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An Overview of Smart Antenna Technology for Wireless Communication
Published in Prashant Ranjan, Ram Shringar Rao, Krishna Kumar, Pankaj Sharma, Wireless Communication, 2023
Prashant Ranjan, Ram Shringar Rao, Krishna Kumar, Pankaj Sharma
In this simplest technique, basic switching function connected between predefined radiated beams of an array or separate directive antennas play an important role. How accurately and quickly the subscriber’s radio link is connected to the best radiated beam (the subscriber resides best signal) without any degradation to voice quality, depends only on the performance of switching matrix. The receivers take the radio frequency signals from the multibeam antennas or array antennas and select the radiated beam to provide the best signal to noise ratio (SNR) or received signal strength. Normally, each beam of multibeam antennas has roughly 2-7dB more directive gain compared to the traditional antennas. Due to the high directivity of the antenna, achieved interference suppression and increased antenna gain. Switched beam antenna is implemented easily in existing cell structures but it contributes a limited improvement.
Theories of Synthetic Aperture Radar
Published in Maged Marghany, Automatic Detection Algorithms of Oil Spill in Radar Images, 2019
where P0 is the power radiated by an antenna device when irradiated by undeviating field of power density SI(x) watts per square meter. Equation 6.2 reveals that the power received by an antenna (in watts) is equivalent to the power density of the electromagnetic energy (in watts per square meter), multiplied by its aperture (in square meters). The greater an antenna’s aperture, the extra power it can gather from a particular electromagnetic field. To actually attain the expected power accessible to P0 polarization of the incoming waves must match the polarization of the antenna, and the load (receiver) must be impendent rivaled to the antenna’s feed point impedance. Ae can be implemented to determine the function of a transmitting antenna also. In this view, Ae is a function of the direction of the electromagnetic wave relative to the alignment of the antenna, since the gain of an antenna G fluctuates in relation to its beam patterns. One of the key parameters of an antenna gain is directivity. In this context, directivity is a constraint of an antenna or optical system, which quantifies the level to which the beam emitted is focused in a single direction. Moreover, it computes the energy density the antenna emits in the path of its strongest emission, as opposed to the energy density emitted by means of a perfect isotropic radiator (i.e., which emits homogeneously in entire directions) radiating the identical entire power [83–86].
Antenna systems
Published in L. Tetley, D. Calcutt, Understanding GMDSS, 2012
The vertical driven element alone would possess an omnidirectional radiation pattern. This pattern is modified by the addition of parasitic elements placed at 0.1 λ wavelength from the driven element. The reflector, placed behind the driven element, is, at 0.55 λ slightly longer than the active element, and has the effect of reducing reverse propagation to a minimum. The director, placed in front of the driven element, is, at 0.45 λ slightly shorter than the active element, and directs the radiation pattern along the antenna axis. Gain is thus achieved by adding more directors to shape the radiation pattern along the axis. However, as gain is increased the beamwidth is decreased, thus creating greater directivity.
Implementation of the Metamaterial Multiband Frequency Reconfigurable Antenna for IoT Wireless Standards
Published in IETE Journal of Research, 2023
Ritesh Kumar Saraswat, Mithilesh Kumar
The experimental radiation efficiency of the antenna is obtained by using an anechoic chamber, where a small amount of power is fed to the antenna with the help of the feed pads and measure the strength of the radiated electromagnetic field in the surrounding space. The proposed design radiates the 22–83% of the energy fed to it (−3 to −2.2 dB) (efficiency = total emitted energy/supply energy). According to the IEEE standards, radiation efficiency is defined as “the ratio of the total power radiated by an antenna to the net power accepted by the antenna from the connected transmitter”. Due to the reflectivity (mismatch) at the antenna, the net power decreases from the forward power from a major portion of the energy back to the source. Antenna gain is directivity plus (total) efficiency in dB. The measured radiation efficiency is attained in an anechoic chamber with the help of a vector network analyzer (VNA). A power meter is also connected with this arrangement to measure the power supplied to the antenna and the E field at the selected sampling points. A calibrated field probe or antenna is required for the E field measurement as well. A VNA is needed to measure the reflection coefficient of the antenna.
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.
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