Electromagnetic interference mitigation by using a spread-spectrumapproach

We investigate a new technique, referred to as spread-spectrum clock generation (SSCG), for reducing the level of radiated emission from devices with digital clock signals. To calculate the radiated emissions from such devices, we model the radiating geometry and compute the radiated field at a multitude of frequencies by using NEC-4, which is an electromagnetic field solver based on the method of moments (MoM). We consider a variety of modulating profiles for the spread spectrum clock and demonstrate that by using a frequency deviation of only 1%, we can achieve from 10 to 30 dB reduction in the radiated emission levels     

High-finesse large band Fabry-Perot fibre filter with superimposedchirped Bragg gratings

Filters with 100 GHz free spectral range (FSR) and finesse up to 16 are demonstrated over the 1525 to 1583 nm band. The photoinduced birefringence results in a polarisation-dependent spectral response. Finesse and FSR uniformity are addressed     

Adaptive Spread-Spectrum Systems Using Least-Squares Lattice Algorithms

Practical communication systems must cope with many uncertainties in addition to determining the transmitted data, e.g., the direction, timing, and distortion of the desired signal, and the spectral and spatial distribution of the interference, all of which may change with time. This paper describes exact least-squares (LS) recursive lattice algorithms which resolve these uncertainties in a direct-sequence spread-spectrum digital communication system. The adaptive LS algorithm is recursive beth in order and time, and converges rapidly to the uncertain parameters. Time-discrete algorithms may be mechanized by a receiver containing integrate-and-dump circuits operating at the chip rate of the pseudonoise (PN) sequence, one in each in-phase and each quadrature channel of each sensor array element's output. Different configurations of optimal time-discrete receivers are presented and transformed into adaptive receivers by taking advantage of the spectral properties of the different kinds of LS filters. Simulation results are presented and some guide lines are given for the architecture of an adaptive direct-sequence spread-spectrum system.     

Hardware monitoring of a multiprocessor system

The Testbed for Distributed Processing, or Ted, consists of Intel Corp.'s iSBC 8086 single board computers (SBCs) organized into groups or clusters. Each cluster consists of several SBCs that communicate via a shared memory. Intercluster communication occurs through an Ethernet interface. A hardware monitor designed and implemented to handle the monitoring activities within a cluster in the Ted system is described. By using specified patterns and don't-care masks, the system can detect accesses to selected data, addresses, or blocks of addresses. This function helps monitor events such as the access or usage of a memory location or a group of mailbox addresses. It also determines the amount of time consumed by the performance of specific operations     

Separation of serotonin from catechols by capillary zone electrophoresis with electrochemical detection

Capillary zone electrophoresis with electrochemical detection is demonstrated with columns having only 9-microns inner diameter. Amperometric detection limits of 0.7 amol are reported for serotonin. The difficult problem of resolving serotonin and dopamine--two neurotransmitters of interest having similar electrophoretic mobilities--is addressed by chemical means to improve selectivity. These include buffer modification with 2-propanol and a system employing borate complexation of the catechol in combination with sodium dodecyl sulfate micelles.     

Feature Reduction via Generalized Uncorrelated Linear Discriminant Analysis

High-dimensional data appear in many applications of data mining, machine learning, and bioinformatics. Feature reduction is commonly applied as a preprocessing step to overcome the curse of dimensionality. Uncorrelated Linear Discriminant Analysis (ULDA) was recently proposed for feature reduction. The extracted features via ULDA were shown to be statistically uncorrelated, which is desirable for many applications. In this paper, an algorithm called ULDA/QR is proposed to simplify the previous implementation of ULDA. Then, the ULDA/GSVD algorithm is proposed, based on a novel optimization criterion, to address the singularity problem which occurs in undersampled problems, where the data dimension is larger than the sample size. The criterion used is the regularized version of the one in ULDA/QR. Surprisingly, our theoretical result shows that the solution to ULDA/GSVD is independent of the value of the regularization parameter. Experimental results on various types of data sets are reported to show the effectiveness of the proposed algorithm and to compare it with other commonly used feature reduction algorithms.     

Obtaining high defect coverage for frequency-dependent defects in complex ASICs

Structured delay tests have been around for years, but how effectively do they identify defective silicon, even at reduced frequency? How much overkill is associated with their use? The authors present data from industrial circuits aimed at these and other aspects of speed testing.