A modification in the structure of substrate has been carried out to reduce weight and improve the performance of microstrip patch antenna in X-band. A step profile is incorporated in the substrate along the radiating edges of the patch. The design is tested on both dielectric and magnetodielectric substrates. Return loss of antenna with varying step riser height and step tread length shows improvement in -10 dB bandwidth to 13.2% for the dielectric and to 12.3% for the magnetodielectric as compared to about 4.8% and 6.9% for unprofiled substrate geometry in dielectric and magnetodielectric respectively. As compared to the unprofiled planar antenna, maximum weight reduction for the stepped antenna on dielectric substrate is 54.75 % and for the magnetodielectric is 58.9% is observed. An equivalent circuit modeling for the stepped structure is carried out for the proposed structure.

In this paper the scanning properties of dual reflector antenna systems constituted by two confocal paraboloidal reflectors fed by a planar array are investigated. This antenna architecture combines the interesting features of reflectors and array antennas. Because of the offset configuration the radiation pattern exhibits an anomalous deviation in the beam pointing when the beam is scanned out of the boresight direction. Heuristic equations, representing an extension of the linear equations available in the literature, are derived, which permit predicting the pointing direction of the overall system as a function of the pointing direction of the feeding array in a significant field of view.

Micro-Doppler (MD) caused by the motion of the ballistic missile can contribute to successful recognition of the ballistic missile. Considering the real observation scenario. This paper proposes a method to derive the MD image of the ballistic missile by applying the range-Doppler algorithm (RDA) based on the real flight scenario and analyzes the factor for the real-time MD imaging. Simulation results using the flight trajectory constructed using the real target parameter demonstrate that we need a new cost function for phase adjustment and a new method for range alignment. In addition, matched-filtering needs to be performed in the baseband, and a sufficient PRF is required to prevent discontinuity of the MD image. Dechirping of MD and filtering of the random movement are also needed for a clear MD image.

This paper reports a 2.45 GHz, low power dual circularly polarized (DCP) and dual access rectenna. It contains two dc-recombined rectifiers and a cross-slot coupled square patch antenna fed by a microstrip line. A judicious dc recombination scheme allows to minimize the RF power imbalance between accesses caused by multipath effects and consequently arbitrary polarized incident waves. The proposed rectenna is then able to harvest linearly polarized, right-hand circularly polarized (RHCP) and left-hand circularly polarized (LHCP) electromagnetic waves, with nearly stable performances. The rectenna has been optimized at -15 dBm per access and dedicated to remote and contactless supply low consumption sensors. It has been experimentally tested with very low power densities from 0.057 μW/cm² (E_rms=0.46 V/m) to 2.3 μW/cm² (E_rms=2.95 V/m). At 1.49 μW/cm² (-15 dBm on each rectifier), the structure exhibits an output dc voltage and a global efficiency of 189 mV and 37.7%, respectively when the azimuthal angle (Φ) of the incident field is equal to 0°. Due to the nearly constant total gain of the DCP antenna and an appropriate dc recombination of the two rectifiers, the global efficiency slightly varies between 37.7% and 41.4% when the azimuthal angle (Φ) varies between -90 and 90°.

The scenarios of achieving effective ionospheric modification are summarized, and the likely physical processes engaging linear and nonlinear mode conversions through plasma inhomogeneity and nonlinearity are revealed. Parametric instabilities, which are the directly relevant processes to achieve effective heating of the ionospheric F region, are formulated and analyzed. The threshold fields and growth rates of instabilities are obtained. The nonlinear Schrodinger equation governing the nonlinear evolution of Langmuir waves is derived and analyzed. The nonlinear periodic and solitary solutions of the equation are obtained. The analyses illustrate the conditions for the generation of Langmuir soliton and nonlinear periodic Langmuir waves.

In this paper, we propose a modified version of the Random Sample Consensus (RANSAC) method for Interferometric Synthetic Aperture Radar (InSAR) image registration based on the Scale-Invariant Feature Transform (SIFT). Because of speckle, the ``maximization of inliers'' criterion in the original RANSAC cannot obtain the optimal results. Since in InSAR image registration, the registration accuracy is in inverse proportion to number of residues. Therefore, we modify the old criterion with a new one --- minimization of residues --- to obtain the optimal results. We tested our method on a variety of real data from different sensors, and the experimental results demonstrated the validity and robustness of the proposed method.

Given the emphasis on increasing wireless network usage for healthcare application, e.g. Wireless Body Area Network (WBAN), the need for high-rate physical layer has become a genuine concern from research and industrial community. The use of the Ultra-Wideband (UWB) is looking especially bright for such systems given its lower energy consumption and performances towards frequency-selective channels. However, the Multi-Band-OFDM-based UWB technique has some inherent limitations as loss in spectral efficiency due to the use of Cyclic-Prefix (CP). In this paper, a new physical layer scheme for high-rate wireless body area networks based on MB-OFDM with Offset Quadrature Amplitude Modulation (OQAM) modulation is presented. The proposed MB-OFDM/OQAM can achieve high spectral and power efficiency than conventional MB-OFDM system. Moreover, the use of the CP Interval in the conventional MBOFDM removes efficiently the Inter-Symbols Interferences (ISI) but remains ineffective towards the Inter-Carriers Interferences (ICI) caused by the channel frequency offset (FO). The performances evaluation of the proposed technique will be carried-out in realistic UWB-WBANs channels with various scenarios, which will be also presented and studied herein.

