# Meander Line Super-Wideband Radiator for Fifth-Generation (5G) Vehicles
## 3 Antenna Design
### Design of 5G FR2 Meander Line Antenna  
FR1 antennas are typically larger and have lower gain. Lower-frequency-band antennas, characterized by longer wavelengths, present inherent limitations that impact their design and performance. One primary constraint is the challenge of accommodating larger physical sizes due to the proportional relationship between antenna size and wavelength. This limitation is particularly significant in portable devices and those with space constraints. Lower-frequency antennas typically exhibit lower directivity and gain, which limits their effective range and coverage area. The constrained bandwidth available in lower frequency bands further limits data transfer rates, which affects the overall throughput of communication systems. These antennas are more susceptible to noise and interference from both natural and man-made sources, which potentially compromises signal quality. The ability of lower frequency signals to penetrate obstacles is also compromised, making them less suitable for applications in urban environments. Regulatory restrictions on certain lower frequency bands further contribute to the challenges in designing and deploying communication systems. While lower frequency bands offer extended propagation ranges, the associated limitations necessitate careful consideration in antenna design and deployment, especially in the context of modern communication requirements. FR1 antennas are optimized for coverage and capacity in the lower frequency range, while 5G frequency range 2 (FR2) antennas are optimized for high data rates and focused coverage in the higher frequency range. FR2 antennas operate in the frequency range from 24.25 GHz to 52.6 GHz. They are used for millimeter-wave (mmWave) 5G deployments, which offer very high data transfer speeds but have limited coverage due to their shorter range [6; 15]. A monopole meander line via continuous ground with modifications of meander line width, length, and turns can obtain wideband and also improve the antenna directivity at 5G FR2 bands. Figure 4 discusses the design flow of a proposed antenna with a continuous ground plane. Antennas Ant2 to Ant4 have been developed based on the key mathematical expressions for 5G FR2 from Equations (11)-(16). The design process initiates with Ant2 and concludes with Ant4. Figure 5 illustrates the S11 parameter and the design flow gain for Ant2 to Ant4. The 5G FR2 design flow for a super-wideband meander line antenna spanning from 24 GHz to 30 GHz in terms of S-parameters is presented in Figure 4(a), with the gain specifically depicted at 28 GHz in Figure 4(b). The initial design of Ant2 incorporates a 50 \(\Omega\) microstrip line feed measuring 22 mm \(\times\) 12 mm \(\times\) 1.6 mm. It primarily focuses on meander width variations with reduced substrate geometry. Ant2 resonates from 26.78 GHz to 28.62 GHz, exhibits a \(-\)13.25 dB reflection coefficient and a peak gain of 7.3 dBi, and showcases a single narrowband frequency at the center frequency of 28 GHz. Ant3 extends the structural design of Ant2 by emphasizing meander length and substrate geometry. With dimensions of 34 mm \(\times\) 15 mm \(\times\) 1.6 mm, Ant3 introduces a wideband frequency range from 24.47 GHz to 30 GHz. At 28 GHz, it displays a \(-\)23.45 dB reflection coefficient and a peak gain of 6.10 dBi, outperforming Ant2. The meander line configuration of Ant3 involves multiple segments with varying widths and increasing lengths that generate numerous resonances that enhance the antenna's bandwidth. To broaden the frequency, Ant3 is fed through a quarter-wave transformer (QWT) feedline. Finally, Ant4 is a meander  
Figure 3: 5G FR1 meander line antenna design: (**a**) Ant1 dimensions (mm), (**b**) ground variations, and (**c**) S-parameter and gain. line antenna featuring width and length variations. It is powered by a 50 \(\Omega\) microstrip line feed and is constructed on a full ground plane to encompass both the lower and upper bands of the 28 GHz range.