A Compact wideband operating from 3 to 18 GHz MIMO antenna with quadruple notches is presented in this paper. The elements in MIMO configuration are arranged in orthogonal fashion with each other to minimize the coupling effects. The antenna consists of circular rings and a modified microstrip feed. By engraving a crescent shaped slot, split ring-shaped slot, circle shaped slot in the circular monopole, rectangular spiral shaped slot engraved along the feed line quadruple notches are attained. The antenna operates from 3 GHz to 18 GHz with notches in the range of 3.2 GHz-4.2 GHz centered at 3.5 GHz, 4.5 GHz-5.5 GHz centered at 4.9 GHz, 6.2 GHz-7.3 GHz centered at 6.6 GHz, and 8.1 GHz-8.8 GHz centered at 8.5 GHz. The element has a very compact size of 0.28λx0.22λx0.016λ at 3 GHz and is hence suitable for portable devices.
Beam Collection Efficiency (BCE), sidelobe level outside the receiving area (CSL), and cost are need to be considered in optimizing the transmitting array of a Microwave Wireless Power Transmission (MWPT) system. To solve the problem of too low BCE caused by dividing a small number of subarrays, this paper proposes a novel one-step subarray partition algorithm named Multi-Particle Multi-Parameter Dynamic Weight Particle Swarm Optimization Subarray Partition (MPMP-DWPSO-SP). The algorithm optimizes the position and structure of each element at the same time, and the number of the subarrays is no more than 4. It is verified by simulation that the BCE obtained by using this algorithm to optimize the Sparse Quadrant Symmetrical Rectangular Array (SQSRA) with an aperture of 4.5λ×4.5λ and the array element number of 8×8 can reach more than 90%. In addition, a new intelligent optimization model is designed for dividing the 8×8 array into 2 subarrays, and BCE and CSL can reach 91.69% and -17.61 dB.
A linear-to-linear cross-polarization converter (CPC) based on metasurface (MS) is proposed. The converter is polarization insensitive and has two wide bands. The MS is composed of periodical unit cells printed on a substrate. The top and bottom MS unit cells are formed with four groups of right-angle triangle pairs whose vertices are connected. Thus, there are eight pairs of triangles on the top and bottom surfaces of the substrate, and these pairs of triangles are arranged alternately in overlapping and orthogonal ways. Simulated and measured results indicate that the polarization conversion ratio (PCR) of the CPC is higher than 95% in the bands of 9.4 to 13.1 GHz (32.9%) and 13.4 to 17.2 GHz (24.8%). Additionally, the PCR remains the same when the electromagnetic (EM) wave is incident at arbitrary azimuth. Furthermore, the polarization rotation angle and elliptic angle are calculated to verify the conversion effect. Finally, the conversion mechanism of the proposed converter is explored by analyzing the surface current distribution and magnetic field. The proposed converter can be applied to the field of satellite communication in Ku-band.
Investigations on radiation characteristics of multilayer antenna having embedment of left-handed material are presented. The proposed engineered comb-shaped structure exhibits both negative permittivity and permeability. The inset-fed patch antenna matched at 50 Ω incorporates a homogeneous array of multilayer comb-shaped resonators. The array demonstrates a major impact on antenna parameters such as resonance, gain, radiation pattern, voltage standing wave ratio, and bandwidth. The novelty in the presented design is that by merely modifying the physical parameters of the negative refractive index resonator, the antenna radiation property can be altered. An artificially realized left-handed stacked material possesses strong inductive and capacitive mutual-coupling. The variations in stacked conductive inclusion illustrate the considerable change in antenna resonance. The antenna resonates at 1.57 GHz, 2.48 GHz, and 3.4 GHz with a bandwidth of around 20.64%, 7.35%, and 4.40% respectively. The proposed antenna electrical size is 0.48λ x 0.56λ at a lower frequency. The antenna exhibits the gain of 3.8 dBi, 6.15 dBi, 4.54 dBi at 1.57 GHz, 2.48 GHz, and 3.4 GHz respectively. The proposed planar stacked negative refractive index-inspired patch antenna model can be utilized for L1 and S-band satellite and maritime operations.
