Inertial properties of the TE-waveguide modal fields are studied in time-domain making use of an analytical method, named as evolutionary approach to electrodynamics (EAE). To achieve inertial characteristics, electric field vector with dimension of volt per meter and magnetic field vector with dimension of ampere per meter in Maxwell's equations are factorized in SI units to obtain new electric and magnetic field vectors with their common dimensions of inverse meter. Having the fields with the common dimensions makes them summable. Using EAE, modal basis elements that depend on transverse coordinates and modal amplitudes that depend on time and longitudinal coordinate are obtained by solving the boundary eigenvalue problem. As a result of using the new electric and magnetic field vectors, the energetic properties are derived as real-valued functions of coordinates and time. Then, the inertial properties (that is, electromagnetic mass and momentum) of the TE-waveguide modes are obtained as the functions of time.

This work provides an in-depth study on a linear antenna array that consists of 32 elements of CRLH unit cells, and the main radiating beam can be controlled by changing the capacitance of the varicap diode that was designed and simulated with Advanced Design System (ADS 2014) software. ADS software was selected because of its flexibility in accommodating complex design equations. Results show that the main beam can be steered up to 50 degrees from the direction of maximum radiation by changing the capacitances. The main beam gain of the antenna array at boresight of 12 dB has been achieved with an impedance bandwidth of 3 GHz at 10 dB gain threshold. The antenna array performance was analysed in the mmWave frequency range at centre frequency of 28 GHz making it suitable for the upcoming 5G applications. The mmWave path losses were handled by increasing the gain of the antenna array and steering the main lobe over 50 degrees to balance the gain coverage trade-off. The direction of the main beam is controlled by changing the varicap capacitance accordingly.

Magnetic field intensity is modeled using Laplacian equations to study the spatial distribution of magnetic field under spherical shell plasma. The influences of different internal and external radii are also considered. In addition, the magnetic field calculation of plasma space is analyzed. The main conclusions are as follows. The external uniform magnetic field H₀ is the scalar magnetic bit, and the magnetic charge of the shell of the plasma is equivalent to that of a magnetic dipole. The magnetic field in the spherical shell is a super position of a uniform field and a magnetic dipole field. The uniform field is composed of an externally applied uniform field H₀ and a uniform field generated by the magnetic charge on the outer surface of the ball. The magnetic dipole field is generated by the magnetic charge on the inner surface of the shell, and the inside of the shell is a uniform magnetic field. When μ₂/μ₁ is high and a/b is low, the ratio of the magnetic field strength H₃ (the regionis r<a) to the magnetic field strength H₀ (the region is r>b) is low. By contrast, when μ₂/μ₁ and a/b are high, the ratio of the magnetic field strength H₃ to the magnetic field strength H₀ is high. When the magnetic permeability of the inner object is small and the spherical shell is thick, the produced plasma sheath is thick, and the external magnetic field in the spherical shell is weak. Therefore, when the shielding effect is good, the possibility that the ``black barrier'' phenomenon will occur is high, and ground radar detection will be difficult.

This paper concerns the analysis of the performance of a Composite Right-/Left-Handed (CRLH) distributed oscillator. In order to increase its output power, a modification of the standard configuration is proposed. The basic idea is to combine the signals from the two output ports of the structure by means of a Wilkinson combiner, so obtaining a single output generator. The power performance of the conventional two output oscillator and the power performance of the new configuration are numerically compared by changing the number of employed transistors. The same procedure is adopted to analyze the amplitude of the higher order harmonics in the generated signals as a function of the number of active elements. On the basis of simulated data an increase of the output power, together with a second harmonic reduction, is expected for the single output oscillator with respect to the standard CRLH topology. Experimental results fully confirm these numerical predictions.

The effect of users on the efficiency of mobile terminal antennas at 15 GHz, 28 GHz and 60 GHz is studied in this paper. It is performed using three four-element planar arrays. The first operates at 15 GHz with a bandwidth of 0.74 GHz, the second at 28 GHz with a bandwidth of 2.5 GHz and finally the third antenna at 60 GHz with bandwidth of 12.5 GHz. The effect of a user's finger is studied when being placed on four different locations over each antenna element, with six distances between the antenna and user's finger. The losses due to the increased shadowing are studied in terms of radiation efficiency (RE), matching efficiency (ME) and two additional multiple-input-multiple-output (MIMO) parameters i.e., envelop correlation coefficient (ECC) and multiplexing efficiency (MUX). For antennas operating at 28 and 60 GHz, the minimum frequency shift is observed when the finger is placed at 1.5 mm distance from the antenna, whereas for 15 GHz, the minimum resonance shift is observed when the finger is at 2 mm distance. Losses of up to 80% and 70% are observed for RE and MUX, respectively, when the finger is placed at 0 mm for all antennas compared to the case without user (WU). Finally, it is observed that the ME and envelop correlation coefficient losses are insignificant regardless of the antenna and finger variation.

