Modeling and measurement of simultaneous switching noise coupling through signal via transition

The signal via is a heavily utilized interconnection structure in high-density System-on-Package (SoP) substrates and printed circuit boards (PCBs). Vias facilitate complicated routings in these multilayer structures. Significant simultaneous switching noise (SSN) coupling occurs through the signal via transition when the signal via suffers return current interruption caused by reference plane exchange. The coupled SSN decreases noise and timing margins of digital and analog circuits, resulting in reduction of achievable jitter performance, bit error ratio (BER), and system reliability. We introduce a modeling method to estimate SSN coupling based on a balanced transmission line matrix (TLM) method. The proposed modeling method is successfully verified by a series of time-domain and frequency-domain measurements of several via transition structures. First, it is clearly verified that SSN coupling causes considerable clock waveform distortion, increases jitter and noise, and reduces margins in pseudorandom bit sequence (PRBS) eye patterns. We also note that the major frequency spectrum component of the coupled noise is one of the plane pair resonance frequencies in the PCB power/ground pair. Furthermore, we demonstrate that the amount of SSN noise coupling is strongly dependent not only on the position of the signal via, but also on the layer configuration of the multilayer PCB. Finally, we have successfully proposed and confirmed a design methodology to minimize the SSN coupling based on an optimal via positioning approach.     

Bisanthracene‐Based Donor–Acceptor‐type Light‐Emitting Dopants: Highly Efficient Deep‐Blue Emission in Organic Light‐Emitting Devices

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene ( BD3 ), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene ( BD1 ) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene ( BD2 ), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue.     

Performance Analysis of Uplink Scheduling Algorithms for VoIP Services in the IEEEE 802.16e OFDMA System

While the voice over Internet protocol (VoIP) services is expected to be widely supported in wireless mobile networks, the performance of VoIP services has not previously been evaluated in the IEEE 802.16e orthogonal frequency division multiple access (OFDMA) system taking the adaptive modulation and coding scheme into consideration. To support real-time uplink service flows, three different types of scheduling have been designed in the IEEE 802.16e standard: the unsolicited grant service (UGS), the real-time polling service (rtPS), and the extended rtPS (ertPS). In this paper, we compare the three real-time scheduling algorithms in terms of the performance of VoIP services by using the analytical and simulation models that we developed.

Aqueous-Base-Developable Benzocyclobutene (BCB)-Based Material Curable in Air

A positive-tone and aqueous-base-developable benzocyclobutene (BCB)-based dielectric material curable in air is described in this paper. The prepolymer is made from divinylsiloxane bisbenzocyclobutene (DVS-bisBCB) and BCB-acrylic acid. The formulation contains antioxidants that allow the prepolymer to cure in air and a diazonaphthaquinone to make it photosensitive. Patterned films have high resolution, and via openings are scum-free without a descum operation. Whether cured in nitrogen or in air, the prepolymer produces a film with optical, electrical, thermal, and mechanical properties desirable for many microelectronic applications, such as packaging applications and as a planarization or insulation layer in display applications     

Analysis of an adaptive rate convolutionally coded multicarrierDS/CDMA system

The analysis of an adaptive rate convolutionally coded multicarrier direct sequence code division multiple-access (DS/CDMA) system is considered. In order to accommodate a number of coding rates easily and make the encoder and decoder structure simple, we use the rate-compatible punctured convolutional (RCPC) code. We obtain data throughputs at several coding rates, and choose the coding rate that has the highest data throughput in the signal-to-interference and noise ratio (SINR) sense. To achieve maximum data throughput, a rate adaptive system is proposed based on the channel state information (the SINR estimate). The SINR estimate is obtained by the soft decision Viterbi decoding metric. We show that the proposed rate adaptive convolutionally coded multicarrier DS/CDMA system can enhance the spectral efficiency and provide frequency diversity     

An efficient frequency offset estimator for OFDM systems and itsperformance characteristics

In this paper, we propose a new frequency synchronization algorithm for orthogonal frequency division multiplexing (OFDM) systems requiring only one training symbol, based on a conventional method which requires two training symbols. While the timing synchronization is obtained by using the conventional method, the carrier frequency offset is efficiently estimated by the proposed method. It is shown that the proposed method not only reduces the number of the training symbols but also possesses better performance than the conventional method without increase in complexity     