A novel layout method of receiving antenna array, which is a sparse random circular aperture array (SRCAA), to raise the power transmission efficiency (PTE) for microwave power transmission (MPT) is proposed in this paper. Different from the conventional antenna array layout, the array element positions of the SRCAA are randomly and uniformly distributed in the circular region. At present, the receiving array mostly adopts the form of uniform full array in the MPT system, and most researches focus on the antenna unit itself to raise the PTE rather than the array layout. In this paper, the initial array is obtained by randomly scattering points in the fixed area, and then the array element position is optimized by the algorithm to maximize the PTE between the transmitter (Tx) and receiver (Rx) of the MPT system. At the same time, the random array element position also plays a significant role in the uniformity of the received power of the receiving array. Therefore, this paper proposes a new index to measure the performance of the receiving array. In order to verify the effective performance of the SRCAA, we carried out a series of numerical simulations. Numerical simulation results show that the SRCAA, as a high-performance and low-cost receiving array, is more suitable for the receiving array of the MPT system than the traditional uniform array.
The present scenario that demands a high data rate by the consumers in wireless communication has imposed a challenge in the present market. Therefore, millimetre wave technology is attracting the interest of researchers and industries. This paper proposes a rectangular planar microstrip antenna with slots in radiating elements as well as in the ground plane. The proposed structure has been designed, simulated and fabricated at a centre frequency of 28 GHz using 5880 RT duroid as a substrate, which has a relative permittivity of 2.2, loss-tangent of 9x10-4, and thickness of 1.6 mm. By performing the simulation using HFSS Ansys Software and also fabrication and testing, the proposed design attains a maximum gain of 8.735 dBi and a frequency band-width of around 2.815 GHz. The impedance bandwidth response ranges from 26.75-29.565 (10.1%) below the -10 dB line of the S11 plot. The proposed antenna is compact with dimensions of 2.19 x 3.95 mm and has wide bandwidth along with high gain, hence is a good candidate for mm-wave applications besides several innovative antenna-based gadgets. Measured S11 and VSWR results are in consistent with the simulated ones.
A miniaturized in size linear multiple-input multiple-output (MIMO) antenna array operating on demand at 28 GHz and 24.8 GHz for 5G applications is presented and investigated in this research work. The antenna array has the capability to switch and operate efficiently from 28 GHz to 24.8 GHz with more than 15 dB gain at each frequency, having 2.1 GHz and 1.9 GHz bandwidth, respectively. The unit cell of the proposed antenna array consists of a transmission line (TL) fed circular patch connected with horizontal and vertical stubs. The vertical stubs are used to switch the operating frequency and mitigate the unwanted interaction between the adjacent elements of the antenna array to miniaturize the overall dimension of the array. The proposed antenna array is compared with the recent works published in the literature for 5G applications to demonstrate the features of miniaturization and high gain. The proposed array is a potential candidate for 5G sensors applications like cellular devices, drones, biotelemetry sensors, etc.
An optical fiber sensor based on thin-core fiber (TCF) and no-core fiber (NCF) interference structures is presented and experimentally demonstrated to measure the curvature and temperature. The fabrication process of the sensor is simple and convenient, and the sensing part is formed by cascading a TCF and an NCF between two single-mode fibers. The dips at resonant wavelengths are generated in the optical transmission spectrum owing to mode interference. The experimental results indicate that an optical curvature sensitivity of -5.76 nm/m-1 is achieved in the linear range of 0.9895-3.2817 m-1, and that a temperature sensitivity of 0.18 nm/˚C is obtained in the temperature range of 25-55˚C. Additionally, the cross-sensitivity problem is solved using the coefficient matrix measurement method, and the cross-sensitivity is as low as 0.0312 m-1/˚C. Therefore, the sensor exhibits a highly reproducible technique and low cross sensitivity, which has a wide range of application prospects in the accurate measurement of mechanical arms and structural health monitoring.
In this paper, a miniaturized dual-band circularly polarized (CP) implantable antenna is proposed. The -10 dB impedance bandwidth of the antenna in Industrial Scientific Medical (ISM) band and the low frequency part of UWB can reach 30.3% (2.02~2.74 GHz) and 39.9% (3.73~5.59 GHz), respectively. The important features are its CP characteristic in two bands and a small volume. The miniaturization of the antenna is realized by half-cutting technique, which is to cut the original antenna meeting the symmetry of structure and electric field distribution into two halves to obtain a compact structure and wider impedance bandwidth, so that the final size is 5×10.4×0.254 mm3. The CP wave performance of the antenna is achieved by exciting orthogonal polarization components on the radiation surface. The proposed antenna provides an axial ratio of less than 3 dB. CP axial ratio bandwidths in the two bands are 24.4% and 18.1%, respectively. In addition, the safety considerations and link margin are evaluated to analyze the performance of the proposed antenna. In order to verify the simulation results, the proposed antenna is fabricated. The measurements are carried out under the human muscle mimicking liquid circumstances. The measured data are in good agreement with the simulation results.
