This paper introduces new compact microstrip line fed dual-band printed MIMO antennas resonating at 28 GHz and 38 GHz which are appropriate for 5G mobile communications. The first design in this work is a two-element conventional rectangular microstrip patch antenna with inset feed intended for 28 GHz and 38 GHz bands. The second design is symmetric dual-band two-element MIMO slotted-rectangular patches via microstrip inset fed lines. The dual-band response is attained from inverted I-shaped slots inserted in main patches. The third design is symmetric dual-band four-element MIMO antenna with inverted I-shaped slotted rectangular patches. A slot formed DGS is inserted in the partial rectangular ground plane. The substrate size is 55 x 110 mm², while the introduced antennas have very modest planar configurations and inhabit an insignificant area which make them fit easier within handset devices for the forthcoming 5G mobile communications. Better return losses and larger bandwidths are realized. The MIMO antennas have low mutual coupling without using any added constructions. The antenna systems offer appropriate values of directivity, gain, and radiation efficiency with anticipated reflection and correlation coefficient characteristics which are seemly for 5G mobile applications. The antenna systems are fabricated by a photolithography process that uses optic-radiation to copy the mask on a silicon slab by the aid of photoresist layers and measured using Vector Network Analyzer ZVA 67 (measures up to 67 GHz frequency) with a port impedance of 50 Ω.

In this article, a parasitic element structure is proposed to reduce the mutual coupling in a miniaturized microstrip dual-band Multiple-Input Multiple-Output (MIMO) antenna, which resonates at (7.8 GHz) for X-band and at (14.2 GHz) for Ku band applications. The design of the primary antenna consists of two identical radiators placed on a 24×20 mm² Fr-4 substrate, which are excited by orthogonal microstrip feed lines. In addition, a single complementary split ring resonator (S-CSRR) is used to improve the performance of proposed antenna. Simulation and measurement were used to study the antenna performance, including reflection coefficients, coupling between the two input ports, radiation efficiency and the radiation pattern. The measured results show that the proposed antenna achieves two operating bands with impedance bandwidths (|S₁₁| ≤ -10 dB) of 560 MHz (7.6 to 8.16 GHz) and 600 MHz (13.8 to 14.4 GHz) and mutual coupling (|S₁₂| < -26 dB), which are suitable for X/Ku band applications.

Compressed sensing (CS) is utilized in antenna measurements. The antenna data are compressed using the CS method, and the performances of different sparse and recovery algorithms of CS are used to solve antenna measurements. Experiments are conducted on various types of antennas. The results show that efficiency can be greatly improved by reducing the number of measurement points. The best reconstruction performance is exhibited by the Discrete Wavelet Transform (DWT) algorithm combined with the Compressive Sampling Matching Pursuit (COSAMP) algorithm.

In this paper, by applying topological theory, we evaluate some left-handed unit structures. Based on the classification of topological deformation, the laws and characteristics of potential electromagnetic parameters are captured. The original left-handed material unit is realized by using a circular C-shaped coupling ring, the whose whole size is 10 × 10 × 0.5 mm³. Through three kinds of topological deformations, to explore the influence of topology on antenna performance, the electromagnetic parameters and left-handed characteristics of the original and modified units are compared and analyzed. For the designed handshake-shaped unit structure, simulation analysis predicts that dual-frequency, or even multi-band left-handed characteristics, can be achieved. To expand the structural performance of the handshake-shaped unit, an annular line for coupling enhancement is added inside the U-shaped structure to form an integrally coupled annular unit structure. Simulation results show that, with amplitudes of reflection coefficients of -27.1 dB and -14.5 dB, the resonance points of the improved unit structure are 3.57 GHz and 5.64 GHz, respectively. Loading the unit structure with a dual-band left-handed characteristic, a UWB antenna is designed and analyzed in detail. Through simulation, antenna performance is most affected by interference within the range of 2.5 ~ 5.0 GHz, which coincides with the double negative frequency band of the loaded left-handed structural unit. The notch frequency band of the designed UWB antenna, which is much wider than traditional notch antennas, is 3.62 ~ 4.54 GHz, with a notch bandwidth of 920 MHz.