This paper presents a theoretical approach to compare the performance of a directive and a quasi-omnidirectional on-body antennas.Two canonical antennas, namely, a dipole and a rectangular aperture, are considered in the 60 GHz band. We first demonstrate that for this on-body configuration, the classically-defined far-field antenna gain depends on the observation distance. Consequently, we derive results in terms of radiation efficiency and link budget. To do so, the antenna input impedance computation is a preliminary step to normalize the input power to allow a fair comparison between the two antennas. The impedance over a lossy half-plane of an aperture illuminated by a TE10 mode normally polarized is therefore derived into a convenient easy-to-compute formulation, which to authors' best knowledge, is not available in the literature. In terms of link budget, it is obtained that the received power due to an aperture is generally higher than the one due to the dipole in the main lobe direction. A constant difference is observed along the distance, and this difference increases with the aperture width for antennas touching the body. Besides, it is shown that the standard aperture waveguide WR15 exhibits a slightly higher efficiency than a vertical dipole with the same vertical size when being placed at a distance less than 3 mm (i.e., 0.6λ) from the body phantom surface. Above this distance, the dipole and the aperture exhibit similar efficiency in the order of 60%.

This paper devises a framework of phased array antennas to radiate multiple beams for a fixed coverage. The phased antenna array is chosen so that the beamforming can be fixed in selected coverage area. The antenna arrays are employed with a Butler matrix (BM) to form required phases of excitation coefficients to the radiating elements. Optimally designed 4×4 or 8×8 Butler matrix is utilized at the I/O ports of the phased antenna array. The grating lobes are reduced by using the principle of orthogonality to the feeds of subarray (group of column arrays of phased array). This article also exploits the concept of skirt elements to reach the desired coverage area while reducing the beam overlapping in the restricted area. Simulation studies highlight the proposed claims with elaborated numerical analysis of different case studies.

This paper presents two novel bandpass filters using sixteenth mode substrate integrated waveguide (SMSIW) and thirty-second mode SIW (TMSIW) cavities, respectively. The overall size of SMSIW and TMSIW cavities can be reduced by a factor of 15/16 and 31/32 in comparison to the filters designed in the conventional SIW resonator, while keeping almost the same resonant frequency. Based on SMSIW cavity, a first-order filter with the center frequency of 2.45GHz and a transmission zero (TZ) located at the upper-stopband is proposed. The second-order TMSIW cavity filter exhibits one TZ at the lower-stopband and two TZs at the upper-stopband, and it has a better performance of the passband than the former with the same size and center frequency. It also has a wider upper-stopband with suppression of an unwanted harmonic at 7.6GHz. Two intersecting rectangular slots are etched between the two cavities with a smaller angle between them of 30 degrees. The whole size of the filter is 24.2 mm×29.1 mm×0.508 mm. The filters are fabricated in SIW technology, and the frequency response shows good agreement between simulated and measured results.

In recent years, wireless indoor positioning systems have attracted significant research interest. However, maximizing system precision remains challenging, especially for three-dimensional (3D) estimates. In this paper, a novel hybrid approach to resolving this problem is proposed through the development of a multiagent system composed of a Bayesian network and a deep neural network for 3D indoor positioning. The proposed system is based on a combination of the multilateration and fingerprint methods in order to reduce the acquisition region of the received signal strength vectors. In addition, the relationship between the quality of the received signal and the noise level, which is influenced by the increase in the number of access points and the number of persons moving within the environment, is considered by the system. The proposed approach exhibits a better performance than other algorithms with an average positioning error of less than 0.9 m. This result represents a difference of more than 22 cm with respect to the most similar algorithm.

