A 3D compact printed monopole antenna for most of the wireless communication applications is proposed in this paper. The proposed antenna has dimensions 40×10 ×1.6 mm³; it is based on multi different length arms of E-shaped monopole with modified ground plane coupled with meander line. The performance of the 3D antenna is almost the same as a 2D antenna with reduction in size, and it could be fit in a wireless transceiver device. The size reduction about 25% compared to the 2D planar proposed antenna is realized on a printed circuit board to reduce the fabrication cost. The coupling between the antenna elements broadens the operating bandwidth, which includes most of the wireless commercial service bands, GSM850/ GSM900/ UMTS/ GSM1800/GSM1900/WCDMA2100 802.11b/g/LTE2600 (82 -2690 MHz) as well as 802.11a/n (5150-5825 MHz). The antenna's simulated and experimental results are in good agreement. It is fabricated on a low-cost FR4 substrate and measured to validate the simulation performances. Measured results display that the proposed antenna produces omnidirectional radiation pattern of -6 dB impedance bandwidth at multi operating bands and average gain of 2 dBi over the operating band.

A low-profile superstrate antenna operated at dual-band is proposed using a metasurface (MTS). In order to design the proposed antenna, the MTS as a partially reflective surface (PRS) has a zero degree reflection phase at dual-band and is composed of a substrate, periodic metallic square patches, and rings on one side and periodic metallic meshes on the other side. To satisfy the resonance condition of Fabry-Perot cavity (FPC) at a certain frequency and height of PRS from the ground plane, the reflection phase of the MTS should be controlled by the dimension of the substrate, square patch, square ring, and mesh. In this paper, the planar radiator having a ring patch and a rectangular patch is employed and designed to operate at 2.1 GHz and 5.8 GHz. Also, the height of MTS from the ground plane is 12 mm, which corresponds to about 0.08λ₀ and 0.23λ₀ at operation frequencies of radiator, respectively. As a result, the gain improvements at 2.1 GHz and 5.8 GHz are measured to be 4.1 dB and 3.2 dB, respectively.

An ultra-wideband frequency selective surface (FSS) for wide incident angles is proposed. Its -3dB bandwidth is from 3.49GHz to 12.13GHz, and the fractional bandwidth exceeds 110%. Some parasitic patches are appended to reduce the deviation of resonant frequency under wide-angle incidence. The proposed FSS exhibits an improved stability when the incident angles are in the range from 0° to 60°. The relative simulated and measured results are provided to validate its effectiveness.

This paper describes experimental studies of passive intermodulation due to metal-metal contacts. These studies cover the in uence of roughness surface prole and of the thin native oxide layer on PIM value versus contact axial forces. A complete description of a dedicated test bench used during dierent studies is done. Moreover, obtained results are compared to observations published earlier.

This paper presents a design of microstrip transmitting and receiving antennas to be used for time reversal ultra-wideband imaging applications. The transmitter and receiver arrays are together known as a time reversal mirror (TRM). Based on the properties of time reversal and its imaging applications, an antipodal Vivaldi antenna and a monopole antenna are proposed for the transmitter and receiver designs, respectively. Simulation and measurement results demonstrate the efficiency of the antennas for a time reversal mirror. The overall system is demonstrated for source and target imaging applications.

This paper presents a novel frequency reconfigurable monopole antenna that has switchable notch characteristic at center frequency of 5.3 GHz. The proposed antenna consists of a defective ground structure (DGS) to enhance the impedance bandwidth from 3.17 to 13 GHz. The F-shaped parasitic element with three stubs (two vertical and one horizontal) are located on the back side of the radiating patch to achieve the band rejection characteristics from 4.9 GHz to 5.7 GHz. The metallic ground plane structure is connected or disconnected to the F-shape parasitic element through stubs by means of p-i-n diodes. Experimental demonstration of applications of the proposed antenna structure as 5.3 GHz notched band ultra-wideband (UWB) antenna with all diodes in the OFF-state and as 5.3 GHz radiator for wireless local area network (WLAN) with all diodes in the ON-state is reported. In both the cases, good agreements between measured and simulated return losses, radiation patterns and realized gains are observed.

