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A Phase- and amplitude-adjustable metasurface radome (PAMR) is proposed to achieve a wideband high gain and low radar cross-section (RCS) antenna with arbitrary sidelobe levels (AS-PGMA) at a 9.8 GHz operating frequency. The proposed PAMR is a special multilayer phase gradient metasurface lens whose amplitude distribution is modified based on the Dolph-Tschebyscheff technique. The AS-PGMA simulation results indicate that a high gain, low RCS, and low sidelobe level (SLL) antenna can be achieved over a broad impedance frequency bandwidth of 9.25–10.1 GHz with in-band average values of 17 dB, −7.5dBsm, −20 dB/−27 dB for gain, RCS, and E-/H-plane SLL, which are measured at 9.8 GHz as 17.4 dB, −9dBsm, and −23.02 dB/−27.91 dB, respectively. Additionally, a novel analytical method for calculating the RCS of the proposed PAMR and AS-PGMA is described and verified by measurement and simulation findings. Measurement results show that the E-/H-plane SLL of the AS-PGMA is improved by 12.2 dB/5.1 dB at the operating frequency, respectively, while its gain and RCS reduction are reduced by 1.6 and 2.1 dB, respectively. Moreover, RCS of the AS-PGMA is reduced over an ultrawide bandwidth of 1–20 GHz for orthogonal polarizations. The analysis, simulations, and measurements are all in good agreement. [ABSTRACT FROM AUTHOR]

In this paper, a dual-band 8 × 8 multi-input multi-output (MIMO) array antenna operating in 3.5 GHz band (3400–3600 MHz) and 5.5 GHz band (5150–5925 MHz) for 5G mobile handset is presented. The proposed hybrid antenna includes a comb-shaped monopole and an L-shaped open slot antenna which are symmetrically located on the inner surface of the side-edge frame of smartphone. Pattern diversity is achieved that can mitigate envelope correlation coefficients (ECCs) and improve the MIMO system performances. The prototype of proposed dual-band eight-element MIMO antenna is fabricated and experimentally measured. The results show that isolation <−10 and <−15 dB, respectively in the lower band and high band without any additional decoupling element are achieved and the desired bands are satisfied under the condition of −6 dB impedance matching. Moreover, the essential parameters for evaluation of the MIMO system performance such as the ECC, mean effective gain (MEG), and ergodic channel capacity are calculated. Furthermore, the influence of user's hand on the radiation characteristics of proposed MIMO antenna are also investigated and discussed. Based on the result, the proposed MIMO antenna is a good candidate for use in future 5G applications. [ABSTRACT FROM AUTHOR]

A novel theory based on the reciprocity theorem is presented for computing the plane wave scattered field of an arbitrary target, from its scattered field due to near-field illumination. The target is supposed to be illuminated by a transmitter probe on a cylindrical surface and the scattered near-field data is recorded in the near-field. The presented theory constructs a bridge between the scattered field due to the near-field illumination by a transmitter probe and that of plane wave illumination. Thus, referring to the definition of Radar Cross-Section (RCS) that assumes the incident field to be a plane wave, the RCS of the target can be analytically evaluated. For the verification of the proposed method, it is applied to an infinite conducting circular cylinder, which has an analytic solution for the infinite line source as a near-field source. Using the proposed theory the scattered field of such a target under plane wave incidence is evaluated, which is exactly identical to the same analytical scattered field under plane wave illumination. [ABSTRACT FROM AUTHOR]

In this paper, a novel SIW microwave sensor is designed to accurately determine the broadband complex permittivity of medium loss and dispersive liquids using a number of higher order modes in 11–20 GHz. To achieve a higher accuracy in characterization, the sensor is equipped with some methods such as Photonic Band Gap method, slow-wave via, and a new feedline, which enhances the quality factor for the higher order TE1,0,n modes. The operating principle of this sensor is based on the cavity perturbation technique, in which the resonant properties of the cavity are utilized to extract the dielectric properties of liquid under test. To provide a method to decrease the LUT consumption, a winding microfluidic channel is designed and embedded in the cavity. The channel increases the interaction between the induced electric field and the LUT. The accuracy of different perturbation technique for determination of permittivity is compared with each other. [ABSTRACT FROM AUTHOR]

Summary: In practical terms, direct data domain least squares (D3LS) beamforming algorithm performance is severely decreased by the array steering vector uncertainty. In this paper, we investigate the performance of D3LS approach for beamforming. Uniform linear antenna array radar of dipole antenna is considered in the presence of mutual coupling between the elements of the array. The performance of D3LS beamforming algorithm is severely affected by uncertainty caused by mutual coupling. In order to test the robustness of the D3LS approach against uncertainty, a quadratic inequality constraint is considered to optimize weight vector of D3LS beamforming algorithm. The convex optimization method is used to calculate optimized weight vector. The proposed convex optimization problem is solved by barrier method. It is a subset of Interior‐point numerical analysis methods. Several different scenarios are used to evaluate the proposed algorithm in MATLAB. [ABSTRACT FROM AUTHOR]

This paper presents a new analytical method based on mode matching technique for a waveguide full of anisotropic material with rods. It is proved that mode matching technique is applicable for the waveguide with anisotropic materials. The problem is considered as a 2D electromagnetic problem assuming no field variation normal to the waveguide length. Incident and scattered fields from circular cylinder rods in ferrite medium are expanded with cylindrical modes, and the fields in the waveguide ports are expanded using progressive and regressive modal summations. In both regions, extraordinary wave number is considered for the fields. Finally, the hybrid mode matching between guided and cylindrical modes is done by projecting continuity equations in the circular boundary containing the rod. The fast Fourier transform is used to solve the matching in the presented method. It is shown, that the new method runs faster than commercial software packages, with very good accuracy. [ABSTRACT FROM AUTHOR]