Myunghoi Kim

System-on-package ultra-wideband transmitter using CMOS impulse generator

In this paper, a low-cost CMOS ultra-wideband (UWB) impulse transmitter module with a compact form factor is proposed for impulse-radio communications. The module consists of a CMOS impulse generator, a compact bandpass filter (BPF), and a printed planar UWB antenna. The impulse generator is designed using a Samsung 0.35-/spl mu/m CMOS process for low-cost and low-power fabrication. The measurement shows the fabricated chip makes a train of sharp triangular pulses with a peak voltage of about 2.8 V under the supply voltage of 3.3 V. To make an impulse fit the Federal Communications Commission (FCC) spectrum mask, the compact BPF is developed using a coupled strip line and a tapered stub. Also, the compact planar UWB antenna is developed. All of the components of the UWB transmitter module are fabricated on a single package using system-on-package technology for miniaturization. The proposed UWB transmitter is tested in an office environment. The measured results show that the generated UWB signal meets the FCC regulation, and the peak-to-peak amplitude of received UWB signal at 1-m distance on line of sight is 16 mVpp with a 10-dB-gain low-noise amplifier in the receiver.

Analytical expressions for maximum transferred power in wireless power transfer systems

In this paper, we present the analytical expressions of the resonant peaks of input impedance and the frequencies of maximum transferred power in the wireless power transfer systems in case of tight magnetic coupling. The analytical expressions predict the frequencies of power source where the maximum power is transferred in both cases of the constant AC voltage source and the constant AC current source. We prove that the resonant frequencies of the input impedance in the wireless power transfer systems coincide with the frequencies at which the transferred power is maximized for the constant AC voltage source and the constant AC current source. The test vehicles of the coupled rectangular coils are simulated with 3D EM solver and fabricated on printed circuit boards. Experimentally, it is verified that the analytical expressions predict the changes in the resonant peaks of input impedance of the wireless power transfer systems, its relationship with frequencies of maximum transferred power and their dependency with the source type in the wireless power transfer systems.

Actin remodeling confers BRAF inhibitor resistance to melanoma cells through YAP/TAZ activation

The activation of transcriptional coactivators YAP and its paralog TAZ has been shown to promote resistance to anti‐cancer therapies. YAP/TAZ activity is tightly coupled to actin cytoskeleton architecture. However, the influence of actin remodeling on cancer drug resistance remains largely unexplored. Here, we report a pivotal role of actin remodeling in YAP/TAZ‐dependent BRAF inhibitor resistance in BRAF V600E mutant melanoma cells. Melanoma cells resistant to the BRAF inhibitor PLX4032 exhibit an increase in actin stress fiber formation, which appears to promote the nuclear accumulation of YAP/TAZ. Knockdown of YAP/TAZ reduces the viability of resistant melanoma cells, whereas overexpression of constitutively active YAP induces resistance. Moreover, inhibition of actin polymerization and actomyosin tension in melanoma cells suppresses both YAP/TAZ activation and PLX4032 resistance. Our siRNA library screening identifies actin dynamics regulator TESK1 as a novel vulnerable point of the YAP/TAZ‐dependent resistance pathway. These results suggest that inhibition of actin remodeling is a potential strategy to suppress resistance in BRAF inhibitor therapies.

Measurement and Analysis of a High-Speed TSV Channel

Using high-speed through-silicon via (TSV) channels is a potential means of utilizing 3-D interconnections to realize considerable high-bandwidth throughput in vertically stacked and laterally distributed integrated circuits. However, although the TSV and a silicon interposer in a high-speed TSV channel lead to a significant decrease of the interconnect length, the received digital signal after transmission through a TSV channel is still degraded at a high data-rate due to the nonidealities of the channel. Therefore, an analysis of the signal integrity in a high-speed TSV channel is necessary. In this paper, a single-ended high-speed TSV channel is measured and analyzed in the frequency-domain and the time-domain. To measure the high-speed TSV channel, two types of test vehicles are fabricated, consisting of TSVs and interposers. With these test vehicles, the channel losses are measured in the frequency-domain up to 20 GHz, and eye-diagrams are measured in the time-domain at 1 Gb/s and 10 Gb/s. Based on these measurements, the channel loss, characteristic impedance, and reflection of the high-speed TSV channel are analyzed and compared to those of the channel in multichip module (MCM) package. Because of the losses from the silicon-substrate and the thin oxide-layer used in the TSVs, the overall loss of the high-speed TSV channel is higher than that of the MCM channel. In addition, the characteristic impedance of the high-speed TSV channel is frequency-dependent, whereas that of the MCM channel is frequency-independent. Moreover, in contrast to the MCM channel, the reflection is negligible in the high-speed TSV channel because the channel is too short and the losses are too high to be affected by the reflection. Finally, the design guidance of a high-speed TSV channel for wide bandwidth is determined based on the analysis of the measurements.

