Kye Yak See

Accurate Extraction of Noise Source Impedance of an SMPS Under Operating Conditions

An accurate measurement method to extract the common mode (CM) and the differential mode (DM) noise source impedances of a switched-mode power supply (SMPS) under its operating condition is developed and validated. With a proper premeasurement calibration process, the proposed method allows extraction of both the CM and the DM noise source impedances with very good accuracy. These noise source impedances come in handy to design an electromagnetic interference filter for an SMPS systematically with minimum hassle.

Systematic Electromagnetic Interference Filter Design Based on Information From In-Circuit Impedance Measurements

Based on a two-probe measurement approach, the noise source and noise termination impedances of a switched-mode power supply (SMPS) under its normal operating condition are measured. With the accurate noise source and noise termination impedances, an electromagnetic interference (EMI) filter can be optimally designed. A practical example of the design of an EMI filter to comply with a regulatory conducted EMI limit using the proposed procedure is demonstrated and compared with the cases, where the noise source and noise termination impedances are not taken into account, or coarse estimates of them are considered. Although all approaches allow filtered SMPS to pass the regulation limits, designing EMI filters with the accurate noise source and termination impedances leads to optimal component values and avoids overdesign.

Phthalonitrile-Based Carbon Foam with High Specific Mechanical Strength and Superior Electromagnetic Interference Shielding Performance.

Electromagnetic interference (EMI) performance materials are urgently needed to relieve the increasing stress over electromagnetic pollution problems arising from the growing demand for electronic and electrical devices. In this work, a novel ultralight (0.15 g/cm(3)) carbon foam was prepared by direct carbonization of phthalonitrile (PN)-based polymer foam aiming to simultaneously achieve high EMI shielding effectiveness (SE) and deliver effective weight reduction without detrimental reduction of the mechanical properties. The carbon foam prepared by this method had specific compressive strength of ∼6.0 MPa·cm(3)/g. High EMI SE of ∼51.2 dB was achieved, contributed by its intrinsic nitrogen-containing structure (3.3 wt% of nitrogen atoms). The primary EMI shielding mechanism of such carbon foam was determined to be absorption. Moreover, the carbon foams showed excellent specific EMI SE of 341.1 dB·cm(3)/g, which was at least 2 times higher than most of the reported material. The remarkable EMI shielding performance combined with high specific compressive strength indicated that the carbon foam could be considered as a low-density and high-performance EMI shielding material for use in areas where mechanical integrity is desired.

Mussel-inspired polydopamine coated hollow carbon microspheres, a novel versatile filler for fabrication of high performance syntactic foams.

Syntactic foams, which can be synthesized by mechanical mixing of hollow microspheres with a matrix material, are a special class of lightweight composite materials. Developing of high-performance syntactic foams remains challenges. In this work, a facile and environmentally friendly surface modification method employing polydopamine (PDA) as a surface treatment agent for hollow carbon microspheres (HCMs) was used, aiming to extend the application of syntactic foams to seldom touched areas. The PDA coating was used as a strategy for interfacial interaction enhancement and also as a platform for further metal coating meant for electromagnetic interference (EMI) shielding. The stronger interfacial interaction between microspheres and polymer matrix provided effective interfacial stress transfer, as a result of the syntactic foams with high strength to weight ratio. Furthermore, the PDA coating on HCMs served as a versatile platform for the growth of noble metals on the surface of PDA-HCMs. Silver nanoparticles was grown by PDA medium. The silver coated HCMs (Ag-PDA-HCMs) impacted the complex permittivity of the syntactic foams leading to high EMI shielding effectiveness (SE). The specific EMI SE reached up to 46.3 dB·cm(3)/g, demonstrated the Ag-PDA-HCMs/epoxy syntactic foam as a promising candidate for lightweight high-performance EMI shielding material.

Ultrathin and Flexible Screen-Printed Metasurfaces for EMI Shielding Applications

An ultrathin, lightweight, and flexible metasurface for band-stop electromagnetic interference (EMI) shielding purpose has been designed and fabricated using screen-printing technology. Using a 1.8 GHz band-stop EMI shield as a design example, a prototype of a screen-printed metasurface has been validated using measured and numerically computed results. Hence, screen printing can be an attractive option for flexible and lightweight shields that can be easily applied on the walls and windows of a room to block specific wireless communication band so as to protect critical electronics instruments from possible EMI.

In-Circuit Characterization of Common-Mode Chokes

The two current probes measurement method was employed by other researchers to measure the radio-frequency impedance of AC power mains. In this paper, with a modified measurement setup, the method is extended to measure the common-mode (CM) impedance of a CM choke under in-circuit condition. With a premeasurement characterization process, the effect of the measurement setup can be determined and eliminated. The proposed measurement provides a more realistic assessment of the CM impedance characteristic of any CM choke under actual operating condition.

Comprehensive Analysis of the Impact of via Design on High-Speed Signal Integrity

In all modern high-speed digital board designs, every slightest discontinuity on the board has to be considered carefully, especially the vias, which are abundantly used in digital design. As frequency increases and signal rise time reduces, via causes impedance discontinuities resulting in signal reflections and hence deterioration of signal integrity (SI) and system performance. The paper carries out a comprehensive study of the impacts of various via design parameters on SI using a full-wave electromagnetic simulator (CST microwave suite). The design parameters under study are via diameter, via height and the excess via stub in a multilayer PCB. The study allows high-speed digital designers to have a more in-depth assessment of via design and its effect on SI performance.

Radio-frequency common-mode noise propagation model for power-line cable

Electromagnetic-interference (EMI) radiation from a power-line communications (PLC) network has been a major concern for the widespread use of broadband PLC technology. It is also well known that the dominant radiation mode of the PLC network is common mode (CM) by nature. Therefore, for electromagnetic-compatibility planning purposes, knowledge of the CM noise propagation path of the power line in the frequency range of 1 to 30 MHz is essential to provide insight of EMI radiation emitted by the power line. Based on a two-current-probe measurement approach, the CM noise propagation model for a three-wire power-line cable can be derived and represented by an equivalent two-wire CM transmission line. The equivalent CM noise propagation model allows us to predict the CM noise current on the power line with reasonable accuracy. The model will serve as a valuable tool in the future to identify effective ways to suppress EMI radiation from the PLC network.

Design of high power density converter for aircraft applications

This paper presents a design methodology for high power density converter (HPDC) operating as an AC aircraft bus provider, which presents a particular gravimetric power density challenge. High power rating 3-phase AC-DC converter design with weight minimization is elaborated. By considering sizing of major converter parts that contribute to total converter weight, optimal switching frequency to yield highest power density is evaluated. The design evaluation for 50 kW converter with SiC power modules yields overall gravimetric power density of 3.76-5.35 kW/kg at optimal switching frequency of 60 kHz and volumetric power density of 7.04-7.38 kW/l respectively.

Integration of Dual-Band Monopole and Microstrip Grid Array for Single-Chip Tri-Band Application

A novel antenna design and packaging solution for tri-band (2.4, 5.2 and 60 GHz) radio application is proposed. The integration of the dual-band monopole antenna and the assembly of the microstrip grid array antenna on a system printed-circuit board (PCB) of practical size are described. A defected ground structure is devised to minimize the impact of the system PCB on the radiation characteristics of the antennas especially in the 5.2-GHz band. Simulated and measured results demonstrate that the novel antenna design achieves excellent performance in the three frequency bands.