Current Issue : January-March Volume : 2023 Issue Number : 1 Articles : 6 Articles
In this design, a novel inverted F antenna with a low profile feed structure is proposed for millimeter-wave (mmW) applications. The array element consists of a printed inverted F antenna and a L-shaped parasitic deflector, approximately forming a structure similar to the Yagi-Uda antenna. The gain could be increased and the impedance bandwidth could be broadened by the structure. And, it is important to realize the miniaturization of the antenna element by bending the parasitic deflector based on the traditional deflector without affecting the performance. The proposed antenna has a low feed substrate height (0.254mm0.02λ0), which makes it easy to integrate with planar circuits. As proof, a 1 × 4 array model with an impedance bandwidth of 20.5% (23.0–28.3 GHz) is designed and measured. The inverted F array demonstrated is an important candidate for mmW applications due to its wide bandwidth, miniaturization, ease of integration with planar circuits, and low manufacturing cost....
A low-profile (LP) metasurface antenna is proposed for broadband circularly polarized (CP) operations. The metasurface radiator, formed by a 5 × 5 array of square patches, has a microstrip line fed at its bottom through a shorted annular-ring slot centered on the ground plane. First, the characteristic mode analysis (CMA) methodology is employed to examine the intrinsic modes of the metasurface. Subsequently, a pair of mutually orthogonal modes is selected and excited by the feeding structure with a 90° phase difference to produce CP radiation. For the purpose of verification, a prototype antenna is developed, and the obtained data reveal that the antenna exhibits an impedance bandwidth of 43.9% ranging from 4.8 to 7.5 GHz (S11<−10 dB). The 3-dB axial ratio bandwidth is 22.2% in the range of 5.6–7 GHz, among which a satisfactory left-handed CP radiation is achieved, and the maximum gain in the broadside direction reaches 9.3 dBic at 6.9 GHz....
In this paper, the precoders capable of maximizing the weighted sum rate (WSR) for multicell scenarios under power budget constraint conditions per cell were considered based on the MIMO system performance. This rate is strongly affected by intracellular interference, so we recommend using coordinated beam forming (CBF). If the number of user equipment provided per cell is small enough to the number of transmit antennas, simple linear beamformers, such as matched filter (MF), achieve higher performance rates. In general cases, two algorithms meet the best performance in terms of the total achievable rate; these are KG (Kim Giannakis) and WSMSE (Weighted Sum Minimum Squared Error) algorithms. In the KG method, the objective function of the sum rate is suggested to be divided into two functions, one function for the desired user rate and the other for the sum rate of the remaining users. In the WSMSE algorithm, maximizing the sum rate is solved by redefining it as the problem of minimizing the MSE (Mean Square Error) function. These functions are convex and nonconvex functions, respectively. In the proposed method, the WSMSEs were modified to reduce the complexity and calculations to provide optimal performance in beamforming....
An improved power-only measurement method is proposed to calibrate phased arrays, which is aimed at solving two remaining problems: little contribution of one antenna element’s phase shifting to the whole array’s power and the ambiguity of solutions. The method includes four steps. Firstly, the random distributed phase of each element is adjusted to guarantee that it is −90° to +90° relative to the reference element. Secondly, the proper number of the elements shifting their phases together is approximately determined. Then, an invertible matrix is formed from the standard Hadamard matrix to split the array into different groups, which applies to an arbitrary number of elements; Finally, the array gets calibrated with an existing method. Numerical simulations and experiments are conducted to validate the effectiveness of the proposed method....
In this paper, a wearable ultra-wideband (UWB) microstrip antenna is designed to meet the demand for Wireless Body Area Network (WBAN).This is a wearable textile antenna, which was formed on a jeans fabric substrate to reduce surface-wave losses. The single-fed circular strip monopole antenna provides good impedance matching over the entire UWB frequency range of 2.910.6 GHz. The dielectric constant εr 2.2, and the loss tangent tan δ 0.04 of the jean substrates are measured by using the coaxial ring method. Theproposed antenna consists of an improved circular radiation patch with the defective ground structure to expand the frequency band of the antenna and improve the radiation characteristics of the antenna with small dimensions of 20 × 30 × 1.4mm3. In addition, structural deformation of the proposed antenna is performed to analyze the flexibility of the proposed antenna. The simulated SAR values follow the FCC limit, making it most suitable for wearable applications....
An ultra-wideband dual-polarized antenna covering multiple communication standards such as LTE700/GSM850/GSM900 is proposed in this paper. The antenna consists of two dipoles that are perpendicularly placed to each other. The two dipoles can generate +45°/−45° linear polarizations, respectively. Dual-loop structure is utilized as the arm of the dipole, while four parasitic patches with shorting walls are coupled to the dipoles to extend the operating bandwidth. The measured results show that the antenna has an impedance bandwidth of 101.4% (0.54 GHz–1.65 GHz) with a reflection coefficient less than −10 dB. The isolation between the two ports is larger than 22 dB, and the cross-polarization is less than −20 dB over the band. Good unidirectional radiation patterns are obtained....
Loading....