Isolation enhanced MIMO antenna for software defined networking (SDN) adapted ultrawide band (UBW) radio tech applications

Journal Pre-proof

Isolation Enhanced MIMO Antenna for Software Defined Networking (SDN) adapted Ultrawide Band (UBW) Radio Tech Applications Indu Nair V Full-Time research scholar , Deepa P Assistant Professor PII: DOI: Reference:

S0141-9331(19)30479-X https://doi.org/10.1016/j.micpro.2019.102965 MICPRO 102965

To appear in:

Microprocessors and Microsystems

Received date: Revised date: Accepted date:

28 September 2019 5 December 2019 21 December 2019

Please cite this article as: Indu Nair V Full-Time research scholar , Deepa P Assistant Professor , Isolation Enhanced MIMO Antenna for Software Defined Networking (SDN) adapted Ultrawide Band (UBW) Radio Tech Applications, Microprocessors and Microsystems (2019), doi: https://doi.org/10.1016/j.micpro.2019.102965

This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Elsevier B.V. All rights reserved.

Isolation Enhanced MIMO Antenna for Software Defined Networking (SDN) adapted Ultrawide Band (UBW) Radio Tech Applications 1

Indu Nair V | DeepaP 1,2

2

ECE Department, Government College of Technology, Coimbatore, Tamilnadu-641013, India. Telephone No.: 0422-2432221, Fax: 0422- 2455230, 1 Full-Time research scholar,1e-mail: *[email protected], [email protected] 2 Assistant Professor, 2e-mail: [email protected]

Abstract In this paper four element, four-port “enhanced bandwidth reduced radius single stub annular ring slot” (EBRRSS-ARS) Multiple Input Multiple Output (MIMO) antenna with isolation enhancement structure is proposed. The prospective antenna with stub in annular slot reduces the mutual coupling has simple and compact structure. The EBRRSS-ARSA resonates at 4.4 GHz with a bandwidth of 0.9 GHz with minimum isolation of 10 dB between its elements.The parametric study for the proposed fabricated antenna agrees well with the measurements KEYWORDS

MIMO, 4-element, 4-port, effective reduction in mutual conductance, better isolation 1INTRODUCTION MIMO antenna provides answer to various modern day communication problems like poor spectral efficiency, fading due to multipath, less gain, channel capacity, data rate and quality of services in NonLine of sight (NLOS) communication channels compared with single input single output (SISO) antenna systems [1] MIMO improves the channel capacity to meet the demand in data communication and improve the communication quality [2]. Conductor coupling losses and proximity effects of radiating elements acutely affect MIMO antenna performance. MIMO antenna design faces a major challenge to obtain low correlation and high average efficiency for good multiplexing [3]. Coupling reduction depends on the type of radiating element, ground plane, feeding approach, and other times on different diversity techniques [4]. Etching of slots with different shapes on patch or ground plane leads to enhanced bandwidth, results in overall size reduction, significant reduction of coupling current to control the mutual coupling amongclosely placed radiating elements [5-6]. One of the low cost solutions to control the coupling effects is the use of slits [7].Several methods have been proposed to enhance the isolation in UWB-MIMO antenna. A parasitic element inserted between two monopoles [8], two

UWB-MIMO elements with different polarizations and patterns incorporated into a USB dongle [9],different polarizations applied to two metal strips [10], miniaturized double-layer Electro band gap (EBG) structures etched on the ground plane for broadband mutual coupling reduction [11], and wideband neutralization line in compact UWB-MIMO antenna [12] reduces the mutual coupling. Various techniques for the greater isolation between two antennas placed nearby [13-17] are studied. An additional coupling element between the two antenna elements [13] and a microstrip line that links the feeding or planar inverted-F antennas (PIFAs) with shorted strips [14-16] obtains good isolation between the two antennas. Mutual coupling among elements in a MIMO system distorts the antenna efficiency, radiation pattern as S12 increases, latest challenge lies in retaining the radiation pattern while reducing the mutual coupling. Techniques to this effect range from low correlation [3] and greater miniaturization [18-22]. Techniques such as simultaneous matching, etching slits in the middle of the ground plane and using EBG substrates takes upsubstantial space on the Printed circuit board (PCB). Further enhancement in isolation among elements is the recent challenge in research [23-26]. In this article, 4-element, four port planar MIMO antenna system is presented for UWB operation to radiate at 4.4 GHz band. The antenna is designed on a commercial FR4 substrate with an area of 60 × 60 mm2. The antenna makes use of microstrip annular slots as its radiating elements are easy to design, occupy less space, with a planar structure. With efficient placement of antenna elements and stub location, good isolation is achieved amidst the antenna elements placed nearby. This article is categorized as follows. In section 2, design of the MIMO antenna is presented. The simulation and measurement results of various antenna parameters and performance evaluation are given in section 3.Finally section 4 concludes the article.

