Netted radar: Network communications design and optimisation

Networks of phased array radars are generally able to provide better counter stealth target detection and classification. Each radar sensor (or node) generates information which requires transmission to a central authority that is able to evaluate the information. This requires a communications network to be established to allow transmission of information to and from any node. Each radar node is limited by range and degree and relies on the formation of a multi-hop network to facilitate these transmissions.This paper presents a model whereby the radar beam itself is used in the formation of a multi-hop network. The phased array’s multi-functional nature allows rapid switching between communications and radar function. A model of how the communication system could operate is presented, and an evolutionary optimisation algorithm based upon the concept of Pareto optimality is used for the topological design of the network. Finally, a simulation environment is presented to show the simulated performance of the communication model and designed networks.     

Third-generation virtualized architecture for the MVNO context

The third-generation architectures have to support multiple mobile virtual network operators (MVNOs). They have also to host different types of these virtual operators. Virtualizing these architectures will allow the MVNOs to rapidly deploy their equipment. It will separate the management domain between them and the mobile host operator. It will also allow sharing resources and reducing the deployment cost. Motivated by these requirements, we propose some MVNO distributed architectures. First of all, we evaluate the physical and virtual deployment time, then we define the utility function of the equipment for the different types of MVNOs. The utility function evaluates the gain in deployment time for each type of MVNO. This function has to be maximized. Our study demonstrates that the data calls type is the best MVNO candidate for virtualization. This latter consistently yields the best overall utility across an important number of network equipment to be virtualized by varying the time required for software installation and the time spent to determine the physical position of the equipment.     

Finite-Impulse-Response Digital Differentiators for Midband Frequencies Based on Maximal Linearity Constraints

Maximally linear digital differentiators (DDs) are known for high accuracy in narrow frequency bands centered at the frequency for which they are designed. In this paper, designs of DDs of odd and even lengths having maximal linearity at the middle of the frequency band are presented. Applying the maximal linearity constraints to the magnitude response of a differentiator gives a system of linear equations, which can be solved for the impulse response coefficients of the differentiator. It is observed that the coefficient matrices of these equations are Vandermonde matrices, and this helps in finding the solution of the equations in closed form. Design examples are presented to show the accuracy of the presented designs, and it is observed that even-length designs are more accurate in a significantly wider frequency band as compared with odd-length designs     

Field theoretical treatment of H-plane waveguide junctionswith anisotropic medium

A method based on the equivalence principle and cavity field expansions is used to analyze an H-plane waveguide junction containing an anisotropic (ferrite or composite ferrite) post. Using the equivalence principle, magnetic surface currents are introduced at the imaginary boundaries chosen between the central region of the junction and the waveguides. The electric displacement in the junction can be completely expressed in terms of a solenoidal set. On the other hand, the magnetic induction in the junction must be expressed in terms of a solenoidal set and an irrotational set. Continuing the tangential magnetic field at the imaginary boundaries leads to a matrix equation, the unknowns of which are the amplitudes of the scattered waveguide modes. Using this method, H-plane waveguide junctions with ferrite and composite ferrite posts are considered. The numerical results show excellent agreement with previously published experimental and theoretical results     

Coplanar waveguide with top and bottom shields in place ofair-bridges

A convenient technique for the elimination of the coupled slot-line mode in coplanar waveguide (CPW) nonsymmetric circuits is proposed. This technique simply uses top and/or bottom ground plane shields and avoids the more costly airbridges. These shields are easy to fabricate; however, they may slightly affect the propagation of the CPW mode in the form of power leakage into the parallel plate TEM mode. This effect can be avoided by restricting operation to lower frequencies. Numerical comparisons between the effect of the shields and the airbridges on a CPW filter are presented     

MIMO iterative receiver SNR estimation strategies for link to system interfacing

This paper presents link to system (L2S) interfacing technique for multiple input and multiple output (MIMO) iterative receivers. In L2S interfacing, usually the post detection signal to noise ratio (SNR)‐based frame error rate lookup tables (LUT) are used to predict the link level performance of receivers. While L2S interfacing for linear MIMO receivers can be conveniently implemented, it is more challenging for MIMO iterative receivers due to unavailability of the closed form SNR expressions. In this paper, we propose three methods for post detection SNR estimation for MIMO iterative receivers. The first is based on the QR decomposition of the channel matrix, the second relies on the residual noise calculation based on the soft symbols, and the third exploits the closed form SNR expressions for linear receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. It is shown that linear and residual noise‐based SNR approximations result in a very good prediction performance whereas the performance of QR decomposition‐based method degrades for higher order modulations and coding schemes. This paper presents link to system interfacing technique for MIMO iterative receivers. A link to system interface model for iterative receivers is developed for evaluating the reference curves for different modulation and coding schemes, and results are validated by comparing the simulated and predicted frame error rates. Three post detection SNR evaluation schemes have been proposed for link to system interfacing all of which give good prediction performance especially at lower order modulation.     

Thermal Aging Effects on Cu Ball Shear Strength and Cu/Al Intermetallic Growth

Intermetallic growth and ball shear behavior of annealed Cu wire bonds on Al have been studied. The shear strength of Cu ball bonds decreased with time, and ductile fracture was the dominant failure mode from 125°C to 150°C. Al pad peel-off occurred as the aging temperature was increased above 150°C. The overall Cu/Al intermetallic thickness exhibited parabolic behavior as a function of time. A linear correlation was established between ball shear strength, metal peel-off occurrence, and intermetallic growth. The Cu/Al intermetallic growth activation energy was 0.23 eV, and the intermetallics identified in the experiment were CuAl₂ and CuAl.     

Multi-Fidelity High-Throughput Optimization of Electrical Conductivity in P3HT-CNT Composites

Combining high-throughput experiments with machine learning accelerates materials and process optimization toward user-specified target properties. In this study, a rapid machine learning-driven automated flow mixing setup with a high-throughput drop-casting system is introduced for thin film preparation, followed by fast characterization of proxy optical and target electrical properties that completes one cycle of learning with 160 unique samples in a single day, a > 10 ×  improvement relative to quantified, manual-controlled baseline. Regio-regular poly-3-hexylthiophene is combined with various types of carbon nanotubes, to identify the optimum composition and synthesis conditions to realize electrical conductivities as high as state-of-the-art 1000 S cm⁻¹. The results are subsequently verified and explained using offline high-fidelity experiments. Graph-based model selection strategies with classical regression that optimize among multi-fidelity noisy input-output measurements are introduced. These strategies present a robust machine-learning driven high-throughput experimental scheme that can be effectively applied to understand, optimize, and design new materials and composites.     

SER and throughput analysis of space–time analog network coded relaying system over shadowed Rician fading channels

Wireless Networks - This research article presents an innovative approach based on analog network coding (ANC) in conjunction with space time block coding (STBC) which is termed as space time...     

Effect of wafer thinning methods towards fracture strength and topography of silicon die

This paper characterizes die damage resulting from various wafer thinning processes. Die fracture strength is measured using ball breaker test with respect to die surface finish. Further study on surface roughness and topography of each surface finish is obtained by atomic force microscopy (AFM) and scanning electron microscopy (SEM) techniques. Stress relief process with 25 μm removal is able to strengthen 100 μm wafer by 20.4% using chemical wet etch and 75 μm wafer by 36.4% with plasma etch. Relatively, plasma etching shows higher fracture strength and flexibility compared to chemical wet etch. This is due to topography of the finished surface of plasma etch is smoother and rounded, leading to a reduced stress concentration, hence improved fracture strength.