In this paper direction-of-arrival estimation (DOA) of multiple narrow-band sources, based on higher-order statistics using propagator, is presented. This technique uses fourth-order cumulants of the received array data instead of second-order statistics (auto-covariance) and then the so-called propagator approach is used to estimate the DOA of the sources. The propagator is a linear operator which only depends on the array steering vectors and which can be easily extracted from the received array data. But it does not require any eigendecomposition of the cumulant matrix of the received data like MUSIC algorithm. Computer simulations are carried out to compare the performance of the proposed method to those of methods based on auto-covariance using MUSIC and propagator algorithms.

A new approach of imaging reconstruction of concealed PEC targets in a dielectric closed box, using azimuth multi-angle measurements, is developed. As the broadband stepped-frequency radar transmits planar wave from different azimuth directions around the target, the backscattered electrical fields in both the amplitude and phase are obtained. The two-dimensional fast Fourier transform (2D-FFT) algorithm for spline interpolation is adopted for uniformly sampled backscattering fields. Then, 2D images of a dielectric box with and without the concealed targets can be numerically simulated. Multi-azimuth backscattering electri- cal fields of complex shaped PEC targets and dielectric surrounding walls are calculated by the method of moments (MoM), which is based on the coupled volume-surface integral equation (VSIE). The concealed targets can be well identified from the imaging reconstruction.

This paper presents a basic analysis about experiment results using planar coils inner ring coils, defining a transformer, when this system is excited by square wave voltage. In this study phenomena of response to step voltage due to parasitic capacitances is analyzed, and a sum of responses when the input square wave frequency increases is given too. These phenomena are uncommon in literature, which can be applied to several areas of researches in electrical engineering, pulse transformers and power electronics.

A highly miniaturized low-pass filter using microstrip open-loop and semi-hairpin resonators is designed and analyzed to enhance the bandwidth and further size reduction of this kind of elements. Initially, two microstrip open ring resonators and separately, two semi-hairpin resonators are arranged and attached back-to-back to each other respectively. A compact LPF is designed and simulated using these modified resonators. The size reduction of this proposed filter is reported about 65% with 190% enhancement of bandwidth in analogy with the conventional low-pass filters.

This paper presents a de-interleaved subsampling receiver architecture suitable for homodyne receivers. The proposed topology requires only a single branch to down-convert and extract the in-phase (I) and quadrature (Q) baseband signals. Using a single-branch receiver eliminates the I/Q mismatch issue of traditional direct down-conversion receivers. The simplicity of the proposed receiver architecture makes it an alternative solution for multi-band and multi-standard applications.

A design methodology of narrow band-pass frequency selective surfaces (FSSs) using the Fabry-Perot approach is presented. The whole FSS structure consists of two identical single layer FSSs separated by a foam layer, which forms a Fabry-Perot interferometer (FPI). The band-pass characteristic is a result of the FPI. The pass band can be controlled by the thickness of the foam, and the bandwidth can be controlled by the reflection coefficients of the single layer FSSs. The effects of both metallic and dielectric losses are discussed. It is interesting to note that the transmission peaks of FPI with high Q factor decline rapidly and finally disappear as the losses increase, and the insertion loss is mainly due to the refection. The relationship between the insertion loss and the Q factor of the FPI is examined. As examples, narrow band-pass FSSs at about 96 GHz with different bandwidths are designed.

In this work, a polarisation agile antenna based on an array of two injection locked oscillators is presented. The proposed topology provides a theoretical relative phase shift range of 360 degrees between the output signals, which can be easily controlled through two DC voltages. The behaviour of the system is studied, both through simulations and measurements of the manufactured prototype, focusing on the joint performance of the oscillators. The data transmission capabilities of the system are analysed, proposing a solution for phase modulated signals.

In this paper, two broadband measurement methods, shorted microstrip method and microstrip trnasmission method, are discussed, and the complex permeability of ferromagnetic thin films is measured from 100MHz to 18GHz. The S-parameters of the two measurement fixtures are measured by vector network analyzer (VNA). The perturbations of the thin film loaded in the measurement fixture are analyzed; the discontinuity between coaxial and microstrip is considered; the effective permeability is deduced from measured S-parameters; the permeability of ferromagnetic thin films is extracted from effective permeability by using conformal mapping. The results show that the experimental results agree with the theoretical ones closely, and higher measurement sensitivity and accuracy are achieved by using shorted microstrip method.

In this paper, a novel microstrip bandstop filter by etching a square split ring in the center of microstrip line is proposed. Low insertion loss in the passband, high rejection level and integrated structure should be mentioned as advantages for this resonator. A transmission line model for this resonator is introduced and its resonant frequency is calculated analytically. Good agreement between the experimental results, full-wave simulation, transmission line model and analytical result has been achieved.

In this paper, a new technique that combines adaptive transmit antenna selection, transmit power allocation and iterative detection is introduced for the modified Turbo-BLAST system. At the transmitter, in order to minimize the BER performance of the overall system, an adaptive transmit antenna selection scheme is proposed to select the appropriate antenna subset for the actual transmission, and the proper power is allocated for the selected antennas subject to the total transmit power constraint. At the receiver the modified MMSE detector taking the imperfect CSI into account is used to remove the co-antenna interference. Finally the turbo principle is employed for iterative detection to further lower the BER results. Simulation results show that the introduced adaptive transmit antenna selection and power allocation algorithm can significantly improve the BER performance, and the iterative detection technique can further enhance the performance.