2 ANTENNA DESIGN The basic configuration of an annular slot antenna is designed based on coaxial line (with one end open and the other terminated in 50Ω) mounted on an infinite ground plane. The size of the annular slot must not go beyond the first root of the following equation (1) [27]. Jo (Ka) No(KaR2) - Jo(KaR2) No(Ka)=0…….. (1) Where R2 is the radius of the slot defined as the ratio of outer radii (b) and inner radii (a) is given in equation (2) for the co-axial line, Jo is the Bessel co-efficient of zero order, K is the wave number R2=b/a ………. (2)

When the maximum width of the slot is λ/2, an approximate solution is attained, with λ being the resonant frequency of the slot. To obtain an omnidirectional radiation pattern, it mandates a constant electric field in the slot.Byutilizing a narrow slot width compared to free space wavelength (λo) the desired result is achieved. The radius of slot is calculated as follows. Radius of the slot is dependent on the field patterns and free space wave number, K0 , where K0 = 2π/λ0 .It is found that if the product of the radius, R2 and K0 is equal to 1 or 2, it results in omnidirectional pattern as given in equation (3)[28]. R(0) =(Ws2 K0 2/4) (E02R22/ϒ2 )[ J12(R2K0sin θ)]------(3) Where Ws-width of the slot,J1-Bessel-coeffiecientof first order, Eo-Maximum field strength. The annular slotis fed by amicrostriplineonthe bottomof the substrate. The feed line crosses the slot and terminates in an open-circuit. For proper matchingthe length oftheline beyond the slotis kept λs/4, where λs, is slotwavelength. The approximate value of λs, is obtained from equation (4) [29] 𝜆𝑠 = 𝜆𝑜 √𝜀𝑟 + 1

-------- (4)

Figure1 depicts the design of a single annular ring slot antenna (ARSA) comprised of square metal ground (Lg×Wg) with circular slot cut, fed by a microstrip line on backside and fabricated using FR4 substrate.The outer radius R1 is determined for the ARSA for the resonant frequency, fr using equation (5) 𝑓𝑟 =

𝑐 2𝜋𝑅1 √𝜀𝑒𝑓𝑓

------ (5)

where c is the speed of light and εeff is computed using equation 6 εeff=2(εr)/(1+ εr)

------(6)

In equation 6, εeff and εr are the effective dielectric constant and dielectric constant of the ring slot respectively, and is expressed in millimeters. R3 in Fig.1 is the slot radius computed by equation (7) R3 =WS/2 ------ (7)

Table 1 and 2 gives the parameters of single ARSA and EBRRSS-ARSA respectively.The proposed EBRRSS-ARS MIMO antenna is constructed on FR4 substrate with relative permittivity ɛ r =4.4, loss tangent tan δ = 0.02 and thickness of 1.6 mm. On the front sides of the substrate, annular slot antennas are etched and back side the feedlines are placed.The antenna elements for UWB-MIMO havethe same electrical characteristics and set within the dimensional requirements as given in Table 2. MIMO antenna system is implemented by placing four ARSA each of various patch angles as shown in Figure.2 as antenna 1(ANT1) and antenna 2(ANT 2) are transmitting antenna, and antenna 3 (ANT3) and antenna 4(ANT4) are receiving antennas. These types of antennas radiate best when the outer radius (R 1) of the annular slot equals the length of the feedline (Lf). The R1 is computed based on in equation (8) R1=Lf =λs/4 ------- (8)

R1 calculated using equation (8) gives a length slightly shorter than actual required value, further optimized for proper impedance matching. For the designed EBRRSS-ARS MIMO antenna, the resonant frequency varies with respect to the radius of the slot.

