# Optimization of a T-Shaped MIMO Antenna for Reduction of EMI

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## Abstract

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## Featured Application

**A four-element wideband multiple-input multiple-output (MIMO) antenna is optimized using a genetic algorithm (GA). The antenna consists of a stub, four reduced ground planes, and four T-shaped radiating elements. The behavior of the antenna is analyzed with the following parameters: return loss, electromagnetic interference (EMI), and operating frequency. The antenna design is applicable to different applications. A 2**.

^{K}factorial design is used to identify the key design parameters responsible for affecting the above-mentioned performance indexes of the antenna. A GA optimization technique is utilized to increase the frequency range, where the return loss is less than −10 dB, while its EMI is reduced to within a 1 m sphere of radiation, so as to reduce the threat of the antenna to nearby devices. The increased frequency range also makes it suitable for various applications such as satellite communication, imaging, and radar communication## Abstract

^{K}factorial design combined with a genetic algorithm (GA) optimization technique were used to identify the key design parameters responsible for affecting the performance quality of the antenna. Optimization of the antenna design for EMI reduction was utilized, and the optimal design showed enhanced bandwidth of the antenna and reduced power consumption.

## 1. Introduction

^{K}factorial design methodology was applied in this work. This methodology is commonly employed for many experimental designs and has been shown to be the most effective experimental design methodology [24]. The 2

^{K}refers to designs with K factors where each factor has just two levels. Through this methodology, we can screen a large number of factors and identify only those parameters that are important so that the scale of optimization can be reduced.

^{K}factorial and GA optimization algorithms, with Minitab and ANSYS High Frequency Structure Simulator (HFSS) software, respectively. EMI was considered the parameter to be optimized, and this optimization also improved the return loss and bandwidth, as will be shown in this work. Optimization helps in reducing the interference and enhancing the operating frequency and bandwidth of the antenna [25], which makes the proposed antenna suitable for various applications such as radar communication, imaging, and satellite communication.

## 2. Antenna Design and Fabrication

_{r}) and loss tangent (tanδ) of the RT/Duroid substrate with frequency and relative humidity [27,28,29].

## 3. 2^{K} Factorial

^{10}experiments, which is too excessive, fractional 2

^{K}factorial was employed [31] with a $\frac{1}{64}$ fraction, which means we can identify the important structural parameters from 32 simulation runs. The maximum and minimum values taken for each parameter are 50% and 150% of their nominal value (shown in Figure 1b). Table 2 provides respective P values for three different responses for which fractional 2

^{K}factorials were performed. The P value helps in identifying the importance of the parameters [32].

## 4. Optimization Results and Discussion

## 5. Conclusions

^{K}factorial and genetic algorithm optimization techniques were used for the optimization of the antenna. It was found that gb, ga, tl, and tw, as defined in Figure 1, were the major dimensional parameters affecting the return loss, peak gain, bandwidth, radiation pattern, surface current distribution, and EMI of the antenna. The optimized antenna had a wider frequency band that ranged from 7.72 to 17.25 GHz. This corresponded to a 1 GHz improvement in the bandwidth due to the improved return loss that provides new opportunities for the antenna’s utilization in different applications. The optimized antenna had lower current distribution that gives lower power dissipation and its 1 m sphere EMI was also reduced.

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Multiple-input multiple-output MIMO antenna with substrate, (

**b**) dimensional geometry of one element in the four-element MIMO antenna, (

**c**) top view of the fabricated antenna, and (

**d**) back view of the ground plane. Substrate is absent in (

**b**) to highlight the ground plane.

**Figure 3.**Antenna design for (

**a**) modified and (

**b**) initial antenna to match the measurement results. Area under the black eclipse represents an area of change, while the red box represents the zoomed-in area.

**Figure 4.**Results for modified antenna (

**a**) return loss, (

**b**) electromagnetic interference (EMI), (

**c**) radiation pattern, (

**d**) peak gain, (

**e**) surface current distribution, and (

**f**) mutual coupling.

**Figure 9.**Radiation patterns for the initial and optimized antennas: (

**a**,

**b**) show 2-D radiation patterns and (

**c**,

**d**) show 3-D radiation patterns.

**Figure 11.**S-parameters of the MIMO antenna for mutual coupling between ports for (

**a**) the initial antenna and (

**b**) the optimized antenna.

The Unit for the Parameters Is mm | Return Loss (dB) | Bandwidth (GHz) | Maximum EMI (V/m) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

A | b | c | d | tl | tw | ga | gb | gc | gd | |||

0.5 | 1 | 0.75 | 0.75 | 12.75 | 4.5 | 16.5 | 1.5 | 12.5 | 0.45 | −41.7 | 8.47 | 15.54 |

1.5 | 1 | 0.25 | 2.25 | 12.75 | 4.5 | 5.5 | 1.5 | 37.5 | 0.15 | −34.2 | 8.51 | 15.78 |

0.5 | 1 | 0.25 | 0.75 | 4.25 | 1.5 | 5.5 | 1.5 | 37.5 | 0.45 | −12.5 | 5.4 | 16.54 |

**Table 2.**List of significant parameters for optimization. None of the interaction terms other than these parameters were found to have P value less than 0.05, hence they are not statistically significant and are not shown here.

Parameter (mm) | P Value (Return Loss (dB)) | P Value (Bandwidth (GHz)) | P Value (EMI (V/m)) |
---|---|---|---|

tl | 0.009 | 0.027 | 0.054 |

tw | 0.012 | 0.048 | 0.089 |

ga | 0.043 | 0.079 | 0.081 |

gb | 0.014 | 0.010 | 0.142 |

**Table 3.**Initial and optimized values of tl, tw, ga, and gb obtained from the genetic algorithm (GA).

Parameter | Nominal Value as Initial Design (mm) | Optimized Value (mm) |
---|---|---|

tw | 3.0 | 2.55 |

tl | 8.5 | 8.62 |

ga | 11.0 | 7.62 |

gb | 3.0 | 3.46 |

Parameter | Initial Antenna Design | Optimized Antenna Design |
---|---|---|

Bandwidth (GHz) | 7.84–16.44 GHz | 7.72–17.25 GHz |

Minimum return loss (dB) | −32 | −37 |

Maximum peak gain (dB) | 5.55 | 5.99 |

Maximum surface current density (A/m) | 125.19 | 82.083 |

Maximum EMI (V/m) | 14.60 | 13.25 |

Radiation intensity (dB) | 15.42 | 15.42 |

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**MDPI and ACS Style**

Kapoor, D.; Sangwan, V.; Tan, C.M.; Paliwal, V.; Tanwar, N.
Optimization of a T-Shaped MIMO Antenna for Reduction of EMI. *Appl. Sci.* **2020**, *10*, 3117.
https://doi.org/10.3390/app10093117

**AMA Style**

Kapoor D, Sangwan V, Tan CM, Paliwal V, Tanwar N.
Optimization of a T-Shaped MIMO Antenna for Reduction of EMI. *Applied Sciences*. 2020; 10(9):3117.
https://doi.org/10.3390/app10093117

**Chicago/Turabian Style**

Kapoor, Dipesh, Vivek Sangwan, Cher Ming Tan, Vani Paliwal, and Nirdosh Tanwar.
2020. "Optimization of a T-Shaped MIMO Antenna for Reduction of EMI" *Applied Sciences* 10, no. 9: 3117.
https://doi.org/10.3390/app10093117