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Complex Aperture Theory
Published in Lawrence J. Ziomek, Fundamentals of Acoustic Field Theory and Space-Time Signal Processing, 2020
The term “beamwidth” refers to some measure of the width of the main lobe of a far-field directivity function (beam pattern). The beamwidth of a far-field beam pattern is the same whether the beam pattern is normalized or unnormalized. However, it is customary to work with normalized far-field beam patterns. The most common measure of beamwidth is the 3-dB beamwidth. Since the maximum value of the magnitude of a normalized far-field beam pattern is equal to 1, or 0 dB, the 3-dB beamwidth is defined as the width of the main lobe between those two points that correspond to magnitude values equal to −3 dB. Note that () 20log10(2/2)=10log1012=−3.01dB.
Radiation Mechanism
Published in Ahmad Shahid Khan, Saurabh Kumar Mukerji, Electromagnetic Fields, 2020
Ahmad Shahid Khan, Saurabh Kumar Mukerji
Figure 20.14 shows a number of constituents of a beam. It may have a main lobe, one or more side lobes, and a back lobe. The main beam will have a direction of maximum radiation, the directions in which the radiation reduces to half of the maximum and the directions of zero radiations. The angular distance between two half-power points is called the half-power beamwidth, and the angular distance between two zero-radiation points is called the beamwidth between the first nulls.
Dielectric Resonator Antenna (DRA)
Published in Rajveer S. Yaduvanshi, Gaurav Varshney, Nano Dielectric Resonator Antennas for 5G Applications, 2020
Rajveer S. Yaduvanshi, Gaurav Varshney
Axial ratio control using an absorber can help to control the beam width of an antenna as aspect ratio gives rise to higher mode generations. Operating at fundamental mode shall provide a particular beam width. This can be seen in 2D radiation patterns. When the same DRA is operated with higher order modes, the beam width shall get reduced and gain will be enhanced. This way DRA beamwidth control can be achieved. One can say that directivity is more when beamwidth is less and vice versa.
Performance Analysis of Dolph-Tschebyscheff Array for Different SLL and Array Length
Published in IETE Technical Review, 2023
Maloth Gopal, S. S. Patil, K. P. Ray
For the large Dolph-Tschebyscheff arrays, scanning near broadside with the range of side lobe levels from −20 to −60 dB, directivity and half power beamwidth are determined using beam broadening factor “f” which is given by [1], The Directivity of the Dolph-Tschebyscheff array is given by, and the Half Power Beam Width (HPBW) is given by, where R0 is the main-to-side lobe voltage ratio, “L” is the length of the array, “d” is the distance between elements and “θ0” is the elevation angle of the main beam. Here, d = λ/2, thus L = (N-1)λ/2. Figure 6 displays the plot of the computed directivity versus number of elements for various side lobe levels using the aforesaid equations. It indicates that as the number of elements increases, the directivity increases. For a given number of elements, the directivity is more for lower R0 than higher R0 because of the decrease in efficiency. For given N, when the side lobe suppression level increases, the directivity of the Dolph-Tschebyscheff array increases at first, then starts decreasing. The half power beamwidth, which increases with decreased directivity, is another characteristic that is affected by directivity.
A multibeam slot antenna using dual-layer metasurface
Published in Electromagnetics, 2021
Tingting Fan, Xinwei Chen, Guorui Han, Liping Han, Yufeng Liu, Wenmei Zhang
Based on the analysis for unit of metasurface, the radiation pattern of antenna 2 and proposed antenna are compared (the results of antenna 1 are neglected because it has similar radiation characteristic with antenna 2). Without losing generality, we show the result at 2.9 GHz when port 1 is excited in Figure 6. For convenience of observation, the normalized radiation patterns of the φ = 0° are also plotted in Figure 6c. As seen in the Figure 6a–c, the antenna 2 has a lower gain of 5.38 dBi, front-to-back ratio (FBR) of 4.23 dB, and the sidelobe level is about 3.84 dB. Moreover, the beam is basically distributed around the z-axis has a wider beamwidth of 83°. The maximum level points at (φ, θ) = (180°, 26°). While for the proposed antenna, the corresponding values are 8.69 dBi, 9.41 dB, and −2.27 dB. In addition, the main beam is steered to (φ, θ) = (180°, 23°) and the 3-dB beamwidth is 42°. The beamwidth is significantly reduced and the radiated beam is more concentrated.
A directional multicasting-based architecture for wireless sensor networks
Published in International Journal of Electronics, 2019
Directional antennas facilitate using very narrow portions spatially of the common transmission medium-air by the nodes that yield simultaneous transmissions to take place which would possibly collide if omnidirectionally carried out. This is achieved by directing the main beam with the increased gain to the desired direction that covers the intended user(s) while utilizing nulls towards other directions to prevent possible collisions (Alpesh & Patrick, 2001; Atmaca et al., 2008; Atmaca, Çeken, & Erturk, 2009; Chryssomallis, 2000). Facilitating simultaneous transmissions inherently increases the system capacity and ultimate throughput. Moreover, shrinking the beam-width increases the antenna gain that renders relaying the signals to the same range with lower levels or transmitting to further distance with the same power level. Obviously, reduction in power usage maximizes the network lifetime which is the major concern for WSNs (Arora & Krunz, 2007; Atmaca, Ceken, & Erturk, 2007; Park, Park, Song, & Pack, 2013; Ramanathan, Redi, Santivanes, Wiggins, & Polit, 2005).