In the paper, a very compact UWB-MIMO antenna with four rejected bands property is introduced and investigated. With a T-shape stepped stub on back ground, impedance bandwidth of 3-11 GHz and isolation of -15 dB are achieved. By etching four pairs of symmetrical L-formed slots into the radiators, four bands are isolated. With only a size of 21 mm × 27 mm, the proposed UWB-MIMO antenna system has low port coupling of -15 dB and wide working bandwidth of 3-11 GHz (S11 ≤ -10 dB or VSWR < 2) except 3.5 GHz WiMAX band, 5.3 GHz lower frequency band of WLAN, 5.8 GHz upper frequency band of WLAN and 7.4 GHz X-band. Moreover, other characteristics, such as radiation patterns, antenna gain, antenna efficiency, and ECC (envelope correlation coefficient) are also studied.
A compact microstrip rat race attained by artificially shortening its lines by inserting stubs is presented. The design starts with a preliminary theoretical length reduction where quarter wavelength lines are shortened thanks to shunt open circuit stubs placed in the line mid-points. Such a preliminary design is then optimized via particle swarm optimization (PSO) within a full wave electromagnetic CAD, also bending the stubs to attain maximum compactness. The resulting design occupies an area up to only 37% of a conventional rat race, with performances comparable to those of a standard rat race.
This research work deals with the plane wave diffraction by a coated perfect electrically conducting wedge with arbitrary apex angle. The uniform layer covering the impenetrable wedge is made of a standard double positive material or an unfamiliar double negative metamaterial with negative permittivity and permeability at the operating frequencies. The propagation mechanism is studied when the incidence direction is perpendicular to the edge of the composite structure, and uniform asymptotic solutions are proposed to evaluate the diffraction contribution for both the polarizations. Such approximate solutions are obtained by using the Uniform Asymptotic Physical Optics approach based on electric and magnetic equivalent surface currents radiating in the neighboring free space. The related expressions are user-friendly and provide reliable field values as verified by numerical tests involving a full-wave electromagnetic solver.
This paper aims to present a highly selective, compact size new ultra-wideband (UWB) bandpass filter with three sharp notches for UWB indoor applications. The fundamental geometry of the filter is based on modified multi-mode resonator (MMR) structure which comprises a open-ended step impedance resonator (SIR) attached to an interdigitated uniform impedance resonator (UIR). Realizing a Comb-shaped resonator structure below the UIR and symmetrically extending the lower arm edge of the interdigital coupled lines, three notches are generated at 6 GHz, 6.53 GHz, and 8.35 GHz. These notches have improved the UWB bandpass filter responses by suppressing the existing interferences in the UWB passband created by Wi-Fi 6E (6 GHz), super-extended C band (6.425 GHz~6.725 GHz), X band satellite communications for satellite TV networks or raw satellite feeds (7.25 GHz~8.395 GHz). Concurrently the notched band filter has achieved superiority in other salient features concerning passband and stop band of the filter such as a high passband fractional bandwidth (115.76%), low return loss (-13.27 dB), low insertion loss (0.44 dB~0.97 dB), wide upper stop band (5.37 GHz), nearly flat group delay (0.28 ns~0.45 ns) etc. The ultimate design of UWB bandpass filter is fabricated and verified by comparing the simulated filter responses with the measured results indicating a good agreement.
Directed energy weapons provide a number of useful functions for the modern fighting force, and hence it is useful to produce a framework in which such a weapon's performance can be predicted. Towards this objective this paper introduces a new stochastic model to determine the number of targets defeated by a directed energy weapon over a given time interval. The key to this is to introduce a general queueing model, where arrivals are modelled by a renewal process, and the service time of a target being affected by the weapon is related to its probability of defeat. The queue is assumed to have an infinite capacity, and it is shown how the waiting time of detected threats can be modelled by an auxiliary delay process. A random variable counting the number of targets processed by the queue is then defined. Several functions constructed from this random variable will be investigated in order to identify a suitable metric for assessing performance. In order to facilitate this an example where a high energy laser is used for threat defeat is examined to investigate the utility of the identified performance metrics. As will become apparent, the modelling framework has considerable utility due to the fact that it can be used for performance prediction of any weapon system where an arrival process of threats and corresponding probability of defeat can be specified.