Electromagnetic band gap (EBG) structures offer unique solutions for effectively manipulating electromagnetic waves over a broad range of frequencies for a wide range of applications. However, most EBG designs reported so far either require sophisticated fabrication processes or have limited tunability and reconfigurability. In this paper, we investigate the potential to implement high performance tunable and reconfigurable EBG components using a novel optical control approach. This technology allows the generation of EBG structures through spatially-resolved photogeneration of free carriers in a semiconductor, without any complex fabrication processes. As a prototype demonstration, a reconfigurable microwave frequency tunable band-stop filter (BSF) based on photo-induced uniplanar EBG structures has been investigated through simulation. In this approach, the required EBG patterns are directly illuminated onto a Ge ground plane mounted to the bottom of a Duroid substrate for tunability using a digital light processing (DLP) projector. On the basis of HFSS simulations, the bandwidth of the BSF can be tuned by modifying the EBG pattern filling factor. The center frequency of the BSF could also be tuned from 8-12 GHz by adjusting the period of the EBG structure. In addition, two limiting factors, i.e., localized heating effects and finite lateral spatial resolution (due to carrier diffusion), that may affect the circuit performance in this technology have been investigated and discussed. By using a mesa-array structured ground plane, this approach is promising for developing tunable and reconfigurable circuits such as filters from the microwave to terahertz regimes.

Design and analysis of a novel wide-band covering, hetero triangle linked hybrid web fractal antenna is presented in this paper. The hetero triangle linked hybrid web structure has been designed through multiple iterations in the CST MICROWAVE STUDIO electromagnetic simulation tool and has been fabricated on FR4 dielectric of ε_r = 4.4 with height of 1.6 mm. The proposed antenna offers a comprehensive bandwidth of 18.055 GHz, covering from 1.945 GHz to 20 GHz. It supports various applications starting from 3G, LTE, ISM, Bluetooth, Wi-Fi, WLAN (2.4-2.48 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.72-5.82 GHz), WiMAX operating in the 2.3/2.5 GHz (2.305-2.36 GHz/2.5-2.69 GHz), 5.5 GHz (5.25-5.85 GHz) and Satellite communication (Ku band: Uplink of 14 GHz and Downlink of 10.9-12.75 GHz). The proposed antenna provides peak realized gain of 7.17 dB with efficiency more than 78% in the operating band. The antenna parameters such as reflection coefficient, gain and radiation patterns are determined through numerical simulation, and good matching is obtained with measured results.

A one-shot rescaling process, namely Automated Scaling Region of Interest (AS-ROI), is combined with an inversion technique of Forward-Backward Time-Stepping (FBTS). The purpose is to alleviate the ill-posedness and nonlinearity of inverse problem by reducing the size of the unknown problem. The inversion solution is carried out to reconstruct tumour as an unknown object in coarse investigation domain of lung area which is then rescaled down corresponding to object location and size. In this paper, edge preserving methods consisting of edge preserving regularization and anisotropic diffusion are imposed alternately on the solution and reconstructed profiles to improve the current method of AS-ROI. Results on the reconstructed lungs and tumours give significant insight of the proposed work. Accuracy level for the reconstructed profiles are significantly improved in spite that spatial resolution is retained as the original setting of FBTS.

Research on RCS evaluation for electrically large objects has been a hot topic for decades. Although multilevel fast multipole algorithm (MLFMA) has been the most popular method in scattering computation, due to the limitation of both CPU speed and memory size in a single computer, realistic large targets require discretization with millions of unknowns still cannot be solved by sequential implementations of MLFMA. In this paper, we introduce a Docker-enabled parallel MLFMA computing system based on MPI, which is proved to be friendly for deployment and economical for scalability, to solve electrically large scattering problems. In addition, the capability of the proposed system has been demonstrated by several canonical examples.

In this work, the design of a switched beam antenna array based on an optimized Butler matrix feeding network was done with a compact microstrip structure and a set of microchip antennas working at 2.45 GHz. The obtained antenna feeding network was tuned and optimized by using suitable unsupervised techniques to obtain a compact and efficient structure. A microstrip antenna array prototype composed by four elements was fabricated and experimentally tested. Good impedance matching and radiation properties have been experimentally verified with reference to the main beam steering capability.

