This paper proposes a novel RF MEMS capacitive shunt switch, which is applied in K-band (18~26.5 GHz). The characteristic impedance matching of the RF MEMS switch is achieved by discontinuous coplanar waveguide (DCPW) structure. Two actuation poles are located at the bottom of the fixed-fixed beam, and they are covered with a dielectric layer of SiN. The pole's thickness is less than that of CPW signal, to avoid the phenomenon of dielectric charging betweenthe beam and the pole. The proposed MEMS switch is fabricated on 400 μm-thickness high resistivity silicon, using the MEMS surface micromachining process. Measured results demonstrate that, at K-band, the return loss is better than 22 dB, and the insertion loss and isolation are better than 0.5 and 17 dB, respectively. The on/off switched timeis 168/54 μs when the DC bias voltage is 0/54 V. This proposed MEMS switch provides a solution for K-band communication system applications.
In this paper, a standard cell radiation pattern is selected to accelerate the synthesis of a large-scale arrays pattern. The radiation patterns distortion of each cell in array is transformed to the additive perturbation in the array manifold matrix of the antenna array, and the weighted total least squares method is developed to solve this matrix problem. The examples of several antenna arrays are presented to verify the method. Benefiting from the direct solution of matrix with the standard cell's radiation pattern, the method is low in computation cost and fast in speed.
In this paper, the sea surface wind speeds are retrieved by using an analytical scattering model, so called the analytically-based geophysical model function (GMF), from C-band Sentinel-1A VV-polarized synthetic aperture radar (SAR) images. The analytical models accurately simulate the rough surface scattering in the incidence angles range of SARs. The accuracy of the scattering results of the models depends on the sea wave spectrum. In this work, the effect of the sea spectral models on the accuracy of the sea surface wind speed retrieving is evaluated. In this regard, for omnidirectional and directional parts of sea spectrum, the Elfouhaily/Hwang spectra and Elfouhaily/McDaniel's models are employed, respectively. The VV-polarized backscattered normalized radar cross-section (NRCS) is calculated by using the first-order small-slope approximation (SSA1) with the four composite models of the mentioned omnidirectional spectra and angular spreading functions (directional part), and the backscattering results are compared with the empirical model CMOD6. Then, from the VV-polarized Sentinel-1A SAR data in two resolutions, the wind speeds are estimated by the analytical and empirical models. The comparison of analytical models with CMOD6 shows that Hwang-Elfouhaily model is the best among the composite models. The results show that the analytical scattering models can be easily used for the sea wind speed retrieving below 20 m/s.
This paper presents a very compact quintuple band bandpass filter utilizing multimode stub loaded resonator. A single symmetric resonator is loaded with a short ended stub at the middle along with four pairs of open-ended stubs. The open-ended stubs are folded towards each other in order to make the design more compact and improve the selectivity of the bandpass filter. Because of symmetry, the circuit is analyzed with the help of even-odd mode analysis. The proposed bandpass filter operates at GSM-900, LTE2300, WiMAX (3.5 GHz), WLAN (5.4 GHz), and RFID (6.8 GHz). The operating mid frequencies of quintuple-band BPF are 0.96 GHz, 2.22 GHz, 3.58 GHz, 5.41 GHz, and 6.64 GHz, and the corresponding 3 dB Fractional Bandwidths are 36.03%, 20.95%, 7.27%, 8.57%, and 3.37%, respectively. The implemented resonator is analyzed in detail, and the formulation is developed in this regard. The proposed filter is developed based on the analysis and is simulated and fabricated. The simulation and measurement responses agree very well.
An interference on a concurrent 4.5-/8.5-GHz-band operation has been effectively suppressed by applying a duplexer technique to high-efficiency GaN HEMT power amplifiers. Each harmonic was also suppressed by a harmonic reactive termination used for a high-efficiency operation. The developed concurrent dual-band amplifier delivered a 73% drain efficiency and a 61% power-added-efficiency (PAE) with 32 dBm output power at 8.24 GHz and a 69% drain efficiency and a 64% PAE with 37 dBm output power at 4.70 GHz. Undesired cross-modulation and intermodulation signals at nearby bands occurring due to dual-band interaction have been successfully suppressed to less than -41 dBc.
The goal of this study is to conduct an analytical study of the properties (permittivity and permeability or refractive index) of a dispersive time-dependent linear isotropic medium interacting with electromagnetic fields. It is found that the permittivity and permeability of the time-dependent dispersive medium may either have an exponential profile or a sinusoidal profile. The permittivity and permeability can vanish or can be negative as in metamaterials. Therefore, the refractive index can vanish, so the electromagnetic wave can propagate at an infinite speed (c ≫ 3·10⁸ m/s). It is also shown that the permittivity and permeability can simultaneously be negative as in left-handed metamaterials (LHM). The general electric field and magnetic field solutions are derived, and the electric and magnetic flux densities are evaluated. The wave dispersion relation is also analysed. The obtained solutions can be used to validate experimental results by applying the initial and boundary conditions which are appropriate to the experimental setup. ε
In this paper, a K-band right hand circularly polarized (RHCP) antenna array with 4×4 elements is designed, fabricated, measured and analyzed. The RHCP pattern is obtained from the helical antenna elements, with a unit cell of every four elements, sequentially counterclockwise by 90 deg. To decrease the profile of the vertical interconnection between the helical antenna and its feeding network, the integration of this RHCP antenna and its feeding networkis realized by low temperature co-fired ceramic (LTCC) technology. The antenna's feeding network consists of eight directional couplers, four circulators, and one power divider. In the feeding network, different RF channels' isolations are improved by the shield structures which are realized by metal filled via holes. For the operating frequency, the measured axial ratio (AR) is better than 1.25 dB. The proposed antenna is small in size, andit is a very good candidate for mobile satellite communications.