An ultra-wideband multilayer-stacked Yagi antenna is presented in this article. The proposed design is based on a capped bow-tie antenna, on which a Yagi antenna is formed simply by capping several pieces of parasitic patches with equal lengths but unequal widths. Thus, the multilayer-stacked antenna attains a small footprint, compact size, customizable gain and simple geometry, which make it promising for various applications. The prototype of this antenna is simulated, fabricated, and measured. Good agreement between simulation and measurement has been observed.

There are three mathematical conditions that must be solved simultaneously for the analysis of a fully-symmetric radio-frequency (RF) crossover. When additional reciprocal two-port networks - which might be of an arbitrarily high complexity - are appended at each port of a crossover, analysis of the modified crossover becomes very tedious. Therefore, this paper examines the requirement of the three conditions in such scenario. We show that two of the three conditions can be invoked without considering the additional two-port networks altogether. This is a remarkable simplification considering that the additional two-port networks, in general, would necessitate dealing with more involved algebraic calculations. To demonstrate the usefulness of the presented theory, for the first time, analysis and design of a dual-frequency port-extended crossover is included. A prototype of the dual-frequency crossover operating concurrently at 1 GHz and 2 GHz is manufactured on a Rogers RO4350B laminate having 30 mil substrate height and 3.66 dielectric constant. The close resemblance between the EM simulated and measured results validates the analytical equations.

This paper presents an accurate analytical explicit expression for the self-inductance of a flat pancake round coil made up of concentric turns. The expression is obtained by converting the semi-infinite integral representation for the mutual inductance between two arbitrary turns of the coil into a finite integral, and then by expanding the integrand into a series of Legendre polynomials. As a result, a sum of simpler integrals is obtained, whose analytical evaluation is straightforward. The self inductance is finally expressed as the sum of logarithmic functions, describing the contributions from the self-inductances of the single turns, plus the mutual-inductance terms originating from all the possible pairs of turns of the coil, each one given by a power series of the ratio between the radii of the turns. Numerical simulations are performed to illustrate the advantages of the proposed solution.

Switched beamforming using electronic phase shifters is commonplace. Digital switched beamformers offer a premise of better performance than electronic phase shift switched beamformers. It is also worth noting that current unknown signal Direction of Arrival (DoA) estimation methods (commonly MUltiple SIgnal Classification (MUSIC) and Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT)) are generally computationally intensive. In this paper, signal DoA estimation and digital switched beamforming using aptly designed Artificial Neural Network (ANN) classifiers are looked into. Initially, signals detected at a rectangular receiving array are mapped onto a DoA through an ANN classifier. A second ANN classifier maps the selected DoA onto an optimal set of beamforming weights leading to an optimal switched beamforming reception pattern. The ANN classifiers' performance in DoA estimation and beamforming is tested over a variety of trials, yielding good results. The designed ANN beamformer premises to yield high-speed and accurate switched beamforming performance, most notably in large array systems. The ANN DoA estimator/beamformer can be easily adapted to non-uniform arrays wherein closed form DoA estimation/beamforming solutions are impractical. MATLAB software environment has been used as the main analysis tool.

In this paper, design of a novel dual-band microstrip bandstop filter is presented. The designed filter is constructed by loading two stepped impedance hairpin resonators to a simple straight transmission line, which also connects to the input and output ports. By virtue of the proposed resonator, the ratio of the first and second resonance frequencies can be obtained as approximately 4.4. Two stopbands centered at 2.34 GHz and 7.81 GHz with the fractional bandwidths of 33.2% and 7.9% can be obtained, respectively. Rejection levels inside the stopbands are obtained as better than 20 dB. Total electrical length of the proposed filter is 0.317λ_gx0.136λ_g, where λ_g is the guided wavelength at the lowest resonance frequency. The designed filter was also fabricated and tested for experimental verifications. The measured results are in an excellent agreement with the simulated ones.

In this paper, design and measurements of a highly selective π-CRLH dual-band bandpass filter, with transmission zeros optimized to serve Wi-Max applications, is presented. The dual-bands are designed at 5.2 and 5.7 GHz with a sharp rejection level between them and transmission zeros before and after the passbands. The filter is designed using coupled gap zerothorder composite right/left-handed (CRLH) resonators, which results in significant filter size reduction. Furthermore, two different coupled π-CRLH filters are discussed through the work development of this paper. The filter design concepts are verified and confirmed using electromagnetic simulations and experimental measurements. Presented results reveal that the proposed filter exhibits a rejection level greater than -20 dB, while maintaining 2 dB insertion loss and better than -25 dB for the transmission zeros with compact size (12×16 mm²) which is 70% smaller than similar conventional filters.

