In airborne systems, where low aerodynamic drag is urgently required, an end-fire antenna is suitable to be used. An effort to develop such an antenna, using planar elements, is described in this paper. Here, a new kind of Microstrip Slotted Antenna with end-fire properties is presented. For investigating the end-fire radiation from microstrip antenna, three antenna elements are proposed during the study - 1) Single Patch Single Feed Microstrip Slotted Antenna, 2) Dual Patch Single Feed Microstrip Slotted Antenna and 3) Dual Patch Dual Feed Microstrip Slotted Antenna. All these proposed antennas are designed and simulated in two different EM tools, which are - CST Microwave Studio (MWS) based on time domain solver and ANSYS HFSS based on frequency domain solver. Thereafter, these antenna prototype models have been fabricated and tested. Good agreement is obtained between the simulated and measured results.

Energy-efficient transmission is fast becoming a critical factor in designing future mobile broadband cellular communication systems. This research work examines the constraints with regard to the achievable throughput and energy efficiency that can be attained on the use of precoding-based massive MIMO systems, bearing in mind the effect of some key performance impacting parameters. We first introduced an absolute energy efficiency-based model to evaluate the deep-down relationship among the packet length, the Bit error rate (BER) and throughput. Then, by means of simulation with cyclic coordinated search algorithm, optimal achievable throughput and energy efficiency performance have been shown and demonstrated for variable capacity of users and number of transmission antennas. This work is expected to be of enormous importance to practical system design on the use of massive MIMO antenna technology for data throughput and energy efficiency maximization in future 5G systems.

This article presents a novel contribution to the improvement of the analytic modeling of electrical machines using two-dimensional (2-D) subdomain technique with Taylor polynomial. To validate this novel method, the semi-analytical model has been implemented for spoke-type permanent-magnet (PM) machines (STPMM). Magnetostatic Maxwell's equations are solved in polar coordinates, and in all parts of the machine. The global solution is obtained using the traditional boundary conditions (BCs), in addition to new radial BCs (e.g., between the PMs and the rotor teeth) which are traduced into a system of linear equations according to Taylor series expansion. The magnetic field calculations are performed for two different values of iron core relative permeability (viz., 10 and 1,000) and compared to finite-element method (FEM) predictions. The results show that a very good agreement is obtained.

Imaging with electromagnetic waves has a wide range of applications from remote sensing of earth to concealed weapon detection, among the others. When data are collected in the far-field (imaging distance in the order of one wavelength or larger), linear electromagnetic imaging techniques mainly suffer a fundamental limit in the resolution called "diffraction limit". To overcome this limit, we propose the use of resonant near-field scatterers incorporated in the holographic imaging techniques. These scatterers convert part of the evanescent spectrum in the vicinity of the object to propagating spectrum that is measured by the antenna in the far-field. Here, we study the improvement in the resolution with decreasing the object-scatterer distance. We also investigate the effect of using multiple scatterers along the range and cross-range directions.

An integer-N quadrature frequency synthesizer for single-band UWB application was designed in 0.18 μm CMOS technology. A modified bottom-series quadrature voltage-controlled oscillator (QVCO) based on reconfigurable LC tank is employed to provide quadrature signals and cover a range from 6.48 GHz to 7.07 GHz. In order to suppress the reference spur levels, an improved charge-averaging charge pump and a highly linear phase-frequency detector (PFD) are used. From the carrier of 6.6 GHz, the measured reference spur is -78.2 dBc, and the measured phase noise is -115.4 dBc/Hz at 1MHz offset. The frequency synthesizer including buffers consumes a total power of 99 mW from a 1.8 V power supply. Chip size is 1.6 mm×0.9 mm.

The electromagnetic characteristics of two-dimensional composite right/left-handed transmission lines (2D CRLH TLs) were investigated for the normal incidence of plane waves. The measured characteristic impedance and reflection phases exhibited resonant high impedance properties (equivalent to zero reflection phase) at a frequency within the left-handed mode for one-dimensional CRLH TL. An equivalent circuit was proposed to explain the measured characteristics. The relationship between the resonant frequency and the circuit parameters for 2D CRLH TLs was clarified by deriving an approximate equation for the resonant frequency. The surface-wave transmission characteristics for the 2D CRLH TLs were compared with those for a mushroom structure.

