain a triangular array of three sectoral antennas. 
In [9] Metamaterial concepts are used to design a novel rectangular patch antenna. The patterned 
metal patch and finite ground plane form a coupled capacitive-inductive (C-L) circuit of negative index 
metamaterial. In order to achieve low VSWR, high efficiency, low loss and wideband a new type of 
antenna is used to design Meta array. The resultant array has more bandwidth than original patch arrays, 
and high gain can also be obtained in a wide frequency band. 
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Ahmad et al., 2011 
In [10] a rectangular patch antenna array for MIMO communications was simulated on a magnetic 
permeability enhanced metamaterial. The antenna performance was compared with conventional array 
constructed on normal substrate. The analysis was taken on the basis of degree of mutual coupling for 
different element spacing, achievable channel capacity, bandwidth and efficiency. The results show the 
array built on the metamaterial substrate has significant size reduction, less mutual coupling and significant 
channel capacity improvement compared to similar arrays on conventional substrates. 
 
2. Antenna Design 
 
In this paper multi-feed Mimo antenna is proposed. The geometry of Mimo antenna is illustrated 
in Figure2. The proposed antenna contains 2 antenna elements having approximately λ/8 (7.5mm). Each 
antenna element is feeded with 2 feeds one from top the other from the bottom. Both the antenna elements 
are on common ground. The dimension of the antenna elements are 43mm*27.6mm, dimension of substrate 
and ground are 105mm*61.5mm. The thickness of the substrate is 1.6mm and have dielectric constant of 
r =4.4. The antenna elements are feeded with transmission line of 3mm*17mm and have impedance of 50 
ohms. Circular slots have been introduced to achieve multibands. A circle with crossing rectangles has been 
introduced in middle of each antenna element. The radius of the central circle is 6mm and rectangles are of 
dimensions 3mm*14mm and 14mm*3mm. four more circles with radius 3mm are introduced on the 
corners of each antenna element. 
 
 
Figure 1: Structure of MIMO Antenna 
 
Structure of antenna in figure 1 has dimension of antenna elements are 41mm*27.6mm. The 
spacing between the two antenna elements in this design is λ/6. The antenna Operates at multiband and the 
results are shown in figure 3.   
 
 
Figure 2: Propsed Structure of MIMO Antenna 
 
The width and antenna elements spacing of Antenna in Figure 1 have been changed to get the 
improved results. The width of each antenna element is increased 2mm from the left-side and the spacing 
between antenna elements is approximately λ/8 (7.5mm). As shown in Figure 2. The results of the proposed 
structure of Mimo antenna is shown in Figure 4. 
The Antenna’s elements width and length are calculated by the following formula taken from [5].                       
0
2
2 1r
cw
f

 
         (1) 
1085 
J. Basic. Appl. Sci. Res., 1(9)1084-1088, 2011 
In the formula (l), W is the element’s width, C is the velocity of light in free space, r is the 
relative dielectric constant, and f0 is the operational frequency. The effective dielectric constant of the 
feeding line is calculated by the formula (2) 
 
 
1
21 1 1 12
2 2
r r
eff h w
          (2) 
Here, h is the height of the dielectric, and w is the width of the conductor. Because the fringing 
field effect occurs around the patch's edges, the quotient of L is needed to compensate for formula (3) 
 
( 0.3)( / 0.264)
(0.412)
( 0.258)( / 0.8)
eff
eff
w h
L h
w h


 
 
 
  (3) 
The antenna element’s length and the effective length are calculated by the formula (4) and (5) 
2
2
L L                                (4) 
 
2eL L L                         (5) 
 
3. SIMULATIONS AND RESULTS 
 
The simulated results of first structure presented in Figure 1 are shown in Figure 3 below. 
 
 
 
Figure 3: Simulated results of Structure of MIMO Antenna 
 
The simulated results of enhanced structure presented in figure 2 are shown in figure 4 below 
 
Figure 4: Simulated results of proposed Structure of MIMO Antenna 
 
The following tables show the detailed frequencies, return loss and bandwidth of both the antennas. 
 
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Ahmad et al., 2011 
Table 1: Simulated results of Structure of MIMO Antenna 
 
Freq (GHz) Bandwidth 
(MHz) 
Return Loss 
(db) 
2.52 180 -15.4061 
3.37 70 -11.6245 
4.42 460 -24.7065 
6.03 180 -13.2527 
7.00 660 -56.2042 
8.75 1130 -22.8125 
Table 1 shows the details about the achieved frequencies, bandwidth and return loss of the Figure 1 of the 
MIMO Antenna. 
 
 
Following figure represents the radiation pattern of the individual frequencies. 
 
 
(a):2.5 GHz 
 
(b):3.21 GHz 
 
(c):4.22 GHz 
 
(d):4.68 GHz 
 
(e):6.49 GHz 
 
(f):6.74 GHz 
 
(g):7.06 GHz 
 
(h):8.35 GHz 
      
Figure 5: Radiation pattern. 
 
