Reduction of Mutual Coupling for UWB MIMO Antenna with a

Broadband Balance T-Line

Imtiaz Alam, Luqman Ali and Syed Asim Ali Shah

Department of Electrical Engineering, Bahria University, Shangrilla road, Sector E-8, Islamabad, Pakistan

Keywords: Mutual Coupling, Ultra-wide Band, Multiple-Input-Multiple-Output.

Abstract: A broadband balance T- type line is proposed to decrease the Mutual coupling of a smaller ultra-wide band

(UWB) multiple-performance Multiple-Input-Multiple-Output receiving antenna. With the decoupling

technique presented in this research, the UWB MIMO receiving antenna described covers the 3.1 – 9.4 GHz

band with a decoupling of more than 17 dBs. The proposed broadband balance T-line is actually set in the

margin area between two MIMO components and can be placed on the copper ground. A margin (radio

antenna range) of 20*10 mm2 is achieved. The UWB MIMO receiving antenna is simulated and S-

Parameters, radiation patterns are found to add productivity.

1 INTRODUCTION

MIMO (Multiple Input Multiple Output) antenna

arrays innovation has always been of interest for

researchers, due to its huge focal points of multitrack

decline and expansion of the channel capacity.

Almost all everyday gadgets, like PC, printers, and

cameras all include ultra-wide band MIMO radio

antennas which are connected to offer a high rate of

information within a short range.

The execution of radio antenna structure in a

compact device is influenced by the mutual

broadband coupling between the ultra-wide band

MIMO components. In addition, the improvement of

wideband segregation is an exceptional test problem,

particularly in the lower UWB band.

To date, several techniques have been introduced

for reducing mutual coupling of UWB MIMO

antenna. A parasitic element was placed between the

monopole elements (Zhang, et al., 2009). A capable

technique for mitigation of coupling effect was first

proposed by (Diallo, et al., 2006), while (Liu, et al.,

2013) applied different polarization with a metal

strip. The reduction of broadband mutual coupling

(Li, et al., 2015) Electro-Band Gap (EBG) were

etched on the ground plane, by using a metal stripped

with a circular disc inserted between UWB MIMO

antenna elements (Zhang & Pedersen, 2016).

However, the challenge to mitigate mutual coupling

effect with a predictable broadband line still exists.

In this research, a T-type broadband line is used

between the two antenna elements for reduction of

coupling effects as shown in Figure 1a and Figure 1b.

The planned ultra-wide band antenna can cover the

frequency band 3.1 – 9.4 GHz with decoupling effect

of more than 17 dBs. The suggested T-type

neutralization line employed above the ground plane,

an antenna area of 20*10 mm2 acting as a small

clearance is achieved in the considered antenna.

Figure 1a: Geometrics of the Antenna.

Figure 1b: Geometrics of the Antenna.

Alam, I., Ali, L. and Shah, S.

Reduction of Mutual Coupling for UWB MIMO Antenna with a Broadband Balance T-Line.

DOI: 10.5220/0006483100930096

In Proceedings of the 14th International Joint Conference on e-Business and Telecommunications (ICETE 2017) - Volume 1: DCNET, pages 93-96

ISBN: 978-989-758-256-1

This technique helped the overall reduction in

mutual coupling and size of the antenna which can

improve the its performance, especially in the lower

band. This research focuses on designing an antenna

using Computer Simulation Technology (CST) and

comparing S-parameters with and without T-type

broadband line with the existing antennas as shown in

Figure 2.

Figure 2: Simulated S-Parameters of ultra-wide band

MIMO antenna comparing without T-type broadband line

to with T-type broadband line.

S-parameters, far-field effect and size is compared with

existing UWB antenna with the recently designed antennas.

In this research, all numerical calculations are carried out

using CST (Studio, 2014). Table 1 shows different

parameters like width, length, radius and thickness of the

substrate feed line T-type broadband line.

Table 1: Different parameters of the substrate feed line T-

type broadband line.

Item Length Width Thickness Radius

Substrate 18mm 20mm 0.9mm -

Ground 10mm 20mm 0.028mm -

Feed Line 7mm 1.5mm 0.028mm -

Triangle 8.5mm - 0.028mm -

T-Line 3.5mm 1mm 0.028mm -

Circle - - 0.028mm 0.5mm

U-shaped 4.1&4mm 1mm 0.028mm -

The broadband line is composed of two metal strips that

are connected to T-type metal strips as shown in Figure 1,

which helped in the reduction of mutual coupling between

the antenna elements. The ground plane of the antenna with

no slot is composed of copper annealed (lossy metal). The

ground plane without any slot are composed of copper

annealed (lossy metal).