Table 3 shows the resonant frequency of EBRRSS-ARSA for various radiuses. From table 3 it is observed that if outer radius of annular slot is increased, the resonant frequency decreases and thus the radius has a direct bearing on the frequency of operation of EBRRSS-ARS MIMO antenna. Though the single element antenna (R1= 10mm, R2= 6mm, R3= 2mm, Lf = 10 mm, Wf = 0.7 mm) radiates well at the desired frequency, due to mutual coupling, the 4-element EBRRSS-ARSA feedline is increased to 12 mm for optimum performance. Design of 2 × 2 MIMO antenna system model, operates at 4.4 GHz uses four antenna elements sharing same substrate, causes the current of one element to be coupled to another through the substrate, which leads to mutual coupling and reduces the isolation between antenna elements. Each antenna is an annular slot and the stubs arranged in transmitting antenna are orthogonal to each other.

The overall size of the MIMO antenna is 60 × 60 × 1.6 mm3, and the size of each single stub annular slot element with R1=10 mm,R2 = 6 mm, R3 = 2 mm, Lf =12 mm, Wf= 0.7 mm. The proposed antenna fabricated on dielectric FR4 substrate of relative permittivity (εr) 4.4 and thickness, 1.6 mm. The antenna’s ground-plane size Lg × Wg is 60 × 60 mm2. The angle made by stub to the horizontal X-Y axis is θ1 for ANT1, θ2 for ANT 2, θ3 for ANT 3, θ4 for ANT4,with 45◦, -45◦, 135◦, and -135 respectively. Stubs placed in antenna elements, ANT 1 & ANT 2 shown in Fig.3 have stubs orthogonal to each other for better isolation which reduces the space-coupling between them. Simulation results indicate that the antenna meets performance requirements of the MIMO antenna systems.

Polarization matching on both sides of the RF link plays an important role with MIMO systems, for increasing diversity and improving transmission quality. Cross polarized isolation between each set of antenna has been introduced to configure opposite polarizations among multiple data streams.90 degree orthogonal polarization obtained between the two transmit antennas by setting two stubs at opposite 45 degree angles creates 30 dB of isolation from one antenna to another. On the receiver side, the stubs configured to match the same 45 degree polarization receives good quality signal.

3 PERFORMANCES OF EBRRSS-ARS MIMO ANTENNA The proposed EBRRSS-ARS MIMO antenna is simulated using Advanced Design System (ADS) ver.15 to resonate at 4.4 GHz. The simulated antenna performance considering -10dB bandwidth is given in table 4.

From table 4, it is inferred that, the single element antenna radiates at 5.3, 5.583, 5.354 and 5.531GHz, whereas 2-element antenna radiate at 5.6 and 5.38 GHz, the four-element MIMO radiates at 4.4GHz. As the number of elements increase to two, the gain, directivity and efficiency falls off, but the gain, directivity, efficiency and bandwidth increases when the elements of MIMO is increased to four, due to reduced mutual coupling between elements. Owing to the same type of radiating structure, the returnloss at different ports is equal hence loss at different ports are equal, i.e. S ii = Sjj = Skk =Sll. Where i=1,j=2,k=3,l=4.Isolation between adjacent ports Sij, Sji, Sil, Sli, Sjk, Skj, Skl, Slk are equal, and also at

diagonal ports S13, S31, S42, S24. To simplify the analysis, only S11, and S12 scattering parameters are considered throughout the paper. By placing one or two elements on the ground plane, the effectiveness of the proposed design has been studied. The MIMO antenna resonates at 4.4 GHz frequency, where the return loss is -17.02 db. Port isolations between the adjacent ports (S12 and S14) and diagonal ports (S13) are at value greater than -20 dB The MIMO antenna is fabricated in FR4 substrate, relative permittivity ɛr =4.4, loss tangent tan δ = 0.02 and thickness =1.6 mm. The prototype of EBRRSS-ARSA is shown in Fig.3.b uses four SMA connectors, when measurements are made in two terminals with other two terminals are terminated in 50 Ω.The antenna radiates at 4.4 GHz with ρe = 0.00322 and the mutual coupling = -20 dB, in the entire UWB from 3.1 to 11.00 GHz. Simulation and measurements are done in the desired band and analyzed for better performance. The parameters such as return loss, mutual coupling, radiation patter and gain were measured to evaluate the performance of EBRRSS-ARSA MIMO

