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EM behavior when the wavelength is about the same size as the object
Published in James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney, Basic Introduction to Bioelectromagnetics, 2018
James R. Nagel, Cynthia M. Furse, Douglas A. Christensen, Carl H. Durney
A typical reflector antenna is the parabolic microwave dish commonly used to receive TV or internet signals from satellites. The parabolic reflector concentrates the microwave energy at its focal point. A visual example of how parabolic reflectors work can be seen in the large parabolic mirrors in operating room lights or the light a dentist typically uses. Lens antennas are used to form EM radiation into beams for transmission into space, or to receive and concentrate EM radiation. Because lens antennas must be large compared to a wavelength if they are to be effective, they are used primarily at higher frequencies where wavelengths are smaller.
Antennas or aerials
Published in Geoff Lewis, Communications Technology Handbook, 2013
Lens antennas respond to electromagnetic waves in a similar manner to an optical lens and light. That is, they convert a spherical wave with diverging energy into a plane wave with directivity to provide a gain parameter. These devices are designed around two basic concepts.
Importance and Uses of Microstrip Antenna in IoT
Published in Praveen Kumar Malik, Planar Antennas, 2021
Lens antennas are mostly used in microwave relay communication and have less side lobes and back lobes. These antennas are difficult to manufacture with a complex structure, and they have lower efficiency and high manufacturing cost.
X-Band Multilayer Stacked Microstrip Antenna Using Novel Electromagnetic Band-Gap Structures
Published in IETE Journal of Research, 2023
Mohit Gaharwar, D. C. Dhubkarya
The revolution in wired and wireless communication systems has an enormous influence on society around the world, and today life without connectivity is hard to imagine. Wireless networks are also of greater interest to the research community because of their inherent advantages, such as limited investment in infrastructure (no wire), ease of implementation, support for end-user mobility, remote access and cost-effectiveness. In addition to other electronics, the antenna is an essential component of a wireless communication network in the transmitter and the receiver. The phenomena of converting electrical energy to electromagnetic energy are performed by antenna and vice versa. Similarly, the receiver side antenna is the first stage and gets a free space signal. The antenna field is almost as old as the contact and research in this area are; it is hard, to sum up here. The Heinrich Hertz was an explorer in the field of antenna, providing a comprehensive theoretical framework for understanding radio waves. The research community has worked hard to give better antennas to support radio communication. Different types of antennas are designed and developed. They can be broadly classified as array, wire, aperture, reflector, microstrip, and lens antennas.
A Wideband Dual-Polarized Tightly Coupled Array with Compact Size for 5G Millimeter-wave Mobile Devices
Published in Electromagnetics, 2023
Chan Bai, Shuai Zhang, Qi Gong, Zixuan Song, Yuguo Liu
Various types of mmW antennas include lens antennas, Vivaldi antennas, slot antennas, patch antennas, magneto-electric (ME) dipole antennas, and so on. Lens antennas have been widely applied in 5 G mmW applications due to their low cost, light weight, enhanced gain, and multibeam function (Basavarajappa et al. 2019; Wang, Pan, and Dong 2022). Vivaldi antennas can support dual polarization, wideband, high efficiency, and large beam steering range (Ikram, Nguyen-Trong, and Abbosh 2020; Kähkönen et al. 2022). Slot antennas have advantages of wideband, high gain, low cost, and ease of fabrication (Guo and Hao 2021; Radenamad, Aoyagi, and Hirose 2011). However, these studied antennas are not small. The size of these antennas is unrealistic to be integrated into mobile phones. Meanwhile, the miniaturized antennas have been widely researched. Patch antennas can support low profile, low cost, lightweight, simple structure, and be easy to be fabricated (Yang, Hong, and Zhang 2014; Yin et al. 2019a). However, these antennas have narrow bandwidth and so they cannot cover dominant 5 G mmW communication bands simultaneously. Magneto-electric (ME) dipole antennas are well known because of their wideband (Hao and Li 2017; Yin et al. 2019b). However, these antennas cannot support large-angle scanning without grating lobes and consequently reduce the connectivity distance and signal coverage. To avoid grating lobes, the element spacing for a phase array should be calculated as d ≤ λ/2 (Robert 2005).
A Brief Review on mm-Wave Antennas for 5G and Beyond Applications
Published in IETE Technical Review, 2023
Paikhomba Loktongbam, Debasish Pal, A. K. Bandyopadhyay, Chaitali Koley
Path loss in mm-wave communication is high compared to the same at lower frequencies, and this loss is also frequency selective. There are mainly two types of losses in mm-wave communication. The first is scattering loss, and the second is absorption loss. Scattering loss is a natural phenomenon for propagating EM waves. This loss is present even in microwave frequencies. The second one is gaseous absorption loss. This occurs because gas molecules are excited by mm-wave and start vibrating. Hence EM energy is converted to kinetic energy and is lost. It is essential to mention here that between 0.2 and 10 THz, the attenuation is dominated by water vapor present in the atmosphere. Attenuation due to rain and fog has a minor effect. This scenario is exactly the opposite of that IR (Infrared) propagation. In IR propagation, fog and smoke significantly affect path loss. Even in the THz regime also atmospheric attenuation depends on altitude and temperature. Due to this high atmospheric losses role of the antenna becomes more and more critical. According to Friis transmission formula [38], the power supplied to a load of a receiving antenna is given by where, , are output power, input power to the transmitting antenna, operating wavelength, distance between the transmitter and receiver, gain of the transmitting antenna, gain of receiving antenna, position of the (in spherical co-ordinate) receiving antenna, position of the (in spherical co-ordinate) transmitting antenna, path power transmission factor and polarization coupling efficiency, respectively. The output power to the load is directly proportional to the gain of the transmitting and receiving antenna. With the help of the reciprocity theorem [38], the same antenna can be used for the transmission and reception purposes. Under this condition, the output power is proportional to the square of the antenna gain. With other parameters remaining constant, the output power is inversely proportional to the square of the distance between the two antennas. Due to the limitation of the source power (Pin), it is necessary to increase the antenna's gain in the mm-wave system to cover the longer distance. Gain is related to directivity by, are the transmitting antenna gain, radiated power by the antenna, input power to the antenna, and directivity of the transmitting antenna, respectively. Hence highly directive antenna is required to overcome the effects of the environmental loss factor. Generally, the lens antennas are used for high directivity in mm-wave frequencies. Silicon has commonly been used as a substrate for the design of lens antennas in mm-wave [39–44] frequencies. Despite high directivity, as it is not compact in size, it is not easy to integrate the same for on-chip applications.