A dispersive delay line (DDL) with compact size, good group delay, and all pass response in 200-800 MHz band is presented. The proposed DDL is composed of a main microstrip transmission line with two shunted open stubs and two complementary slot lines, and a coupling slot line in ground plane. The length of the complementary slot line is reduced approximately from λ_g/2 to λ_g/4 through the upper end being opened, hence achieves miniaturization for the proposed DDL (λ_g is the guided wavelength at the center frequency). The overall area is 0.196×0.093λ_g² with a peak group delay time of 3.2 ns. The proposed DDL has the advantages of compactness, good capability, and easy fabrication without any external matching network.

The presence of the O and X modes in the HF skywave propagation has previously been investigated experimentally for their role in providing polarization diversity and improving channel capacity when a MIMO structure is employed. A mathematical treatment of MIMO channel modelling and capacity improvement has also been reported but limited to NVIS links only. This paper reports the mathematical derivation of the HF 2×2 polarized MIMO channels when cross-dipoles, i.e., a pair of orthogonally polarized horizontally-oriented dipoles, are used at both ends to examine the cross-polarization property and the capacity improvement factor (CIF), with the transmitter-receiver range being near enough to allow single-hop paths only but also distant enough to make the trajectory oblique. Results on the cross-polarization property suggest that the power contributions of the waves from the two transmitters that arrive at each receiver are equal. In addition, the signal from any one of the transmitters is received by the two receivers with unbalanced powers that depend on the phase shift difference between the O and X paths. It is also observed that on average the MIMO channels with oblique paths have lower capacity than the NVIS MIMO channels due to the reduced orthogonality between polarizations of antennas in the dual-antenna system at each end. The above hypotheses are confirmed through ray-tracing simulation and field measurement over a 575 km HF radio link.

Space Sensing Models promulgates the channeling sequels of interstellar environs. A fractal array with sun-shaped irregular molds has arisen to solar activities by interchangeably pointing in the direction of sun and off source with beam swapping, whilst weighing the sun's position (psi, phi)-space (phi demarcates the antenna azimuth proportionate to north, psi contours the beam elevation over horizon) and its solid radioactivity hoarded in the antenna's beam width. The research feedback has incidents of solar fluxes and brightness temperatures to depict sun's activity. Phenomenally, nature-space fractals have been crucial quintessence in intuiting sun's after math pertaining to weather and biological sways {Weierstrass C(x,y)} on landscape, swirling with fractal clock underpinning magnetic flipping and irradiance fluctuations at phase vicissitudes have periodically wedged on territory. The remote alliance algorithms with random fractal contours have subsidized paths of self-affine topographic surfaces and space-earth stoichiometry. In this paper, antenna solar scan corollaries at X-band to detect the solar activity on fractal boresight physiognomies of 3-dB HPBW around 0.5° solar diameter with 36° crest atmospheric stray radiations (SLL) rope inpetite sidelobes 60˚ near the core flamboyant region, return loss S₁₁<-10 dB at X/Ku-band on horizontal and vertical tilting bearings have been estimated.

The transition towards next generation communications has increased the need for fast and accurate propagation models that can predict all aspects of the wireless channel. This paper develops a very accurate approach for indoor propagation modelling based on the volume electric field integral equation (VEFIE). The three-dimensional form of the VEFIE is used to predict frequency domain characteristics. Whilst, a 2D to 3D model is developed based on the 2D VEFIE to perform accurate and efficient time domain predictions. The 2D to 3D model applies correction terms to the solution of the 2D VEFIE to account for three-dimensional propagation. Both models are compared against frequency and time domain measurements as well as popular empirical models for both scenarios.

In the paper, we present a novel PCE-based approach for the effective analysis of worst-case scenario in a wireless telecommunication system. Usually, in such analysis derivation of polynomial chaos expansion (PCE meta-model) of a considered EM field function for one precise set of probability densities of random variables does not provide enough information. Consequently, a number of PCE meta-models of the EM field function should be derived, each for the different joint probability density of a vector of random variables, e.g., associated with different mean (nominal) values of random variables. The general polynomial chaos (gPC) approach requires numerical calculations for each PCE meta-model derivation. In order to significantly decrease the time required to derive all of the PCE meta-models, the novel approach has been introduced. It utilizes the novel so-called primary approximation and the novel analytical formulas. They significantly decrease the number of numerical calculations required to derive all of the PCE meta-models compared with the gPC approach. In the paper, we analyze the stochastic EM fields distributions in a telecommunication system in a spatial domain. For this purpose, analysis of uncertainties associated with a propagation channel as well as with transmitting and receiving antennas was introduced. We take advantage of a ray theory in our analysis. This allows us to provide the novel method for rapid calculation of a PCE meta-model of a telecommunication system transfer function by using the separate PCE meta-models associated with antennas and a propagation channel.

