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Basic Theory and Design of Printed Antennas
Published in Binod Kumar Kanaujia, Surendra Kumar Gupta, Jugul Kishor, Deepak Gangwar, Printed Antennas, 2020
Shilpee Patil, Binod Kumar Kanaujia, Anil Kumar Singh
The definition of radiation pattern as reported by IEEE Standards [24] is ‘the spatial allocation of a quantity that characterizes the electromagnetic field vectors generated by antenna’. Radiation pattern is also defined by Balanis [25] that is explain in terms of the position of observers a regular arc draw by a line or surface throughout all direction of radiation of antenna. The radiation pattern is represented in terms of 2D/3D space allocation of power flux density, field strength, radiation intensity, directivity, phase or polarization. An isotropic antenna is not feasible, but may be applied in the process of comparison with practical antennas to evaluate their performance, as a reference antenna. As shown in Figure 1.5, the radiation pattern gives the information about antenna beam width, side lobes’ features and antenna resolution.
Elements of Bioelectromagnetics
Published in Jitendra Behari, Radio Frequency and Microwave Effects on Biological Tissues, 2019
The mode of energy absorption in biological tissues or systems, as in the human body, contributes to the RF/microwave effect. This raises gives the question of whether a whole-body average absorption rate can be used as the only determining factor in evaluating biological effects of RF and microwaves. Other features of the radiation also need to be considered. A radiation diagram typical of a communications antenna is shown in Figure 6.1b. A paraboloid antenna is placed at the coordinate origin. The gain Gi(θ, ø) of the antenna varies with the direction (θ, ø). The gain of an antenna is defined as the ratio of the power transmitted by the antenna in a given direction to what which would be transmitted by an isotropic antenna (transmitting the same power in all directions) placed in the same location. It is usually expressed in decibels (dB).
The Fundamental Principles of Antenna Theory for V2I Deployments
Published in Fei Hu, Vehicle-to-Vehicle and Vehicle-to-Infrastructure Communications A Technical Approach, 2018
In Figure 11.2b, the azimuth plane is a hypothetical antenna pattern with a signal strength of +5 decibels relative to isotropic (or +5 dbi). The term isotropic has origins from “iso” meaning the same and “tropic” meaning direction. The isotropic antenna has a pattern that is equal in radiation all directions. In Figure 11.2a, the antenna pattern is characterized in terms of lobes: the main lobe, side lobe, and back lobe. The main lobe radiates in the direction of 0 degree if we continue to assume the antenna is orientated in the direction of 90 degrees, while the back lobe is radiating in the direction of 180 degrees. The maximum radiation is in the direction of 0 degree. The signal strength becomes weaker when moving in the direction of 30 and 330 degrees. In other words, there is a tremendous signal loss when a measurement is made outside of the two-leaved rose curve. In this hypothetical case, the back lobe is identical to the main lobe in signal strength and in the opposite direction. The side lobes radiate in the direction of 90 and 180 degrees with a signal strength at −15 dbi. The side lobes are a region of undesirable radiation and are several times lower in magnitude than the maximum radiation power of the main beam. In reality, the antenna pattern may be comprised of several side lobes but the manufacturer’s technical specification may only list the first and nearest (or highest) side lobe to the main beam.
Design and simulation of a novel 3-point star rectifying antenna for RF energy harvesting at 2.4 GHz
Published in Cogent Engineering, 2021
J. O Olowoleni, C. O. A Awosope, A. U Adoghe, Okoyeigbo Obinna, Udochukwu Ebubechukwu Udo
The gain and directivity of a designed antenna are two very important antenna performance indicators, typically measured in reference to an isotropic antenna. i.e. an “ideal” antenna which receives or transmits energy uniformly in all directions. For a receiving antenna, the gain best describes the antenna’s ability to capture incident radio/microwaves coming from a particular direction, in comparison to an isotropic antenna. The antenna’s directivity on the other hand is a measure of the degree to which the antenna’s radiation can be concentrated into a specific direction as against being uniformly spread in all directions. The simulated gain and directivity values achieved for the designed square patch microstrip antenna were 5.15101 dBi, and 6.2903 dBi respectively. However, for the proposed “3-point star” antenna design, gain and directivity values of 6.28 dBi and 7.54 dBi respectively were achieved. A combined plot of the antenna gain and directivity for the two featured antenna designs are presented in Figure 12 and Figure 13
PSO AND IFS TECHNIQUES FOR THE DESIGN OF WEARABLE HYBRID FRACTAL ANTENNA
Published in International Journal of Electronics, 2021
Sandeep Singh Sran, Jagtar Singh Sivia
Gain of the antenna defines how much the antenna radiates RF waves in the desired direction as compared to the isotropic antenna. The ratio of the peak value of radiofrequency waves radiated by the proposed antenna to the isotropic antenna is called gain. The dB scale is used to express this ratio. Suppose if the gain is 3 dB, then it means that the proposed antenna has 3 dB higher gains than that of an isotropic antenna with the same power input. Figure 10 shows the three-dimension graph of the proposed MKWHFA at resonant frequencies. The proposed antenna has gain 5.61 dB, 8.55 dB, 5.07 dB, and 3.24 dB at 2.4508 GHz, 5.4005 GHz, 6.6503 GHz and 8 GHz resonant frequencies respectively.
A directional multicasting-based architecture for wireless sensor networks
Published in International Journal of Electronics, 2019
Omni-directional also called isotropic antennas radiate and receive signals in every direction at equal energy levels. Propagating signals in undefined direction manner causes just a small fraction of the original radiated energy to be caught by the receiver (Korakis, Jakllari, & Tassiulas, 2008). The energy is unnecessarily consumed owing to this untargeted signal propagation which ultimately results with a shortage in coverage range. The inverse-square law states that a physical intensity is inversely proportional to the distance of the source of that intensity. When a point source radiates energy in three-dimensional space at equal energy levels in all directions, as the signals travel spherically further from the source, the intensity will spread out over a larger area. The area of the sphere that the original intensity spread overextends because of the reason that, the distance from the source indeed is the radius of the sphere. Thus, the original intensity level gets weaker by going further from the source. Three models have been mostly referenced in the literature to identify the predicted power level at the receiver: free-space, two-ray ground reflection and shadowing model. When the transmitter and receiver are apart from each other less than the crossover distance (dc) that is clarified in Equation (1), free-space model (Equation (2)) better predicts the received power since at this proximity there is a single nearly-clear line-of-sight path between the communicating pair (Dang, Hong, Lee, & Lee, 2012; Friis, 1946; Gajurel, Malakooti, & Wang, 2007; Hekmat & Van Mieghem, 2004; Prasad, 1998; Rappaport, 1996; Zhu, Guo, Yang, & Conner, 2004).