This paper proposes a joint estimation algorithm based on sparse-Bayesian learning (SBL) for the gain-phase problem between array antenna channels. The algorithm uses the idea of the iterative method to jointly estimate the direction-of-arrival (DOA) and gain-phase error calibration coefficients in the iterative process, combining self-calibration and calibration with a calibration source. At each iteration, the rough value of DOA is first estimated using SBL, and then the DOA estimate is used to calculate the gain-phase error calibration coefficient. The value obtained in each iteration is brought into the error cost function, which is constructed based on the principle of signal and noise subspace orthogonality. Iterations are continued until convergence to find the minimum value of the cost function. The algorithm does not require a priori knowledge of array perturbations and has good performance in DOA and array gain and phase error estimation. Simulations and experimental measurements show that the method has better calibration performance than other methods based on optimization algorithms, and the algorithm effectively improves the antenna gain.
In this paper, a wideband polarization-independent broad angular insensitive absorber is proposed with miniaturization novelty. A 12*12 octagon element with parasitic elements interconnected by lumped resister has been fabricated on an FR4 structure with an air gap. Large air gap and lower thickness of substrate material as well as corner notched rectangular with octagonal shape causes the improvement of bandwidth. The proposed wideband absorber exhibits absorptivity above 90%. The same has been achieved from 2.84 GHz to 9.12 GHz with 6.27 GHz fractional bandwidth in TE and TM configurations with an angle from 0˚ to 30˚. The design is λ/6.67 in size and λ/3.33 in thickness miniaturization at the highest cutoff wavelength. The outcome from the proposed model is highly promising and closely matches the simulated configuration. This design has a vital application in absorbing the signal from aircraft, missiles, submarines, satellites, and radar, termed stealth technology.
This paper introduces an original study of low-pass (LP) negative group delay (NGD) circuit. The family of the proposed passive network cross-topology was rarely investigated in the literature. It acts as a tri-port passive circuit presenting a cross-shaped topology. The present study of tri-port passive circuit is originally based on S-matrix modelling. The identification method of LP-NGD function type is established. The considered passive tri-port topology is innovatively constituted by a resistorless LC-passive network. Thanks to the impedance 3-D matrix modelling, the cross-circuit S-parameters are analytically expressed. Then, the NGD analysis at very low-frequencies is presented. The LP-NGD behavior existence condition of the cross-circuit in function of the L and C components is established. The relevance of the tri-port NGD circuit theory is verified by a proof-of-concept of resistorless cross-circuit. Analytical modelling, simulation, and experimentation confirmed the LP-NGD design feasibility with NGD value of about -2 ns and 6.67 MHz cut-off frequency.
In this article, a compact Coplanar Waveguide (CPW) fed band-notched monopole antenna is designed and optimized. The unique feature of this article is to provide an approach for designing an antenna in the best way using machine learning techniques. Machine Learning can be used to speed up the antenna design process. There are five algorithms employed: Decision Tree, Random Forest, XGB Regression, K-Nearest Neighbor (KNN), and Artificial Neural Network (ANN). Among all algorithms, KNN gives the best result with accuracy up to 98%. From the obtained result, we can estimate the dimensions of the desired parameters, which could not be done previously by High Frequency Structure Simulator (HFSS) Electromagnetic (EM) simulator. The optimized antenna design is also fabricated and tested, which confirms its frequency range between 2.9 and 21.6 GHz. Stable radiation features in between the operating frequency range makes it suitable for Ultra-Wideband (UWB) applications.
We present a parametric analysis for a compact notch filter based on meta-material elements, suitable for the mitigation of interferences occurring at 5.9 GHz and impacting a 5.8 GHz DSRC receiver. The filter adopts a defected ground plane structure, which is derived by the class of complementary split ring resonator (CSRR) structures and further developed to improve the selectivity. The designed filter preserves the 5.8 GHz DSRC signal and attenuates the 5.9 GHz ITS-G5 signal of more than 20 dB, thus suited to improve dynamic range of DSRC vehicular receivers. This work introduces the new filter structure characteristics, its design principles, and the corresponding experimental validation.
The integrals arising in magnetic field integral equation (MFIE) can become highly singular, rendering their numerical computation extremely challenging. Here, we propose a technique by which the singular integrals of the MFIE can be accurately and efficiently evaluated. In this technique, the corresponding integrals are separated into singular and regular parts. The regular parts are computed using a very simple Fast Fourier transform, whereas the remaining singular parts are evaluated based on two three-terms recurrence relations. The accuracy of the proposed method is demonstrated by analyzing the scattering of various bodies with smooth or non-smooth geometries and comparing the results with the literature.