3.1 RETURN LOSS AND ISOLATION

The MIMO antenna is characterized using E83628 network analyzer. Fig. 4 shows simulated and measured return loss S11 and isolation S12. From Fig. 4, it is observed that EBRRSS-ARS MIMO antenna achieves wider bandwidth. The measured S12 in Fig.4 performs satisfactorily below -20 dB and the designed antenna covers the UWB bandwidth and is measured using VNA. The fabricated S parameters, S11, S12 using VNA gives less than -10 dB and -20 dB in UWB bandwidth. The amount of coupling between the antennas in MIMO mainly depends on distance between the antennas. The measured results are similar to the simulations analysis with -7 dB deviation in resonant frequency due to fabrication tolerance. Though there is a deviation still the return loss is in acceptable range. The measured isolation is favorable and hence addition or removal of area is not required in PCB plane. The isolation was less than -20 dB at the resonant frequency in UWB band and hence the results are of practical utility.

3.2 RADIATIONPATTERN AND GAIN

The measured radiation patterns in E-plane (xz) and H-plane (xy) at the resonant frequency 4.4 GHz are shown in Fig. 5 and 6 respectively. Fig. 5 and 6 shows the measured radiation pattern in E-plane and Hplane for EBRRSS-ARS MIMO antenna. For pattern measurement, the proposed antenna is mounted on a turntable. The fabricated antenna

has been tested in

Anechoic Chamber to measure its radiation

properties. It has been observed that E-field had an almost omnidirectional pattern and H-field had taken the shape of eight. For the designed dimensions, the measured results indicate the radiation efficiency

nearly 87% in UWB range. The measured co-polarization ECO and cross polarization ECROSS shown in Fig.5 indicates a nearly Omni-directional and eight pattern respectively. Similarly for H-plane the copolarization and cross polarization shows eight patterns. The H-plane is very stable with changes in frequencies and is shown in Fig. 6. Fig.7 shows the simulated and measured gain of the EBRRSSARSA. The measured gain of the antenna is 4.16 dB at 4.

3.3 DIVERSITY ANALYSIS Another significant parameter of MIMO antenna is envelope correlation coefficients (ECC) and diversity gain (DG). The MIMO diversity has been evaluated using ECC. 𝐷𝐺 = 10√1 − ǀ𝜌𝑒 ǀ2 -------- (9)

And S11_New, calculated using equation (10) S11-new=10^ (dB/20) -------- (10) The ECC is calculated using the equation 11 [30].The value of ECC for various frequencies is given in table 5.For MIMO system ECC <0.5[31]. Computed ECC given in table 5 reveals that fabricated MIMO

antenna

satisfies

the

criteria.

It

is

observed

that

the

proposed

antenna

has

ECC<

0.04 for the entire UWB range. The DG computed using the equation (9) for various frequencies are given in table 5. The proposed EBRRSS-ARS MIMO antenna has DG > 9.5 dB for the entire UWB range is within an acceptable limit

3.4 PERFORMANCE COMPARISON

Performance of the proposed EBRRSSARSA and previous reported UWB-MIMO antenna are given in Table 6. It has been observed that EBRRSS-ARSA MIMO provides better results compared with the existing MIMO antennas. Compared to the existing MIMO antennas [4, 5, 20, 21, 22, and 23] the EBRRSS-ARS MIMO antenna has much better ECC, higher isolation in 3.1-5 GHz. The stubs placed orthogonally changes the current distribution between antenna elements and suppresses near-field and far-field coupling, resulting in higher isolation. The ECC gain of the antenna is 20 % is higher than the existing MIMO antenna except for [4]. In [4], the ECC is 90% more than EBRRSS-ARS MIMO antenna

4. CONCLUSION

This paper presents a single band EBRRSS-ARS MIMO antenna with reduced ECC for UWB application. The proposed EBRRSS-ARSA is a four element four port MIMO to cover UWB and resonates at 4.4 GHz. The designed EBRRSS-ARSA is fabricated and the parameters return loss, isolation, radiation pattern, gain are measured and compared with existing UWB. The return loss is less than 10 dB in entire range from 3.3 to 5.1 GHz. Isolation is satisfied and is ˃20 dB in the UWB operating frequency range. Additionally ECC (ρe) is calculated and is in the desired range 0.003˂ ρe ˂0.007 which is considered lower than 0.5 required for MIMO application. The measured radiation patterns are appropriate for UWB application and nearly Omni directional radiation pattern is obtained.

