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Design and Characterization of the Radiating Elements
Published in Brijesh Iyer, Nagendra Prasad Pathak, Multiband Non-Invasive Microwave Sensor, 2018
Brijesh Iyer, Nagendra Prasad Pathak
One of the major factors that differentiate the antenna from others is its radiation pattern. Hypothetically, it is assumed that the isotropic antenna radiates equally in all directions. On the other hand, an omnidirectional antenna has a nondirectional pattern in azimuth and a directional pattern along the direction of elevation. In contrast, a directional antenna is one that has its radiation pattern concentrated in some specific direction only. It inherently acts as a filter for the directions other than it is intended for. The E-plane pattern is defined as the radiation pattern in a plane having the electric field vector and the direction of maximum radiation. The H-plane pattern is the radiation pattern in the plane containing the magnetic field vector and the direction of maximum radiation.
Sensor Systems for Indoor Position Computation
Published in Krzysztof W. Kolodziej, Johan Hjelm, Local Positioning Systems, 2017
Krzysztof W. Kolodziej, Johan Hjelm
Where the wireless signals are digitally modulated, an adaptive equalizer may be deployed at the receiver. Adaptive equalizers pass the receive signal through a tapped delay line. The tap take-off parameters are adaptively adjusted to cancel out echoes. As a further alternative, directional antennas may be used at one of or both the transmitter and receiver. At the transmitter, a directional antenna limits the number of paths that the transmitted wireless signal may take. At the receiver, a directional antenna reduces the number of paths from which wireless signals can be received. In either case, the direct signal path can be strengthened in relation to the reflected or echo signals. However, directional antennas are inconvenient and have limited use because they must be oriented to direct or receive the wireless signals.
Antennae
Published in Le Nguyen Binh, Wireless And Guided Wave Electromagnetics, 2017
An antennae tower is a tall structure to support antennae as aerials for telecommunication and broadcasting. The first tower was constructed in Munich Olympic Park for the television broadcasting purposes of the 1972 Olympics. A dipole antenna is a simple antenna usually constructed from two wires in opposite phases positioned end to end with respect to each other. A horn antenna is a type of directional antenna shaped like a horn. An omnidirectional antenna is an antenna system that radiates power uniformly in all directions in one plane. A parabolic antenna is an antenna shaped like a parabola in one or both planes.
An efficient multiple access control protocol for directional dense urban traffic surveillance system
Published in Journal of Intelligent Transportation Systems, 2020
Zhongjiang Yan, Bo Li, Qianqian Li, Mao Yang
Directional antenna concentrates the wireless signal in a specified direction, such that the received power of the receiver can be enlarged, and the data rate of the directional communication link can be increased. The directional range extension networks are studied (Macleod & Margetts, 2016; Shake, 2017; Shake & Amin, 2017). An aircraft with a directional antenna acts as a relay (Macleod & Margetts, 2016) of the ground nodes, to expand the communication range of the ground network, and to increase the interconnectivity of the whole network and the availability of the communication links (Shake & Amin, 2017). Proulx et al. (2017) stated that in military and civilian networks, the use of directional antennas will reduce the probability of detection, and increase the anti-interference capability. However, at the same time in that scenario, there may be a long distance (more than hundreds of kilometers) between nodes, so the propagation time is usually much larger than the packet transmission time, which causes the communication time (between the transmitter and the receiver) extension problems (CTEP). Furthermore, the CTEP makes the random multiple access protocol based on physical or virtual carrier sensing multiple access protocol inefficient (Proulx et al., 2017). For example, the carrier sensing multiple access with collision avoidance/detection (CSMA/CA or CSMA/CD) belong to that category.