# Radiator Enablers for Wireless Communication Evolution
## 3 Radiators' Novel Technologies, Design, and Implementation Issues
### Advanced Antenna Designs in the mmWave Frequencies
#### 3.5.4 Example Designs of mmWave and FR2 Antennas  
In Table 10, noticeable antenna designs for mmWave and FR2 antennas are listed. An antenna, consisting of elements specially designed to achieve left-handed circular polarization (LHCP), is presented in ref. [101]. It is proposed to construct a 4 \(\times\) 4 array with dimensions of 36 \(\times\) 40 \(\times\) 25 mm\({}^{3}\), operating frequencies of 19-31 GHz, and a bandwidth of 48%. The maximum gain is 21.9 dBic, and the efficiency of the antenna is 90%. In ref. [102], an antenna is suggested, which uses a diode to select the desired polarization (right-handed, left-handed, and linear). The authors end up with a 2 \(\times\) 2 antenna array, achieving an axial ratio bandwidth (ARBW) of 19.61% in LHCP and 23.87% in RHCP, with a gain of 11,7 \(\pm\) 1.0 dBic/dBi. The operating frequency ranges from 23 to 29 GHz. The antenna dimensions (4.11 mm \(\times\) 2.88 mm \(\times\) 0.095 mm) are relatively small compared to other similar structures. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Antenna Type** & **Operation Frequency (GHz)** & **Bandwidth** & **Gain** & **Efficiency** & **Characteristic** \\ \hline Waveguide antenna (ref. [101]) & 19–31 & 48\% & 21.9 dBic & 90\% & \begin{tabular}{c} Radiation absorption with \\ many small \\ waveguide antennas \\ \end{tabular} \\ \hline Polarization-changing antenna (ref. [102]) & 23–29 & \(\sim\)20\% & \(11.7\pm 1\) dBic & 80\% & \begin{tabular}{c} Change of polarization \\ with diode \\ \end{tabular} \\ \hline Antenna for vehicles (ref. [103]) & 24–32 & 8 GHz & 4.4–4.5 dBi & \(>\)90\% & Increased performance \\ \hline Flexible mmWave antenna for BS (ref. [104]) & 29–31 & 2 GHz & 12.1 dBi & - & Flexible \\ \hline A simple patch antenna for compact devices (ref. [105]) & 26.01–31.58 & 5.57 GHz & 5.06 dB & 80.18\% & \begin{tabular}{c} Compact size and low \\ reflection coefficient \\ \end{tabular} \\ \hline Patch antenna for mini devices (ref. [106]) & 26.5–32.9 & 6.4 GHz & 5.42 dB & 83\% & Small-scale antenna \\ \hline Low cost antenna (ref. [107]) & 24–44 & 60\% & 7 dBi & - & \begin{tabular}{c} Satisfactory characteristics and \\ simple construction \\ \end{tabular} \\ \hline Thin Antenna for 5G Mobile Terminals (ref. [108]) & 24–40 & 50\% & 10.8 dBi & 78\% & \begin{tabular}{c} Matches network with a special \\ structure and construction to \\ optimize characteristics \\ \end{tabular} \\ \hline A parameterized folded dipole (ref. [109]) & 26.3–29.75 & 3 GHz & 9.98 dB & 90.4\% & Technique with via on PCB for folded dipole \\ \hline Patch antenna for smartphones (ref. [110]) & 23.6–43.5 & 60\% & 7.1 dBi & 95\% & \begin{tabular}{c} Cheap and simple \\ antenna construction \\ \end{tabular} \\ \hline Impressive antenna (ref. [111]) & 2–60 & 30:1 & 6.8 dBi & - & Wideband antenna \\ \hline Low-Cost 5G Beam-Switching Antenna (ref. [112]) & 55–65 & - & 3.1 dBi & \(\sim\)80\% & \begin{tabular}{c} Beem steering with SPDT \\ and p-i-n \\ \end{tabular} \\ \hline Beautiful antenna geometry (ref. [113]) & 60 & 57–67 & 8.5 dB & 88\% & Transparent antenna \\ \hline Array antenna for 100 GHz (ref. [114]) & 97.8–107 & 9.2\% & 26.5 dBi & 78\% & \
\begin{tabular}{c} Two feed techniques: SIW \\ and RGW \\ \end{tabular} \\ \hline Dual-polarized patch for 120 GHz (ref. [115]) & 107.5–132.5 & 25 GHz & 9.8 dBi/dBic & \(\sim\)85\% &
\begin{tabular}{c} Dual-polarized antenna with \\ high isolation on a \\ soft substrate \\ \end{tabular} \\ \hline AiP Array (ref. [116]) & 135–155 & 20 GHz & 16.8 dBi & - & BT-Based Substrate \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Noticeable antenna designs for mmWave and FR2 antennas. For communication applications on vehicles in ref. [103], a solution is proposed. The antenna has relatively satisfactory dimensions (12 \(\times\) 12 mm), with an operating frequency of 24-32 GHz and a bandwidth of 8 GHz. Also, it exhibits an efficiency of about 90% and a gain ranging from 4.4 to 4.5 dBi, depending on the operating frequency.