A Compact and Wideband Electromagnetic Bandgap Structure Using a Defected Ground Structure for Power/Ground Noise Suppression in Multilayer Packages and PCBs

In this paper, we propose a compact and wideband electromagnetic bandgap (EBG) structure using a defected ground structure (DGS) to significantly enhance the wideband suppression of power/ground noise coupling in multilayer packages and printed circuit boards. The proposed EBG structure is implemented simply by adding a rectangular-shaped DGS which is etched periodically onto the ground plane without changing any other geometrical parameter from a mushroom-type EBG structure. The DGS effects on the fL and fU are thoroughly analyzed using the dispersion characteristics. We experimentally verified that the proposed EBG structure achieved the wideband power/ground noise suppression (below -40 dB) between 2.5 and 16.2 GHz. In addition, we demonstrated the considerable reduction in fL from 3.4 to 2.5 GHz and a significant increase in fU from 9.1 to 16.2 GHz when compared with the mushroom-type EBG structure.

Through-silicon via (TSV) depletion effect

The effects of through-silicon via (TSV) depletion are analyzed based on the frequency- and time-domain measurements in this paper. As TSV dc bias voltage increases, a TSV depletion region is generated; this region decreases TSV noise coupling at frequencies below 1 GHz. It also creates duty-cycle distortion of the coupled signal, which results from the nonlinearity of the TSV.

A Wideband and Compact EBG Structure With a Circular Defected Ground Structure

We propose a new analysis method to determine the bandgap characteristics of an electromagnetic bandgap structure with a defected ground structure (DGS). The proposed method is based on a 1-D segmented transmission line model and a piecewise linear approximation of Zo within a unit cell. Although the previous method is only applicable to rectangular DGSs (RDGSs), the proposed method is applicable to any DGS shapes. As an example, the proposed method is applied to a circular DGS and shows a good agreement with full-wave simulations of the unit cell and measurements of 11 × 11 unit cells. The circular DGS achieves a 15% improvement in the stopband bandwidth over the RDGS with the same perforation area. The proposed method allows us to explore a variety of DGS shapes in the search for better stopband characteristics. It also offers the basis for numerical optimization techniques to be used in synthesizing DGS shapes to meet required stopband characteristics.

Vertical Stepped Impedance EBG (VSI-EBG) Structure for Wideband Suppression of Simultaneous Switching Noise in Multilayer PCBs

In this paper, we propose a vertical stepped impedance electromagnetic bandgap (VSI-EBG) structure with a stopband enhancement and a size reduction for a wideband suppression of simultaneous switching noise (SSN) coupling in multilayer printed circuit boards (PCBs). The proposed VSI-EBG structure forms the stepped impedance EBG structure of power planes, which is implemented with a vertical branch, high-impedance (hi-Z) and low-impedance (low-Z) metal patches on different layers. Test vehicles are fabricated using a multilayer PCB process to verify the proposed VSI-EBG structure. Through experimental measurements, we verified the enhanced suppression of SSN coupling (below -40 dB) between 650 MHz and 20 GHz. In addition, we demonstrated that fL is reduced from 2.4 GHz to 650 MHz compared to the previous EBG structure, which allows an approximately 86% size reduction.

Impact of PCB design on switching noise and EMI of synchronous DC-DC buck converter

Synchronous DC-DC buck converters operate under a few MHz but generate broadband noise up to GHz range due to its switching operation. The noise causes EMI problem through radiation and switching noise at the converter output from direct conduction. To control EMI and switching noise at the converter output, proper PCB design plays a critical role. This paper evaluates three types of GND plane layout and three types of high-voltage AC node layout for synchronous DC-DC buck converter test benches with 4-layer stack-up PCB. Transverse electromagnetic (TEM) cell measurement and time-domain measurement of switching noise at the converters output were performed for the evaluation. The source of EMI, switching noise and magnitude difference over layouts were analyzed by the impedance measurement on the test benches.

Magnetic resonant wireless power transfer for propulsion of implantable micro-robot

Recently, various types of mobile micro-robots have been proposed for medical and industrial applications. Especially in medical applications, a motor system for propulsion cannot easily be used in a micro-robot due to their small size. Therefore, micro-robots are usually actuated by controlling the magnitude and direction of an external magnetic field. However, for micro-robots, these methods in general are only applicable for moving and drilling operations, but not for the undertaking of various missions. In this paper, we propose a new micro-robot concept, which uses wireless power transfer to deliver the propulsion force and electric power simultaneously. The mechanism of Lorentz force generation and the coil design methodologies are explained, and validation of the proposed propulsion system for a micro-robot is discussed thorough a simulation and with actual measurements with up-scaled test vehicles.