Two compact dual-band bandpass filters (BPFs) with closely spaced passbands are presented in this paper. Each of the filters consists of a stub loaded resonator, to which shorted lines are coupled. The ratio of the center frequencies of two passbands can be easily adjusted from 1.2 to 1.1 by changing the gap of the coupled line. In addition, seven transmission zeros (TZs) can be yielded to obtain high passband selectivity and enhance the out of band performances. As an example, two filters are designed, fabricated and measured. Both filters exhibit the merits of high passband selectivity, very low center frequency ratio, and wide stopband suppression.

In this paper, a multi-frequency broadband planar reconfigurable antenna is designed for smart mobile phone applications. The antenna comprises two monopole strips and a parasitic shorting strip, and generates several independent resonant modes through this kind of stub loading. The miniaturization and broadbandization of the antenna is achieved by bending the strip line and using coupling feed. In addition, loading the matching circuit at the feeding point, the bandwidth can completely cover 824-960 and 1710-2690 MHz. In order to cover a lower band LTE band 20 (800 MHz), a RF switch at shorting point is used to switch low frequency to 791 MHz. So the proposed antenna can work at GSM850,900; DCS1800; PCS1900; WCDMA bands 1, 2, 4, 5, 8; TD-SCDMA bands A, F; CDMA BC0,BC1 and LTE bands 1, 3, 5, 7,8, 20, 38, 39, 40, 41. Also, the total size of the antenna is 15 mm×30 mm×0.8 mm, which is very suitable for 4G slim smart mobile phone applications.

A novel method for generating electromagnetic field with orbital angular momentum (OAM) and correspondingly a practical design based on conical horn antenna are proposed in this paper. The OAM modes of ±m for r/φ field components and ±(m-1) for x/y ones can be generated by superposing the two orthogonal polarization degenerate TE_mn modes in circular waveguide through a mode-transformation section, and then radiated from the horn in the far end. The effectiveness of the proposed method is analyzed from physical mechanisms and demonstrated by both simulation and experiment for the presented new-typed OAM horn antenna.

A novel six-band metamaterial absorber based on four multiple-mode Ω-shaped resonators (MMORs) is presented, analyzed and measured in this paper. The discrete absorption responses, determined by horizontal-oriented and vertical-oriented MMORs, can be combined to add the total number of absorption peaks. Among the six absorption peaks, four absorption peaks are excited by horizontal-oriented MMOR, and the other two are excited by vertical-oriented MMOR. The absorber, composed of a simple resonators-dielectric-sheet sandwich structure, has six distinct near-perfect absorption peaks with the polarization-insensitive characteristic in the range from 2 to 17 GHz. To reveal the physical mechanism, the distributions of surface current and power loss density, and the equivalent circuit model are also investigated at the six absorption peaks. Moreover, the measured results are in good agreement with the simulated ones and show that the average absorption rate of proposed absorber is over 97.21%.

A novel Vivaldi antenna utilizing a tapered slot edge with a stepped structure (TSESS) to achieve miniaturization is presented in this paper. Compared with a conventional Vivaldi antenna of the same size, the proposed TSESS significantly extends the low-end bandwidth limitation and also improves the low-end antenna gain and radiation characteristics. The proposed antenna is fabricated and tested for validating the reliability of the design. The measured results show reasonable agreement with simulated ones. Moreover, a good time-domain response is indicated from the measured group delay, showing that the antenna meets the requirements of a UWB system.

In this paper, a fractal tetrahedron shaped dielectric resonator antenna (DRA) design for wideband applications is proposed. Two triangular-shaped fractal slots of different sizes are introduced to reduce Q-factor of DRA and in turn to achieve wide bandwidth (BW). Internal coaxial feeding is utilized for good impedance matching and ease of fabrication. The proposed fractal DRA is fabricated and tested. The measured results are in good accordance with the simulated ones. Measured impedance bandwidth of about 72.3% covering frequency band of 3.8-8.1 GHz is achieved. Good separation between co- and cross-polarized radiation patterns in broadside direction is achieved. Various design parameters and associated results are discussed in this paper.