Conflict of Interest This paper has not communicated anywhere till this moment, now only it is communicated to your esteemed journal for the publication with the knowledge of all co-authors.

Ethical approval This article does not contain any studies with human participants or animals performed by any of the authors.

RE F E R E N CE S

[1] Alexiou A, Haardt M. Smart antenna technologies for future wireless systems: trends and challenges. “IEEE Communications Magazine.2004;42(9):90-97. [2] Sun D., & Wei C. Analysis and Design of 4× 4 MIMO-Antenna Systems in Mobile Phone. “Journal of Computer and Communications,2016; 4(02), 26 [3] Zhang S., zunov, A. A. G Z. Ying, He S. IEEE Transactions on Antennas and Propagation, 2013:61 [4] Rezaeieh S, Pouyanfar N. Double channel triple band MIMO antenna with high isolation performance and pattern diversity for wireless applications. Microw Opt Technol Lett. 2012; 54(12):2689-2691. [5] Khan M, Sharawi M. A dual-band microstrip annular slot-based mimo antenna system Microw Opt Technol Lett. 2014; 57(2):360-364. [6] Andújar A, Anguera J. MIMO multiband antenna system with nonresonant elements. Microw Opt Technol Lett. 2014; 57(1):183-190.. [7] Chiu C, Cheng C, Murch R, Rowell C. Reduction of Mutual Coupling Between Closely-Packed Antenna Elements. IEEE Trans Antennas Propag. 2007; 55(6):1732-1738. [8] Shuai Zhang, Zhinong Ying, Jiang Xiong, Sailing He. Ultrawideband MIMO/Diversity Antennas With a Tree-Like Structure to Enhance Wideband Isolation. IEEE Antennas WirelPropag Lett. 2009; 8:1279-1282. [9] Zhang S, Lau B, Sunesson A, He S. Closely-Packed UWB MIMO/Diversity Antenna With Different Patterns and Polarizations for USB Dongle Applications. IEEE Trans Antennas Propag. 2012; 60(9):4372-4380. [10]

Liu L, Cheung S, Yuk T. Compact MIMO Antenna for Portable Devices in UWB Applications. IEEE Trans

Antennas Propag. 2013;61(8):4257-4264. [11]

Li Q, Feresidis A, Mavridou M, Hall P. Miniaturized Double-Layer EBG Structures for Broadband Mutual Coupling

Reduction Between UWB Monopoles. IEEE Trans Antennas Propag. 2015;63(3):1168-1171. [12]

Zhang S, Pedersen G. “Mutual Coupling Reduction for UWB MIMO Antennas With a Wideband Neutralization

Line”. IEEE Antennas WirelPropag Lett. 2016;15:166-169. [13] Jui-Han Lu, Jia-Ling Guo. “Small-Size Octaband Monopole Antenna in an LTE/WWAN Mobile Phone”IEEE Antennas WirelPropag Lett. 2014;13:548-551. [14] Karimian R, Oraizi H, Fakhte S, Farahani M. Novel F-Shaped Quad-Band Printed Slot Antenna for WLAN and WiMAX MIMO Systems. IEEE Antennas and Wireless Propagation Letters. 2013;12:405-408. [15] Byeongkwan Kim, Yongsoo Park, Hyunho Wi et al. Isolation Enhancement of USB Dongle MIMO Antenna in LTE 700 Band Applications. IEEE Antennas WirelPropag Lett. 2012;11:961-964. [16] Kim S, Jin Z, Chae Y, Yun T. Small Internal Antenna Using Multiband, Wideband, and High-Isolation MIMO Techniques. ETRI Journal. 2013; 35(1):51-57. [17] Choukiker Y, Sharma S, Behera S. Hybrid Fractal Shape Planar Monopole Antenna Covering Multiband Wireless Communications With MIMO Implementation for Handheld Mobile Devices. IEEE Trans Antennas Propag. 2014; 62(3):1483-1488. [18] Lee J, Kim S, Jang J. Reduction of Mutual Coupling in Planar Multiple Antenna by Using 1-D EBG and SRR Structures. IEEE Trans Antennas Propag. 2015;63(9):4194-4198. [19] Ramachandran A, Valiyaveettil Pushpakaran S, Pezholil M, Kesavath V. A Four-Port MIMO Antenna Using Concentric Square-Ring Patches Loaded With CSRR for High Isolation. IEEE Antennas WirelPropag Lett. 2016;15:1196-1199.

