On the Computation of Correlation Sequences in 3-D Recursive Digital Filters

In this paper we are concerned with the computation of correlation sequences and complex integrals arising in Three-dimensional (3-D) recursive digital filtering applications. In particular, we focus on presenting a reliable and accurate method for evaluating triple complex integrals having a rational-form integrand. The basic idea is to reduce the triple complex integral into a double complex integral. The main computational tasks involved in the method includes the product-to-sum decomposition of the rational-form integrand, the integration of a definite integral, and the finding of inside-unit-circle (IUC) roots of 1-D polynomials. The proposed method of evaluating multiple complex integrals has its great applications in the design of optimal 3-D nonseparable-denominator recursive digital filters with minimum sensitivity and/or roundoff error. To demonstrate the effectiveness of the presented method, two numerical examples are given.     

On the development of a cooperative tutoring environment on computer networks

In developing a tutoring system, one of the most difficult tasks is to collect tutoring knowledge from multiple educators, especially courses in which the contents change frequently, due to the advent of new technologies. We propose a Web-based intelligent tutoring strategy construction system, which is able to elicit, analyze, and integrate tutoring knowledge from multiple educators systematically. Experiments on two courses have been performed to evaluate the time, completeness, and accuracy improvement in constructing tutoring knowledge bases with our approach. According to the experimental results, it can be inferred that for most cases, our approach achieves desirable performance.     

Advances in multibeam communications satellite antennas

The evolution of satellite antennas over the past quarter of a century is presented. Five major areas of advances in communications satellite antenna technology are reviewed: single offset reflectors with feed arrays, shaped reflector systems, active phased arrays, phased-array-fed dual reflector systems, and lightweight feed elements. Examples are given of existing systems and of the ongoing development of new technologies     

Novel iterative equalization based on energy-spreading transform

In this paper, novel iterative equalization for intersymbol interference (ISI) channels is proposed. Different from the existing turbo equalization, the proposed one is based on energy-spreading transform (EST), which separates equalization and coding, and therefore works for uncoded systems. The complexity of the proposed scheme is comparable to that of decision-feedback equalization (DFE). However, analytical and simulation results demonstrate that its performance is very close to the matched-filter bound (MFB) when the signal-to-noise ratio (SNR) is above a threshold.     

A 3 Gb/s transmitter with a tapless pre-emphasis CML output driver

A 3 Gb/s wireline transmitter (Tx) with a tapless pre-emphasis current-mode logic output driver is presented in this paper. The proposed output driver can support 2.5, 6 and 10 dB pre-emphasis without any additional current tap. It can reduce the current consumption of the output driver by 30 %. The 1.5 GHz phase-locked loop (PLL), multi-phase generator, and 26-to-1 serializer are utilized to serialize 26-bit parallel data to 1-bit 3 Gb/s serial data stream. The rms and peak-to-peak jitters of PLL are 2.97 and 22.5 ps, respectively. The eye opening of the proposed output driver at 3 Gb/s is 0.8UI with a 10 dB loss channel. The current consumption of the output driver is only 5.14 mA, and the Tx is 9 mA. The area of the Tx is 0.72 mm² using the 0.11 μm CMOS process.     

Analysis of singularities from modulus maxima of complex wavelets

Complex-valued wavelets are normally used to measure instantaneous frequencies, while real wavelets are normally used to detect singularities. We prove that the wavelet modulus maxima with a complex-valued wavelet can detect and characterize singularities. This is an extension of the previous wavelet work of Mallat and Hwang on modulus maxima using a real wavelet. With this extension, we can simultaneously detect instantaneous frequencies and singularities from the wavelet modulus maxima of a complex-valued wavelet. Some results of singularity detection with the modulus maxima from a real wavelet and an analytic complex-valued wavelet are compared. We also demonstrate that singularity detection methods can be employed to detect the corners of a planar object.     

A novel way to improve the dispersion-limited transmission distance of electroabsorption modulated lasers

We propose and demonstrate a way to improve the dispersion-limited reach of electroabsorption modulated lasers (EMLs). We generate continuous-phase frequency-shift keying/amplitude-shift keying (ASK) signals with the EML by applying a small current modulation to the laser diode (LD) on top of electroabsorption-modulated ASK signals. The amount of frequency deviation induced by the current modulation is adjusted to have the EML output signals experience /spl pi/ phase shift at every space. The experimental demonstration shows that with the proposed scheme we can increase the dispersion-limited transmission distance of the EML-based transmitter by 25%-75%, and it can be further improved by employing an LD with flat frequency-modulation response.     

1.5 V Sub‐mW CMOS Interface Circuit for Capacitive Sensor Applications in Ubiquitous Sensor Networks

In this paper, a low‐power CMOS interface circuit is designed and demonstrated for capacitive sensor applications, which is implemented using a standard 0.35‐μm CMOS logic technology. To achieve low‐power performance, the low‐voltage capacitance‐to‐pulse‐width converter based on a self‐reset operation at a supply voltage of 1.5 V is designed and incorporated into a new interface circuit. Moreover, the external pulse signal for the reset operation is made unnecessary by the employment of the self‐reset operation. At a low supply voltage of 1.5 V, the new circuit requires a total power consumption of 0.47 mW with ultra‐low power dissipation of 157 μW of the interface‐circuit core. These results demonstrate that the new interface circuit with self‐reset operation successfully reduces power consumption. In addition, a prototype wireless sensor‐module with the proposed circuit is successfully implemented for practical applications. Consequently, the new CMOS interface circuit can be used for the sensor applications in ubiquitous sensor networks, where low‐power performance is essential.     

Simulations and experiments of three-dimensional paddle shift for IC packaging

Paddle shift is one of the most serious defects which may arise during the IC encapsulation of leadframe-type packages. The term “paddle shift” means the deflection of the leadframe-pad and die as a result of the pressure difference between the top and bottom mold cavities. In extreme cases, paddle shift could lead to a substantial reduction in the reliability of package.This paper employed a computational approach to predict the paddle shift quantity during the IC packaging process. The approach was based on precise finite element (FE) models and flow-structure decoupled analyses. Two kinds of FE models were needed for the decoupled analyses, namely a 3D FE model for the mold filling analysis (i.e. fluid-flow mesh) and a 3D FE model for the structural analysis (i.e. paddle mesh). The aim of the mold filling analysis was to identify the pressure distribution acting on the paddle structure during the encapsulation process, while the objective of the structural analysis was to determine the amount of paddle shift which was caused by pressure distribution.To investigate the relationship between the package geometry and the amount of paddle shift, the present simulations considered six TQFP (Thin quad flat package) models with different geometrical parameters. The simulation results for the paddle shift were compared with the experimental results to demonstrate the accuracy of the proposed numerical approach. It was found that a good agreement exists between the two sets of results.