A wideband elliptical bowtie impulse antenna is proposed and investigated in this paper. Simulated results reveal that it can achieve an impedance bandwidth of 141% for S₁₁≤-10 dB, a broadside gain of 2.4-5.3 dB, and stable radiation pattern over the whole operating band. The measured reflection coefficient is less than -10 dB over the frequency from 1.30 to 6.65 GHz, and it agrees well with the simulated results. The characteristics of frequency-domain such as radiation pattern, phase center and time-domain behaviors are discussed. The antenna electrical dimension is 0.31λ₀, where λ₀ is the free-space wavelength at lower edge of the operating frequency band. Parameters are studied to optimize the antenna performance.

We present a new RADAR system able to perform Phase Conjugation experiments over the ultrawideband [2-4] GHz. The system is equipped with a transmit/receive linear array made of eight antennas connected to a 2-port Vector Network Analyzer through eight independent couples of digitally-controlled RF attenuators and phase shifters. Thus, each channel can selectively transmit or receive and can as well attenuate and phase shift the RF signal. For each frequency, either the Phase Conjugation or the Decomposition of the Time Reversal Operator (DORT) is applied to the received signal and the appropriate amplitude and phase law is coded into the prototype; the focusing wave is then experimentally re-emitted by the array. The quality of the achieved backpropagation is evaluated both in frequency and time domain: in this sense we can speak of Time Reversal. The excellent agreement between measured and theoretical results validates the potential of our system.

Strong interests are recently emerging for development of solid-state devices operating in the so-called "terahertz gap" region for possible application in radio astronomy, industry and defense. To fill the THz gap by using conventional electron approach or transit time devices seems to be very difficult due to the limitation that comes from the carrier transit time where extremely small feature sizes are required. One way to overcome this limitation is to employ the traveling wave type approach in semiconductors like classical traveling wave tubes (TWTs) where no transit time limitation is imposed. In this paper, the analysis method to analyze the properties of drifting plasma waves in semiconductor-insulator structure based on the transverse magnetic (TM) mode analysis is presented. Two waves components (quasi-lamellar wave and quasisolenoidal wave), electromagnetic fields (E_y, E_z and H_x) and ω-and k-dependent effective permittivity are derived where these parameters are the main parameters to explain the interaction between propagating electromagnetic waves and drifting carrier plasma waves in semiconductor. A method to determine the surface impedances in semiconductor-insulator multi-layered structure using equivalent transmission line representation method is also presented since multi-layered structure is also a promising structure for fabricating such a so-called plasma wave device.

Electromagnetic scattering by conducting bodies of revolution (BOR) coated with homogeneous chiral media above a lossy half-space is formulated in terms of the Poggio-Miller-Chang-Harrington-Wu surface integral equation combined with combined field integral equation. A field decomposition scheme is utilized to split a chiral media into two equivalent homogeneous media. The spatial domain half-space Green's functions are obtained via the discrete complex image method. Due to the rotational symmetry property of BOR, the method of moment for BOR (BORMoM) is applied to the linear system solved by the multifrontal direct solver. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

Characteristics of electromagnetic wave propagation through a magnetized plasma slab with linear electron density profile is analysed. In the numerical analysis, cold, weakly ionized, collisional and steady state plasma layer is divided into sufficiently thin, adjacent subslabs, in each of which plasma parameters are constant. Reflection and transmission coe±cients are calculated for discretised plasma by considering electron density profile with positive and negative slopes. Wideband absorbtion characteristic is obtained with high collision frequency and high electron density combination in linearly decreasing profile as well as wideband transmission characteristic is obtained for low collision frequency and low electron density combination in linearly increasing profile of finite length. The general results show that in steady state, plasma layer behaves as a frequency selective medium satisfying the major requirements of current shielding applications as the function of plasma parameters and the strength of external magnetic field excitation. Proposed plasma layer can be used in current shielding and stealth applications as a matching layer between the surface and the incident electromagnetic wave.

In this paper, a directional slot antenna with parasitic patch and windowed superstrate is presented. Through this composition, high-gain property can easily be obtained by this proposed antenna. The proposed antenna has a measured impedance bandwidth of 2.41-2.49 GHz for S11<-10 dB, which can cover the 2.4-2.484 GHz frequency band of WLAN application. Simulated and measured results show that high-gain features up to 11.50 dBi across the corresponding impedance band are achieved. Details of the proposed slot antenna configurations and design procedures are given; the experimental results are also given and discussed.

A novel rectangular slot antenna with embedded self-similar strips is proposed for wireless local area network (WLAN) applications. The proposed antenna comprises a T-shaped monopole and inverted self-similar strips embedded in the rectangular slot etched on the ground plane. The measured results of the fabricated antenna show that the impedance bandwidths (VSWR<2) are 180 MHz from 2.36 to 2.54 GHz and 920 MHz from 5.05 to 5.97 GHz, which cover all the 2.4/5.2/5.8 GHz WLAN operating bands. And the radiation patterns are almost omni-directional in the azimuthal plane within the lower operating bands.