This paper presents a parsimonious Bayesian indoor wave propagation model for predicting signal power in multi-wall multi-floor complex indoor environments. The received power is modeled as a Bayesian multiple regression model. The parameters of the model are assessed and validated using a two-tier validation strategy in which Bayes factor and posterior probability are used in the first tier and second tier, respectively. The performance of the two-tier strategy is then assessed using Bayesian information criterion. The proposed indoor propagation model is tested in a two-storey building with access points operating at 2.4 GHz.

The ionized field under HVDC transmission lines have an impact on environment and people. With the industrial pollution and environment deterioration, the suspended particles that will influence the ionized field cannot be ignored. So the meshless local Petrov-Galerkin (MLPG) method based on moving least square (MLS) shape function is applied in this paper to calculate the ionized field of unipolar transmission line. Based on the calculation, the analysis of the ionized field within the influences of suspended particles has been done by establishing the charging model of suspended particles. The research shows that suspended particles indeed influence the ionized field by increasing space charge density, reducing corona onset electric field, and reducing the ion mobility.

This article discusses about the design and development of an ultrathin triple band microwave absorber using a miniaturized metamaterial structure for near-unity absorption characteristics. In order to design a miniaturized metamaterial (MTM) absorber unit cell with triple band response, two resonators, named as Structure-I and Structure-II, are configured within the single unit cell. The geometrical proportions of the suggested resonators have been chosen in such a manner so that Structure-I can contribute one absorption band while Structure-II can contribute two absorption bands. Therefore, the combination of two resonators offers triple band response with the highest absorption values of 99.04%, 99.62%, and 99.33% at the frequencies of 4.25 GHz, 8.35 GHz, and 11.06 GHz, respectively. Additionally, the suggested absorber unit cell claims miniaturization with total electrical size of 0.156λ₀ × 0.156λ₀ × 0.014λ₀, where λ₀ corresponds to the free-space wavelength at the first peak absorption frequency of 4.25 GHz. Additionally, the electric field and vectored surface current distribution along with the input impedance graph has been used to discuss the absorption methodology of the suggested structure. Further, the MTM belongings of the suggested structure have been illustrated with the dispersion curve.

A general auxiliary differential equation (ADE) finite difference time-domain (FDTD) method with Crank-Nicolson (CN) scheme is proposed to model electromagnetic wave propagation in dispersive materials in this paper. The proposed method introduces an ADE technique that establishes the relationship between the electric displacement vector and electric field intensity with a differential equation in dispersive media. The CN scheme applies only to Faraday's law, resulting in reduced memory usage and computing time. To validate the advantages of the proposed approach, two examples with plane wave propagation in dispersive media are calculated. Compared with the conventional ADE-CN-FDTD method, the results from our proposed method show its accuracy and efficiency for dispersive media simulation.

A compact two-element multiple-input-multiple-output (MIMO) antenna with high isolation is proposed in this paper. It is based on a half-mode substrate-integrated-waveguide (SIW) cavity where three edges are shorted by metallic vias, and one edge is opened to radiate cavity energy into free space. Fed by coaxial ports, two antenna elements are constructed in the SIW cavity, and a narrow T-shaped slot is introduced to enhance the isolation between them. High port isolation can be achieved by adjusting the slot length although these antenna elements are connected with each other. A prototype has been fabricated and measured. With the compact cavity size of 0.22λ₀ × 0.44λ₀, the fabricated antenna achieves the operating frequency of 3.51 GHz, enhanced isolation of 18.0 dB, low envelope correlation coefficient of 0.006, peak gain of 5.2 dBi, and high efficiency of 82.6%. Therefore, the proposed MIMO antenna has potential applications for wireless communication.

