Design and Analysis of MIMO Antenna for ISM band Application

Design and Analysis of MIMO Antenna for ISM band Application

R. Abirami#, Student, K. Srividhya, Assistant Professor, Department of Electronics and Communication,

Sri Venkateswara college of Engineering, Sriperumbudur

Abstract The design and analysis of MIMO antenna with U shaped ground structure is proposed for ISM band application. The antenna comprises of semicircular patch with t slot etched and U shaped ground structure to reduce the mutual coupling between closely spaced antenna elements. The overall dimensions of the antenna are 40×38.5×1.6 mm3. This antenna is designed and its performance is analyzed from the ADS simulation software. The proposed MIMO antenna resonates at the frequency 2.4GHz with return loss<-27dB and isolation<-25dB. At this frequency band simulated gain is about 0.58dBi, directivity is about 7.1dBi. For the proposed MIMO antenna the Envelope Correlation Coefficient is below 0.5. Hence it has high isolation with closely spaced antennas to be suitable for MIMO communication.

Keywords Compact MIMO antenna; Slot; Defected Ground Structure; ECC; Isolation;

1. INTRODUCTION

   Nowadays Multiple antenna configurations can be used to overcome the effects of multi-path and fading when trying to achieve high data throughput in limited-bandwidth channels. MIMO exploits spatial diversity by having several transmit and receive antennas. It can greatly increase the capacity of channels by independently sending streams of date across multiple antennas. Isolation is the important consideration in MIMO antenna. Hence U shape ground structure contributes to electromagnetic shielding. Under this circumstance, the induced current magnitude is nearly zero around the middle of the AIPD, leaving room for the RFIC and other components, ultimately reducing the risk of potential electromagnetic interference [1].

   Many authors have proposed several solution to improve mutual coupling such as defected ground plane, cutting resonant slot in ground plane, electromagnet band gap (EBG), placing parasitic element between antenna element and neutralization lines [2][3]. These solution tend to improve mutual coupling for example in paper defected ground plane has been used to achieve isolation up to 20dB with minimum distance between antenna element is lesser. Some authors have also used tree like structure over the modified ground plane in order to achieve good isolation between antenna elements as discussed in [4]By using DGS and parasitic element a 2x 1 compact 4-shaped multiple-input-multiple- output (MIMO) antenna is designed. A defected ground plane structure (DGS) is etched in the ground plane to reduce mutual coupling effect between two antennas. Parasitic elements in F shape is added at comer to improve the isolation.

   This proposed antenna covers two frequency band in lower and higher frequency band which is 2440MHz-2560MHz and 5120MHz- 5260MHz. By DGS the lower band isolation<- 14.S4dB at and higher band isolation <-20.9. The gains of these antennas are 1.4dBi and 2.5dBi at 2.5GHz and 5.2 GHz. Parasitic elements are mainly used to improve the gain of MIMO antenna [5].

   For MIMO antennas, a wide band printed dipole using V-shaped ground branches is designed. To improve the impedance matching dipole with an integrated balun and V shaped ground branches are introduced. All three WiMAX bands (2.30, 2.50, and 3.30 GHz) and the 2.40 GHz WLAN band are covered. This antenna is most suitable for wireless routers and adapters [6]. A Dual ISM band MIMO Antenna was typically employed for WiFi and WiMax Application. The antenna has two sickle shaped radiator patch with microstrip feed line. In ground plane the rectangular shape slot and trident shape structure is employed to provide isolation between closely spaced antennas. For this configuration the antenna achieved better operating bandwidth at 2.4 and 5.2 GHz with satisfactory return loss and isolation [7].

2. MIMO ANTENNA DESIGN

   1. MIMO Antenna Structure

      c1

      s1

      3

      c3 s2 s

      c2

      c4

      m1

      d

      m2

      Fig. 1 MIMO Antenna Structure

      The MIMO Antenna structure comprises of two antenna elements as semi circular etched with t shaped slot. The feed

      is given at the microstrip line. The dimensions of the antenna is shown in Table I. The parameters of the antenna elements are c1, c2, c3, c4, s1, s2, s3, m1, m2, d.