A novel microstrip-to-CPW resonator is presented, which can be employed to design bandwidth-tunable bandpass filter. The tri-mode resonator is composed of a dual-mode microstrip resonator and a CPW stub printed on a single piece of substrate. Two varactors embedded in the resonator are utilized to adjust the frequencies of the first and third resonant modes independently, thus flexible bandwidth control can be achieved. For demonstration, a prototypical filter is implemented with fixed center frequency of 1.72 GHz and 9.3%-32.6% fractional bandwidth (FBW) tuning range. Good agreement is obtained between the simulated and experimental results.

An asymptotic solution of a 3D vector diffraction problem for a vibrator system placed over a rectangular perfectly conducting screen of finite dimensions is obtained in the framework of the uniform geometrical theory of diffraction (UGTD) using the asymptotic expressions for the impedance vibrator currents. The system consists of two orthogonally crossed vibrators with equal dimensions but different surface impedances. The vibrators are excited in-phase. An algorithm and respective software for computing the directional, power and polarization characteristics of the radiation field of this antennas system are developed. The conditions required to form a circularly polarized radiation with a maximally attainable directivity in the normal direction to the screen are determined depending on the screen dimensions and the distance between the vibrators and the screen.

In a recent study, the classical problem of a large circular loop antenna carrying uniform current and situated at the Earth's surface has been revisited, with the scope to derive a totally analytical explicit expression for the radial distribution of the generated magnetic field. Yet, the solution arising from the study exhibits two major drawbacks. First, it describes the vertical magnetic field component only. Second, it is a valid subject to the quasi-static field assumption, which limits its applicability to the low-frequency range. The purpose of the present work is to provide the exact canonical solution to the problem, describing all the generated electromagnetic field components and valid in both the quasi-static and non-quasi-static frequency regions. These two features constitute an improvement with respect to the preceding solution. The canonical solution, which is obtained by reducing the field integrals to combinations of known Sommerfeld integrals, is seen to be also advantageous over the previous numerical and analytical-numerical approaches, since its usage takes negligible computation time. Numerical simulations are performed to show the accuracy of the obtained field expressions and to investigate the behavior of the above surface ground- and lateral-wave contributions to the fields in a wide frequency range. It is shown that in the near-zone the two waves do not predominate over each other, while the effect of the lateral wave becomes negligible only when the source-receiver distance is far greater than the skin depth in the Earth.

In this paper, Gysel type Unbalanced-to-Balanced (UTB) Power Divider (PD) with arbitrary power division is proposed. UTB PD is a five-port device, and a standard scattering matrix for a five-port PD with arbitrary power division isderived. Design equations are obtained analytically. Using design equations, a UTB PD is designed at 2 GHz for power division ratio of 1:2, and simulation is carried out using HFSS. A prototype is fabricated, and measurement is performed to verify the simulation results of PD. Measured results are in good agreement with the simulated ones. The proposed PD shows in-phase characteristic within ±5◦. Measurement results show that isolation between two output ports is greater than 20 dB. Greater than 20 dB common-mode suppression from input port to output balanced ports is achieved. Differential-mode power is divided in power division ratio of 1:2 from unbalanced port to balanced ports. Measured fractional bandwidth of the proposed PD is 21%.

The existing target localization algorithms almost cannot be used to near-field target localization in Multiple-Input Multiple-Output (MIMO) radar, and this paper presents a novel method. This algorithm uses Chan algorithm to obtain initial estimate of the targets. Then we define a new residual matrix and use the weighted least square (WLS) method to get a more accurate positioning result. The Fuzzy C-Means (FCM)algorithm is introduced to get more stable and accurate estimation. Furthermore, this algorithm achieves accurate positioning of the MIMO radar demonstrated by simulations.