A compact ultra-wideband (UWB) antenna with triple band-notch characteristics is proposed. The proposed antenna employs fractal and two via edge located (TVEL) electromagnetic band gap (EBG) structures near the feed line to cause triple frequency band notch characteristics over WiMAX (3.3 to 4.0 GHz), WLAN (5.1 to 5.8 GHz) and satellite downlink communication (7.2 to 7.8 GHz) frequency bands. The proposed antenna is designed and fabricated on a 24 × 24 × 1.6 mm³ FR4 substrate. Itoffers impedance bandwidth (VSWR <2) from 2.9 to 11.2 GHz except over the notched bands. The antenna has nearly omnidirectional radiation patterns and steady gain over the desired UWB. The measured results agree with the simulated ones.

The suppression of the side-lobe level (SLL) of antenna arrays is a significant factor that can enhance the reliability and validity of a communication system. Recently, metaheuristic algorithms have been widely implemented in the design of antenna arrays, in order to find the optimal minimization for the side-lobe level of the array's radiation pattern. In this paper, we propose a new hybrid algorithm that combines the characteristics of two stochastic algorithms, Antlion Optimization (ALO) algorithm and Grasshopper Optimization Algorithm (GOA). ALO, which is an evolutionary algorithm, is robust in exploitation and has been effectively used in many articles in the literature. GOA has strong capability of exploration all over the search space due to the swarm nature of the algorithm, which has been proven in several articles in the literature. Therefore, combining these characteristics and overcoming the drawbacks of ALO and GOA are the main motivation behind hybridizing ALO and GOA in one hybrid algorithm. Simulation results show that the proposed hybrid algorithm has a good performance in the radiation pattern optimization of circular antenna array (CAA) and fast convergence rate compared with other strong optimization algorithms, which prove the efficiency, robustness, and stability of the hybrid algorithm.

This paper presents a direct synthesis approach for UWB BPFs. The modified Chebyshev filtering function is used to characterize the frequency response over the whole frequency range of the BPF. As for the filter's circuit, open circuited MMR capacitively coupled with I\O ports is used, and two shunt short-circuited stubs are placed at the two ends of the connecting line to sharpen the rejecting skirt of the passband. The equivalent circuit's transfer function is derived. By equating the filtering function to the transfer function of the circuit, the design parameters are obtained. The uniform connecting line is then replaced by nonuniform line to suppress spurious harmonics and achieve very wide stopband. In order to avoid critical precision requirement in the fabrication of the filter, we design the filter using suspended stripline (SSL) technology to replace the parallel-coupled microstrip lines (PCML) with very small coupling gaps. Finally, a filter prototype is designed and fabricated to experimentally validate the presented method. Experimental results show good agreement with EM-simulated and theoretical ones.

In this paper, an analytical calculation of the magnetic field in a consequent-pole bearingless permanent magnet (PM) type motor with rotor eccentricity is proposed. The analytical method is based on the resolution of Laplace's and Poisson's equations. Due to the presence of consequent-pole, the general solution of the first-order for the vector potential distribution in the air-gap is presented considering the first harmonic. Here, the magnetic field distributions by the analytical method are compared with those obtained from finite element (FE) analyses. Then, the corresponding performances are quantitatively assessed by the finite-element method.

A three-box model, composed of a triangular memory polynomial, a look-up table, and a cross item among memory times, is proposed for power amplifiers. The model acquired good accuracy and linear effect and reduced the calculation coefficient. Moreover, the paper proposes the GRLS_IVSSLMS adaptive predistortion algorithm. This algorithm is based on the structure of indirect learning. This work uses 16QAM signal to drive a strongly nonlinear Doherty amplifier. Experimental results show that the proposed method is suitable for the adaptive predistortion of power amplifiers.

