# Recent Developments and Challenges on Beam Steering Characteristics of Reconfigurable Transmitarray Antennas

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Beam Steering/Beam Forming Principle of Transmitarray

_{n}shown in Equation (1).

_{n}= k

_{o}n Δs+ φ

_{0}

_{n}= φ

_{n+1}− φ

_{n}.

_{0}), the dielectric constant (εr) and thickness (h) of the dielectric substrate are 2.2 and 3.2 mm, respectively. From 1 mm to 9.1 mm, a transmittance of 0.8 or more and a change in transmission phase of about 400 degrees can be obtained. A high gain transmission antenna using a metasurface composed of 10 × 10 circular patch array unit cells is presented. The total size of the transmitarray is 200 mm (about 4 λ

_{0}), and the distance between the source antenna and the metasurface is 50 mm (about 1 λ

_{0}).

_{a}) is defined in terms of the taper efficiency (η

_{t}), spillover efficiency (η

_{s}), polarization efficiency (η

_{pol}), transmission efficiency (η

_{tran}), phase efficiency (η

_{ph}), and random surface as in Equation (4). It can be calculated as the product of the error efficiency (η

_{r}) [72].

_{rad}are the area of the metasurface and the radiation power of the source antenna, respectively. It is vital to determine the source antenna, the distance between the source antennas and the plane array (F), and the size (D) of the transmitarray to optimize the aperture efficiency of the transmitted antenna using the TA.

## 3. Beam Steering/Beam Forming Using Reconfigurable Components

#### 3.1. PIN Diodes

_{0}/3. A 16 × 16 element 12.5 GHz reconfigurable transmitarray was designed and tested. The maximum gain of 17.0 dBi corresponds to an aperture efficiency of 14.0% presented in experimental results. The H-shape coupling slot transmitarray realizes a beam scanning angle within ±50 degrees for E- and H-planes. The 3 dB gain bandwidth retains 9.6% in the measured results.

#### 3.2. Varactor Diodes

_{max}/C

_{in}, meaning a large capacitance ratio results in a wide range of tuning capacitance. There is a detail Summary of beam steering reconfigurable transmitarrays with varactor diodes shown in Table 2.

#### 3.3. MEMS Switches

#### 3.4. Microfluids

_{g}) gas. DC-bias voltage is applied to the end of the cylinder. The frequency of plasma argon gas (Ar

_{g}) is varied, leading to variation in the reflection coefficient from 0–305 degrees corresponding to the maximum reflection coefficient that reaches up to −8 dB. The continuous transmission phase shift control executes from 0–345 degrees. Moreover, the remaining phase control compensates due to plasma frequency variation. Plasma transmitarray/reflectarray is accomplished with a 2D beam scanning ability of ±30 degrees for the H-plane and E-Plane at 19.75 GHz and 19.39 GHz, respectively.

## 4. Beam Steering/Beam Forming Using Variable Source Antenna

## 5. Future Challenges and Scope

#### 5.1. Terahertz and Optical Frequencies

#### 5.2. Multi-Bit Structures

#### 5.3. Dual-Band Frequency

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

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**Figure 2.**Conceptual diagram of the wavefront of (

**a**) fixed beam transmitarray and fixed source antenna (

**b**) active transmitarray with fix source and variable phase shift of TA.

**Figure 3.**(

**a**) Conceptual diagram of the wavefront of fixed beam transmitarray and variable source antenna; (

**b**) phase variation concept of fixed transmitarray and variable source antenna.

**Figure 4.**(

**a**) Geometry of Vivaldi reconfigurable transmitarray with WIAM metasurface; (

**b**) fabricated 1 × 16 subarray prototype (reprinted with permission of [76]. Copyright 2021 Xiao, Y., et al.).

**Figure 5.**Geometry of 3 × 3 1 bit RTA element with biasing circuit; (

**a**–

**f**) exploded view, top view; (

**g**) measures radiation pattern of E-plane and H-plane, respectively (reprinted with permission of [80]. Copyright 2021 Kozlov, D., et al.).

**Figure 6.**(

**a**) Exploded view of the proposed unit cell; (

**b**) simulated results of transmission magnitude and phase shift (reprinted with permission of [84]. Copyright 2020 Wang, M., et al.).

**Figure 7.**(

**a**) Layer stack view of proposed unit cell, (

**b**) layout view, (

**c**) 3D view, (

**d**) top layer, (

**e**) bottom layer (reprinted with permission of [94]. Copyright 2019 Frank, M., et al.).

**Figure 8.**(

**a**) FSS proposed unit cell; (

**b**) equivalent circuit diagram (reprinted with permission of [97]. Copyright 2021 Reis, J.R., et al.).

**Figure 9.**(

**a**) Proposed unit cell with MEMS bridge; (

**b**) unit cell with bias bridge (reprinted with permission of [100]. Copyright 2004 Schoenlinner, B., et al.).

**Figure 10.**(

**a**) Top view of unit cell; (

**b**) nested ring split ring prototype (reprinted with permission of [109]. Copyright 2015 Erdil, E., et al.).

**Figure 11.**(

**a**) Proposed mechanism of beam scanning transmitarray; (

**b**) actual implementation of variable source transmitarray (reprinted with permission of [47]. Copyright 2019 Massaccesi, A., et al.).

