Yes / In this paper, single-element and MIMO microstrip antenna with two pairs of unequal slits is proposed as a circularly polarized antenna with negligible back radiation for 5G mid-band handsets. The unequal pairs of slits are engraved on the antenna patch to guarantee the presence of the circular polarization (CP). The proximity-coupled feeding technique is used to excite the proposed microstrip antenna in order to provide larger antenna -10 dB bandwidth which approaches 10.8% (3.48-3.87 GHz). A novel analysis technique is proposed in this paper that demonstrates the 3D axial ratio pattern in order to generate CP in the broadside direction without affecting the structure of the ground plane which ensures weak back radiation. The 3 dB axial ratio bandwidth (ARBW) is found to be equal to 4.1% extended along the range (3.58-3.73 GHz). To make the design more compatible with the 5G mid-band handsets, the 2 × 2 MIMO structure of the proposed antenna with reduced mutual coupling (less than -20 dB) is also presented in this work. The simulation and measured results are in good agreement, and both verify the CP characteristics and the weak back radiation of the proposed antenna. / This paper is partially funded by British Council “2019 UK-China-BRI Countries Partnership Initiative Programme” with project titled “Adapting to Industry 4.0 Oriented International Education and Research Collaboration”.

No / In this paper the sensitivity of the decoupling matrix used for mutual coupling compensation in small size uniform circular arrays has been studied. The compensation matrix is calculated using the receiving mode technique for a 5-element uniform circular array and applied to two groups of direction finding algorithms, namely phase comparison-based (interferometry) and subspace-based algorithms. In the tracking application considered the receiver array is deployed on a car roof or aircraft, so the geometry of the platform influences the compensation results. In this work, the effect of different ground plane geometries in terms of the standard deviation of angular error for each estimation algorithm using simulation results is investigated. The results show that the calibration conditions used to determine the compensation matrix affect the AOA estimation accuracy.

No description available.

no / This study presents an investigation of the mutual coupling between two printed elements antenna for a multiple-input-multiple-output (MIMO) antenna performance. It consists of two crescent shaped radiators placed symmetrically, and a neutralization line is applied to improve the mutual coupling. Theoretical and experimental characteristics are presented and compared. The antenna yields an achieved impedance bandwidth of 18.67 % (over 2.04–2.46 GHz) with a reflection coefficient <−10 dB and mutual coupling minimization of <−20 dB in addition to a reasonable and stable radiation pattern and envelope correlation.

No / This paper presented a planar printed multiple-input-multiple-output (MIMO) antenna with a dimension of 100 x 45 mm2. It composed of two crescent shaped radiators placed symmetrically with respect to the ground plane. Neutralization line applied to suppress mutual coupling. The proposed antenna examined both theoretically and experimentally, which achieves an impedance bandwidth of 18.67% (over 2.04-2.46 GHz) with a reflection coefficient < -10 dB and mutual coupling minimization of < -20 dB. An evaluation of MIMO antennas is presented, with analysis of correlation coefficient, total active reflection coefficient (TARC), capacity loss and channel capacity. These characteristics indicate that the proposed antenna suitable for some wireless applications.

No / A printed crescent-shaped monopole MIMO antenna is presented for handheld wireless communication devices. The mutual coupling between the two antenna elements can be minimised by implementing a I-shaped common radiator. Both the simulated and measured results agree that the antenna covers the operating frequency band from 1.6 to 2.8 GHz with the return loss and isolation better than 10 dB and 14 dB respectively. To further verifying the MIMO characteristic including far-field, gain, radiation efficiency, channel capacity loss and envelope correlation, the results confirm that the antenna can operate effectively in a rich multipath environment.

Yes / A metasurface based decoupling structure that is composed of a square-wave slot pattern with exaggerated corners that is implemented on a rectangular microstrip provides high-isolation between adjacent patch antennas for Synthetic Aperture Radar (SAR) and Multi-Input-Multi-Output (MIMO) systems. The proposed 1×2 symmetric array antenna integrated with the proposed decoupling isolation structure is designed to operate at ISM bands of X, Ku, K, and Ka. With the proposed mutual coupling suppression technique (i) the average isolation in the respective ISM bands listed above is 7 dB, 10 dB, 5 dB, and 10 dB; and (ii) edge-to-edge gap between adjacent radiation elements is reduced to 10 mm (0.28λ). The average antenna gain improvement with the metasurface isolator is 2 dBi. / H2020-MSCA-ITN-2016 SECRET-722424 and the financial support from the UK Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E0/22936/1

yes / Size constraints and mutual coupling on the performance of a two-element PIFA assembly are investigated for a design frequency of 2.4 GHz. A benchmark antenna assembly, employing a normal metallic ground plane is compared with an EBG modified ground plane. The height of the antenna elements over the EBG is optimised, and an isolation factor of 9.12 dB is achieved for a gap of 2.5 mm. Prototype structures have been constructed and measured for both cases.

Wideband phased arrays require very tight element spacing to permit wide angle scanning of the main beam over the wide bandwidth. The consequence of tight spacing is very high mutual coupling among the elements in the array. Previous efforts by Virginia Tech Antenna Group has shown that the strong coupling can be utilized in arrays to obtain broadband frequency response while maintaining a small element spacing. However, mutual coupling between elements in a tightly coupled array can sometimes dramatically change the operating frequency, bandwidth, and radiation pattern from that of the single isolated element. Thus, there are some fundamental questions that remain regarding the effective operation of highly coupled arrays for beam forming, beam scanning, and aperture reconfiguration. Existing antenna pattern analysis techniques including the active element pattern method are inadequate for the application in highly coupled arrays. This dissertation focuses on the development of a new antenna array analysis technique. The presented method is based on the scattering parameter network descriptions of the array elements, associated feed network and the active element patterns. The developed model is general. It can be applied to an array of any size and configuration. The model can be utilized to determine directivity, gain and realized gain of arrays as well as their radiation efficiency and impedance mismatch. Using the network model, the relationship between radiation pattern characteristics and the input impedance characteristics of the array antennas becomes clear. Three types of source impedance matching conditions for array antennas are investigated using the model. A numerically simulated array of strip dipole array is used to investigate the effects of various impedance matching methods on the radiation pattern and impedance bandwidth. An application of network analysis is presented on an experimental investigation of $3\times 3$ Foursquare array test bed to further verify the concepts. / Ph. D.

The effect of mutual coupling between elements plays a crucial role to the performance of the antenna arrays. The radiation patterns of antenna arrays will be altered by the coupling effect from the adjacent elements thus reducing the accuracy and resolution in direction finding application. This research developed and validated the novel 3-D Algorithm to calculate the far-field pattern of dipole arrays arranged in three dimensions and in any configuration (both in straight and slanted position). The effect of mutual coupling has been accounted using the Induced EMF method. The computation is performed on 2x2 parallel dipoles and 12 dipoles arranged at the edge of a cube. The results are validated with other electromagnetic techniques such as Method of Moment (MoM) and Finite Difference Time-Domain (FDTD). Then, a 2x2 dipole array is chosen for beam steering and experiment validation due to its ease of implementation and feeding network. The array optimisation to control the pattern is performed using a genetic algorithm. The far-field pattern computed using the 3-D algorithm might be less accurate than other 3-D electromagnetic techniques but its array optimisation is faster and efficient. The simulation and measurement results are in good agreement with each other confirmed the validity of the 3-D algorithm.