1087 
J. Basic. Appl. Sci. Res., 1(9)1084-1088, 2011 
In Figure 5 the radiation pattern shows the Theta and Phi Pattern with values of 0, 90 degrees. 
Radiation pattern most commonly refers to the directional (angular) dependence of the strength of the radio 
waves from the antenna. The radiation patterns are plotted with respect to E-field and H-field: 
 
H-field: 
Theta=all values 
Phi= 0’ 90 (0= XZ-Plane, 90=YZ-Plane) 
E-field :(XY-Plane) 
Theta=90 
Phi= All values 
 
Table 2: Simulated results of proposed Structure of MIMO Antenna 
 
Freq (GHz) Bandwidth 
(MHz) 
Return Loss 
(db) 
2.50 180 -14.4958 
3.21 100 -13.1467 
4.21 250 -17.8958 
4.68 160 -12.1023 
6.51 840 -18.5250 
6.74 840 -19.4977 
7.07 840 -13.7091 
8.35 1320 -23.7154 
   
Table 2 shows the details about the achieved frequencies, bandwidth and return loss of the Figure 2 of 
the MIMO Antenna which is much better than the results of Figure 1, here got more bandwidth and 
achieved more frequencies. 
 
4. Conclusion  
 
A Compact low profile MIMO diversity antenna system with multiple feeds with a size of 
105mm*61.5mm is proposed in this paper. Multiple feeds are used to provide maximum power to antenna 
elements so that signal can propagate a long distance. The proposed antenna is achieving multiple 
frequencies, i.e. 2.5 GHz, 3.21 GHz, 4.22GHz, 4.68GHz, 6.5GHz, 6.74 GHz, 7 GHz and 8.35 GHz. 
Measured S-parameters show the isolation is -23.715 db. The maximum achievable bandwidth is 1.32 GHz 
(1320 MHz). This antenna can be applicable at Wimax, WLAN, LTE and Satellite Bands. 
 
REFERENCES 
 
[1]. G. J. Foschini and M. J. Gans, “On limits of wireless communications In a fading environment when 
using multiple antennas,” Wireless Personal Commun.no. 6, pp. 311–335, 1998. 
[2]. Min-Seok Han; Jaehoon Choi; “Multiband MIMO Antenna with a Band Stop Matching Circuit for 
Next Generation Mobile Applications” IEEE Conferences  Publication Year: 2009 , Page(s): 1 - 4  
[3]. AbuTarboush, H.F.; Al-Raweshidy, H.S.; Nilavalan, R.; “Triple band double U-slots patch antenna for 
WiMAX mobile applications” IEEE Conferences  Publication Year: 2008 , Page(s): 1 - 3  
[4]. S. arkar, I.; Sarkar, P.P.; Chowdhury, S.K.; “A NOVEL COMPACT, MICROSTRIP ANTENNA WITH 
MULTIFREQUENCY OPERATION” IEEE Conferences  Publication Year: 2009 , Page(s): 147 - 151  
[5]. Hyeonjin Lee; Taehong Kim; Yeongseog Lim; “Wide-Band Microstrip Patch Antenna Design For 
LMDS Band” IEEE Conferences  Publication Year: 2000 , Page(s): 709 - 712  
[6]. Ka-Ming Mak; Hang Wong; Kwai-Man Luk; “A Shorted Bowtie Patch Antenna With a Cross Dipole 
for Dual Polarization ” IEEE Journals  Volume: 6  Publication Year: 2007 , Page(s): 126 - 129  
[7]. Xuan Wang; Zhengwei Du; Ke Gong; “A Compact Wideband Planar Diversity AntennaCovering UMTS 
and 2.4 GHz WLAN Bands”  IEEE Journals Volume: 7 Publication Year: 2008 , Page(s): 588 - 591 
[8]. Capobianco, A.D.; Pigozzo, F.M.; Boscolo, S.; Midrio, M.; Sacchetto, F.; Assalini, A.; Brunetta, L.; 
Zambon, N.; Pupolin, S.; “A Novel Compact MIMO Array based on PlanarYagi Antennas for 
Multipath Fading Channels” IEEE Conferences Publication Year: 2010 , Page(s): 93 - 96  
[9]. Le-Wei Li; Ya-Nan Li; Ke Xiao; “Broadband and High-Gain Metamaterial Microstrip Anetnna 
Arrays” IEEE Conferences  Publication Year: 2010 , Page(s): 1 - 4  
[10]. Mookiah, P.; Dandekar, K.R.; “Performance Analysis of Metamaterial Substrate Based MIMO 
Antenna Arrays” IEEE Conferences  Publication Year: 2008 , Page(s): 1 - 4  
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Low Profile MIMO Diversity Antenna with Multiple Feed

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Low Profile MIMO Diversity Antenna with Multiple Feed

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