Current Issue : January - March Volume : 2019 Issue Number : 1 Articles : 7 Articles
Radio frequency (RF) measurement technology provides a relative navigation solution that can be of great importance to have\nsignificant potential for application to the satellite groups. With the development of the RF relative measurement sensors, it is\nfound that the antenna configuration of the sensors affects the precision of relative position and attitude measurement. This\nstudy proposes improvements to the precision of the sensors by the virtue of the optimal antenna configuration. Furthermore,\nthe concept of dilution of precision (DOP) is extended to the RF relative measurement sensors, and a new dilution called IDOP\nis proposed as a benchmark to determine the precision of relative position and attitude measurement in engineering applications\nof the space mission. In order to select the optimal antenna configuration in real time in a scene where the intersatellite position\nand attitude change dynamically, this study presents an optimal antenna configuration selection strategy and models the antenna\nconfiguration selection as a combinatorial optimization problem. Furthermore, the genetic algorithm (GA) with two encoding\nmechanisms is proposed to solve this problem. Finally, numerical results are presented to verify the robustness....
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In a broadband adaptive array antenna with a space-time filter, a delay filter is required before digital beam forming when the Frost\nalgorithm is used to obtain the weight vector. In this paper, we propose a Farrow structure instead of a direct form FIR structure to\nimplement the time delay filter since it can satisfy the demand for real-time update and is very suited for the FPGA platform.\nFurthermore, a new off-line algorithm to calculate the Farrow filter coefficient is presented if the filter coefficient is symmetric.\nFinally, simulations are presented to illustrate that the design methodology for the Farrow filter is correct. The simulations also\nprove that the Frost broadband adaptive antenna effectively mitigates the interferences with a Farrow filter....
Wearable antennas play an important role in transmitting signals wirelessly in body-worn\nsystems, helping body-worn applications to achieve real-time monitoring and improving the working\nefficiency as well as the life quality of the users. Over conventional antenna types, ultra wideband\n(UWB) antennas have advantages of very large operating bandwidth, low power consumption,\nand high data transmission speed, therefore, they become of great interest for body-worn applications.\nOne of the strategies for making the antenna comfortable to wear is replacing the conventional rigid\nprinted circuit board with textile materials in the manufacturing process. In this study, a novel\nthree-dimensional woven fabric integrated UWB antenna was proposed and fabricated with pure\ntextile materials. The antenna electromagnetic properties were simulated and measured and its\nproperties under bending were investigated. The antenna operated in a wide bandwidth from 2.7 to\n13 GHz with the proper radiation pattern and gain value. At the same time, the antenna performance\nunder bending varied in a reasonable range indicating that the antenna is prospectively applied\non the curved surfaces of the human body. Additionally, the current distribution of the antenna\nshowed that different conductive parts had different current densities indicating the uniqueness of\nthe three-dimensional textile-based antenna....
A symmetrically crossed-loop antenna featuring very high radiation efficiency across the entire LTE frequency bands for metalrimmed\nsmartphones with only 2mm ground clearance is proposed, analyzed, and verified. The employment of even and odd\nmodes is utilized to achieve wide bandwidth across 698â??960MHz (low-frequency spectrum), 1710â??2170MHz (middle-frequency\nspectrum), and 2300â??2690MHz (high-frequency spectrum). Empirical analysis confirms the crossed-loop topology results in a\n180° phase shift of the electric current distribution on the ground plane, resulting in enhancement of the radiation resistance. As a\nresult, the devised LTE antenna exhibits more than 48% to 75% total system efficiency across the entire band of interest, which is\nthe highest efficiency reported in literature for metal-rimmed smartphones with extremely small ground clearance....
This paper presents, for the first time, the hybrid use of loading techniques (which involve terminating the spiral arms with different\nstructures to give a resistive or capacitive effect) and a novel technique of cavity groove in order to enhance the performance of twoarm,\ncavity-backed, 2â??18 GHz spiral antenna. The antenna is made on Duroid 5880 and has the smallest form factor (50mm\ndiameter), meeting all the performance metrics, which are targeted for efficient performance of a spiral antenna for ultrawideband\n(UWB) applications. Measured results match the simulated results and show that by the utilization of hybrid loading\nand cavity groove, the gain is increased by a factor of 3.65 dBi and the axial ratio is improved by 2.73 dB at (2 GHz) as compared\nto a simple Archimedean antenna made on Duroid 5880, without increasing the size. The proposed antenna shows 2.25 dB\nmore gain and improved axial ratio performance as compared to a simple Archimedean spiral antenna made on Tmm4, without\nthe utilization of the hybrid techniques proposed earlier in the literature...
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