This work presents an ultra-wideband (UWB) low noise amplifier (LNA) with active shunt-feedback technique for wideband and flat gain by using standard 0.18 μm CMOS processes. Different from past resistive shunt-feedback technique, the capacitor supersedes by a transistor in active shunt-feedback technique. The active shunt-feedback provides input matching generating a 50 Ω real part with proper design and achieves flat gain from 2.5 GHz to 12 GHz. The UWB LNA achieved 11.4±0.2 dB gains, 4.5~5.2 dB noise figure (NF), 13.5 mW power consumption at frequency 3.1 GHz to 10.6 GHz, -15 dBm of 1-dB compression point (P1dB), and -3 dBm of input third intercept point (IIP3) at 6 GHz. The chip size including pads is only 0.6×0.5 mm².

Recently, we have introduced a numerical method for calculating local dispersion of arbitrary shaped optical waveguides, which is based on the Finite-Difference Time-domain and filter diagonalization technique. In this paper we present a study of photonic crystal waveguides at interfaces and double hetero-structure waveguides. We have studied the waveguide stretching effect, which is the change in lattice constant of photonic crystals along waveguiding direction. Hybrid modes at photonic crystal heterostructure interfaces are observed, which are the results of superposition of existing modes in adjacent waveguides. The dispersion at the interfaces of a double hetero-structure waveguide tends to the dispersion of outer waveguides. The effective area still holding the dispersion of the middle waveguide is shorter than the geometrical length of the middle waveguide. The results of this study present a clear picture of dispersion at interfaces and the transmission in photonic crystal hetero-structures.

This paper presents a multiband meandered loop antenna for smart phone applications. The proposed antenna which features a meandered folded-loop generates two resonance modes in the LTE/GSM bands. The current distributions of the excited resonance modes are analyzed to investigate the mode characteristic. By using a capacitively coupled feed on the backplane, the impedance bandwidth is broadened to cover LTE/WWAN bands. The simulation performed in this research used a high frequency structure simulator (HFSS) to optimally design the antenna, and a practical structure was constructed for the test. Details of the various antenna parameters are presented and discussed in this paper.

Several georeferenced measurements of electric field were done in a pilot area of Caracas, Venezuela, to verify that the magnitude of radio frequency electromagnetic fields is below the human exposure limits, recommended by the International Commission on Non-Ionizing Radiation Protection. The collected data were analyzed using geographical information systems, with the objective of using interpolation techniques to estimate the average electromagnetic field magnitude, to obtain a continuous dataset that could be represented over a map of the entire pilot area. This paper reviews the three methods of interpolation used: SPLINE, Inverse Distance Weighting (IDW) and KRIGING. A statistical assessment of the resultant continuous surfaces indicates that there is substantial difference between the estimating ability of the three interpolation methods and IDW performing better overall.

A scanning antenna at THz region is proposed and developed based on the quasi-optical techniques. It is composed of extended hemispherical lens/dielectric waveguide feed, inverse Cassegrain antenna, and transform lens. The extended hemispherical lens/dielectric waveguide feed is the key innovation of the scanning antenna. The inverse Cassegrain antenna is realized at THz region with special process and techniques, and the transform lens is used to match the input beam and the quasi-optical feed. The properties of the quasi-optical antenna are simulated with the FDTD method, and the experiments are carried out. The measured radiation pattern of the antenna is in agreement with the simulated result.

Novel compact microstrip quadruple-mode stub-loaded resonator and broadband bandpass filter (BPF) are proposed in this letter. As a starting part of designing a quadruple-mode broadband BPF, the initial novel triple-mode open impedance-stepped stub loaded resonator characteristic is investigated to choose its proper dimensions. Based on these pre-determined dimensions of the triple-mode resonator, two identical short-circuited stubs are loaded against the impedance-stepped open stubs in the resonator to generate a tuned resonant mode and a transmission zero in lower stopband which leads to a high rejection skirt. A compact broadband BPF with the quadruple-mode resonator is simulated, fabricated and measured. The measured results agree well with the EM simulations.

This paper presents a miniaturized branch-line coupler with suppression of wideband harmonics based on a unit of transmission-line section with triple-stub. This fundamental unit produces three transmission zeros and exhibits wide stopband response due to the triple stubs. It is used to replace a quarter-wavelength line in conventional branch-line coupler, leading to size reduction and wideband harmonics suppression. The closed-form equations are given for the coupler design. As an example, a branch-line coupler operating at 1.0 GHz is designed, fabricated and measured. Measurements agree well with simulations, and show that the proposed branch-line coupler occupies 56% size of a conventional one and achieves wideband harmonics suppression (better than 17 dB) from 1.8 GHz to 6.4 GHz. The 2nd, 3rd, 4th, 5th, and 6th harmonics are suppressed better than 34 dB, 19 dB, 30 dB, 17 dB, and 32 dB, respectively. With the theoretical analyses and practical results, it is shown that the proposed one has the advantages of simple structure, convenient analysis and wideband harmonics suppression.

