# Optimization of Log-Periodic TV Reception Antenna with UHF Mobile Communications Band Rejection

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## Abstract

**:**

## 1. Introduction

## 2. Conventional LPDA Geometry

_{n}and d

_{n}are, respectively, the length and the diameter of the nth dipole. In addition, the parameter σ shown in (1) is called the “spacing factor” and is defined as:

_{n}is the spacing between the nth dipole and its consecutive (n + 1)th dipole. The overall physical dimensions of the antenna significantly depend on the above two factors (τ and σ). Sometimes, a fixed diameter is used for the dipoles in order to simplify the antenna design and reduce costs.

## 3. Proposed LPDA Geometry

_{1}, L

_{2}and L

_{3}, and their distances, i.e., s

_{0}, s

_{1}, s

_{2}, and s

_{3}, are the only parameters considered for optimization. The optimization settings for the TRF algorithm are taking into consideration that the optimal values of these parameters cannot deviate more than 30% from the respective values of a conventional LPDA design. Therefore, by multiplying the parameter values of this conventional design by 0.7 (30% less) or by 1.3 (30% more), we find the parameter boundaries, which are listed in Table 2. These boundaries are used to restrict the search area of every parameter and thus help the optimization algorithm converge faster.

_{n}is length of the nth dipole, s

_{n}is distance between the nth and (n + 1)th dipole, s0 is the distance between the start of the boom and the first dipole, L-boom is length of the boom, W-boom is width of the boom, H-boom is height of the boom, and gap is the distance between the two parallel booms. The cuboidal fastener for the antenna was designed using the dimensions specified for Stub_length, Stub_width, and Stub_height in Table 3. An LPDA can be matched to the desired impedance by varying the seperation gap between the two conducting booms. The initial model that was designed using Carrel’s design equation had a matching impedance of 75 ohms, where the booms were 10 mm apart. However, in case of the proposed optimized LPDA, the separation gap between the booms was reduced from 10 mm to 5 mm in order to match the antenna to 50 ohms impedance. Thereafter, the proposed antenna was fabricated using alluminium components at the University of Huddersfield Manufacturing laboratory. Figure 4 shows the fabricated model that follows the exact dimensions of the CST-optimized LPDA design.

## 4. LPDA Simulations and Measurements

^{−4}were used to model this antenna in CST. A discrete 50 Ω port that connects the center points of both the booms at front end of the antenna is used to provide the excitation. The antenna was simulated in the frequency range from 450 MHz to 1000 MHz with 10 MHz resolution, because the frequency of interest involves UHF TV, LTE-800, and GSM-900 bands. The anechoic chamber at the National Physical Laboratory (NPL), UK was used to test and measure the fabricated LPDA design.

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**CAD (Computer-Aided Design) model of Carrel’s conventional model (

**left**) and the proposed LPDA (

**right**) shown as a top view.

**Figure 5.**Surface current density of the optimized antenna at (

**a**) 470 MHz, (

**b**) 630 MHz, (

**c**) 790 MHz, and (

**d**) 960 MHz from simulation.

**Figure 6.**S11 plot of Carrel’s conventional LPDA design and the optimized LPDA design of this paper.

**Figure 8.**FBR (front-to-back ratio) plot of Carrel’s conventional design and the optimized LPDA design.

**Figure 10.**The test setup to measure the radiation patterns: (

**a**) E-plane and (

**b**) H-plane of the fabricated optimized LPDA in an NPL anechoic chamber.

**Figure 11.**E-plane normalized radiation patterns at (

**a**) 470 MHz, (

**b**) 630 MHz, (

**c**) 790 MHz, and (

**d**) 960 MHz.

**Figure 12.**Normalized radiation patterns on the H-plane at (

**a**) 470 MHz, (

**b**) 630 MHz, (

**c**) 790 MHz, and (

**d**) 960 MHz.

Parameter | Goal | Frequency (MHz) | Weight |
---|---|---|---|

S11 | <−14 dB | 470–790 (Passband) | 10.0 |

Realized gain | >10 dBi | 470–790 (Passband) | 1.0 |

Front-to-back ratio | >14 dB | 470–790 (Passband) | 0.2 |

S11 | >−1 dB | 810–960 (Stopband) | 5.0 |

Realized gain | >−10 dBi | 810–960 (Stopband) | 1.0 |

Parameter | Initial Values from [18] | Lower Boundary | Upper Boundary |
---|---|---|---|