Simulation and experimental measurement of a new design of an oblique incidence and polarization insensitive metamaterial absorber with multiband absorption is presented in this paper. The unit cell of the proposed metamaterial absorber comprises concentric continuous rings of different radii and widths placed in four different quadrants with identical pair of rings placed diagonally opposite, with each ring responsible for high absorption. The calculated dispersion behavior of MM absorber in terms of effective permittivity (εeff), effective permeability (μeff), and refractive index (ηeff) shows the metamaterial characteristics. The surface current and field distributions in MM absorber are simulated to understand the occurrence of absorption bands. The measured results show the absorption peaks of 99.5%, 99.8%, 99.5% and 99.9% at 7.20 GHz, 9.3 GHz, 12.61 GHz, and 13.07 GHz, respectively. The simulated results are well supported by the experimentally measured performance of the fabricated metamaterial absorber. It offers multiband absorption with bands lying in C-band, X-band and Ku-band for mobile communication, satellite communication and radar applications. With merged third and fourth absorption peaks, the proposed metamaterial absorber structure exhibits a broadband absorption.

In recent years, radio tomographic imaging (RTI) is an emerging device-free localization (DFL) technology enabling the localization of people and other objects without requiring them to carry any electronic device. Different from other DFL techniques, the RTI method makes use of the changes of received signal strength (RSS) measured on links of the network to estimate the radio frequency (RF) attenuation field and forms an image of the changed field. This image is then used to infer the locations of targets within the deployed network. However, there still lacks an efficient scheme which can achieve robust location estimation performance with low computational cost. To solve this problem, we propose a lightweight robust RTI approach in this paper. The proposed method not only can reduce the algorithm's storage and computational resource requirements, but also exploits the location information of wireless measurement nodes to improve the accuracy of the localization result, which ensures its robust performance. The effectiveness and robustness of the proposed scheme are demonstrated by experimental results where the proposed algorithm yields substantial improvement for localization performance and complexity.

This paper presents a general theoretical analysis of the Wireless Power Transfer (WPT) efficiency that exists between electrically short, Perfect Electric Conductor (PEC) electric and magnetic dipoles, with particular relevance to near-field applications. The figure of merit for the dipoles is derived in closed-form, and used to study the WPT efficiency as the criteria of interest. The analysis reveals novel results regarding the WPT efficiency for both sets of dipoles, and describes how electrically short perfectly conducting dipoles can achieve efficient WPT over distances that are considerably greater than their size.

This paper presents the design and fabrication of a coplanar waveguide (CPW) rectenna using a sequential modular approach. The rectenna is printed on high permittivity, low-loss board ARLON AD1000 (εr = 10.35 and tanδ = 0.0023 @ 10 GHz). The rectier section is realized with a single reverse-biased schottky diode SMS-7630 in reverse topology for which a diode model is obtained at -20 dBm for frequencies F0 = 2.45 GHz and 2F0= 4.9 GHz. The low-pass lter and the impedance matching are synthesized from passive CPW structures. Co-simulation technique is used to overcome CPW simulation limitation and to integrate the diode characteristic. The antenna consists of a circular slot loop antenna with stub matching such that its input impedance is close to 50 Ω. The goal of this work is to design a rectifier to simplify and speed up the fabrication process of a rectenna array. We reduced the number of processes to etch the rectifier on the board and minimized the number of lumped elements. At -20 dBm, simulation of the rectifier with an ideal impedance matching network shows rectification at 2.45 GHz with efficiency of 12.8%. The rectifier and rectenna shows efficiency of approximately 10% at an operating frequency of 2.48 GHz.

This paper presents a novel miniaturized dual-band fractal antenna for WLAN/WiMAX applications. The miniaturization of the proposed antenna is achieved by inserting, in the center ground of the antenna, square slots to excite two resonant modes simultaneously, leading to dual-band operation. The novelty of the proposed antenna is miniaturized size and ability to support multiband operations, which can be integrated in many electronic applications and wireless communication. This antenna has a compact size of only 25×25 mm2 and fed by a 50 Ω-microstrip feed line. To validate the design approach, an experimental prototype is fabricated and measured. The simulation and measurement results show that the antenna provides dual-band operation at 2.4 and 3.75 GHz with omnidirectional radiation pattern.