[20] Ghosh S, Tran T, Le-Ngoc T. Miniaturized Four-Element Diversity PIFA. IEEE Antennas WirelPropag Lett. 2013; 12:396-400. [21] Jiang Xiong, Mingyu Zhao, Hui Li, Zhinong Ying, Bingzhong Wang. Collocated Electric and Magnetic Dipoles With Extremely Lowcorrelation as a Reference Antenna for Polarization Diversity MIMO Applications. IEEE Antennas WirelPropag Lett. 2012; 11:423-426. [22] Malviya L, Panigrahi R, Kartikeyan M. A low profile planar MIMO antenna with polarization diversity for LTE 1800/1900 applications. Microw Opt Technol Lett. 2017; 59(3):533-538. [23] Luo Y, Chu Q, Li J, Wu Y. A Planar H-Shaped Directive Antenna and its Application in Compact MIMO Antenna. IEEE Trans Antennas Propag. 2013;61(9):4810-4814. [24] Liu Y, Liu M, Xu F, Xu J, Huang X. A novel four-port high isolation MIMO antenna design for high-capacity wireless applications. Microw Opt Technol Lett. 2018;60(6):1476-1481. [25] D. Thiripurasundari, S. Sameer International Journal Of Advanced Research In Electronics And Communication Engineering (IJARECE) 5.; 2016. [26] Yu J, Liu X, Shi X, Wang Z. A COMPACT FOUR-ELEMENT UWB MIMO ANTENNA WITH QSCA IMPLEMENTATION. Progress In Electromagnetics Research Letters. 2014;50:103-109. [27] Levine H.& Papas C H. Theory of the circular diffraction antenna. Journal of applied physics, 1951; 22(1): 29-43 [28] Bahl, I. J., &Bhartia, P. Microstrip antennas. Artech house. 1980. [29]Gupta, K. C., Garg, R., & Bahl, I. J. Microstrip Lines and Slotlines (Artech House, Dedham, MA, 1979. 263-265 [30]Blanch S., Romeu J., &CorbellaI.Exact representation of antenna system diversity performancefrom input parameter description. Electronics letters, 2003; 39(9): 705-707 [31]Kulkarni A N.,& Sharma S K A multiband antenna with MIMO implementation for USB dongle size wireless

Indu Nair V received the Bachelor Degree in Electronics and Communication Engineering in 1992 from Bharathiar University, Coimbatore, Tamil Nadu, India. She received M.E. degree in Communication System in the year 2004 and has 12 years of teaching experience. Currently she is pursuing Ph.D. degree in Information and Communication Engineering from Anna University, Chennai, Tamil Nadu, India. Her research area includes Antenna design, communication, etc. Her research papers published in various journals and she presented papers in national and international conferences P. Deepa received the Bachelor Degree in Electronics and Communication Engineering in 2002 from Bharathiar University, Coimbatore, Tamil Nadu, India. She received M.E. degree in VLSI Design in the year 2007 and Ph.D. degree in Information and Communication Engineering in 2013 from Anna University, Chennai, Tamil Nadu, and India. She is working as an Assistant Professor, Department of Electronics and Communication Engineering, Government College of Technology, Coimbatore, Tamil Nadu, India. Her research area includes Low Power VLSI Design and Image Processing. Her research papers published in various journals and she presented papers in national and international conference.

FIGURE 1. Dimension of single stub annular slot

FIGURE 2. Geometry of a 2 × 2 MIMO antenna a) Front view b) rear view

FIGURE 3.EBRRSS-ARS MIMO antenna a) ADS Layout b) front view of fabricated antenna c) rear view of fabricated antenna.

