This article proposes a 4-port MIMO antenna for 5G mid band application resonating from 4.5-5.1 GHz which comes under n79 band, an FR1 5G NR band used in smart phones. The first design involves a single-element microstrip patch antenna with a diamond shaped slots and partial ground structure of size 30 × 43 × 1.6 mm³. Using this single element antenna as reference, a 4 port MIMO antenna is presented which operates at 4.9 GHz resonance frequency with proper spacing, resulting in much improved isolation between the elements. The proposed 4 port MIMO antenna is designed and fabricated over a commercially available low-cost FR-4 substrate having a relative dielectric permittivity of 4.4 and thickness of 1.6 mm. The W × L dimension of this MIMO antenna is 56 × 56 mm². Simulation of the S-parameters and radiation pattern of all purposed designs is performed using the CST studio suite, and test results of the return loss are presented using the Keysight N9916A 14 GHz vector network analyzer. Antenna gain is 3.8 dB, and efficiency is 87% with a low (less than 0.1) envelope correlation coefficient (ECC) between any two radiating elements, paired with a positive diversity gain (DG), indicating that the proposed antenna is well designed. As a result, the proposed antenna is an excellent candidate for deployment in 5G networks.

We study three comb-line antennas to increase the bandwidth for a 3 dB axial ratio criterion. Each antenna comprises linear radiation elements with loops and a coplanar feedline above the ground plane. First, we analyze a reference antenna with a straight feedline using the method of moments. Next, the straight feedline is transformed into a round one for a sequential rotation technique. It is found that the antenna has an increased bandwidth of 30%, which is three times as wide as that of the reference antenna. Last, we propose a novel antenna with a straight feedline. It is revealed that the antenna shows a 3 dB gain drop bandwidth of 29% (40% for the axial ratio bandwidth). The simulated results are validated by experimental work.

A rigorous solution is presented for description of the plane electromagnetic wave diffraction by two parallel slots in a perfectly conducting screen of finite thickness, placed before a dielectric layer, operating as a receiver of radiation in the near zone. The field in this layer is studied for the case of small obstacle dimensions being of the order of the wavelength. It is shown that the best spatial resolution of images from two slots in a dielectric layer is reached together with their optimal focusing, which can be determined by the method proposed earlier for one-slot diffraction.

This paper demonstrates a compact two-port multi-input multi-output optical nano-antenna with polarization diversity. The proposed antenna consists of a silicon-based radiating element that explores the possibilities of using a highly efficient dielectric resonator over the conventional metallic antennas at THz regime The specific position of the Gaussian pulse excitation generates the 90° phase difference between the field components travelling across the edges of the silver nanostrip feedlines. This generates the orthogonal field components which results in the achievement of circular polarization. Furthermore, any deviation in the excitation position at the port disturbs the field components resulting in linear polarization. This approach provides the polarization diversity using different excitation positions at ports. Considering the analytical stage of this proposed work, the detailed design guidelines and analysis are also discussed. The antenna provides circularly polarized radiations having 6.78% of 3 dB axial-ratio bandwidth and linearly polarized response using the optimized feeding positions at the respective ports for obtaining the polarization diversity performance. The isolation of more than 15 dB is maintained between the ports over the entire operating passband of the antenna. The proposed antenna with the optimized dimensions can be utilized for the optical C- and L-band applications.

For the research of 5G NR band mobile phone bezel antenna, this paper proposes an 8-Element Multiple-Input Multiple-Output (MIMO) handset bezel antenna design for 5G New Radio (5G NR) bands. Moreover, the MIMO antenna's array is implemented by loading 8 identical antennas (Ant1-Ant8) into the metal bezel of the smartphone to form an 8-antenna array for a sub-6 GHz 8×8 MIMO system. In this setting, each antenna unit is a slot antenna type consisting of a Chinese character ``卫''-shaped slot, as well as a 50 Ω micro-strip feeder; note that a satisfactory impedance matching is achievable in the upper-frequency band by loading a tuning stub on the feeder. The proposed 8-element antenna array covers 5G new radio (NR) band including N77 (3.3-4.2 GHz), N78 (3.3-3.8 GHz), N79 (4.4-5.0 GHz), and a Wi-Fi (2.4 GHz) band with a 10 dB impedance bandwidth. It is important to note that in addition to exhibiting ideal antenna efficiency and envelope correlation, the isolation between adjacent array elements is >10 dB, and the peak gain is 3 dBi. In summary, the influence of the user's hand on the antenna is analyzed to ensure the robustness of the MIMO antenna system in practical applications.

