# Modified U-Shaped Resonator as Decoupling Structure in MIMO Antenna

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## Abstract

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## 1. Introduction

## 2. Design Methodology

#### 2.1. Unit Antenna

#### 2.2. MIMO Antenna without Decoupling Structure

#### 2.3. MIMO Antenna with Decoupling Structure

## 3. MIMO Parameters

#### 3.1. Envelop Correlation Coefficient (ECC) and Diversity Gain (DG)

#### 3.2. Channel Capacity Loss (CCL)

## 4. Results and Discussions

## 5. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**Geometry of the initially designed MIMO antenna (${a}_{p}$ = 16.8, ${b}_{p}$ = 12.91, $gap$ = 5.82, ${W}_{s}$ = 3.1, g = 0.7, and $lg$ = 4.5 [unit = mm]).

**Figure 2.**Radiation resistance of the antenna with varying g (when lg = 4.5 mm) and lg (when g = 0.7 mm).

**Figure 3.**(

**a**) Equivalent circuit model of the single-unit antenna, and (

**b**) input impedance (resistance and reactance) comparison of the EM model (solid lines) and circuit model (dashed lines).

**Figure 4.**(

**a**) Equivalent circuit model of the two-element MIMO antenna without decoupling structure, and (

**b**) S-parameters comparison of the EM model (solid lines) and circuit model (dashed lines).

**Figure 5.**Geometry of the proposed MIMO antenna with decoupling structure (${a}_{p}$ = 16.8, ${b}_{p}$ = 12.91, ${W}_{s}$ = 3.1, g = 0.7, and $lg$ = 7, a = 44, b = 37, c = 5, d = 22, e = 20, f = 2 [unit = mm]) and fabricated prototype.

**Figure 6.**(

**a**) Equivalent circuit model of the two-element MIMO antenna with decoupling structure, and (

**b**) S-parameters comparison of the EM model (solid lines) and circuit model (dashed lines).

**Figure 10.**Surface current distribution of the antenna at 5.4 GHz in the presence and absence of decoupling structure.

**Figure 11.**Simulated (with and without decoupling structure) and measured (with decoupling structure) S-parameters of the antenna.

**Figure 12.**Simulated (with and without decoupling structure) and measured (with decoupling structure) gain and efficiency of the antenna.

**Figure 13.**Simulated (with and without decoupling structure) and measured (with decoupling structure) radiation pattern (E- and H-plane) of the antenna at 5.4 GHz.

Ref. | Technique | Centre Frequency (GHz) | Edge to Edge Distance | Isolation Improvement | FTBR (dB) | ECC | CCL (bps/Hz) |
---|---|---|---|---|---|---|---|

[7] | Slotted ground | 5.8 | 0.33${\lambda}_{\circ}$ | 40 | NA | NA | NA |

[9] | EBG | 7.5 | NA | 4 | NA | NA | NA |

[10] | UC-EBG | 5.56 | 0.5${\lambda}_{\circ}$ | 10 | NA | NA | NA |

[11] | Metamaterial | 5.8 | 0.135${\lambda}_{\circ}$ | 9 | NA | <0.1 | <0.05 |

[17] | I-shaped resonator | 2.8 | 0.056${\lambda}_{\circ}$ | 8–10 | NA | NA | NA |

[26] | EBG | 6 | 0.5${\lambda}_{\circ}$ | 8 | NA | <0.01 | NA |

[30] | Serpentine structure | 2.45 | 0.05${\lambda}_{\circ}$ | 10–34 | NA | <0.007 | NA |

[34] | metamaterial polarization-rotator | 60 | NA | 16 | NA | <0.1 × 10${}^{-6}$ | NA |

ThisWork | U-Shapedresonator | 5.4 | 0.1${\lambda}_{\circ}$ | 14 | 22.1 | <0.1 | 0.07 |

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**MDPI and ACS Style**

Iqbal, A.; Altaf, A.; Abdullah, M.; Alibakhshikenari, M.; Limiti, E.; Kim, S. Modified U-Shaped Resonator as Decoupling Structure in MIMO Antenna. *Electronics* **2020**, *9*, 1321.
https://doi.org/10.3390/electronics9081321

**AMA Style**

Iqbal A, Altaf A, Abdullah M, Alibakhshikenari M, Limiti E, Kim S. Modified U-Shaped Resonator as Decoupling Structure in MIMO Antenna. *Electronics*. 2020; 9(8):1321.
https://doi.org/10.3390/electronics9081321

**Chicago/Turabian Style**

Iqbal, Amjad, Ahsan Altaf, Mujeeb Abdullah, Mohammad Alibakhshikenari, Ernesto Limiti, and Sunghwan Kim. 2020. "Modified U-Shaped Resonator as Decoupling Structure in MIMO Antenna" *Electronics* 9, no. 8: 1321.
https://doi.org/10.3390/electronics9081321