Adaptive gain and delay mismatch cancellation for LINC transmitter

Linear amplification with Nonlinear Component (LINC) transmitter architecture is an efficient solution for high efficiency amplification of signals. Nonetheless, this solution suffers both from gain impairment and delay mismatch between the two signal paths. Indeed, a mismatch in propagation time between the paths degrades the quality of the transmit signal but also disrupts the convergence of the gain correction algorithm resulting in a degradation of its performance. In this paper, we present an adaptive algorithm based on a gradient descent formulation for the identification and correction of these delays. We also demonstrate its effectiveness when applied prior to the gain adjustment procedure. The identification approach is preferred here, to ensure monitoring facilities.     

Performance evaluation of fault-branch detection in TDM passive optical networks by spectral analysis of interferometric signals

A new fault-branch detection scheme is proposed to troubleshoot the breaks of any distribution fibers in a time-division multiplexing (TDM) passive optical network. We employ a continuous optical frequency sweeper at the optical line terminal (OLT) and an interferometric (IF) device at each optical network unit (ONU). By analyzing the spectrum of the returned combined signals at the OLT, we can obtain the status of all branches. This detection method not only uses a small optical frequency band for surveillance monitoring, but is also simple to operate. Furthermore, a modified architecture is proposed to relax the specifications of IF devices. The tolerance of the IF device length was analyzed using the Monte–Carlo simulation method.     

Total Power Optimization for Combinational Logic Using Genetic Algorithms

Power consumption is a top priority in high performance circuit design today. Many low power techniques have been proposed to tackle the ever serious, highly pressing power consumption problem, which is composed of both dynamic and static power in the nanometer era. The static power consumption nowadays receives even more attention than that of dynamic power consumption when technology scales below 100 nm. In order to mitigate the aggressive power consumption, various existing low power techniques are often used; however, they are often applied independently or combined with two or at most three different techniques together, and that is not sufficient to address the escalating power issue. In this paper, we present a power optimization framework for the minimization of total power consumption in combinational logic through multiple V _dd assignment, multiple V _th assignment, device sizing, and stack forcing, while maintaining performance requirements. These four power reduction techniques are properly encoded into the genetic algorithm and evaluated simultaneously. The overhead imposed by the insertion of level converters is also taken into account. The effectiveness of each power reduction mechanism is verified, as are the combinations of different approaches. Experimental results are presented for a number of 65 nm benchmark circuits that span typical circuit topologies, including inverter chains, SRAM decoders, multiplier, and a 32 bit carry adder. Our experiments show that the combination of four low power techniques is the effective way to achieve low power budget. The framework is general and can be easily extended to include other design-time low power techniques, such as multiple gate length or multiple gate oxide thickness.     

2.5D Quantitative Millimeter Wave Imaging of a Hidden Object on a Simplified Human Body Model Using Value Picking Regularization

In this contribution, the authors provide a proof of principle for quantitative imaging of concealed objects on the human body using millimeter waves. A two-and-a-half-dimensional (2.5D) quantitative millimeter wave imaging algorithm is applied to reconstruct a hidden dielectric object on a clothed simplified human body model. At millimeter wave frequencies, the incident field is typically a fully three-dimensional (3D) Gaussian beam, illuminating only a limited spot on the body. Due to the large dimensions of the human body in terms of wavelengths, a 3D discretization is hardly feasible. Therefore, it is assumed that the electromagnetic properties of the body do not significantly change within the illuminated spot, along the longitudinal direction of a person. Hence, only the cross-section of a human body model is discretized. This 2.5D assumption however is still not sufficient to reduce the forward problem to a feasible size. Therefore, a priori knowledge on the illumination and on the scattering properties of the clothed human body is used to deduce a simplified model to describe the cross-section of the clothed human abdomen. The complex permittivity profile of a small dielectric object, hidden underneath clothing and representing some type of explosive, is reconstructed. The complex permittivity profiles of all other scatterers are assumed to be known. The presented quantitative inverse scattering algorithm is based on a Newton-type optimization, combined with an approximate line search and regularized by applying Stepwise Relaxed Value Picking regularization. The input data of the quantitative inverse scattering problem are synthetic scattering data since the authors are not aware of any amplitude and phase measurement data for concealed weapon detection yet made available to the inversion community at these high frequencies.     