Recursive convolution FDTD method is employed to study the bistatic radar cross section (RCS) of a conductive plate covered with an inhomogeneous magnetized plasma shroud. The results of numerical simulations reveal that for a plasma of number density 5×1017 m-3 and collision frequency of 1 GHz, RCS reduction (RCSR) is improved i.e., its maximum reduction, bandwidth, and angular width are enhanced, when a perpendicular magnetic field of intensity B=0.25 T is applied. However, increase of the magnetic field to 0.4 T leads to a much lower RCSR specially for the backscattered wave. As the collision frequency is increased to 10 GHz, the RCSR is enhanced both in the presence and absence of the magnetic field. However, with further increase of collision frequency to 60 GHz, the RCSR is significantly reduced and the problem is more severe in the backward direction. The resonant absorption is dominant at low to moderate collision frequencies, for magnetic field intensity above 0.1 T, but becomes almost inefficient when the collision frequency is increased to 60 GHz. The RCSR is considerably weakened when the plasma number density is reduced and the effect is prominent for small angles. A plasma inhomogeneity length scale of 5 cm provides the maximum RCSR in the presence of the magnetic field. With increase of the length scale, the maximum RCSR, the corresponding wave frequency, and bandwidth all are reduced. Therefore, it is conclude that a plasma with number density of 5×1017 m-3, collision frequency of 10 GHz, and length scale of 5 cm, with a perpendicular magnetic field of 0.25 T is the best choice for optimum RCSR of a conductive plate.
A general theoetical framework for MIMO digital wireless communications is proposed for sending classical M-ary information over quantum states instead of classical electromagnetic waves. The basic theory of quantum MIMO architecture suitable for spatial diversity application is proposed and analyzed. The fundamental design equations are derived and shown to be equivalent to a special constrained nonlinear optimization problem. The main advantage of the MIMO architecture is that it provides new resources for the system designer since using multiple Tx quantum antennas coupled with judicious choice of optimum positions for the multiple Rx quantum measurement operators can enhance the ability to realize quantum communication systems. Therefore, additional degrees of freedom are expected to become available in the proposed quantum MIMO systems. The proposed system is expected to be best physically realized using electromagnetic process in second-quantized (photon) states, ideally coherent or squeezed radiation states.
In this paper, a low-profile, dual-band, unidirectional, tag antennais proposed for ultra-high frequency band (UHF) radio frequency identification (RFID) applications. The antenna consists of a compact printed dipole, a metasurface of 4 × 4 periodic metallic plates, and a metallic reflector. The dipole antenna is fed by a modified T-matching network for a conjugate impedance matching with the UCODE G2XM chip. The metasurface is designed to work as an artificial magnetic conductor surface, which allows low-profile configuration and unidirectional radiation. More interestingly, the finite-sized metasurface generates extra resonance for the antenna system, which is combined with the dipole resonance for the dual-band operation. For an easy realization and low cost, the dipole and metasurface are built on the top and bottom sides of a thin FR-4 substrate, respectively. The final design with overall size of 190 mm × 190 mm × 15.8 mm (0.532λ × 0.532λ × 0.044λ at 840 MHz) yields a simulated |S11| < -10 dB bandwidth of 840-855 MHz and 916-932 MHz and a unidirectional radiation with a directivity of 7.0 dB and 5.8 dB at 925 MHz and 845 MHz, respectively. The antenna has been fabricated and tested. The measured readable range agrees rather closely with the predicted values. The measurements result in the maximum readable range of 6-m and 4.4-m at standard frequency bands of FCC (902-928 MHz) for North America and IN (840-845 MHz) for India, respectively.
This paper introduces a novel MIMO UWB antenna with dual notches. The proposed antenna is based on Quasi Self Complementary (QSC) method to give wide impedance bandwidth from 2.4 GHz to more than 12 GHz. The proposed antenna consists of a semi-elliptical patch that is fed by a tapered microstrip line. The antenna is designed on an FR-4 substrate with compact size 20 mm × 15 mm × 1.5 mm. The dual notched bands are achieved by using a square ring printed on the bottom of the substrate to reject WiMAX at 3.6 GHz. Also, a C-shaped slot is etched in the radiating patch to reject interference with the WLAN band at 5.8 GHz. In the proposed MIMO antenna, the isolation reduction is achieved utilizing diversity technique to minimize the mutual coupling between the antennas. The isolation between MIMO elements is more than 20 dB. The envelope correlation coefficient (ECC), diversity gain (DG), total active reflection coefficient (TARC), furthermore, channel capacity loss (CCL) are measured and calculated. The proposed antenna is designed, simulated, and measured. A good agreement is shown between the experimental and simulated results.
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.
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.
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.
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.
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.
In order to design differential phase shifters (DPS) from metamaterial-based transmission lines, research had a long tradition of usingbalanced transmission lines which are a particular case of metamaterials, specifically characterized byasimplified equivalent circuit model. This paper presents an innovative way of designing DPS metamaterials by exploiting metamaterial properties more widely, using both balanced and unbalanced cases to obtain a broader set of solutions. These solutions are acquired through the dedicated method this paper expounds, and conceived with the help of a new use of metamaterials. For the sake of ensuring time efficiency and implementation easiness of this design method for industrial purpose, the full wave parametric optimization is reduced to its minimum by exploiting as much as possible in analytic parametric study. This method is illustrated by an application of 180° DPS on C-Band (5-6 GHz). Three prototypes were fabricated, and the measurements show that the best case of DPS has less than 9° of phase error over the targeted 20% bandwidth, with a return loss less than -14 dB and insertion losses lower than 1 dB.