# A Critical Examination of the Beam-Squinting Effect in Broadband Mobile Communication: Review Paper
## 3 Studies Related to the Beam Squint Effects
According to the authors of this study, phased array antennas are not affected by the same factors that cause RF lens antenna beam squint. According to [PERSON]'s law, if an electromagnetic wave passes through a dielectric lens, it will be bent. Refraction is a result of permittivity being a function of frequency, one of the reasons of beam squint, according to the Drude-Lorentz model [62]. Due to the resonance frequency and damping constant, permittivity is also nonlinear. Permittivity has both genuine and fictitious components. The real component is represented by the dielectric constant, and the tangent loss is the ratio of the real to the imaginary component. As can be seen, the component of the refractive index, known as the real part, is the one that determines the degree to which the beam is deflected. Because permittivity affects the actual portion of the refractive index, the beam squints at the lens when a wave with a different frequency band travels through a material with a different degree of refraction, as shown in Figure 14. This occurs because a wave with a different frequency band travels through a material with a different degree of refraction. To make fully digital beamforming less complicated, the authors developed hybrid beamforming. The lens structure at the front of the antenna array and the antenna array itself formed the two components of the RF lens antenna. The analog beamforming process uses the lens structure to concentrate the beam produced by the antenna array. With the antenna switched on and off, beam steering was accomplished utilizing lens refractions. Under comparable circumstances for beam squint, beamforming gain, and received power, the authors compared and contrasted the lens antenna and the phased array. Through study, they were able to confirm that stable permittivity materials can be used to minimize the beam squint issue with the RF lens system. Then, they demonstrated the reduced  
Figure 14: Indoor mmwave software-defined radio (SDR) testbed with a fabricated RF lens for beam squint [61]. spectral efficiency brought on by beam squint for both the lens antenna and the phased array using 3D ray tracing in an interior setting. Finally, they used the constructed RF lens to illustrate the indoor mmwave link level and to confirm that beam squint negatively affects performance. In [63], the authors proposed a transceiver design based on lens antenna subarray (LAS) and analog sub-band filters to compensate for the beam squinting. The design is based on the idea of dividing the ultra-wideband signal into narrowband beams and controlling them with a simplified exhaustive search-based precoding that is proposed to align the beam angle to the target direction. Analysis was based on various performance parameters, such as beam gain, complexity, power consumption, and capacity. The proposed design involved using both phase shifters and switching networks to steer the beam to compensate for the beam-squinting problem while maintaining the intended beamwidth performance. Phase shifters were used to steer the beam to the desired direction on the basis of the location of the targeted user, and the switching mechanism was used to select an antenna element under the lens that can correct/minimize the deviation of the beam (due to squinting) from the intended direction. The results of this study showed significant performance improvement. However, this study requires the use of high-quality narrow-band filters for higher frequencies. This can increase the complexity of the system as well as the cost. Another approach, based on reconfigurable intelligent surface for satellite-to-terrestrial relay networks, was developed and described in [64]. The Taylor expansion and penalty function methods were used in this approach to optimise phase shifters between the surface unit cells by adding a weight function in order to maximise the channel performance under certain conditions.