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Problems of Design and Placement of Antennas
Published in Boris Levin, Antennas, 2021
In principle, the array may consist of active and passive radiators. But the use of passive radiators requires the development of switched reactances, which must be designed for high power and also tune in the frequency range. At the same time, phasing of active radiators can be performed in pre-amplification stages, i.e., at a low power level. Therefore, preference should be given to the array from active radiators. It is also advisable to use uniform arrays, in which the amplitudes of the currents in the radiators are the same, and the phases vary linearly. It is known that one can optimize the radiation pattern of the antenna array, i.e., to select the amplitudes of currents in separate radiators to reduce the width of the main lobe of the array and to lower the level of the side lobes. However, the implementation of arrays with optimized directional patterns in a ship is difficult, since the influence of the surrounding metal bodies significantly distorts their shape.
Antennas
Published in J. Dunlop, D. G. Smith, Telecommunications Engineering, 2017
However, some convention must be agreed upon, and that normally used is to define the beamwidth as the angular separation, in a given plane, between the points on either side of the main lobe that are 3 dB in power below that of the maximum. On an E field radiation plot, which has a normalized maximum of unity, the beamwidth is between those points on each side of the main lobe which have field values of 1/√2.
Synthesis of Directional Radiators
Published in Boris Levin, Antenna Engineering, 2017
As already mentioned, one of the important tasks of antenna engineering is creating a radiator, which ensures in a wide frequency range a field maximum in the plane perpendicular to the radiator axis. An ordinary linear radiator fails to meet this requirement: if the radiator arm is larger than 0.7λ, the radiation in the plane, perpendicular to the antenna axis, decreases. In this case one can use V-antenna formed by two converging inclined wires. If arm length L is greater than 0.7λ, an ordinary V-antenna has preferential radiation along the bisector of the angular aperture. However, the side lobes of the directional pattern increase with growing frequency, and the main lobe of this pattern diminishes in the antenna plane. If the arm length is greater than about 1.251, the main lobe splits, and the radiation along the bisector sharply decreases.
Acoustic response characterization of thermoacoustic CNT thin film arrays
Published in Journal of Thermal Stresses, 2018
Wang Xu, Zhenhuan Zhou, Zhenzhen Tong, C.W. Lim, Xinsheng Xu
To facilitate the characteristics analysis of ultrasonic transducer array, the beamwidth and side-to-main lobe ratio are introduced. The beamwidth is defined as the distance between the two zero-crossing points of the main lobe in the -axis, one at the left-end and the other at the right-end of the main lobe. The maximum pressure occurs in the main lobe direction such that a narrow lobe width will produce a well-defined beam directivity. The side-to-main lobe ratio is quantitatively represented by the highest amplitude ratio between the peak side lobe and the main lobe. Acoustic energy leaks through the side of the ultrasonic transducer array. Hence, it is desirable to suppress the side-lobe amplitude in order to improve energy efficiency. The material properties used in the examples at are listed in Table 1.
Performance improvement of antenna array element for mobile communication
Published in Waves in Random and Complex Media, 2023
The half-power beam width of the antenna is shown by the efficiency of the polar plot in Figure 7. The antenna has a 72.5-degree half-power beam with a 6.5-dB main lobe and a −18.5-dB side lobe. The antenna's half-power beam width is 40.5 degrees, with a 25.6 dB main lobe and a −19.8 dB side lobe. The antenna gain and strength have both enhanced with the component array. (a)–(d). Radiation pattern of E-plane and H-plane antenna.