A novel miniaturized bandpass half-mode substrate integrated waveguide (HMSIW) filter which uses dual-iris coupling method to load complementary split-ring resonators (CSRRs) into HMSIW is proposed in this paper. By modifying traditional CSRRs through nesting method combined with step impedance structure, a nested stepped-impedance complementary split-ring resonator (NSICSRR) structure with higher equivalent capacitance and inductance of CSRR is obtained. Based on the traditional single-iris coupling method, a dual-iris coupling method is developed. And NSICSRR is loaded into HMSIW by using the dual-iris coupling method, which can reduce the resonant frequency of the structure. In order to verify the effectiveness of the technology above in realizing the miniaturization of HMSIW filter, a second-order HMSIW filter is designed and measured. It can be found in the measured results that the filter has the center frequency of 6.35 GHz, the 3 dB bandwidth of 690 MHz, the return loss of better than 14 dB within the passband, and the size of 0.0396λ_g². The experimental results are basically consistent with the simulation ones.

In order to design a robust passive temperature sensing tag that can operate over a wide temperature range, temperature-sensitive characteristic of UHF radio frequency identification temperature sensing chip and corresponding tags are studied. The devices under test include dipole tags with different antenna impedances. Simulation data, experiment design, system setup, measurement procedures, and test results are given. The results show that as temperature increases, the real part of chip impedance increases, and the absolute value of the imaginary part decreases, which are consistent with simulation data. In the full temperature range, the overall performance of sensing tags designed for high-temperature conditions is better than tags designed only for room temperature conditions.

A dielectric resonator (DR) based MIMO (Multiple Input Multiple Output) antenna with enhanced isolation is proposed in this letter. The proposed MIMO antenna consists of four hemispherical shaped dielectric resonator (HDR) radiating at 4.9 GHz. The isolation between two consecutive radiators is enhanced by rotating feeding line of one element at an angle of 180˚. The antenna is studied in terms of S-parameters, gain, envelope correlation coefficient (ECC), channel capacity loss (CCL) and diversity gain (DG). All the parameters are found to be within acceptable range. The proposed design is fabricated, and it is found that measured results are in good agreement with simulation.

This research presents a novel integrated multiband antenna system manufactured and tested for Smart Industries applications. The proposed system consists of a miniaturized planar antenna with multi-arms conceived to cover the most required frequency bands in industry 4.0 such as GPS Band, UMTS Band, ISM Band, LTE Bands, and WiMax Bands. The manufactured design was verified using Arduino programmable circuit board interfaced to SIM900 module and digital sensors for data collection. Depending on the commands received through the human machine interface (HMI) from the end-user, the developed algorithm within the Arduino controls the SIM900 to select the adequate wireless technology to transmit the data and thus reconfigures the antenna to radiate at the target frequency band. The proposed system is easy to deploy inside industrial machines and cost-effective for large scale use. The paper first introduces the main challenges and benefits of miniaturized low-cost antennas systems for Smart Industries and Internet Of Things. Further the parametric study and final dimensions of the design and simulation results are discussed. The proposed design is fabricated, and the measurements of the radiation pattern and return loss are performed. The antenna, with measured maximum gain up to 10 dBi and measured S₁₁ up to -20 dB, exhibits excellent performance for all the frequencies required in Smart Industries such as 1.6 GHz, 1.8 GHz, 2.3 GHz, 2.4 GHz, 2.6 GHz, 3.5 Ghz, and 5.8 GHz. The proposed antenna system was implemented and tested inside an industrial machine for Yogurt and Milk production and compared to existing commercial solutions. This study shows that the proposed antenna system is suitable for smart factories since it is miniaturized for internal integration, and it has self-frequency-adaptation and low power consumption, allowing the end-user to remotely control and monitor machines and smart devices.

A new compact broadband circular fractal antenna is presented to simultaneously cover the operations in S-, C-, X-, and Ku-bands. Fractal geometry of the radiator including an iterative circular patch with a square slot, a modified feed-line with step technique, and slot-loaded semi-circular ground plane is used to achieve a broad impedance bandwidth more than 151% from 3 to 21.5 GHz (|S₁₁|< -10 dB). The simulation results are verified by experimental measurements. Measured data are in good agreement with the simulated results. The frequency- and time-domain characteristics of the antenna including impedance matching, far-field patterns, gain, group delay, and fidelity factor are presented and discussed. The proposed broadband antenna features small size of 38×36×1.4 mm³ and nearly omnidirectional radiation patterns that make it excellent candidate for integration in broadband wireless communication systems.