      TABLE I

      DIMENSION PARAMETERS OF THE ANTENNA ELEMENT

      c1	5.6mm	s2	4.7mm
      c2	4.4mm	s3	1.1mm
      c3	1.5mm	m1	9.3mm
      c4	2.1mm	m2	0.5mm
      s1	1.1mm	d	12.9mm

   2. MIMO Antenna Ground Structure

      The ground structure is shown in figure 2 in which the U shaped slot is etched and it acts as a shielding for electromagnetic interference around the antenna gap. The ground structure consists of two sets of complementary facing strips and each U shaped slots acts as a shielding of interference. Hence it will improve the isolation of the MIMO antenna to be suitable for wireless communication. It will reduce the mutual coupling between closely spaced antenna elements.

      g5

      Fig. 3 MIMO Antenna Geometry

3. SIMULATED RESULTS

   The following figure 4 shows the antenna structure with ports. Figure 5 showing simulated results of scattering parameters for ISM band MIMO Antenna. Here S11, S22, S12 and S21 are obtained from Advanced Design System simulation software version 11.01.

   g4

   g7

   g8

   g3

   g6

   g2

   g1

   Fig. 2 MIMO Antenna Ground Structure

   The dimensions of the ground structure and its U shaped slots are listed in the table II. The following are the parameters g1, g2, g3, g4, g5, g6, g7 and g8.

   TABLE III

   DIMENSION PARAMETERS OF THE GROUND STRUCTURE

   g1	36mm	g5	3.1mm
   g2	5mm	g6	6.8mm
   g3	18.5mm	g7	0.3mm
   g4	3.1mm	g8	15.3mm

   1. MIMO Antenna Geometry

   The overall configuration of the proposed MIMO antenna is shown in the following figure 3.

   Fig. 4 MIMO Antenna Structure with ports

   The S11 is the Return loss of antenna element 1 and S22 is the Return loss of antenna element 2. S12 and S21 are the mutual coupling or Isolation between antenna element 1 and 2. Figure 5 and 6 shows the return loss which is <27dB and isolation is <25dB for antenna 1. Figure 7 shows both the S11 and S21 for antenna 1. The figure 8 and 9 shows the return loss and isolation which is <-27dB and <25dB for antenna 2. Similarly figure 10 shows both the return loss and isolation for antenna element 2 which is same as the antenna 1. The simulation results of radiation pattern, gain and directivity, absolute fields and polarization are also presented.

   0

   -5

   -10

   Return Loss in dB

   -15

   -20

   -25

   -30

   -35

   -40

   -45

   -50

   0.0

   dB(S(1,1))

   0.5 1.0 1.5 2.0 2.5

   Frequency in GHz

   3.0

   0

   -5

   Return Loss in dB

   -10

   -15

   <>-20

   -25

   -30

   0.0

   dB(S(2,2))

   0.5 1.0 1.5 2.0 2.5

   Frequency in GHz

   3.0

   Fig. 5 Return Loss for Antenna 1

   Fig. 8 Return Loss of Antenna 2

   0

   -5

   -10

   Isolation in dB

   -15

   -20

   -25

   -30

   -35

   -40

   -45

   -50

   dB(S(2,1))

   0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0

   Frequency in GHz

   0

   -10

   Isolation in dB

   -20

   -30

   -40

   -50

   0.0

   dB(S(1,2))

   0.5 1.0 1.5 2.0 2.5

   Frequency in GHz

   3.0

   Fig. 9 Isolation for Antenna 2

   Fig. 6 Isolation for Antenna 1

   0

   Return Loss and Isolation in dB

   -5

   -10

   -15

   -20

   -25

   -30

   -35

   -40

   -45

   -50

   0.0

   dB(S(1,1))

   dB(S(2,1))

   0.5 1.0 1.5 2.0 2.5

   Frequency in GHz

   3.0

   0

   Return Loss and Isolation in dB

   -5

   -10

   -15

   -20

   -25

   -30

   -35

   -40

   -45

   -50

   1.4

   dB(S(2,2))

   dB(S(1,2))

   1.6 1.8 2.0 2.2 2.4 2.6

   Frequency in GHz

   2.8

   Fig. 7 Return Loss and Isolation for Antenna 1

   Fig. 10 Return Loss and Isolation for Antenna 2

   The 3D structure of the proposed antenna is shown in figure 11. The main design criteria for MIMO wireless communication is Envelope Correlation Coefficient (ECC).