**Figure 12.**(

**a**) Simulated transmitarray with ACMP feed source; (

**b**) gain pattern with variable source feeds. (reprinted with permission of [112].Copyright 2019 Liu, G., et al.).

Ref. | Unit Cell Technique | Phase Control Device | Frequency (GHz) | Polarization | Phase Range | Gain (dBi) | Aperture Efficiency (%) | Band Width | Beam Scanning Capacity |
---|---|---|---|---|---|---|---|---|---|

[32] | PCB stacked patch | PIN diode | 5.4 | LP, CP | 1-B1T | 17 | 28.5 | 8.5 | ±50° E and H plane |

[73] | O-U slot patches | PIN diode | 29 | CP | 1-B1T | 28.5 | 9.5 | 14.6% | ±60° E and H plane |

[74] | double O-slot patches | PIN diode | 29 | LP | 2-B1T | 19.8 | 15.9 | 16.2% | ±60° E and H plane |

[76] | microstrip Vivaldi | PIN diode | 13.6 | LP | 1-B1T | 22.3 | 25.6 | 1.9% (1-dB) | ±40° E and H plane |

[79] | coupled slot | PIN diode | 12.5 | LP | 1-B1T | 17 | 14 | 9.6% | ±50° E and H plane |

[80] | Square ring patch | PIN diode | 5.75 | CP | 1-BIT | 14 | _ | 2.5% | ±30° E and H plane |

[83] | H and I shape coupling slot | PIN diode | 12.5 | LP | 1-BIT | 17 | 14 | 9.6% | ±50° E and H plane |

[84] | C-shaped probe-fed patch | PIN diode | 12.1 | LP | 1-B1T | 22.1 | 22.2 | 16% | ±60° E and H plane |

[85] | split circular rings | PIN diode | 5 | LP | 1-B1T | 16.8 | 18.4 | 17% (1-dB) | ±40° E and H plane |

[86] | multilayer annular ring patches | PIN diode | 14 | LP | 1-B1T | 20.4 | 33.4 | 33% | ±50° E and H plane |

Ref | Unit Cell Technique | Phase Control Device | Frequency (GHz) | Polarization | Phase Range | Gain (dBi) | Aperture Efficiency | Band Width | Beam Steering Capacity |
---|---|---|---|---|---|---|---|---|---|

[94] | stacked layers | varactor diode | 24.6 | LP | 360° | _ | _ | 1 GHz | ±50° E and H plane |

[95] | compact varactor based phase shifters | varactor diode | 5.6 | LP | 360°, 1-BIT | 15.7 | 33.3 | 16.7% | 60° E and H plane |

[96] | FSS | varactor diode | 5.2 | LP | 480° | 20.2 | _ | 13% | ±30° E and H plane |

[98] | integrated leaky wave | varactor diode | 4.8 | LP | 400° | 15.6 | 34 | 9% | ±45° E and H plane |

Ref | Unit Cell Technique | Phase Control Device | Frequency (GHz) | Polarization | Phase Range | Gain | Aperture Efficiency | Band Width | Beam Scanning Capacity |
---|---|---|---|---|---|---|---|---|---|

[100] | FSS | MEMS | 30.2 | CP | 360° | _ | _ | 1.6GHz (1 dB) | _ |

[103] | antenna filter antenna | MEMS | 32 | LP | 2-bit | 26.5 | _ | _ | ±60° E and H plane |

[104] | antenna filter antenna | MEMS | 34.8 | LP | 2-bit | 9.6 | 6.2 | _ | ±40° E and H plane |

Ref. | Beam Steering Method | Control Elements/Devices | Advantages | Disadvantages |
---|---|---|---|---|

[74,75,76,77,78] | Active Transmitarray | PIN diodes | Broadband transmission and differential phase shift characteristics | Complexity of design due to half via for biasing |

[82,83] | PIN diodes | Coupling Slots TA, large-angle beam scanning capability | Results are not symmetric through out the obtain frequency | |

[84] | PIN diodes | Excellent beam steering performance but the degradation of antenna efficiency | The degradation of antenna efficiency | |

[90,91] | Varactor diodes | Excellent beam steering performance, but complicated bias circuit | complicated bias circuit | |

[93] | Varactor diodes | High gain, simple circuitry, narrow beam scanning | narrow beam scanning | |

[94] | Varactor diodes | Parametric study of the unit cell, more stack unit cell high internal resistance | more stack unit cell high internal resistance | |

[100] | MEMS | 2 bit phase quantization, directivity loss | High insertion loss, directivity loss | |

[105] | MEMS | High insertion loss, poor power efficiency | High insertion loss, poor power efficiency | |

[109] | Microfluids | Narrow beam steering angle | Narrow beam steering angle | |

[112] | Variable Source Transmitarray | Seven 2 × 2 aperture couple source antenna | Reduce visual impact important for 5G and small cell steering | Discrete beam steering angle |

[113] | multi-focal source | Excellent beam steering performance, quad-focal phase shift distribution | Multiple focal source |

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**MDPI and ACS Style**

Ali, Q.; Shahzad, W.; Ahmad, I.; Safiq, S.; Bin, X.; Abbas, S.M.; Sun, H.
Recent Developments and Challenges on Beam Steering Characteristics of Reconfigurable Transmitarray Antennas. *Electronics* **2022**, *11*, 587.
https://doi.org/10.3390/electronics11040587

**AMA Style**

Ali Q, Shahzad W, Ahmad I, Safiq S, Bin X, Abbas SM, Sun H.
Recent Developments and Challenges on Beam Steering Characteristics of Reconfigurable Transmitarray Antennas. *Electronics*. 2022; 11(4):587.
https://doi.org/10.3390/electronics11040587

**Chicago/Turabian Style**

Ali, Qasim, Waseem Shahzad, Iftikhar Ahmad, Shozab Safiq, Xi Bin, Syed Muzahir Abbas, and Houjun Sun.
2022. "Recent Developments and Challenges on Beam Steering Characteristics of Reconfigurable Transmitarray Antennas" *Electronics* 11, no. 4: 587.
https://doi.org/10.3390/electronics11040587