# Broadband Microstrip Antenna for 5G Wireless Systems Operating at 28 GHz

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Characteristics of the 5G System

- From 694 to 790 MHz (700 MHz band);
- From 3400 to 3800 MHz (3.6 GHz band);
- From 27.50 to 28.35 GHz (28 GHz band).

## 3. Frequency Range for Local Multipoint Distribution Service

## 4. Analysis of Current Antenna Solutions Operating in 5G Systems at a 28 GHz Frequency

## 5. Broadband Microstrip Antenna Designed for Use in 5G Systems

- Determine operational frequency;
- Determine operational bandwidth;
- Choose a substrate;
- Choose substrate height;
- Determine the dimensions of the patch;
- Determine the power supply;
- Determine the electrical parameters and characteristics of the antenna;
- Optimize the antenna to obtain the best possible parameters in the given frequency range.

_{r}, and the relative permittivity, ε

_{r}, of the dielectric layer of the copper laminate, which are the foundation of the new antenna [24].

_{r}= 28.00 GHz. Choosing the thickness of the substrate is one of the most important stages in the antenna design process, as the thickness of the substrate directly affects the efficiency and bandwidth of the microstrip antenna. One of the assumptions for this antenna is to obtain the widest bandwidth possible. As the thickness of the substrate increases, the antenna’s bandwidth increases, while its efficiency decreases. The upper value of the substrate thickness was determined from the following relationship [14,15]:

_{r}= 2.2, and tanδ = 9.0 × 10

^{−4}. In the next calculation step, the width of the radiating element should be determined from the following relationship [16,17]:

_{reff}, of the substrate must first be calculated. It is defined by the following relationship [18,19]:

_{reff}, the effective length of the patch Le should be determined from the following relationship [20,21]:

_{C}= 50 Ω, we start the determination of auxiliary variables a and b as:

## 6. Optimization Process and Discussion of Simulation Results

Specify maximum number of runs by the solver:The optimization process ends when the FEKO solver has been run a certain number of times during the optimization process. In the case of PSO and GA methods, if a full swarm or generation is not generated within the allowed number of assigned runs, optimization may be completed before the indicated number of runs by the solver. If the optimization process is terminated prematurely, due to a reduction in the number of runs by the solver, the software will provide the optimal solutions found up to that point, as well as information about the optimization process.

Optimization convergence accuracy (standard deviation):This option allows adjustment of accuracy levels required for the optimization process. Three options for selecting the accuracy level are available, i.e., high, normal, and low. The selected accuracy level of the optimization process modifies the conditions in which the search algorithm will converge, and the effect depends on the selected method.

_{s}, W

_{e}, L

_{s}, and L

_{e}), the length and width of the radiator (L

_{p}and W

_{p}), the length and width of the power line (L

_{f}and W

_{f}) and the length and width of the patch inset (Y

_{0}and X

_{0}) were changed. Other structural elements, such as thickness and permittivity of the substrate, were not changed [28,29,30,31].

- Impedance goal (input impedance, input admittance, reflection coefficient (S
_{11}), transmission coefficient, VSWR, return losses, current); - Near-field goal (E field – electric field, H field – magnetic field, directional component, coordinate system);
- Far-field goal (E field, antenna gain, directivity, RCS – Radar Cross Section);
- S-parameter goal (coupling coefficient, reflection coefficient, transmission coefficient, VSWR, return losses);
- SAR (Specific Absorption Rate) goal;
- Power goal (efficiency, active power, power loss);
- Transmission/reflection coefficients goal (reflection, transmission, co-polarization, and cross-polarization);
- Receiving antenna power goal (efficiency, active power, and power loss).

_{11}, which was calculated during the calculation of the S parameter in the multiport model. The voltage standing waveform factor for the observed input impedance is considered in relation to the indicated reference impedance.

#### 6.1. Q Factor

#### 6.2. Reflection Coefficient

_{11}parameter was obtained by powering the antenna using the edge port. The antenna has an operating bandwidth of 5.57 GHz, which gives a relative operating bandwidth of 19.89%. The bandwidth determined from the results of computer simulations is slightly smaller than the theoretical bandwidth determined on the basis of Relation (13), due to the inset feed used as a power supply. Nevertheless, this method of supplying power to a microstrip antenna provides us with better impedance matching (lower reflection factor value) for a resonance frequency.

#### 6.3. Voltage Standing Wave Ratio

#### 6.4. Input Impedance

#### 6.5. Antenna Gain

#### 6.6. Current Distribution in the Antenna

#### 6.7. Radiation Characteristics

## 7. Comparison of the Proposed Antenna with Other Antennas

_{11}parameter of the proposed antenna may not be the lowest as compared with the S

_{11}values obtained for the antennas presented in [18,20,32], but it is relatively low.