Thinner substrate designs of square and circular microstrip antennas using fractal variations of U-shape and half U-shape slot cut ground plane are proposed for circularly polarized response. The 1st, 2nd, and 3rd order fractal variations of slots on the ground plane are studied. The fractal slot cut variations degenerate patch fundamental mode into dual orthogonal resonant modes, and an optimum spacing between them yields circularly polarized characteristics. Amongst all the designs, circular microstrip antenna using the 1st order fractal U-slot design yields optimum result. It offers axial ratio bandwidth of 60 MHz (2.14%) with a broadside radiation pattern and peak gain of 5.5 dBi, on a substrate of 0.02λ_g thickness and patch area 1.44λ_g. Against the reported designs, the current work presents a low profile single patch circularly polarized configuration.

This study presents the generation of a scalable model based on measurement aided numerical calculations for MiMCap (Metal-Insulator-Metal Capacitor) structures with a 0.25 µm SiGe-C BiCMOS technology. Various MiM capacitor structures with several different area and peripheral sizes are fabricated in an in-house developed BiCMOS process. A set of fix-size models and a generic scalable model are developed based on numerical EM calculations. The validity of the constructed model is verified with the measurement results. The model includes the breakdown voltage ratings which are also extracted through the measurements. The model, EM simulations and measurement results are in good agreement.

This paper presents a new compact dual-band bandpass filter (BPF) with a stub-loaded resonator structure that can independently change its operating band to support GSM and WiFi applications for modern wireless communications. A short-circuit stub with a metal through hole is placed into the symmetrical resonator together with a pair of step impedance stubs and a pair of uniform open-circuit stubs. Inside the resonator, the open stubs fold in on themselves, minimizing the circuit for integration with other parts and enhancing the selectivity of the filter. Even-odd mode theory can be employed to investigate the circuit because of the resonator geometric symmetry. The first and second operational frequency bands can then be built using the calculated odd and even mode frequencies to match our requirements. The manufactured experimental dual-band filter is compared to the simulation results, and the statistics revealed good agreement. The calculated structural measures 0.13λ_g × 0.1λ_g.

Through wall radar imaging and detection applications are growing significantly. However, the target response is usually accompanied with a strong clutter which veils the target detection. In this paper, a new algorithm is proposed for clutter reduction and target downrange correction in through wall monostatic radar imaging. The proposed algorithm arranges the received radar signals in a matrix and then splits this matrix to frames. The frames are individually processed and filtered in frequency domain, then they are returned to time domain and merged together in a new matrix. The final step is enhancing the target response via a matched filter. The proposed algorithm performance is evaluated by target to clutter ratio (TCR), signal to clutter ratio (SCR), and downrange target position error (DTPE) in three different simulated scenarios. The simulation results exhibit the proposed algorithm capability in both removing the clutter and adjusting the target downrange to be with an evident appearance and accurate position. In the most complicated scenario which consists of two separated walls and a target behind them, using the proposed algorithm improves the performance in terms of TCR, SCR and DTPE by 49.7 dB, 70.7 dB, and, 7.6% respectively.

This paper presents a narrow notch band, flexible, wearable ultra-wideband antenna built on a jeans substrate. Prior to designing the antenna, the dielectric properties of the jeans substrate are experimentally investigated. The effects of antenna shape and substrate loss characteristics on resonant performances are discussed with reference to the notch characteristics. The proposed antenna is shaped like a cumulative rugged element, with two identical legs. The investigation of the designed antenna shows the operating frequency ranges (S₁₁ ≤ -10 dB) in 2.4-4.2 GHz and 5.86-10.7 GHz bands with notch properties in telemetry/mobile communications (4.4-4.99 GHz) and WLAN (5.15-5.85 GHz) band. Additionally, the prototype is investigated under on-body conditions. Measured results are also included for the validation of the designed prototype.