   Fig. 11 3D View of the proposed MIMO antenna

   The ECC is calculated from the formula,

   11

   =|S* S21- S*12 S22| 2/(1-|S11|2-| S21|2) (1-|S22|2-| S12|2)….(1)

   where represents the Envelope Correlation Coefficient. The proposed MIMO antenna has ECC as 0.3 which is less than

   0.5. Since having low ECC it has high isolation to be suitable for high datarate MIMO communication.

   Fig. 13 Antenna Parameters

   Absolute Fields

   Etheta Ephi

   90°

   0.8

   135°

   0.6

   0.4

   Mag. [V]

   180°

   0.2

   0.0

   225°

   270°

   Phi (0.000 to 360.000)

   Htheta Hphi

   90°

   0.0020

   45°

   45°

   135°

   0.0015

   0.0010

   Mag. [A]

   180°

   0.0005

   0°

   0°

   0.0000

   225°

   315°

   315°

   270°

   Phi (0.000 to 360.000)

   Fig. 14 Absolute Fields

   Circular Polarization

   E_left E_right

   90°

   -17.78

   45°

   135°

   -17.80

   Linear Polarization

   E_co E_cross

   90°

   45°

   135°

   -13

   Fig. 12 Radiation Pattern of the Proposed MIMO antenna

   The MIMO antenna radiation pattern shows the omni direction pattern which is shown in figure 12. The antenna parameters are shown in the following figure 13.

   The simulated gain and directivity of the proposed MIMO antenna at 2.4GHz are 0.5dBi and 7.1dBi. The

   -17.82

   -17.84

   -17.86

   0°

   Mag. [dB]

   180°

   -17.88

   -17.90

   225°

   315°

   270°

   Phi (0.000 to 360.000)

   -33

   Mag. [dB]

   -53

   0°

   180°

   -73

   225°

   315°

   270°

   Phi (0.000 to 360.000)

   absolute fields of E theta, E phi and H theta, H phi at 2.4GHz is shown in figure 14, 15.

   Fig. 15 Polarization of the Proposed MIMO Antenna

4. CONCLUSION

A Semi circular shaped MIMO antenna element with t shaped slot and with U shaped ground is presented. U shaped ground structure is implemented to reduce the mutual

coupling between closely spaced antennas and hence isolation is improved. The isolation obtained at 2.4GHz ISM band is

<25dB with compact MIMO antenna structure. It has low ECC which results in further proof of better isolation to be suitable for MIMO communication. The Return loss is less than 27dB. The observed gain of an antenna is 0.5dBi and directivity is 7.1dBi at 2.4GHz. Hence this antenna is suitable for ISM band application.

REFERENCES

1. Tzu-Chun Tang, and Ken-Huang Lin, MIMO Antenna Design in Thin-Film Integrated Passive Device, IEEE Trans vol. 4, no. 4, pp. 648655 April 2014

2. Chan Hwang See, Raed A Abd-Alhameed, Zuhairiah Z. Abidin, Neil J. McEwan, and Peter S. Excell "Wideband Printed MIMO/Diversity Monopole Antenna for WiFi/WiMax Applications" iEEE Transaction on Antennas and propagation, Vol. 60, No. 4, pp. 2028-2034, Apr. 2012.

3. S. Zhang, Z. Ying, J. Xiong, and S. He, "Ultra-Wideband MIMO/diversity antennas with a tree-like structure to enhance wideband isolation," iEEE Antennas Wireless Propag. Letter, Vol. 8, pp. 1279-1282,2009.

4. Hussein Hamed Mahmoud Ghouz, Novel Compact and Dual- Broadband Microstrip MIMO Antennas for Wireless Applications, PIERS Proceeding, Vol.63, 107-121, 2015.

5. Komal A. Kalamkar, S. Khade, S.L.Badjate, A 4-shaped MIMO Antenna for WLAN Application, IEEE ICCSP 2015 conference.

6. Han Wang, Lngsheng Liu, Zhijun Zhang, Yue Li, and Zhenghe Feng, A Wideband Compact WLAN/WiMAX MIMO Antenna Based on Dipole With V-shaped Ground Branch, vol.63, No.5, May 2015.

7. Rakesh Roshan, Rajat Kumar Singh, Dual ISM Band MIMO Antenna fr WiFi and WiMax Application, IEEE ICSPCT, pp.209-213, 2014.