This paper presents an analysis about the results of experiments using planar coils inner ring coils to determine a transformer. The excitation of this system was a square wave voltage, where experiments were realized in two ways: considering planar coil as primary and observing responses on secondary being ring coil (direct system) and the inverse (ring coil as primary and planar coil as secondary-inverted system). In this study, a phenomenon not common in literature on system response is analyzed, showing effects of changes on transfer function in both cases when varying turn numbers of each coil and several variations on responses due to changes on resistances, parasitic capacitances, self and mutual inductances of the coils. The uncommon phenomenon appears as modulated response on specific turn ratio. The obtained results can be used to researches in areas as power electronics and pulse transformers.

Radio over Fiber (RoF) system has attracted much industry and research interest to extend the wireless cell coverage and reduce the cost by using the distributed remote antenna units (RAUs). However, the effective transmission fiber length in the RoF systems would be limited due to the time division duplex (TDD) mode used in the practical WiMAX access. Here, we study the transmission limitations and performances of the standard WiMAX signal for RoF systems. The throughputs and packet-losses at different fiber lengths are also investigated and analyzed. Besides, in order to increase the emitting power of the RAUs, a robust TDD switching mechanism is proposed in each RAU for RoF system.

In this paper, an approach based on a multi-scaling strategy for the reconstruction of the non-measurable components of equivalent current distributions is tested against experimental data. An extensive set of simulations is carried out considering single and multiple scatterers with homogeneous as well as inhomogeneous properties. Selected results are reported and discussed to show potentialities and limitations of the method.

This paper introduces a new configuration for a two phase field assisted hybrid switched reluctance generator, which can operate in motoring mode as well. This concept allows higher output power production compare to standard SRG. The proposed novel generator consists of two magnetically independent stator and rotor sets (layers), where each stator set includes four salient poles with windings wrapped around them, while the rotor comprises of two salient poles with different arc lengths and no windings. There is a stationary reel, which has the field coils wrapped around it and is placed between the two-stator sets. In this format, the developed magnetic field from the stator poles travels to the rotor then to the rotor shaft and finally completes its path via the generator housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. The analysis is carried out for the machine in self exited generator mode as well as field assisted mode. In the numerical analysis, the finite element analysis is employed, whereas in the experimental study, a proto-type generator has been built and tested.

We report on the modeling of light reflection in disordered chirped mirrors with a photonic band gap in the visible. The stop band limits have a threshold-like behavior as a function of disorder and sustain a certain amount of disorder before changing. We determine the disorder value that leads to a substantial broadening of the total reflection range.

This work presents a novel design for high-impedance surface (HIS) embedded dielectric resonator (DR) structures to efficiently control bandwidth of suppressing simultaneous switching noise (SSN) in high speed digital printed circuit boards (PCBs). The proposed structure is designed by periodically embedding high dielectric constant materials into the substrate between a continuous power plane and a middle patch. A conventional HIS structure has only one resonance frequency to produce stopband while the proposed structure has two resonances to widen the suppression bandwidth. The -30 dB stopband of the proposed structure is about two times wider than that of a conventional HIS structure. The excellent SSN suppression behavior was verified by measurements and simulations.

In traveling wave tube (TWT) amplifiers, an axial focusing magnetic field is required to keep electrons traveling in a narrow, pencil-like beam over the considerable length of the circuit. Conventionally, this focusing has been accomplished by using a periodic permanent magnet system housing axially polarized ring magnets. Making the structure to this point has been a complicated process consisting of brazing multiple metals together and honing the piece to the desired specifications. We present a new method of fabricating this housing structure monolithically using iron, developing magnetically oversaturated housing regions, and saving processing time and effort.

In this paper, the wave propagation and the cutoff frequencies of a rectangular metallic waveguide, partially filled the metamaterial multilayer slabs have been studied. The equations of the TMM method are not complex and the numerical examples show that we can easily obtain the characteristics of the metamaterial multilayer's rectangular waveguide satisfyingly. The cutoff frequencies of the metamaterial waveguide show very different characteristics compared with the usual waveguide.

Strong visible green upconversion emission in nanocrystalline BaZrO₃:Yb³⁺ powder, obtained by a hydrothermal process at 100ºC, is reported. The unconverted emission has a quadratic dependence on the pump intensity with a lifetime around half that of the NIR lifetime. Results suggest cooperative upconversion as the mechanism responsible for the green fluorescence. This efficient Yb³⁺-based cooperative up-conversion process allows the development of novel emitting materials in the UV-VIS range.

This paper demonstrates a novel way to enhance the temperature sensitivity in one-dimensional (1D) photonic band gap (PBG) material by using a ternary periodic structure (i.e. three material layers constituting a period of lattice). The temperature sensitive wavelength band shift of (Si/SiO₂) periodic structure was significantly enhanced when the structure was modified by sandwiching a thin layer of Bi₄Ge₃O₁₂ between every two layers, constituting a period of lattice. When the thickness of sandwiched layer was increased further enhancement in temperature sensitivity was observed. These 1D ternary PBG structures can be substituted in place of 1D binary PBG for enhancing the temperature sensing performance.