In this manuscript, a miniaturized Multi-Input Multi-Output (MIMO) antenna with dual-notch characteristics is designed for Ultra-Wideband (UWB) indoor positioning system. The proposed UWB MIMO antenna has a compact size of 35*35 mm² with four orthogonally placed antenna elements on the print circuit board (PCB) with FR4. Each radiating element utilizes the combination of a rectangle and an irregular pentagon, and etches two inverted L-shaped slits to generate two notches in WLAN (5.00 GHz-5.82 GHz) and X-band (7.11 GHz-8.20 GHz). On the grounding planes, the rectangle grounding units are modified into L-shaped branches, on which stepped open-circuit slots and right-angled triangle truncations are etched to broaden the impedance bandwidth. Furthermore, three equidistant rectangular decoupling slits are etched to improve the isolation. The measured results are in good agreement with the simulated ones, which shows an impedance bandwidth of 116.68% (2.96-11.25 GHz) with isolation better than 17 dB. The antenna also has excellent characteristics of good radiation characteristics, total active reflection coefficient (TARC), diversity gain (DG>9.99), low envelope correlation coefficient (ECC<0.005) and channel capacity loss (CCL<0.4 bits/sec/Hz), which can be used in portable UWB-MIMO indoor positioning system.

This paper presents a novel reverse salient pole flux controllable permanent magnet (RSP-FCPM) motor topology, and the motor rotor is reasonably designed to have reverse salient pole characteristics and flux controllable characteristics. After selecting the design variables for the RSP-FCPM motor using sensitivity analysis, a multi-objective genetic algorithm is applied for multi-objective optimization. The optimized RSP-FCPM motor is simulated and compared, and the results show that the optimal RSP-FCPM motor has better flux weakening capability, wider speed range, and constant power output area. it can solve the problem of difficult flux changes of the conventional interior permanent magnet motor, and other electromagnetic performances are also more advantageous. To confirm the reliability of the rotor structure during operation, a stress analysis of the rotor is performed, and the results show that the rotor structure can fully withstand high-speed and high-temperature conditions and can operate safely and stably. It also has more advantages in noise performance, which has great prospects for application in the field of electric vehicles.

A novel variable flux permanent magnet vernier machine (VFPMVM) is proposed by introducing the concept of hybrid excitation, and its flux modulation poles (FMPs) and excitation winding are emplaced in stator teeth and the adjacent FMPs, respectively. It can offer several merits, such as wide speed range operation through the processing of flux-enhancing and flux-weakening without increasing machine bulk, as well as the numbers of stator slot and rotor pole. Moreover, as one sort of flux modulation machine based on magnetic field modulation effect, VFPMVM features low speed, large torque, simpler mechanical structure and better utilization of PM materials than traditional flux modulation machines. The working principle of proposed machine is studied, and basic electromagnetic characteristics are calculated by finite element method, including no-load magnetic flux linkage, no-load back electromotive force, cogging torque, and output torque. In addition, the processes of flux-enhancing and flux-weakening are analyzed. Finally, one prototype with one kilowatt was built, and its static characteristics were tested. The results show that the proposed VFPMVM has the merits of high torque density, small cogging torque, and wide speed range, which is a promising candidate for electric vehicle direct drive field.

In wireless technology, microstrip patch antennas are often used in communication systems with various designs. However, the effect of geometrically folded antennas on wireless communication performance is unclear. To address this problem, an in-depth study of the flexible antenna parameters was performed through V-folding analysis. A systematic and complete analysis of the percentage of folding in patch antennas was performed. The folding of patch antennas is expected to become mandatory because patch antennas are integrated and molded according to specified object shapes. The designed antenna was operated at 0.1-5.0 GHz to investigate the folding performance in the frequency range of 1.00-3.78 GHz used in many wireless applications, such as the GPS, GSM, and LTE standards. A promising operating frequency for flat (unfold) antennas is 1.42 GHz with an achieved multiband bandwidth of 31.6 MHz, which shifted according to the folding angle but with good performance. The results of this study can be used to predict the performance of an antenna when it is placed on a product of any shape, according to the designed object pattern.

In underwater wireless sensor networks (UWSNs), the limited availability and non-rechargeability of sensor node batteries necessitated the advancement of energy optimization techniques. Optimal clustering is one such technique that reduces the energy consumption of the networks. In this letter, we propose optimal cluster compression technique jointly with energy harvesting. In optimal clustering compression, we perform optimal clustering of networks with singular value decomposition (SVD) as compression technique to reduce the redundant data generated at the cluster heads (CHs). Besides, adopting energy harvesting technique, node batteries are periodically recharged. The performance of the proposed model is evaluated in terms of network lifetime and throughput.