In this paper, we apply the parallel method of moments (MOM) to solve the Electric and Magnetic Current Combined Field Integral Equation (JMCFIE) for scattering by large, three-dimensional (3-D), arbitrarily shaped, homogeneous dielectric objects. We first derive the JMCFIE formulation which produces well-conditioned matrix equation when the MOM with Galerkin's type testing and Rao- Wilton-Glisson (RWG) functions is applied. We then develop a parallel conjugate gradient (CG) method on personal computer (PC) clusters using message passing interface (MPI) for solving the matrix equation obtained with JMCFIE. The matrix is decomposed by the row and stored in distributed memory of the node. Several numerical results are presented to demonstrate the accuracy and capability of the proposed method.

An efficient method is presented for rigorous description of three-dimensional electromagnetic diffraction fields in slot systems containing several parallel plane interfaces between dielectrics and conductors. For such structures, the method employs the representation of spatial field components in terms of two complex scalar functions. They specify two field polarizations, which reflect and refract on all parallel dielectric interfaces independently, one from the other, which essentially simplify the total solution of diffraction problem. As an example, the application of eigen-function expansions and mode-matching technique solves the specific problem of three-dimensional diffraction of a plane electromagnetic wave by a slot in a thin conducting screen located ahead of a half-infinite dielectric.

Synthetic aperture radar (SAR) imagery technology is one of most important advances in space-borne microwave remote sensing during recent decades. Completely polarimetric scattering from complex terrain surfaces can be measured. Polarimetric SAR (POLSAR), and its relevant technologies, such as POL-interferometric SA (POLINSAR), bistatic SAR (POL-BISAR), high resolution (in m and dm resolution) SAR, inverse SAR (ISAR) etc., have been providing rich all-weather, all-time and high resolution data and images of active miscrowave remote sensing. Fully understanding and retrieving information from polarimetric scattering signatures of natural media and SAR images have become a key issue for the SAR remote sensing and its broad applications. Many researches on polarimetric scattering and SAR imagery technology have been carried out (e.g., [1-6]). This paper presents a review of the research works in Fudan University (FDU) during recent years on theoretical modeling of the terrain surface for polarimetric scattering simulation and Mueller matrix solution, mono-static and bistatic SAR image simulation, new parameters for unsupervised surface classification, DEM inversion, change detection from multi-temporal SAR images, and reconstructions of buildings from multi-aspect SAR images, etc. [7-46]. Some applications are briefly reported.

We study the characteristics of nano-optical antenna made of two gold nano-particles by three dimensional numerical calculations in visible and near infrared bands. To carry the computational burden and guarantee the precision and speed of a three dimensional FDTD calculation, adaptive mesh refinement technology is used. In this paper, we first highlight the concrete way of controlling the emitter position and orientation to fulfill the requirements of larger spontaneous emission enhancement. Then, we analyze the far field distribution and find that the far fied directivity is strongly influenced by surface plasmon polaritons (SPPs). Choosing the incident wavelength of 600 nm, we compute the decay rates and radiant efficiency as a function of antenna geometry limitations. Next, the particle aspect ratio is optimized, and we obtain that L/R = 4 is the best for our optical-antenna. Furthermore, we present a spectrum analysis. Around 5000 fold spontaneous emission enhancement is successfully achieved. Finally, we find a piecewise linearity relationship between the particle length and resonant wavelength.

The feasibility of using a capacitive sensor to sense the proximity of an external load, especially a finger, to a mobile terminal antenna was experimentally studied using a PIFA-type antenna as one of the sensor's electrodes. It was found that with the proposed arrangement it is possible to detect objects with permittivity close to that of body tissue or the conductivity level of aluminium and the size of a human finger at distances up to 15 mm.

Rotating coils constitute a type of electrical transformers used to produce alternating voltage pulses exploiting the phenomenon of electromagnetic induction. In this study, we investigate the influence of the electromagnetic scattering from a metallic obstacle located inside the moving component. In particular, a perfectly conducting spherical core is positioned eccentrically inside a thin circular ring, rotating around an arbitrary axis passing through its own center, under plane wave excitation. Methods and formulas implemented in scattering and induction problems have been utilized for the derivation of the developed potential difference around the loop. Several graphs of the voltage output versus the geometrical characteristics of the conguration, are shown and explained.