8. Qian Li, Alexandrs P.Feresidis, Marina Mavridou, and Peter S. Hall, Miniaturized Double-Layer EBG Strucures for Broadband Mutual Coupling Reduction Between UWB Mnopoles, IEEE transactins on Antennas and Propagation, vol.63, No.3, March 2015.

9. T.K.Roshna, U.Deepak, V.R.Sajitha, K.Vasudevan, and P.Mohanan, A Compact UWB MIMO Antenna With Reflector to Enhance Isolation, IEEE transactions on Antennas and Propagation, vol.63,pp.1873-1877, No.4, April 2015.

10. Chandrakanta Kumar and Debatosh Guha, Reduction in Cross- Polarized Radiation of Microstrip Patches Using Geometry- Independent Resonant-Type Defected Ground Structure (DGS), IEEE Transactions on Antennas and Propagation, vol.63, No.6,pp.2768- 2772.

11. Jian Ren, Dawei Mi, and Yingzong Yin, Compact Ultra wideband MIMO Antenna with WLAN/UWB Bands Coverage, PIER C, vol.50,121-129, 2014.

12. J. Ou Yang, F.Yang, and Z.M, Wang, Mutual Coupling of Closely Spaced Microstrip MIMO Antennas for WLAN Application, IEEE Antennas and Wireless Propagation letters, vol.10, pp.310-313, 2011.

13. R. Suga, H. Nakano, Y. Hirachi, J. Hirokawa, and M. Ando, Cost effective 60 GHz antenna package with end-fire radiation for wireless file-transfer system, IEEE Trans. Microw. Theory Tech., vol. 58, no. 12, pp. 39893995, Dec. 2010.

14. F.-J. Huang, C.-M. Lee, C.-Y. Kuo, and C.-H. Luo, MMW Antenna in IPD process for 60-GHz WPAN applications, IEEE Antennas Wireless Propag. Lett., vol. 10, no. 6, pp. 565568, Jul. 2011.

15. J.-F. Li, Q.-X. Chu, and T.-G. Huang, A compact wideband MIMO antenna with two novel bent slits, IEEE Trans. Antennas Propag., vol. 60, no. 2, pp. 482489, Feb. 2012.

16. Z. Li, Z. Du, M. Takahashi, K. Saito, and K. Ito, Reducing mutual coupling of MIMO antennas with parasitic elements for mobile terminals, IEEE Trans. Antennas Propag., vol. 60, no. 2, pp. 473451, Feb. 2012.

17. S.-H. Wi, J.-S. Kim, N.-K. Kang, J.-C. Kim, H.-G. Yang, Y.-S. Kim, et al., Package level integrated LTCC antenna for RF package application, IEEE Trans. Adv. Packag., vol. 30, no. 1, pp. 132141, Feb. 2007.

18. Y. P. Zhang, M. Sun, and W. Lin, Novel antenna-in-package design in LTCC for single-chip RF transceiver, IEEE Trans. Antennas Propag., vol. 56, no. 7, pp. 20792088, Jul. 2008.

19. Y. P. Zhang, Enrichment of package antenna approach with dual feeds, guard ring, and fences of vias, IEEE Trans. Adv. Packag., vol. 32, no. 3, pp. 612618, Aug. 2009.

20. Y. P. Zhang, M. Sun, K. M. Chua, L. L. Wai, and D. Liu, Antennain- package design for wire bond interconnetion to highly integrated 60 GHz radios, IEEE Trans. Antennas Propag., vol. 57, no. 10, pp. 2842 2851, Oct. 2009.

21. Y. P. Zhang and D. Liu, Antenna-on-chip and antenna-in-package solutions to highly integrated millimeter wave devices for wireless communications, IEEE Trans. Antennas Propag., vol. 57, no. 10, pp. 28302841, Oct. 2009.

22. L. Liu, S. W. Cheung, and T. I. Yuk, Compact MIMO antenna for portable devices in UWB applications, IEEE Trans. Antennas Propag., vol. 61, no. 8, pp. 42574264, Aug. 2013.

23. A. P. Feresidis and Q. Li, Miniaturised slits for decoupling PIFA array elements on handheld devices, IET Electron. Lett., vol. 48, no. 6, pp. 310312, 2012.

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