(a)

(b)

(c)

FIGURE.4.EBRRSSARS MIMO antenna, Simulated and Measured S11 and S12

Figure 5.Measured normalized ECO and ECROSS at 4.4 GHz for EBRRSS-ARS MIMO antenna

Figure 6.Measured normalized HCO and HCROSS at 4.4 GHz for EBRRSS-ARS MIMO antenna

FIGURE 7.Measured and simulated gain of EBRRSS-ARS MIMO antenna

Table 1. Parameters of single ARSA Parameter

value

Inner radius of annular ring(R1,mm)

10

Outer radius of annular ring(R2,mm)

6

Width of the slot(WS,mm)

4

Substrate material used

FR4

Relative permittivity of the substrate

4.4

Length of ground plane(Lg, mm)

60

Width of the ground plane(Wg, mm)

60

Width of the feedline(Wf, mm)

0.7

Length of the feedline(Lf,mm)

12

Table 2. EBRRSS-ARSA MIMO specification

Characteristic Frequency range(GHz)

3.1-11.00

Return loss across band (dB)

-10

Required peak gain (dBi)

˃4

Efficiency

˃75%

number of antenna elements

4

Isolation

˃30 dB

ECC

0.005˂ρ ˂ 0.025

Table 3 Resonant frequency for various radius of the slot

S.

R1

Lf

ARSA

(mm)

(mm)

(Fr,

No

MIMO S11 (dB)

GHz)

(Fr,

S11 (dB)

GHz)

1

14

14

4.395

-21.535

3.5

-14

2

13

13

4.419

-38.311

4.475

-32.224

3

12

12

4.981

-22

4.4

-6.917

4

10

10

4.46

-46.99

4.4

-51.55

No of elements

Table 4. Antenna performance considering -10dB bandwidth Resonant S11 Impedance Peak Directivity

Antenna efficiency

Frequency

(dB)

(%)

(dB)

(GHz)

Bandwidth

Antenna Gain

(GHz)

(dB)

ANT 1

5.641

-8.926

0.5

3.047

5.234

60.4

Single

ANT 2

5.583

-20.95

0.7

3.772

5.289

70.6

element

ANT 3

5.38

-10.94

0.2

2.630

4.935

58.8

ANT 4

5.531

-46.99

0.9

4.017

5.297

74.5

2-Element MIMO

5.641

-18.94

0.6

4.319

5.787

71.3

5.354

-51.55

0.7

3.079

4.893

60.4

4.4

-17.02

1.00

5.768

5.164

87

(ANT 2 & 4) 2-Element MIMO (ANT 1 & 3) EBRRSS-ARSA MIMO

Table 5. ECC and DG for various frequencies S_New

S

ECC

DG

0.5623

0.03071

9.995284098

0.1778

0.4732

0.07917

9.96861019

0.1413

0.1778

0.4898

0.04529

9.989736568

0.3981

0.1413

0.1679

0.3981

0.02267

9.997430746

-12

0.2512

0.1778

0.1995

0.2512

0.01106

9.99938802

-13

-19

0.1409

0.1995

0.2239

0.1122

0.00322

9.999948285

-14

-13

-17

0.1549

0.1995

0.2239

0.1413

0.00449

9.999899165

-13.5

-15

-14

-16.5

0.2113

0.1778

0.1995

0.1496

0.00525

9.99986213

-13

-15

-14

-16

0.2239

0.1778

0.1995

0.1585

0.00594

9.999823327

s11

s12

s21

s22

s11

s12

s21

s22

3.4

-4

-24

-18

-5

0.631

0.0631

0.1259

3.6

-6

-15

-6.5

0.631

0.1585

3.8

-6.2

-17

-15

-6.2

0.4898

4

-8

-17

-15.5

-8

4.2

-12

-15

-14

4.4

-17.02

-14

4.6

-16.2

4.8 5

-1 6

TABLE 6. Comparison of Proposed Work with Considered Reference

Ref. No

Frequency\Bands

No.

of

Size (mm2)

Elements

Isolation

ECC

ECC Gain

(dB)

[4]

1.8/1.9/3.5

2

50×50

>24

<1023

5.3 (peak)

[5]

2.45/5.2

4

60×60

>18

<1022

3.46 (peak)

[20]

5.5 GHz

4

–

>10 dB

–

–

[21]

3.5/5.7/6.8 GHz

4

–

>15 dB

–

–

[22]

3.1 - 10.6 GHz

2

-

≤ -15 dB

<0.3

4(avg)

[23]

3.5/5.5/8.5 GHz

4

-

≤ -15 dB

0.004/0.02

-

3/0.012 EBRRSSARSA MIMO

4.4

4

60×60

>30 dB

<0.00322

4.16