In this paper, studies on broadband microwave absorption and electromagnetic shielding effectiveness are reported in flexible rubber composites with low filler content of nanosize conducting carbon over 8-18 GHz frequency range of electromagnetic spectrum. Rubber based composites are prepared by loading of 1-15 wt% nanosize conducting Carbon Black (CB) in silicone rubber matrix. Effect of percentage loading of nanosize CB on DC conductivity, dielectric & microwave absorption properties and electromagnetic Shielding Effectiveness (SE) of silicone rubber composites is studied. The percolation threshold is achieved at low concentration (3 wt%) of CB in composites. The observed complex permittivity values revealed that composites with concentration of 5 wt% CB can provide more than 90% microwave absorption (Reflection Loss > -10 dB) over 8-18 GHz at composite thickness of 1.9-2.7 mm. Further, composites with concentration of 15 wt% of CB shows -40 dB SE over the broad frequency range 8-18 GHz at thickness 2.8 mm. The effect of composite thickness on microwave absorption properties and shielding effectiveness is also analyzed. Thus, the prepared rubber composites with suitable concentration of nanosize CB as filler may be used as microwave absorber in stealth applications as well as for EMI shielding of electronic equipments in various civilian and military areas.

Illumination optics in emerging naked-eye 3D display, especially in time-spatial multiplexing, or directional backlight naked-eye 3D display system, is systematically examined. Key issues in directional backlight system include: 1) Directional transmission of the left- and right-eye images to the corresponding viewing zone with small crosstalk; 2) The luminance on the screen should be homogeneous even for the viewers moving around. In this paper, we propose an adaptive optimization solution based on root mean square (RMS) for the design of illumination optics of the naked-eye 3D system. Based on the designed free-form backlight illumination, the overall design schemes for both single-user and multi-user naked-eye 3D display are proposed and demonstrated. By utilizing the novel dynamic synchronized backlight technique, the temporal crosstalk is effectively brought into control. The display defects such as the dark bands appearing at the joints of the lens array or at the middle of the Fresnel lens are simulated numerically and tested experimentally, hence providing effective design guidelines for the optical components as well as their fabrication error tolerance. Additionally, we propose a continuous backlight technique to improve the luminance homogeneity. Furthermore, a quantitative evaluation mechanism for the moiré pattern based on the Fourier analysis method, by introducing the contrast sensitivity function (CSF), is presented. A novel arrangement of a quasi-random RGB sub-pixel array is proposed to reduce the visibility of moiré pattern. As a result, full HD glassless 3D display suitable for glassless virtual and augmented realities is demonstrated with an unprecedented display quality.

Sparse reconstruction technique can be used to provide high-resolution imaging result for through-the-wall radar (TWR) system. Since conventional sparse imaging reconstruction algorithms usually require a tremendous amount of computer memory and computational complexity, it is very difficult to apply in the practical large-scale TWR imaging applications. To solve the above problem, an efficient sparse imaging reconstruction algorithm is proposed in this paper. The proposed imaging method combines the spectral projection gradient L1-norm (SFGL1) algorithm with nonuniform fast Fourier transform (NUFFT) technique to achieve imaging reconstruction. Benefiting from the function handle operation of SPGL1 and computational efficiency of NUFFT, the proposed imaging algorithm can significantly reduce the memory requirement and computation complexity. The simulated and experimental results have shown that the proposed imaging method can significantly reduce the required computer memory and computational cost while providing the similar recovered image quality as the conventional sparse imaging method.

A compact polarization diversity ultra-wideband (UWB) antenna with size 32×32 mm² is presented in this paper. The proposed antenna consists of a linear tapered slot (LTS) ground, two orthogonal micro-strip feed lines and a floating fork-shaped decoupling structure located diagonally across the two orthogonal microstrip feed lines. The ground is in one side of the substrate, and the feed lines and the decoupling structure are in the other side. In addition, two rectangular slots are made in both the ground and feed lines to widen impedance bandwidth. Simulated and measured results indicate that the band covers from 3.1 to 12GHz with S₁₁<-10dB and S₁₂<-15dB.