FDTD modeling of transient microwave signals in dispersive and lossy bi-isotropic media

In this paper, we present a novel finite-difference time-domain model of transient wave propagation in general dispersive bi-isotropic media with losses. The special properties of these materials may lead to new applications in microwave and millimeter-wave technology. While their frequency-domain properties have been well described in the literature, their time-domain behavior has only been modeled thus far for special sub-classes and monochromatic time dependence. We have validated our method by first computing time-harmonic wave propagation through a bi-isotropic medium and comparing it with analytical results. Agreement is typically better than 1%. We have then computed transient field propagation in a general lossy dispersive bi-isotropic medium.     

Improving Quality of Service and Assuring Fairness in WLAN Access Networks

As public deployment of wireless local area networks (WLANs) has increased and various applications with different service requirements have emerged, fairness and quality of service (QoS) are two imperative issues in allocating wireless channels. This study proposes a fair QoS agent (FQA) to simultaneously provide per-class QoS enhancement and per-station fair channel sharing in WLAN access networks. FQA implements two additional components above the 802.11 MAC: a dual service differentiator and a service level manager. The former is intended to improve QoS for different service classes by differentiating service with appropriate scheduling and queue management algorithms, while the latter is to assure fair channel sharing by estimating the fair share for each station and dynamically adjusting the service levels of packets. FQA assures (weighted) fairness among stations in terms of channel access time without decreasing channel utilization. Furthermore, it can provide quantitative service assurance in terms of queuing delay and packet loss rate. FQA neither resorts to any complex fair scheduling algorithm nor requires maintaining per-station queues. Since the FQA algorithm is an add-on scheme above the 802.11 MAC, it does not require any modification of the standard MAC protocol. Extensive ns-2 simulations confirm the effectiveness of the FQA algorithm with respect to the per class QoS enhancement and per-station fair channel sharing     

Electron Transfer-Induced Metal Spin-Crossover at NiCo2S4/ReS2 2D–2D Interfaces for Promoting pH-universal Hydrogen Evolution Reaction

The development of an efficient pH-universal hydrogen evolution reaction (HER) electrocatalyst is essential for practical hydrogen production. Here, an efficient and stable pH-universal HER electrocatalyst composed of the strongly coupled 2D NiCo₂S₄ and 2D ReS₂ nanosheets (NiCo₂S₄/ReS₂) is demonstrated. The NiCo₂S₄/ReS₂ 2D–2D nanocomposite is directly grown on the surface of the carbon cloth substrate, which exhibits excellent HER performance with overpotentials of 85 and 126 mV at a current density of 10 mA cm⁻² and Tafel slopes of 78.3 and 67.8 mV dec⁻¹ under both alkaline and acidic conditions, respectively. Theoretical and experimental characterizations reveal that the chemical coupling between NiCo₂S₄ and ReS₂ layers induces electron transfer from Ni and Co to interfacial Re-neighbored S atoms, enabling beneficial H atom adsorption and desorption for both acidic and alkaline HER. Simultaneously, an electron transfer-induced spin-crossover generates high-spin interfacial Ni and Co atoms that promote water dissociation kinetics at the NiCo₂S₄/ReS₂ interface, which is the origin of the superior alkaline HER activity. NiCo₂S₄/ReS₂ also shows decent catalytic activity and long-term durability for oxygen evolution reaction, and finally bifunctionality for overall water splitting. This study suggests a rational strategy to enhance water dissociation kinetics by inducing spin-crossover via electron transfer.     

Organic and Inorganic Blocking Layers for Solution‐Processed Colloidal PbSe Nanocrystal Infrared Photodetectors

A PbSe solution‐processed nanocrystal‐based infrared photodetector incorporating carrier blocking layers is demonstrated, and significant reduction of dark current is achieved. Detectivity values close to 10¹² Jones are achieved by using poly[(9,9′‐dioctylfluorenyl‐2,7‐diyl)‐co‐(4,4′‐(N‐(4‐sec‐butyl))diphenylamine)] (TFB) and ZnO nanocrystals (NC) as the electron blocker and hole blocker, respectively. An improvement in lifetime is also observed in the devices with the ZnO NCs hole blocking layer.