A compact and simple interdigital capacitor inverted-F antenna (IFA) operated at its quarter-wavelength (λ/4) mode as the fundamental resonant mode for achieving multiband operation in the mobile phone is designed. The proposed antenna consists of a monopole antenna and an IFA. The proposed interdigital capacitor IFA has a simple structure of comprising two meandered radiating strips of length about λ/4 and is fed using an interdigital capacitor coupling feed. The two meandered radiating strips also generate two λ/4 resonance modes at about 900 MHz and 2100 MHz to cover the GSM850/900/1800/1900/DCS/PCS/UMTS bands and the 2.4 GHz WLAN (IEEE 802.11b) band operations. Further, the proposed antenna has a simple planar structure and occupies only a small area of 10×40 mm² on the system circuit board of the mobile phone. This proposed antenna with multiband, broadband matched impedance, stable radiation patterns, constant antenna gains, good radiation efficiency and compact size can be suitable for mobile phone applications.

A novel time-domain physical optics (TDPO) is proposed to determine the transient response of electromagnetic scattering of electrically large homogeneous dielectric targets modeled with triangular facets. Formula of the novel TDPO is derived, in which a time-domain convolution product between the incident plane wave and the time-domain physical-optics (PO) integral is included. The time-domain PO integral is evaluated with a closed-form expression based on a Radon transform interpretation, which makes the novel TDPO highly efficient in speed. The wideband rador cross section (RCS) is conveniently obtained from the transient response with a fast Fourier transform (FFT). Numerical results demonstrate the efficacy of the new method.

The Epsilon-Near-Zero (ENZ) super-tunneling structure with weakly coupled cascaded ultra-narrow channels is proposed and demonstrated to have notably wider bandwidth than single stage tunneling structure. An extensive parametric study for such structures is performed to investigate the factors which can affect super-tunneling performance. It is found that the coupling between the ultra-narrow channels is required to be weak enough to ensure a continuous supertunneling band. In addition, electric field in the cascaded channels is enhanced, compared with that in the single channel structure.

We present a rigorous 2D numerical study of the transmission, reflection and crosstalk coefficients of the perpendicular, identical dielectric crossing waveguide with various core-cladding index contrasts for both TE and TM polarizations. Our method is based on a hybrid frequency-domain finite-difference (FD-FD) technique computed with the cross-symmetry model. By varying the intersection profile, such as the circular, filleted, tapered and elliptical shapes, we achieve, even for a large 3.5 to 1.5 index ratio, a low 0.25dB insertion loss, a nontrivial reduction over the straight direct crossing case.

Adaptive nulling algorithms that minimize the total array output power from the array require constraints on the adaptive weights, otherwise nulls would be placed in the main beam and the desired signal rejected. The concept of cancellation patterns is reviewed and extended to partial adaptive nulling. Cancellation patterns are then extracted from adaptive nulling results with a genetic algorithm and a 32 element dipole array model. The cancellation patterns provide insight into the constraints needed for the successful implementation of a power minimization adaptive algorithm.

A two-layer nondestructive method for characterizing the electric and magnetic properties of lossy conductor-backed magnetic materials using a flanged rectangular-waveguide probe is examined. The two reflection measurements necessary to determine both permittivity and permeability are made by first applying the probe to the material under test and then applying the probe to a knownmaterial layer placed on top of the material under test. The theoretical reflection coefficient is obtained using a rigorous full-wave solution, and an extrapolation scheme is used to minimize the error due to truncating the modal expansion of the waveguide fields. An error analysis is performed to compare the performance of the technique to the two-thickness method, which utilizes two different thicknesses of the material under test. The properties of the known material layer that result in the least error due to network analyzer uncertainty are determined. The sensitivity of the two-layer method is also explored and discussed.

The paper discusses a retrieval technique of complex permittivity of ore minerals in frequency ranges of 12--38 GHz and 77--145 GHz. The method is based on measuring frequency dependencies of transmissivity and reflectivity of plate-parallel mineral samples. In the 12--38 GHz range, the measurements were conducted using a panoramic standing wave ratio and attenuation meter. In the 77--145 GHz range, frequency dependencies of transmissivity and reflectivity were obtained using millimeter-band spectrometer with backward-wave oscillators. The real and imaginary parts of complex permittivity of a mineral were determined solving an equation system for frequency dependencies of transmissivity and reflectivity of an absorbing layer located between two dielectric media. In the course of the work, minerals that are primary ores in iron, zinc, copper and titanium mining were investigated: magnetite, hematite, sphalerite, chalcopyrite, pyrite, and ilmenite.