L_{1} | 138 | 96.6 mm | 179.4 mm |

L_{2} | 111.8 | 78.26 mm | 145.34 mm |

L_{3} | 126.2 | 88.34 mm | 164.06 mm |

s_{0} | 28 | 19.6 mm | 36.4 mm |

s_{1} | 15.3 | 10.7 mm | 19.9 mm |

s_{2} | 18.6 | 13.0 mm | 24.2 mm |

s_{3} | 22 | 15.4 mm | 28.6 mm |

Parameter | Carrel’s Design | Proposed Design in [19] | Proposed Design |
---|---|---|---|

Variable name | Value (mm) | Value (mm) | Value (mm) |

L_{1} | 98 | 138 | 145.4 |

L_{2} | 110 | 111.8 | 128.4 |

L_{3} | 124 | 126.2 | 112 |

L_{4} | 140 | 121.4 | 121.4 |

L_{5} | 160 | 157.2 | 157.2 |

L_{6} | 180 | 180.2 | 180.2 |

L_{7} | 206 | 203.6 | 203.6 |

L_{8} | 232 | 235.4 | 235.4 |

L_{9} | 264 | 267 | 267 |

L_{10} | 298 | 302.6 | 302.6 |

L-boom | 356 | 356 | 356 |

H-boom | 15 | 15 | 15 |

W-boom | 15 | 15 | 15 |

Dipole diameter | 4 | 4 | 4 |

Stub width | 15 | 15 | 15 |

s_{0} | 30 | 28 | 24.1 |

s_{1} | 16 | 15.3 | 11.4 |

s_{2} | 18 | 18.6 | 14.9 |

s_{3} | 20 | 22 | 17.9 |

s_{4} | 22 | 25.3 | 25.3 |

s_{5} | 26 | 27.3 | 27.3 |

s_{6} | 28 | 27 | 27 |

s_{7} | 34 | 36.3 | 36.3 |

s_{8} | 37 | 40.4 | 40.4 |

s_{9} | 42 | 40.6 | 40.6 |

gap | 10 | 11.7 | 5 |

Stub length | 79 | 45 | 45 |

Stub thickness | 35 | 35 | 35 |

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**MDPI and ACS Style**

Mistry, K.K.; Lazaridis, P.I.; Zaharis, Z.D.; Chochliouros, I.P.; Loh, T.H.; Gravas, I.P.; Cheadle, D.
Optimization of Log-Periodic TV Reception Antenna with UHF Mobile Communications Band Rejection. *Electronics* **2020**, *9*, 1830.
https://doi.org/10.3390/electronics9111830

**AMA Style**

Mistry KK, Lazaridis PI, Zaharis ZD, Chochliouros IP, Loh TH, Gravas IP, Cheadle D.
Optimization of Log-Periodic TV Reception Antenna with UHF Mobile Communications Band Rejection. *Electronics*. 2020; 9(11):1830.
https://doi.org/10.3390/electronics9111830

**Chicago/Turabian Style**

Mistry, Keyur K., Pavlos I. Lazaridis, Zaharias D. Zaharis, Ioannis P. Chochliouros, Tian Hong Loh, Ioannis P. Gravas, and David Cheadle.
2020. "Optimization of Log-Periodic TV Reception Antenna with UHF Mobile Communications Band Rejection" *Electronics* 9, no. 11: 1830.
https://doi.org/10.3390/electronics9111830