In this paper, the design, simulation andmeasurementof a dual-band polarizationinsensitive metamaterial inspired microwave absorber are presented.The unit cell is composed of two concentric closed ring resonator(CRR) structures forming octagonal rings which arecarved on an FR-4 dielectric substrate to give maximum absorption at dual frequencies of 2.09 GHz and 2.54 GHz. At these frequencies, the minimum reflection coefficients of -29.15 dB and -18.76 dB are achieved with absorption rates of 99.88% and 98.67% andnarrow 10 dB bandwidths of 2.62% and 2.76%, respectively. Microwave absorption property of the proposed absorber structure is simulated by setting the perfect electric boundary conditions in four planes whose surface normal vectors are directed perpendicular to the wave propagation direction. These numerical computation settings replicate the rectangular waveguideto be used in the experimental measurements for the comparison between the simulated and experimental results. It is experimentally verifiedby the waveguide measurement method that the absorption rates about 99% are achieved for dual bands with polarization insensitivity, thereby meeting the absorption requirements of LTE-band frequenciesfor a real time microwave absorber based energy harvesting systems.

The distorted Born approximation (DBA) of volume scattering was previously combined with the numerical solution of Maxwell equations (NMM3D) for rough surfaces to calculate radar backscattering coefficients for the Soil Moisture Active Passive (SMAP) mission. The model results were validated with the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) data. In this paper, we extend the existing model to calculate the bistatic scattering coefficients for each of the three scattering mechanisms: volume, double bounce and surface scattering. Emissivities are calculated by integrating the bistatic scattering coefficients over the hemispherical solid angle. The backscattering coefficients and emissivities calculated using this approach form a consistent model for combined active and passive microwave remote sensing. This has the advantage that the active and passive microwave remote sensing models are founded on the same theoretical basis and hence allow the use of the same physical parameters such as crop density, plant height, stalk orientation, leaf radius, and surface roughness, amongst others. In this paper, this combined active and passive model is applied to four vegetation types to calculate both backscattering coefficients and brightness temperature: wheat, winter wheat, pasture and canola. This model uses a single-scattering and incoherent vegetation model, which is applicable for the vegetation fields studied in this paper but not suitable for vegetation types where collective scattering or multiple scattering effects are important. We demonstrate the use of the DBA/NMM3D for both active and passive using the same input parameters for matching active and passive coincident data. The model results are validated using coincident airborne Passive Active L-band System (PALS) low-altitude radiometer data and Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data taken during the SMAPVEX12 field campaign. Results show an average root mean squared error (RMSE) of 1.04 dB and 1.21 dB for backscatter at VV and HH, respectively, and 4.65 K and 6.44 K for brightness temperature at V-pol and H-pol, respectively. The results are comparable to those from the tau-omega model which is commonly used to compute the brightness temperature, though the physical parameters used in this model are different from the empirically adjusted parameters used in the tau-omega model.

A frequency reconfigurable patch antenna is proposed. The antenna has a rectangular patch with two meandered slots. It can be switched between four bands using two PIN diodes by altering current distribution across the slot edges. The overall dimension of the antenna patch is 11.51 mm × 8.37 mm and fabricated on an FR4 substrate. The design is investigated by simulation and measurement, and the result includes S11 parameters, radiation patterns, measured directivity and gain. With different combinations of PIN diode biasing conditions, the antenna can be set to 6.80 GHz, 7.34 GHz, 7.80 GHz and 8.18 GHz, which collectively covers a continuous frequency range of 1.80 GHz (- 10 dB band width). The antenna also shows consistent radiation patterns at all the reconfigured frequency bands with an average beam width of about 75°. In the accessible frequency range an average gain of 5.14 dBi and low level of cross polarizations are also recorded. A good agreement between measured and simulated results validates the presented concept of frequency reconfiguration.