Weng-Yew Chang

Characterization of Component Under DC Biasing Condition Using an Inductive Coupling Approach

Based on a two-probe inductive coupling approach, a novel measurement method to characterize the impedance of any passive component (R, L, or C) under a direct-current (dc) biasing condition has been developed. With a premeasurement calibration process, the proposed method has the ability to eliminate errors due to the measurement setup. Using resistors and inductors as devices under test, impedance characterization of a component up to 1 GHz with good accuracy has been demonstrated. The proposed method provides insight of the impedance behavior of a critical circuit component under its intended biasing condition, so that proper choice of a component can be made for a specific biasing condition to achieve optimal circuit performance.

Electromagnetic shielding analysis of printed flexible meshed screens

Based on the screen-printing technology, conductive meshed patterns are printed on a flexible substrate with different loadings. Using empirical formulae, the shielding effectiveness (SE) for the different printed meshed screens is first determined and later verified through experiment. Both the calculated and experimental results demonstrate that reasonably good SE for this type of printed meshed screens is achievable.

An Empirical Approach to Develop Near-Field Limit for Radiated-Emission Compliance Check

Based on measurements from a near-field scanner and far-field measurements obtained in a semi-anechoic chamber, a statistical relationship is established between a magnetic field in the near field and an electric field in the far field. The relationship makes it possible to transform a radiated-emission regulatory limit from the far-field to the near-field zone. The transformed near-field limit can allow efficient prediction of radiated-emission compliance for high-speed printed circuit boards. The presented results demonstrate the feasibility of the proposed method for a quick radiated-emission precompliance check without heavy equipment investment.

Filter design for suppression of noise coupling from PCB to DC power supply

Based on an in-circuit measurement approach, a systematic EMI filter design procedure is developed to suppress the noise from a digital board to the power supply. The two-probe technique adopted for the in-circuit measurement allows the impedances of the power supply and the PCB to be determined under its actual operating condition. With the measured impedance information, a suitable filter topology can be selected and component value computed without any guessing.

Comprehensive analysis of serpentine line design

Serpentine lines have been widely used in digital circuits to provide the required timing delays. Based on a full-wave simulation tool, some critical parameters that affect the delay characteristic of a serpentine line are carefully studied and analyzed. With the comprehensive study and analysis, a set of practical and useful design guides are concluded for designing a serpentine line to meet the delay specification.

Development of near-field emission limit from radiated-emission limit based on statistical approach

This paper discusses a novel approach to transforming a radiated-emission limit (e.g., CISPR 22 and FCC) from the far-field to the near-field region. The proposed approach combines data from a near-field scanner and a gigahertz transverse electromagnetic cell with statistics to establish a simple relationship between a near-field magnetic field and a far-field electric field. It is shown that the proposed approach has the potential to be a simple, quick, and fairly inexpensive tool for electromagnetic compatibility pre-compliance purposes.

Impacts of EMI filter on high speed interconnects for digital circuits design

Todays digital data lines are clocking at very high speed, in excess of 100MHz with rise time in the sub-nano second range. The effects of EMI radiation even from short traces are becoming significant and cannot be ignored. The use of resistive termination versus the EMI filter has long been a compromise in terms of cost and necessity. EMI compliance is now becoming a major design challenge for product development rather than a mere good-to-have specification of low emission. This paper carries out a comprehensive study on filter selection, application, impact on receiver waveform signal integrity and far-field emission suppression using a full-wave electromagnetic simulator (CST Microwave Studio). This study will provide high-speed digital designers an in-depth assessment of the use of EMI filter for radiation suppression in high-speed digital layout.

Comprehensive study of crosstalk isolation for high-speed digital board

A comprehensive crosstalk analysis for different layout configurations has been carried out. Using a full-wave electromagnetic simulation tool, crosstalk reduction techniques based on trace-to-trace separation, guard traces, inter-layer ground plane are studied. With the comprehensive simulated results, useful design guidelines are established so that the designers can select the appropriate layout methodology to achieve the desired level of crosstalk isolation.

The Effects of Signal Trace's Termination on Ground Bounce and Common-Mode Radiation

Based on the method of moments, the ground bounce on any arbitrary printed circuit structure as well as the common-mode current on any conductor that attached to the printed circuit structure is predicted. The method of moments is applied to obtain the impedance matrix, which can be used to determine the unknown current vector and the inductance matrix. With the inductance matrix and current vector, the potential difference between any two adjacent nodes is predicted. The effects of the signal traces termination on ground bounce and common-mode radiation are discussed through numerical results.

Evaluation of fibre weaving of substrate on differential microstrip using an analytical approach

Depending on the PCB fiber weave style, electrically long differential microstrip signal traces may introduce significant signal skew due to weave effect that deteriorates the signal quality. As closed-form expression for the effective permittivity that includes the weave effect is not readily available, full-wave method is often used to study the weave effect. As such, a novel analytical method is proposed in this paper to study the fibre weave effect in differential microstrip.