_{11}≤ −10 dB (VSWR ≤ 2) 5.57 GHz, and is centered exactly at 28 GHz, while in [20] the operating band is 2. 63 GHz and is also centered exactly at 28 GHz, in [18] the operating band is 2.85 GHz and is also centered at about 28.1 GHz (shift of about 100 MHz), and in [32] the operating band is 1.07 GHz and is also centered exactly at 28 GHz.

## 8. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

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**Figure 5.**The reflection coefficient as a function of frequency for the proposed antenna working in the fifth generation (5G) system.

**Figure 6.**The chart of the voltage standing wave ratio as a function of frequency for the proposed antenna working in the 5G system.

**Figure 7.**The chart of the complex input impedance as a function of frequency for the proposed antenna working in the 5G system (real part, blue line and imaginary part, green line).

**Figure 8.**The chart of antenna gain as a function of frequency for the proposed antenna working in the 5G system.

**Figure 9.**Surface current distribution for the proposed 5G antenna at different frequencies. (

**a**) 27.51 GHz; (

**b**) 28.0 GHz; (

**c**) 28.35 GHz.

**Figure 10.**The three-dimensional (3D) view of radiation pattern for the proposed 5G antenna model at different frequencies. (

**a**) 27.51 GHz; (

**b**) 28.0 GHz; (

**c**) 28.35 GHz.

**Figure 11.**The normalized radiation patterns for the proposed antenna model operating in the 5G system for 27.51 GHz (blue line), 28.0 GHz (green line), and 28.35 GHz (red line) in polar coordinates for vertical polarization.

**Figure 12.**The normalized radiation patterns for the proposed antenna model operating in the 5G system for 27.51 GHz (blue line), 28.0 GHz (green line), and 28.35 GHz (red line) in polar coordinates for horizontal polarization.

**Figure 13.**The reflection coefficient as a function of frequency for the proposed antenna and antennas from other works.

**Figure 14.**The voltage standing wave ratio (VSWR) as a function of frequency for the proposed antenna, and antennas from other works.

Antenna Component | Symbol | Dimensions (mm) |
---|---|---|

Ground plane width | Ws = We | 13.59 |

Ground plane length | Ls = Le | 12.00 |

Patch width | Wp | 4.17 |

Patch length | Lp | 2.58 |

Copper thickness | Cu | 0.05 |

Substrate thickness | h | 1.57 |

Permittivity | Er | 2.20 |

Feed line width | Wf | 3.07 |

Feed line length | Lf | 4.71 |

Antenna Component | Symbol | Dimensions (mm) |
---|---|---|

Ground plane width | Ws = We | 8.40 |

Ground plane length | Ls = Le | 6.20 |

Patch width | Wp | 3.66 |

Patch length | Lp | 2.14 |

Copper thickness | Cu | 0.05 |

Substrate thickness | h | 1.57 |

Permittivity | Er | 2.2 |

Feed line width | Wf | 1.26 |

Feed line length | Lf | 3.10 |

Inset feed gap | Y0 | 0.50 |

Width feed gap | X0 | 0.68 |

**Table 3.**Comparisons among the bandwidth achieved in the present work to those achieved in other published works.

Performance Measure | Present Work (Proposed Antenna) | Work of [18] | Work of [20] | Work of [32] | |
---|---|---|---|---|---|

Center frequency | 28.00 GHz | 28.10 GHz | 28.00 GHz | 28.00 GHz | |

BW | VSWR ≤ 1.25 | 1.15 GHz | 0.45 GHz | 0.79 GHz | NA |

VSWR ≤ 1.5 | 2.68 GHz | 1.74 GHz | 1.57 GHz | 0.55 GHz | |

VSWR ≤ 2 | 5.57 GHz | 2.85 GHz | 2.63 GHz | 1.07 GHz | |

Relative BW | 19.89% | 10.14% | 9.39% | 3.83% | |

Gain | 5.06 dBi | 6.59 dBi | 6.37 dBi | 6.72 dBi |

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**MDPI and ACS Style**

Przesmycki, R.; Bugaj, M.; Nowosielski, L. Broadband Microstrip Antenna for 5G Wireless Systems Operating at 28 GHz. *Electronics* **2021**, *10*, 1.
https://doi.org/10.3390/electronics10010001

**AMA Style**

Przesmycki R, Bugaj M, Nowosielski L. Broadband Microstrip Antenna for 5G Wireless Systems Operating at 28 GHz. *Electronics*. 2021; 10(1):1.
https://doi.org/10.3390/electronics10010001

**Chicago/Turabian Style**

Przesmycki, Rafal, Marek Bugaj, and Leszek Nowosielski. 2021. "Broadband Microstrip Antenna for 5G Wireless Systems Operating at 28 GHz" *Electronics* 10, no. 1: 1.
https://doi.org/10.3390/electronics10010001