The S-parameters simulated in this work for the

proposed ultra-wide band MIMO radio antennas are given

in Figure 2. The intended MIMO receiving apparatus

covers the 3.1 – 9.4 GHz band with a shared coupling of

significantly less than 17 dBs. As a correlation, the

parameters without the broadband balance, the line is also

given, and with the planned decoupling system, the

segregation between two MIMO components of UWB can

be productively improved by 12 – 22 dBs. In addition, the

capacitance between the equilibrium line and the ground

will grow which is due to a substantial part of the

equilibrium line being above the ground plane.

Since the broadband balance line is associated with two

MIMO components, it will eventually marginally increase

the Q-element of the MIMO radio antenna components and

will somewhat decrease the data transfer capability.

(Zhang, et al., 2013). In any case, the transfer speed of the

proposed UWB MIMO cable can in any case effectively

cover the lower ultra-wide band of 3.1 – 9.4 GHz.

In general, due to high radiation capacity, the

connection between components of MIMO antennas are

low mostly when the antenna that receives MIMO operate

in a high, e.g. greater than 1.7 GHz, recurrence band.

(Vaughan & Andersen, 1987). While varying qualities in

the upper band, the aggregate efficiencies of the

components of the MIMO receiving apparatus are shown in

Figure 3 with the limits of execution of MIMO. The

proposed broadband balance line can effectively upgrade

disconnections between MIMO components so that the

aggregate productivity of the receiving ultra-wide band

MIMO antenna receives the possibility of advancement.

The addition reproduced to the efficiencies of the proposed

MIMO ultra-wide band receiving apparatus with a

broadband as well as without a broadband (NL) balance line

are shown in Figure 4.

The aggregate change of competition with the

broadband T-type line is clearly seen. It shows that even in

the large space between elements, the proposed dissociation

strategy can work productively.

To demonstrate the viability of decoupling, the current

allocations of the present MIMO ultra-wide band radio

antenna proposed with broadband balance line and without

a broadband balance line are shown in Figure 5. The current

allocations are gained when Port 1 (the MIMO component

on the left side as shown in Figure 3) is energized at 3.3, 4

and 4.7 GHz. The coupling current from port 1 when flows

towards port 2 in case of with broadband balance line can

suffocate significantly, which causes the lower common

couplings.

The current allocations at the rear of the proposed

MIMO UWB receiving apparatus at a frequency of 4 GHz

are given in Figure 3. Within the ground plane, the current

is extremely important. For different frequencies in the

range of 3.1 – 9.4 GHz, the currents are also important. In

fact, this region is used for radio frequency circuits, where

circuits affect the non-side in the execution of the receiving

cable. In this research, we have used it to establish the

encouraging link to diminish the impacts of the link in the

MIMO proposal that receives the execution of the cable.

DCNET 2017 - 8th International Conference on Data Communication Networking

Figure 3: Proposed ultra-wide band MIMO Antenna current distributor with and without T-type broadband line.

Figure 4: Simulated total efficiency of proposed ultra-wide

band MIMO with and without T-type broadband Line.

Figure 5: Current distribution on Ground for proposed ultra-

wide band MIMO Antenna (colour slab is same as shown

in Figure 3).

Reduction of Mutual Coupling for UWB MIMO Antenna with a Broadband Balance T-Line

2 RESULTS

When comparing antenna’s area clearance, isolation in dB

and bandwidth in GHz for our introduced antenna versus

the existing antenna as shown in Table 2 below. It can be

observed that the antenna’s area clearance is the least,

isolation is average which is very good and the bandwidth

coverage is also from 3.1 – 9.4 GHz.

Table 2: Comparing antenna clearance, isolation and

bandwidth of proposed antenna with existing antennas.

Reference

Antenna Area

Clearance Size

mm2

Isolation

(dBs)

Bandwidth

(GHz)

(Zhang, et al.,

2009)

35*27.25 16 3.1-10.6

(Liu, et al.,

2013)

32*26 15 3.1-10.6

(Li, et al., 2015) 60*40 20 3-6

(Zhang &

Pedersen, 2016)

35*16 22 3.1-5

This work 20*10 17 3.1-9.4

3 CONCLUSIONS

In this research, an ultra-wide band Multiple Input Multiple

Output antenna has been designed which is smaller than

another previous antenna. It mitigates the coupling effect

more efficiently and covers a range of frequencies from 3.1

GHz to 9.4 GHz with the isolation of 17 dBs. The clearance

size area of proposed antenna is 20*10 mm2, this clearance

area is by far the least according to the current antennas

commercially available, which can be used in situations

where a small antenna is required. The current circulation

and parametric revision was explored and the decoupling

effect was removed from the new proposed T-Type as

compared to other previous design antenna in which the

broadband line exists.

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