Bulk Nanostructured Thermoelectric Materials: Preparation,Structure and Properties

Bulk nanostructured materials have recently emerged as a new paradigm for improving the performance of existing thermoelectric materials. Here, we fabricated two kinds of bulk nanostructured thermoelectric materials by a bottom-up strategy and an in situ precipitation method, respectively. Binary PbTe was fabricated by a combination of chemical synthesis and hot pressing. The grain sizes of the hot pressed bulk samples varied from 200 nm to 400 nm, which significantly contributed to the reduction of thermal conductivity due to the enhanced boundary phonon scattering. The highest figure of merit ZT of the binary PbTe sample reached 0.8 at 580 K. Mg₂(Si,Sn) solid solutions have shown great promise for thermoelectric application, due to good thermoelectric properties, non-toxicity, and abundantly available constituent elements. The nanoscale microstructure observation of the compounds showed the existence of nanophases formed in situ, which is believed to be related to the relatively low lattice thermal conductivity in this material system. The highest ZT of Sb-doped Mg₂(Si,Sn) samples reached 1.1 at 770 K.     

Analysis of Scattering Characteristics for Strip Grating Sandwiched between Two Dielectric Layers under Oblique Incidence and Its Applications in Spatial Filters and Circular Polarizers

Scattering characteristics of strip grating sandwiched between two dielectric layers in the case of plane-wave arbitrary oblique incidence are carefully investigated by a new method which combines coordinate revolving theory with the rigorous mode matching method. Comparisons between the results obtained with the present method and those given by the other methods verify the effectivity and practicability of the present method. The spatial filter characteristics of the new strip grating structure are given. It shows that the ultra-wideband bandpass characteristics can be realized using the present structure. Besides, a new circular polarizer is proposed. It is indicated that the new circular polarizer can realize complete circular polarization for every frequencies by means of changing the structure parameters of the dielectric uniform layers, which overstep the limitation of single strip that can achieve circular polarization only in a fixed frequency. The present investigation gives some useful guidelines for accurate design of the spatial bandpass filters and circular polarizers.     

The self-formation graded diffusion barrier of Zr/ZrN

In this paper, the 5 nm ZrN diffusion barrier was deposited by high vacuum magnetron sputtering method on Si substrate and the 300 nm Cu(Zr) alloy film or Cu film was sputtered on ZrN barrier without break vacuum. The self-formation graded Zr/ZrN diffusion barrier was obtained by annealing Cu(Zr)/ZrN bilayer system in N₂/H₂ (10% H₂) atmosphere. The X-ray diffraction (XRD) and four-point probe method were used to study graded Zr/ZrN diffusion barrier. The results revealed that the self-formation Zr barrier and ZrN barrier all obviously improved the thermal stability of Cu/Si system.     

Design of Concentric Circular Antenna Array with Central Element Feeding Using Particle Swarm Optimization with Constriction Factor and Inertia Weight Approach and Evolutionary Programing Technique

In this paper the maximum sidelobe level (SLL) reductions without and with central element feeding in various designs of three-ring concentric circular antenna arrays (CCAA) are examined using a real-coded Evolutionary Programming (EP) to finally determine the global optimal three-ring CCAA design. Standard real-coded Particle Swarm Optimization (PSO) and real-coded Particle Swarm Optimization with Constriction Factor and Inertia Weight Approach (PSOCFIWA) are also employed for comparative optimization but both prove to be suboptimal. This paper assumes non-uniform excitation weights and uniform spacing of excitation elements in each three-ring CCAA design. Among the various CCAA designs, the design containing central element and 4, 6 and 8 elements in three successive concentric rings proves to be such global optimal design set with global minimum SLL (−39.66 dB) as determined by Evolutionary Programming.     

Evolution of the AgCdO Contact Material Surface Microstructure with the Number of Arcs

This paper describes a study of the evolution of the AgCdO contact material surface microstructure as a function of the number of electrical arcs imposed on the switching surface. Five power switching devices were tested under different conditions. They were subjected to, respectively, 1, 2, 3, 10, and 100 electrical arcs under the same operating conditions: supply current of 400 A, circuit voltage of 28 V direct current (DC), and resistive load. For the analysis, a binocular microscope and a scanning electron microscope with an energy-dispersive x-ray spectrometer were used.     

Investigation of W-band Integrated Horn Array by Using Full-wave Simulation

To obtain a very good performance antenna in W-band, an integrated horn array with matching network of the antenna/mixer is investigated. The array is mounted on the wafer substrate, where a quasi-optically fed mixer is integrated with some annular slots. High gain and wide-band have been realized, and a minimized size has been obtained due to this compact structure. Meanwhile, to design this device efficiently, a modified alternating-direction implicit pseudo-spectral time-domain method combining with a hybrid matrix manipulation technique is developed. Full-wave simulation is verified at the design distributed stage. Numerical results are in very good agreement with the experimental data.