Based on the multi-mode interference effect in the periodic dielectric waveguide, a novel waveguide crossing structure is proposed and analyzed. The structure can achieve crossing connection of three periodic dielectric waveguides at the same position with low crosstalk and relative high transmission coefficient. Based on electromagnetic numerical simulation methods, the proposed crossing structure of three periodic dielectric waveguides is calculated and analyzed in details, and at the optical communication wavelengths near 1.55 μm, crosstalks below 22 dB between the three crossing periodic dielectric waveguides are achieved.

An omnidirectional compact antenna based on dual-band Split Ring Resonators (SRRs) for 2.45 GHz wireless local area network (WLAN) and 3.5 GHz worldwide interoperability for microwave access (WiMAX) applications is presented. Dierent and new properties of SRRs, such as dual-band or multi-band performance in the design of compact antennas, can be obtained by making the rings unequal and asymmetric. The dual-band SRR antenna is designed with a bandwidth control technique based on stored electromagnetic energy on the resonator rings. The obtained results show that the SRR antenna has good omnidirectional radiation pattern for both bands and good impedance bandwidth. In addition, compactness and flexibility are obtained with a simple structure of the SRRs.

Generally, the null steering is performed by controlling the amplitude and/or phase weightings of all element excitations or only a small number of them. In such cases, a need for extra RF components such as variable attenuators and variable phase shifters with each element in the array is inevitable. In this paper, an alternative method is introduced where the null steering is performed by thinning (or turning off) only a small subset of the elements in the uniform linear arrays. To find an optimum combination of active (on) and inactive (off) elements, a binary genetic algorithm is used. In large arrays, the number of required nulls is much smaller than the total number of array elements, thus only a small subset of the array elements could be sufficient for producing the required nulls rather than optimizing all the array elements. By this way, a faster convergence speed of the optimizer and lowest peak sidelobe level can be obtained. The effectiveness of the proposed method with various subset configurations will be demonstrated and compared with some standard null steering methods.

With the ever-growing requirements of human security check in public, near-field millimeter wave (MMW) imaging techniques have been developing rapidly in recent years. Due to the lack of MMW images, low resolution and indistinguishable texture in most MMW images, it is still a great challenge to do high performance object detection task on MMW images. In this paper, we propose a novel framework to automatically detect concealed weapons and potential dangerous objects based on a single human millimeter wave image, in which a deep convolutional neural network (CNN) is presented to simultaneously extract features, detect suspicious objects, and give the confidence score. Unlike traditional optical image level solutions, we comprehensively analyze the original MMW data for object representation, incorporate domain-specific knowledge to design and train our network. Moreover, combined with the modern focal loss theory, we devise an effective loss function elaborately to optimize our model. Experimental results on both our dataset and real world data show the effectiveness and improvement of our method compared with the state-of-the-arts.

Using uniform linear array (ULA), a passive localization algorithm is presented for mixed far-field (FF) and near-field (NF) signals scenarios. Based on the high-order cumulant (HOC) technique, a special Hermite matrix is constructed by three fourth-order cumulant matrices, which are calculated by dividing the ULA into two sub-arrays. Then, the special matrix of signals is decomposed to obtain the source subspace. According to ESPRIT algorithm, two transformation matrices of all sub-arrays can be obtained. Meanwhile, the two transformation matrixes could be used to calculate the range and angles of arrival (AOA) of NF sources, as well as AOAs of FF sources. Moreover, compared with twostage MUSIC (TSMUSIC) and four-order cumulant MUSIC method, the proposed algorithm has higher accuracy for localisation of both FF and NF sources without any spectral search.

This paper presents a Ka-band TDD transceiver system module for the secondary surveillance radar application with attractive temperature characteristic. Four multifunction chips and a MEMS filter are designed and fabricated in GaAs pseudomorphic high electron mobility transistor (pHEMT) process and MEMS technology in this work, respectively. These multifunction chips and MEMS filter with some other commercial chips are assembled in a compact cavity to form the transceiver system. The temperature characteristics of the designed chips and the whole transceiver module are measured respectively in this work. Benefiting from the designed temperature compensation circuits on the chips, the transceiver is able to work from -55˚C to +75˚C with little performance fluctuation. The noise figure of the receiver is less than 3.7 dB in the 400 MHz working bandwidth. Its dynamic range is more than 59 dB with more than 23.9 dB power gain. The maximum output power of the transmitter is larger than 30.3 dBm. The system only has two input/output ports and one control bus, which is suitable for the large-scale system integration.