This paper investigates the use of double concentric circular ring elements arranged in a sub-wavelength grid on a single layer of substrate, in an effort to enhance the beam-scanning capability of reflectarrays. The work is done at 10 GHz on a 405 mm×405 mm aperture. In addition to a broad gain bandwidth, the reflectarray with a sub-wavelength grid exhibits a superior beam-scanning performance compared to the one with λ/2 grid. The measured results show that the reflectarray with 0.3λ grid spacing achieves a 1-dB gain bandwidth of 22% with an aperture efficiency of 56.6%. With the reflectarray fixed, this paper studies the possibility of beam scanning by displacing the feed horn laterally. The results show that beam scanning of ±15º is possible while preserving the broadband characteristics. It is also observed that a 1-dB gain bandwidth of 28% is achieved for the 0.3λ array when the feed is displaced laterally with an angle of 30º.

With the advancement of wireless networks and cloud computing, people are becoming increasingly surrounded by a variety of displays - rich electronic devices: TV, Phone, Pad, Notebook and other portable or wearable devices. These electronic products put high demands on the quality of the visual interface. Paper-like displays are reflective and do not require a backlight. They have received much attention after electrophoretic-based electronic paper displays were commercialized in 2004. Paper-like displays combine excellent reading experience with ultra-low power consumption. In particular, their outdoor readability is superior to transmissive liquid crystal displays (LCDs) and organic light emitting devices (OLEDs). In this paper, we give an overview onvarious paper-like display technologies with emphasis of the status and future development of electrophoretic display and electro-fluidic display principles. We focus on both technologies because electrophoretic displays have been commercialized successfully, and electro-fluidic display has high potential to deliver video and full color.

In this paper, a compact asymmetric coplanar strip (ACS)-fed printed monopole antenna for tri-band WLAN/WiMAX applications is presented. The proposed antenna is composed of a circular-arc-shaped stepped monopole with dual operating frequencies at 2.4/5.7 GHz and a simple circular-arc-shaped strip with the third operating frequency at 3.5 GHz. The three resonant frequencies of the antenna can be controlled by adjusting the geometries and the sizes of the stepped monopole, the strip and the ground plane. The antenna occupies a very compact size of 22.1×12 mm² including the ground plane, has nearly omnidirectional radiation characteristics and reasonable gain in the operating bands. The simple feeding structure, compactness and uniplanar design make it easy to be integrated within the portable device for wireless communications.

Equilateral-triangular slot antennas with modified edges for wideband circular polarization are proposed in this paper. Circular polarization was firstly obtained by adding two asymmetric perturbations to two edges of triangular slot. Then fractal-like boundaries were adopted in the antenna design for size reduction and broadband operation. Two antenna prototypes for RFID readers were fabricated to cover RFID UHF band and ISM 2.4 GHz band, respectively. Measured results show that the presented antennas obtain fairly wide 3-dB axial ratio bandwidths of 15.7% (820-960 MHz) and 19.8% (2.18-2.66 GHz).

An analytical expression of AC resistance of a single-layer air-core Helmholtz coil is presented. Proximity effects between both bundles and strands of litz-wire as well as skin effect are considered. To obtain an accurate analytical expression of proximity effect on bundle level and strand level, a precise distribution of magnetic field is discussed. The analytical expression of AC resistance and quality factor is verified with the experimental results, and the theoretical predictions are in agreement with the measured results.

A novel dual-band filter based on substrate integrated waveguide (SIW) is presented in this paper. The proposed filter is composed of two filters with different center frequencies and bandwidths, where they share the input and output ports with source-load coupling using rectangular SIW cavity structure. Muliti-transmission zeros have been obtained through electrical coupling between the source and load, which improves the frequency-selective characteristics of the filter greatly. Finally, a Ku-band substrate integrated waveguide dual-band filter with bandwidths of 220 MHz and 120 MHz was finally designed, fabricated, and measured. The measurement results are found to be in good agreement with the simulation results.

In this paper, a number of different application fields of inorganic luminescent materials are being discussed. In a tutorial manner, it will be shown how device requirements are being translated into properties the luminescent materials need to have. To this end many different material properties that have a strong influence on the device performance are discussed, such as the shape, the spectral position of the absorption- and emission bands and the decay time of the emission. The light yield under excitation with ionizing radiation, the energy resolution and the occurrence of afterglow are being treated as well. Subsequently, strategies are shown how to optimize these properties. Examples are given for light sources (fluorescent lamps and LEDs), radiation sources used for disinfection purposes and also for devices used in medical imaging and in horticultural applications.