In this paper, a new dual-band bandpass filter (BPF) using a cross ring resonator is designed. The cross ring resonator is modified from a typical dual-mode ring resonator and has four parallel coupling gaps (g). The resonant modes of the proposed cross ring resonator is investigated first. It is found that the first mode and the second mode can be tuned individually. The filter performances are simulated by using full-wave simulator IE3D. A filter example having two passbands operated at 2.4/5.2 GHz of wireless local area network (WLAN) applications is described to verify the design concept. The fabricated filter has measured characteristics including average insertion losses of 2.0 dB and 1.8 dB and return losses larger than 22 dB and 10 dB for 2.4/5.2 GHz, respectively. Two transmission zeros with high frequency selectivity of 40 dB and 42 dB are obtained near the first passband at 2.2 GHz and 2.7 GHz, respectively. This design is very simple as compared to other design methods, and the measured results prove the design concept of the proposed structure.

Deceptive jamming plays an irreplaceable role in electronic counter measures (ECM) due to its flexibility and high power efficiency. Based on digital channelized receiver, this paper proposes a novel deceptive jamming method for linear frequency modulation (LFM) radar, side lobe jamming, which builds decoy group utilizing filter side lobes. Via adjusting the filter structure properly, this method produces false targets at specific positions. Unlike intermittent sampling repeater jamming (ISRJ) which forms a train of symmetric decoys, side-lobe jamming can generate asymmetric false targets, which is more deceptive. On the other hand, it can produce much more false targets than ISRJ, which has a certain suppressive effect on the radar. The experimental results with simulated data verify the effectiveness of the proposed algorithm.

Here, a multi-stopband frequency selective surface (FSS), covering commercial frequency bands CDMA, GSM-900, GSM-1800, LTE-2200 MHz, Wi-Fi, and Bluetooth for mobile communication applications has been proposed employing a pair of concentric square ring patches as a unit cell. Possibilities of annular ring patch type FSS are explored first. Finally, the design comes up with a compact square ring patch type single layer FSS. It is also explored that by increasing the width of the inner ring, operating bandwidth can be enhanced to cover closely spaced commercial frequency bands in a single band. Thereby the mutual coupling between the closely spaced resonators for multiple bands can be minimized. The proposed design is flexible enough to tune the desired resonance frequency by changing the length of the individual ring resonators. The design concept has been formulated using linear polynomial regression (LPR) techniques and validated through proper measurement of the fabricated prototype. This FSS can be used as a mobile back cover to protect mobile users from harmful radiations.

In this paper we determine the statistical distributions of the co- and cross-polarized Layered Rough Surface Index (LRSI) for three-dimensional layered structures with an arbitrary number of slightly rough interfaces illuminated by an electromagnetic plane wave. For infinite surface areas and Gaussian centered height distributions, we show within the framework of the first-order small perturbation method that the LRSI under a given observation direction is a random variable, whose statistical distribution is only function of two parameters. Contrary to the intensity ratio which follows a heavy-tailed distribution, the LRSI has finite mean and variance. For a structure air/clayey soil/rock, we analyze the influence of a snow layer upon the probability laws in the cases of Gaussian or exponential correlation functions.

This paper presents a new technique to enhance impedance bandwidth of single layer half width microstrip leaky wave antenna (HW-MLWA) with continuous main beam scanning. The enhancement is realized by etching four circular slots on the radiation element. Two of the circular slots are placed close to the feed port, and the others are close to the matching load. The wide main beam scanning is between +12˚ and +70˚ when operation frequency sweeps between 4.3 GHz and 6.5 GHz. A comparison between the Uniform HW-MLWA (reference) and the proposed HW-MLWA with circular slots is providedto study the effectiveness of the added circular slots. The proposed HW-MLWA is fabricated and tested. The measured impedance bandwidth is 49.9% (4.28 GHz to 7.13 GHz) with peak gain 10.31 dBi at 5 GHz, hence the proposed antenna can be considered as a suitable candidate for C-band applications.

