China
Africa
Explore chapters and articles related to this topic
Advanced Microstrip Antennas for Vehicular Communication
Published in Praveen Kumar Malik, Planar Antennas, 2021
Antenna is the device that will transmit and/or receive the electromagnetic waves. Antennas are being used in the modern vehicles for getting multiple applications. The antennas for vehicular communication platforms will fall under one or many of the following applications (Table 9.1).
Unmanned Aircraft Systems (UAS) Communications
Published in R. Kurt Barnhart, Douglas M. Marshall, Eric J. Shappee, Introduction to Unmanned Aircraft Systems, 2021
An antenna radiates efficiently when EM energy is guided through a transmission line under matched conditions (meaning most of the incoming energy is transmitted to the antenna with little reflection taking place at the antenna–transmission line interface). Time-varying voltages and currents in a transmission line carry electric fields and magnetic fields. The electrical fields start on positive charges and end in negative charges and magnetic fields are formed around current carrying conductors. These fields do not end at the antenna but have been observed to be radiating into free space. The question then arises as to what holds these fields in place without the presence of charges or how these guided waves are detached from the antenna. One can conclude that while the charges are required to excite these fields, they are not required to sustain them. As an analogy to this phenomenon, it has been observed that when a pebble tossed into a pool of water, it will create ripples long after it has settled in the bottom (Balanis 2005, 7–16). Some commonly used types of antennas include the horn, dipole, monopole, spiral, and patch antennas (Figure 13.4).
Smart Antennas for Contemporary Wireless Communication Systems: Concepts, Challenges, and Performance
Published in Devendra Kumar Sharma, Rohit Sharma, Bhadra Pokharel, Vinod Kumar, Raghvendra Kumar, Advances in Antenna, Signal Processing, and Microelectronics Engineering, 2021
Garima Srivastava, Neeta Singh, Sachin Kumar
An antenna is a device through which electrical signals from the transmitter are radiated into free space in the form of radio frequency (RF) energy. The contemporary wireless applications need versatile and dynamic antennas that can adapt according to the system requirements. The smart antenna is composed of steerable transmitting/receiving systems that dynamically make changes in the antenna radiation pattern to encounter channel fading effects [1]. In this way, the smart antenna solves the issue of multipath fading in the band of interest, thereby achieving an output with a better signal-to-noise ratio. The smart antenna senses electromagnetic (EM) waves in an adaptive fashion by using signal processing algorithms [2]. The signal processing algorithms and steerable mechanism in smart antennas improve the performance/capacity of the wireless system, without increasing the channel bandwidth or transmit power.
Compact dual-band MIMO cubical antenna for automotive applications
Published in International Journal of Electronics, 2023
Lekha Kannappan, Sandeep Kumar Palaniswamy, Malathi Kanagasabai, Mohammed Gulam Nabi Alsath, T. Rama Rao
The housing effect is investigated in order to determine the reliability of the antenna when mounted in a vehicle. The performance of the antenna can be affected by several factors such as nearby conductors or another antenna. A metal plate is used to mimic the roof of the car. The metal plate is positioned in the xz- (case-1) and yz-planes (case-2) to investigate the effects of antenna housing. The size of the metal plate is fixed as 40 × 40 × 5 cm3, and the distance between the antenna and the metal plate is kept as 10 mm. Figures 16 and 17 represent the antenna element housing and its corresponding reflection coefficients. Figures 18 and 19 depict the MIMO antenna housing and its reflection coefficients, respectively. The simulated reflection and transmission coefficient characteristics show that the antenna performance remains consistent even in the presence of a metal plate.
Antenna Array Pattern Synthesis Using Metaheuristic Algorithms: A Review
Published in IETE Technical Review, 2023
An antenna is an aerial, sensor, or transducer that transmits or receives electromagnetic waves and is an essential component of the wireless communication system. In today’s digital world, there are billions of users who are accessing the wireless services through smart phones, laptops, iPad, and other smart internet of things (IoT) devices. Most of the developed countries are focusing on establishing 5G communication network so as to provide higher bandwidth and smooth internet services to their citizens. With the exponential increase in data traffic, researchers across the world are exploring new technologies such as cognitive radios and multiple-input–multi-output (MIMO) [1] antenna to meet the requirement of the present wireless communication system. MIMO uses antenna arrays to best utilize the spectral resources of millimeter-wave technology and provides more throughput, lower latency, and spectral diversity. Smart antenna [2] uses antenna array for estimating the direction of users and thereafter directing the beam in the desired direction also known as adaptive beamforming.
Ground penetrating radar applications and implementations in civil construction
Published in Journal of Structural Integrity and Maintenance, 2023
Macy Spears, Saman Hedjazi, Hossein Taheri
Another aspect to be considered is the antenna bandwidth, which is the frequency range that allows the antenna to properly function. Instruments of GPR are ultra-wide band (UWB) tools since they consist of a wide domain of frequency ranges, from 10 MHz to 3 GHz (Forte et al., 2014; Poluha et al., 2017). The electrical properties of the material determine the velocity in which the signal is transmitted, and the unit of time it takes for the information to be transmitted is proportional to the bandwidth (Al-Quadi et al., 2010). The use of a higher bandwidth or higher operating frequency results in a higher spatial resolution, which is defined as the system’s ability to detect differences between two objects, vertically or horizontally (Kot et al., 2021; Rial et al., 2009; Travassos et al., 2018). However, as the resolution increases, the signal’s penetration depth decreases. This trade-off is acceptable for applications where the target is close to the surface. For inspections that require penetration deep beneath the surface, a lower frequency can be used, but the resolution of results will decrease.