# Far-Field Radiation Characteristics of Folded Monopole Antennas over a Conducting Ground Plane

## Abstract

**:**

## 1. Introduction

^{TM}software for the simulations. The following sections present the methods and the parameters, results, a detailed discussion on numerical and simulated impedances, and conclusions.

## 2. Materials and Methods

^{TM}[19] numerical simulation software to create far-field electric radiation fields of the folded antenna models. We also used MATLAB

^{TM}for statistical plotting. Altair FEKO software is widely used in industry and academia for numerical electromagnetic simulations and the student version is open source. For the sake of comparison, we initially modeled a quarter-wavelength monopole antenna resonating at 75 MHz. The 75 MHz frequency was used for surface radio-controlled models. At 75 MHz, the height of the quarter-wavelength monopole antenna is 1 m. The wire radius of the monopole was kept at 1.5 mm. The antenna material was copper. The conductive ground plane of the antenna was also made with copper and the radius of the ground plane was 5 m. The mesh dimensions for simulations were kept at the wire radius since it is the smallest dimension.

## 3. Results

#### 3.1. The Single-Fold Monopole

#### 3.2. The Two-Fold Monopole

## 4. Discussion

^{TM}[20]. In this case, the goal was to identify the operational mode of the structures implemented in this article. The radiation pattern of a folded monopole without the ground plane was similar to the radiation pattern of a conventional dipole. Hence, the structures implemented in this work were operating in the common mode. In the differential mode, the feed wire current and the return wire current are 180° out of phase similar to a transmission line.

#### 4.1. Characteristic and Input Impedance

#### 4.2. Numerical and Simulated Input Impedance

## 5. Conclusions

- Folded antennas are good candidates when antenna height is restricted, since folding the antenna increases the resonance length of the antenna without increasing the physical height of the antenna.
- Folding the antennas changes the resonance frequency of the antennas compared to a monopole. At the same time, folding the antennas introduces additional parameters and all those parameters affect the resonance frequency of the antenna differently. By adjusting these parameters, a folded antenna model can be designed to have the same resonance frequency as a monopole.
- With every fold, the far-field radiation power decreases. With every halving of the antenna height, and the radiation power also halves.
- For single-fold antenna models, the biggest effect on the far-field radiation power is attained by reducing the wire-to-wire separation (d) and by increasing the ground-to-wire separation (w). The highest far-field radiated power is obtained by increasing the ground-to-wire separation.
- The beam widths achieved from the single-fold monopoles and the traditional monopole are the same and there were no significant differences between the gains either.
- For the two-fold monopoles, the far-field radiation power can be increased by increasing the ground-to-wire separation similar to the single-fold monopoles.
- In both single-fold and two-fold cases, doubling the ground-to-wire separation increased the radiated power by 0.2 W compared to other single- and two-fold models.
- The two-fold antenna models show more directivity compared to the other models.
- There are significant differences between the calculated and simulated input impedance. Hence, appropriate measurements are needed to validate the models and equations.

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 7.**Directivity of the antennas at the resonance frequency in spherical coordinates at $\varphi =0$.

**Figure 12.**Directivity of the antennas at the resonance frequency in spherical coordinates at $\varphi =0$.

**Figure 14.**Common mode characteristic impedance of single-fold (SF) antenna models with respect to frequency. SF models 4 and 5 will show similar characteristic impedance as SF model 1.

**Figure 15.**Differential mode characteristic impedance of single-fold (SF) antenna models with respect to frequency. SF models 4 and 5 will show similar characteristic impedance as SF model 1.

**Figure 16.**Common mode characteristic impedance of two-fold (TF) antenna models with respect to frequency. TF models 4 will show similar characteristic impedance as TF model 1. Here we have modeled the two fold antenna as two single-fold antennas in series.

**Figure 17.**Differential mode characteristic impedance of two-fold (TF) antenna models with respect to frequency. TF models 4 will show similar characteristic impedance as TF model 1.

**Figure 18.**Input impedance of single-fold (SF) antenna models with respect to frequency calculated from Equation (4). Numerically SF models 4 and 5 will show similar characteristic impedance as SF model 1.

**Figure 19.**Input impedance of two-fold (TF) antenna models with respect to frequency calculated numerically. TF models 4 will show similar characteristic impedance as TF model 1. Here we have modeled the two fold antenna as two single-fold antennas in series.

**Figure 22.**The magnitude of the input impedance of the monopole and the single-fold antenna modals from FEKO.

Model | ${\mathit{l}}_{1}$ (cm) | ${\mathit{l}}_{2}$ (cm) | d (cm) | w (cm) | ${\mathit{\rho}}_{1}$ (mm) | ${\mathit{\rho}}_{2}$ (mm) |
---|---|---|---|---|---|---|

Monopole | 100 | - | - | - | 1.5 | - |

SF model 1 | 50 | 40 | 10 | 10 | 1.5 | 1.5 |

SF model 2 | 50 | 40 | 20 | 10 | 1.5 | 1.5 |

SF model 3 | 50 | 40 | 5 | 10 | 1.5 | 1.5 |

SF model 4 | 50 | 30 | 10 | 20 | 1.5 | 1.5 |

SF model 5 | 50 | 45 | 10 | 5 | 1.5 | 1.5 |

SF model 6 | 50 | 40 | 10 | 10 | 3.0 | 1.5 |

SF model 7 | 50 | 40 | 10 | 10 | 0.75 | 1.5 |

Model | ${\mathit{l}}_{1}$ (cm) | ${\mathit{l}}_{2}$ (cm) | d (cm) | w (cm) | ${\mathit{\rho}}_{1}$ (mm) | ${\mathit{\rho}}_{2}$ (mm) |
---|---|---|---|---|---|---|

TF model 1 | 25 | 20 | 5 | 5 | 1.5 | 1.5 |

TF model 2 | 25 | 20 | 5 | 5 | 3.0 | 1.5 |

TF model 3 | 25 | 20 | 5 | 5 | 0.75 | 1.5 |

TF model 4 | 25 | 15 | 5 | 10 | 1.5 | 1.5 |

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**MDPI and ACS Style**

Maxworth, A.
Far-Field Radiation Characteristics of Folded Monopole Antennas over a Conducting Ground Plane. *Eng* **2022**, *3*, 142-160.
https://doi.org/10.3390/eng3010012

**AMA Style**

Maxworth A.
Far-Field Radiation Characteristics of Folded Monopole Antennas over a Conducting Ground Plane. *Eng*. 2022; 3(1):142-160.
https://doi.org/10.3390/eng3010012

**Chicago/Turabian Style**

Maxworth, Ashanthi.
2022. "Far-Field Radiation Characteristics of Folded Monopole Antennas over a Conducting Ground Plane" *Eng* 3, no. 1: 142-160.
https://doi.org/10.3390/eng3010012