Non-metallic objects, such as match box and cigarette box, detection and identification are quite an essential task during personal screening from standoff distance to protect the public places like the airport. Although various imaging sensors such as microwave, THz, infrared and MMW with signal processing techniques have been demonstrated by the researchers for concealed weapon detection, it is still a challenging task to detect and identify different types of small size targets such as a matchbox, pocket diary and cigarette box simultaneously. Therefore, in this paper, an attempt has been made to develop such an algorithm/methodology by which different types of small targets, such as a matchbox and cigarette box, which is fully or half-filled or empty and pocket diary at different orientations beneath various cloths can be detected and identified with an MMW radar system. For this purpose, an optimal method has been proposed to form an image, and after that, in post processing a novel adaptive approach for detection and identification of considered targets has been proposed. The data were collected by MMW system at V-band (59 GHz-61 GHz). The proposed algorithm/methodology gives s quite satisfactory result.

A novel high-gain and high-power cavity slot antenna is presented in this paper. The antenna consists of a slotted cavity cover, a driven antenna and a polarization twist reflector. The driven antenna is a balanced-fed dipole. And a 2×4 slots array is etched on the top surface of the cavity cover. To excite the cavity slots with uniform amplitude and phase, the polarization twist reflector is used here. Compared with the antenna without the twister, the gain is improved by almost 4.0 dB across the operating band. In addition, the field distributions of the proposed antenna are analyzed through simulation, which proves a high power-handling capacity of 3.94 MW. To verify the design, a prototype operating at 5.8 GHz bands has been fabricated and measured. The measured maximum gain and radiation efficiency are 13.6 dBi and 95%, respectively.

Space-time antijamming problem has received significant attention recently in the passive radar systems, such as Global Navigation Satelite Systems (GNSS). These space-time beamformers use two adaptive filters, i.e., spatial filter and temporal filter for canceling interference signals. However, most of the work on spacetime antijamming problem presented in the literature require multiple antennas and delay taps. In this paper, a virtual space-time adaptive beamforming method is proposed. The temporal smoothing technique is utilized to add a structure of the received data model for the implementation of the proposed method without delay tap. Compared with the previous work, the presented method offers a number of advantages over other recently proposed algorithms. For example, the space-time weight vector can be obtained by simple algebraic operations. It has lower computational complexity.It can reduce system overhead since the temporal smoothing technology is used instead of multiple delay taps. Simulation results are presented to verify that effectiveness of the proposed method.

Fluctuations of the reentry plasma sheath can affect the propagation of Electromagnetic waves. The relations between fluctuations and the propagation of electromagnetic waves are analyzed. The effects on polarization propertiesin L-band, S-band and Ka-band during a typical reentry process are studied using methods derived by synthesizing the compressible turbulent flow theory, plasma theory, and electromagnetic wave theory together. Results show that in L-band and S-band, the effects increase with the altitude, while in Ka-band, the effects decrease with altitude. The effects at high altitude above 60 km are prominent in L-band and S-band, while the effects at middle and low altitude below 60 km in Ka-band are obvious. The effects in L-band and S-band are much bigger than that in Ka-band and can affect the signal properties of TT&C systems significantly, while the effects in Ka-band are much milder. The waves with large oblique incident angle can encounter much more severe conditions than that with small angle.

We introduce a novel two-stage approach for rapid design of massive metamaterials (MTMs), where performances of thousands of microstructures require evaluation. In Stage I, an equivalent circuit model is synthesized via rational function modeling to represent the frequency response of MTMs microstructures. In Stage II, Gaussian process (GP) regression models are unitized to build the relation between the physical setting of the microstructure, including geometric design variables and incident angles of electromagnetic (EM) waves and the representing parameters of the equivalent circuit model. As a consequence, the mapping from the microstructure physical parameters to the frequency response is easy to achieve and with high accuracy. We offer two metamaterial prototypes to illustrate that the proposed approach allows high efficiency in facilitating the design of massive MTMs. The experimental results demonstrate that our method is no longer limited by the complexity of microstructures and the spatial dispersion, induced by the variation of incident angle. We compare the accuracy of predicted responses against the reference data, and both examples yield average RMSE less than 0.05, which meets the requirements for many MTMS engineering applications.