In this paper, a wide-band, polarization-insensitive, wide-angle terahertz metamaterial absorber is presented. Simulated results show that the absorber can achieve polarization-insensitive, wide-angle absorptions in a wide band from 4.15 to 4.85 THz. The retrieved impedance shows that the impedance of the absorber could be tuned, in the absorption band, to match approximatively that of free space on one side and to mismatch on the other side, rendering both the reflectance and transmission minimal and thus the corresponding absorbance maximal. The simulated absorbances under three different loss conditions suggest that high absorbance is mainly due to the metallic absorption (Ohmic loss). The dielectric loss of the substrate is minor compared with the metallic absorption. The distribution of the surface current density indicates that the electric and magnetic responses are mainly caused by the front structure. This wide-band terahertz metamaterial absorber has potential applications in many functional devices such as microbolometers, thermal detectors, and solar cells.

An important application of electromagnetic band-gap (EBG) structures is reducing the mutual coupling and eliminating the scan blindness for array antennas. However, some array antennas have small element spacing,and traditional mushroom-like EBG materials are too large. Under this condition, miniature EBG structures are desired for these array antennas. In this paper, a novel method using spiral ground plane is proposed to reduce EBG structure sizes. A low frequency band-gap can be obtained by adjusting the width and length of the spiral arms. An experimental prototype is fabricated to validate the analysis. The measurement results show a good agreement with the simulation data. Compared with traditional mushroom-like EBG structures, the proposed EBG achieves more than 77% size diminution.

This article describes the design and performances of a rectenna that collects low incident power density levels, at a single ISM-band frequency (f₀=2.45 GHz). A new rectenna topology consisting only of an antenna, a matching circuit, a Schottky diode, and a DC filter has been modeled using a global simulation. A circular aperture coupled patch antenna is proposed to suppress the first filter in the rectenna device, and in addition, the losses associated with this filter. The harmonics rejection of the antenna is primarily used to reduce the rectenna size. The implementation of the filter in the antenna structure, combined with a reduction of the rectenna size, gives several advantages in several applications where the size and weight are critical criteria. The maximum energy conversion efficiency in this configuration is 34% and is reached for a load of 9.2 kΩ and a RF collected power of S_RF=17μW/cm²(≈-10 dBm RF incident upon the diode).

Both explicit analysis and FEM numerical simulation are used to analyze the field distribution of a line current in the so-called Maxwell's fish eye lens [bounded with a perfectly electrical conductor (PEC) boundary]. We show that such a 2D Maxwell's fish eye lens cannot give perfect imaging due to the fact that high order modes of the object field can hardly reach the image point in Maxwell's fish eye lens. If only zeroth order mode is excited, a good image of a sharp object may be achieved in some cases, however, its spot-size is larger than the spot size of the initial object field. The image resolution is determined by the field spot size of the image corresponding to the zeroth order component of the object field. Our explicit analysis consists very well with the FEM results for a fish eye lens. Time-domain simulation is also given to verify our conclusion. Multi-point images for a single object point are also demonstrated.

3-dimension finite-difference time-domain (FDTD) method is used to simulate the enhanced blue light emission of gallium nitride light emitting diode (GaN-LED) using the surface-plasmons (SPs) coupling with the quantum wells. The numerical simulation results demonstrate that when the silver film is coated on GaN-LED, the excited SPs play a key role in the enhanced blue light emission, and the enhancement depends on the geometries of GaN-LED and silver film. An enhancement factor is given to describe the enhancement effect of light emission. By changing the structure parameters of GaN-LED and silver film, the enhanced peak of the light emission in the visible region can be controlled. Under the optimal parameters, about 17 times enhancement at 460 nm can be obtained, and the enhancement effect is evidently demonstrated by the SPs field distribution.

A microstrip-line-fed Isosceles Trapezoidal Dielectric Resonator Antenna (ITDRA) with a parasitic strip and modified ground plane is introduced. It is proved by simulation and experiment that the antenna's resonant frequency can be lowered and the bandwidth can be increased considerably by introducing a slot and optimizing its position and dimensions in the ground plane. The proposed antenna is a wide band antenna with a 2:1 VSWR bandwidth of 21.5% centered at 2.51GHz and exhibits good radiation characteristics and moderate gain in the entire operating band. The antenna covers important application bands viz. ISM: Bluetooth/WLAN 2.4/Wibree (802.11 b/g/n)/ZigBee, WiBro and DMB. The wideband response in the relatively lower frequency range which includes the above mentioned application bands are not much seen anywhere in literature. Details of the design along with experimental and simulation results are presented and discussed.