This paper presents a phase-resolved optical coherence tomography (OCT) system that uses the polarization quadrature encoding method in a two-channel Mach-Zehnder interferometer. OCT is a powerful optical signal acquisition method that can capture depth-resolved micrometer-resolution images. In our method, a complex signal is optically generated, and its real and imaginary components are encoded in the orthogonal polarization states of one sample beam; absolute phase information can then be acquired instantaneously. Neither phase modulation nor numerical Fourier or Hilbert transformation to extract phase information is required, thereby decreasing data acquisition rates and processing time. We conducted signal post-processing to select data from the instabilities of reference scanning delay lines; the measured phase sensitivity was as low as 0.23°, and the corresponding path-difference resolution was 265 pm. A localized surface profile measurement of a chromium-coated layer deposited on a commercial resolution target surface was conducted. The results confirmed that successful images can be obtained even with very small optical path differences using the proposed method.

Design of array antennas for satellite applications is always a trade-off between physical constrains and pattern requirements. In this paper, the focus is on the design of a large array antenna for earth coverage applications using spot beams. The array antenna has a diameter of 1 m and consists of circular polarized horn antennas positioned in a non-uniform grid. By using a binary coded genetic algorithm (BCGA) the desired element positions and their excitations are optimized to fulfill the pattern requirements. In addition thinning has been used to study the possibility of maintaining good antenna performance when reducing the number of elements. The proposed antenna design has robust side lobe level, beam width and gain; all remain virtually unchanged under a change of operating frequency ±7% and under lobe steering over earth ±8.8^o.

This work presents an accurate and realistic positioning approach for indoor environments based on fingerprinting and ray-tracing techniques. Fading caused by multipath seriously degrades the performance of communication systems operating inside buildings. For this reason, the proposed localization method considers multipath effects due to reflections and diffraction from walls, roof and floor. However, fading in indoor environments can also be caused by the movement of people or the presence of furniture. Because people are the primary absorption agents in indoor channels, their influence on the radio propagation channel must be considered. The proposed localization method takes into account the effects of human body shadowing to provide a realistic estimation of the mobile station position. Numerical calculations in real indoor scenarios show reasonable results.

In this letter, a novel compact UWB bandpass filter (BPF) with sharp rejection skirt is realized using quintuple-mode stub-loaded resonator. The resonator can generate three odd-modes and two even-modes in the desired band. By simply adjusting the lengths of open stubs in shunt and shortcircuited stubs, the first five resonant modes of the resonator can be roughly allocated within the 3.1-10.6 GHz UWB band meanwhile the sixth resonant mode in the upper-stopband can be suppressed. The pair of short stubs can generate two transmission zeros near the lower and upper cut-off frequencies, leading to a sharp rejection skirt. A quintuple-mode UWB BPF is designed and fabricated and the measured results demonstrate the feasibility of the design process.

A compact elliptic-function band-pass filter (BPF) is introduced using microstrip folded quasi multi-mode resonator. The prototype filter is synthesized from the two-port network and equivalent circuit models using available element value tables. To optimize the performance of the filter, electromagnetic simulation (EM) is used to tune the dimensions of the filter. The filter using dual cascaded quasi multi-mode resonators provides a very sharp cut-off frequency response with low insertion loss. It also realized a broad band pass-band, a compact size and two transmission zeros at both the lower and upper stop-bands. The filter is also evaluated by experiment and simulation with good agreement.

A new method is presented to design dual-band, high-directivity, EBG-resonator antennas using simple, single-resonant, single-layer partially reflective surfaces (PRS). The tailored abrupt reflection phase change of partially reflecting surfaces, observed only at the resonance frequency of the PRS resonant inclusions (such as dipoles and slots), is exploited for this purpose. An example single-resonant PRS, based on a frequency-selective surface (FSS) composed of a printed slot array, was designed. Then it is used to design an EBG-resonator antenna to demonstrate the feasibility of achieving dual-band performance. Cavity models are employed, together with the reflection characteristics of the PRS, to understand the operation of the device at critical frequencies such as cavity resonance frequencies and the PRS resonance frequency. Antenna simulations and computed results confirm the dual-band operation of this very simple, singlelayer, low-profile EBG-resonator antenna. It resonates in two bands centered at 10.5 GHz and 12.3 GHz. The peak directivity in each band is 18.2 dBi and 20.5 dBi, and the 3dB directivity bandwidth of each band is 7.5% and 8.7%, respectively.

This paper proposes an efficient and automatic means of achieving a reduced model of a transfer function for UWB antenna design. According to the formulation of a transfer function, we have derived two factors, which are critical in determining the radiation pattern and input impedance respectively. Their special formula allow us to establish a reduced model automatically using the Model Order Reduction (MOR) techniques of a second order system. The process is free of any human factors and suitable to any antenna systems, thus enabling a direct and efficient interface with the optimization process in the design of a UWB antenna system. In addition, the proposed way of establishing a transfer function of the whole antenna system has successfully cascaded the entire system into separate subsystems, thus offering deeper insights in analyzing a UWB antenna system.