A compact novel lamp slotted upper WLAN band rejected ultrawideband (UWB) radiator integrated with Ku and partial K bands is reported. The intended radiator consists of a novel lamp slotted patch structure with a 50 Ω tapered microstrip feed line along with a novel semicircular defected ground structure (SCS-DGS). The size of the suggested radiator is 16×22 mm² with an impedance bandwidth ranging from 3.63 to 21.94 GHz to cover UWB integrated with Ku and partial K bands, and a novel via notched element is utilized to notch the upper WLAN band from 5.31 to 6.05 GHz. The proposed antenna has stable radiation patterns, consistent gain, and a peak radiation efficiency of 92.15% except for the notched band which mak it suitable for upper WLAN band notched UWB wireless communication applications.

This paper presents the mathematical formulation for the generalized closed-form expressions to calculate sideband power (P_SR) of a nonuniform period time modulated array (NTMA) antenna with volumetric geometry by using pulse shifting strategy. For the arbitrary array geometry, the generalized expression of P_SR is obtained by considering the universal omnidirectional element pattern in the form sin^aθ|cosθ|^b, a > -1, b > -1/2. Then, corresponding to different array structures such as linear, planar, and volumetric ones, the derived expression is simplified for different element patterns with possible combination of `a' and `b'. Through representative numerical results it is demonstrated that the obtained simplified expressions without hypergeometric function are useful to accurately calculate the amount of power losses due to sideband radiations with significantly less time than the conventional numerical integration (NI) method.

A new defected ground structure (DGS) with two transmission zeros is presented for the first time by loading the conventional dumb-bell-shaped (DBS) DGS with the comb-shaped structure. Equivalent circuits are developed and electric parameter extraction is derived. The low-pass filter (LPF) design method based on the proposed new DGS is given. The fabricated filter demonstrates a sharp, wide and high stopband rejection with an ultra-wide 20 dB rejection bandwidth of 21.9f_c and the sharp attenuation rate is more than 129.4 dB/GHz.

This article presents a broadband circularly polarized (CP) semi-annular ring-shaped printed monopole antenna for wireless applications. A semi-annular monopole with symmetric partial ground plane is designed to achieve the impedance bandwidth with a behaviour of linearly polarized (LP) radiation wave. To achieve the CP behaviour with broadband axial ratio (AR) bandwidth, an asymmetric stair shaped partial ground plane is incorporated in the semi-annular ring-shaped monopole structure. Different analysis of CP radiation is presented by analysing the surface current distribution, electric field distribution and also its mathematical modelling using CST-MWS solver. Moreover, an equivalent circuit model of the proposed monopole antenna is developed using Foster canonical forms. The measured -10 dB impedance bandwidth and 3-dB AR bandwidth are 8.78 GHz [3.22-12.0 GHz] and 2.21 GHz [7.58-9.79 GHz] respectively. The peak realized gain and antenna efficiency are 4.32 dB at 7.61 GHz and 82% at 4.83 GHz respectively. The proposed antenna can be suitable for C-band (4-8 GHz) and X-band (8-12 GHz) applications.

An Ultra-wideband Microstrip fed patch antenna with a defective ground surface is presented in this paper. The above-mentioned antenna comprises a T-slot in the ground plane and a Pi-slot in a rectangular patch. The proposed antenna is developed and modeled using the High-Frequency Structure Simulation tool on an RTDuroid 5880 substrate with a thickness of 1.6 mm and a dielectric constant of 2.2. A T-shaped defect is carved in the ground plane to enhance the antenna's radiation properties, gain, and bandwidth. A conventional Pi-slotted patch antenna operating at 9.74 GHz with a return loss of 19.7 dB is designed, followed by an ultra-wideband antenna embedded with a T-slot in the partial ground surface operating from 7.15 GHz to 10.925 GHz with an impedance bandwidth (S₁₁ < −10 dB) of 3.775 GHz. It showcases exceptional characteristics with a peak gain of 6.99 dBi at 8.95 GHz. A satisfactory agreement is found between the experimental data and simulation results. The proposed Pi-slot patch antenna with the defective ground has applications in radar, satellite, weather monitoring, and vehicle speed detection for law enforcement.