A broadband printed quadrifilar helical antenna (BPQHA) integrated with a broadband feeding network for satellite communications is proposed. Using a multiple arm technique, satisfactory antenna characteristics over a wide bandwidth are realized. To feed the antenna, a novel compact broadband feeding network composed of a frequency independent 180° out-of-phase power divider, two Wilkinson power dividers and two broadband 90° phase shifters is designed. The measured boresight gain remains positive with a reflection coefficient lower than -11 dB over a bandwidth of approximately 26%. The axial ratio is below 1.7 dB and the half-power beamwidth is more than 120° over the same bandwidth. Details of the proposed antenna design are provided and discussed, as well as the experimental results.

A novel design of miniaturized dual-bandantenna based on mushroom cell and interdigital capacitor is presented in this paper. Four transmission line (TL) elements are loaded in a microstrip antenna, and each one is composed ofamushroom cell and interdigital capacitors. The interdigital capacitors contribute to the series capacitance and metallicvia-hole of mushroom structuresresult in the shunt inductance in the equivalent circuit model. The antenna works as a zeroth-order (f₀= 2.51 GHz) and first-order (f₁ = 3.78 GHz) resonant antenna with varied radiation patterns. Omnidirectionalradiation pattern and unidirectional radiation pattern are obtained at 2.51 GHz and 3.78 GHz, respectively.The overall size of the antenna is only 0.25×0.25×0.017λ₀³ (at f₀= 2.51 GHz). The proposed antenna features compact structure, low profile and easy fabrication. Good agreement between the simulated and measured results is also achieved, validating our design concept.

A new metamaterial-inspired polarization reconfigurable microstrip antenna is presented in this paper, in which a square slot is etched on the ground plane and two PIN diodes are mounted across the slot for polarization reconfigurability. A complementary split ring resonator (CSRR) can be formed by integrating the square slot with two diodes. By controlling the working states of two diodes, we can change the gap position of CSRR which will alter the polarization of the microstrip antenna. Therefore, the polarization of the microstrip antenna can be switched among linear polarization (LP), left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), respectively. The planar electromagnetic bandgap (EBG) structure is further introduced to extend the bandwidth of the 3dB axial ratio. In addition, the proposed metamaterial-inspired antenna with agile polarization reconfiguration can be feasibly controlled by using a simple biasing circuit. The simulations and experiments are given to verify the effectiveness and correctness of the proposed reconfigurable antenna design.

A novel ultra wideband (UWB) multiple-input-multiple-output (MIMO) antenna with different polarizations and band-notch characteristics is proposed in this letter. The antenna consists of two monopole antenna radiating elements with gradual change structure, which are placed perpendicularly to each other and printed on each side of the substrate to achieve a wide bandwidth and different polarizations. Band-rejected filtering property in the WLAN band is achieved by etching a H-shaped slot and employing a resonant L-shaped strip on two antenna elements. The proposed antenna has a small size of 27×37×1 mm³ with a bandwidth of 128.6% (2.35-10.82 GHz). Within the required band, the isolation for the two ports exceeds 18 dB. The envelope correlation coefficient is also measured.

Circularly polarized graphene based transmitarray for terahertz applications is proposed. The characteristics of the graphene material is explained. The cell element of the transmitarray is made of square Quartz cell. Dual circular graphene rings are printed on both sides of the Quartz substrate. The graphene ring radius is varied to change the transmission coefficient phase and magnitude. The effect of the graphene chemical potential on the transmission coefficient is demonstrated. Transmitarray is composed of 9×9 unit cell elements. A circularly polarized circular horn is used to feed the transmitarray at f=6 THz. The left- and right-hand field components in the E- and H-plane are determined. The variation of the gain and the axial-ratio with the frequency are explained. The peak gain is 18.63 dB and 1-dB gain bandwidth is 6.8%. The transmitarray produces a circular polarization from 5.5 THz to 6.5 THz.

The recent extension of the orbital angular momentum (OAM) concept from optical to microwave frequencies has led some researchers to explore how well established antenna techniques can be used to radiate a non-zero OAM electromagnetic field. In this frame, the aim of the present paper is to propose a new approach to generate a non-zero OAM field through a single patch antenna. Using the cavity model, we first analyze the radiated field by a standard circular patch and show that a circular polarized (CP) TM_nm mode excited by using two coaxial cables generates an electromagnetic field with an OAM of order ±(n-1). Then, in order to obtain a simpler structure with a single feed, we design an elliptical patch antenna working on the right-handed (RH) CP TM₂₁ mode. Using full-wave simulations and experiments on a fabricated prototype, we show that the proposed antenna effectively radiates an electromagnetic field with a first order OAM. Such results prove that properly designed patch antennas can be used as compact and low-cost generators of electromagnetic fields carrying OAM.