This paper proposes an improvement to the whale optimization algorithm (WOA), which is based on the Levy flight technique. The improvement allows improved whale optimization algorithm (IWOA) to have a good diversity of population, faster convergence and overcome premature. The test by using different benchmark functions is conducted to demonstrate the effectiveness of improvement on the algorithm performance. Finally, IWO algorithm is applied to optimize the problems of two-way pattern of MIMO radar system, involving the achievements of sidelobe reduction, deep null and wide null at the prescribed directions. The obtained numerical results demonstrate that IWOA can not only efficiently fulfill the expected deep nulls and wide nulls at the prescribed directions, but also enable the peak sidelobe level to retain in the smaller level at the same time than several state-of-the-art algorithms.

A non-iterative inverse-source solver is introduced for the 2D Helmholtz boundary value problem (BVP). Microwave imaging within a chamber having electrically conducting walls is formulated as a time-harmonic 2D electromagnetic field problem that can be modelled by such a BVP. The novel inverse-source solver, which solves for contrast sources, is the first step in a two-stage process that recovers the complex permittivity of an object of interest in the second step. The unknown contrast sources, as well as the (permittivity) contrast, are represented using the eigenfunction basis associated with the chamber's shape; canonical shapes allowing for analytically defined eigenfunctions. This whole-domain eigenfunction basis allows the imposition of constraints on the contrast-source expansion at virtual spatial points or contours outside the imaging domain. These constraints effectively regularize the inverse-source problem and the result is a well-conditioned matrix equation for the contrast-source coefficients that is solved in a least-squares sense. The contrast-source coefficients corresponding to different illuminating fields are then utilized to recover the contrast expansion coefficients using one more well-conditioned matrix inversion. The performance of this algorithm is studied using a series of synthetic test problems. The results of this study are promising as they compare very well with, and at times out-perform, state-of-the-art inversion algorithms (both in terms of reconstruction quality and computation time).

Simple, compact and high sensitivity metamaterial-inspired microfluid sensors are developed to detect and classify dielectric fluids in the X-band regime using reflection coefficients. Multi-negative refractive index band metamaterial structure is specifically designed as a sensing enhancer, where the multi negative bands can effectively trigger the electromagnetic properties, as well as enhance the differentiation between the testing samples. The geometry of the metamaterial enhancer and its arrangement with the microfluidic channel and radiating patch antenna are optimized to reach the highest sensitivity of the samples' depiction. The proposed sensors were tested on methanol and ethanol traces, where sets of complex permittivity were varied. Distinguishable frequency responses generated from different samples at three resonances specify the capability of classifying the fluid concentration.

A simple and compact, self-isolated printed antenna able to operate in the 2.4 GHz (2400-2484 MHz) and the 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands in notebook computers is introduced. The design is built on a low-cost substrate with the dimensions 6 mm × 30 mm (about 0.05λ × 0.24λ at 2.4 GHz) and comprises a symmetrical coupled-fed loop and two parasitic shorted strips. For size reduction, the 2.4 GHz loop is loaded with a pair of L-shaped stubs above the feeding and coupling T strip. The parasitic strips shorted on both sides of the coupling T strip are further added to generate the 5 GHz band resonance. The results show that good radiation characteristics can be obtained in the bands of interest. In addition, when grouping three proposed designs with a gap of 4 mm between them, the results for each antenna impedance bandwidth, the isolation between any two of the three designs, and the envelope correlation coefficient (ECC) are also satisfactory.

A new design idea of MIMO beamforming antenna array for compact and thin handheld devices is investigated, where the beamforming function is used for transmitting and the MIMO function for receiving. The new design idea is illustrated by an antenna array consisting of eight printed planar inverted-F elements operating at GSM1900 (1880-1920 MHz) and LTE2300 (2300-2400 MHz). The 8-element antenna array is printed on an FR4 substrate of dimensions 136 mm × 68.8 mm × 1 mm. By using the radiation pattern diversity, good isolations, envelope correlation coefficients and mean effective gains are achieved for MIMO receiving. To realize the beamforming function when the antenna is used for transmitting, an optimal feeding mechanism is introduced by the method of maximum power transmission efficiency, which is then implemented by a continuously adjustable feeding circuit board. With the optimized feeding mechanism, the gain of the antenna array in the desired direction can be significantly enhanced. The effects of the human body on the performance of antenna array are also examined, and the results indicate that the proposed design still exhibits good MIMO and beamforming performances in a practical scenario.