A high efficiency low noise rf-to-dc converter employing gm-boosting envelope detector and offset canceled latch comparator

This work presents a high efficiency RF-to-DC conversion circuit composed of an LC-CL balun-based Gm-boosting envelope detector, a low noise baseband amplifier, and an offset canceled latch comparator. It was designed to have high sensitivity with low power consumption for wakeup receiver (WuRx) applications. The proposed envelope detector is based on a fully integrated inductively degenerated common-source amplifier with a series gate inductor. The LC-CL balun circuit is merged with the core of the envelope detector by sharing the on-chip gate and source inductors. The proposed technique doubles the transconductance of the input transistor of the envelope detector without any extra power consumption because the gate and source voltage on the input transistor operates in a differential mode. This results in a higher RF-to-DC conversion gain. In order to improve the sensitivity of the wake-up radio, the DC offset of the latch comparator circuit is canceled by controlling the body bias voltage of a pair of differential input transistors through a binary-weighted current source cell. In addition, the hysteresis characteristic is implemented in order to avoid unstable operation by the large noise at the compared signal. The hysteresis window is programmable by changing the channel width of the latch transistor. The low noise baseband amplifier amplifies the output signal of the envelope detector and transfers it into the comparator circuit with low noise. For the 2.4 GHz WuRx, the proposed envelope detector with no external matching components shows the simulated conversion gain of about 16.79 V/V when the input power is around the sensitivity of −60 dBm, and this is 1.7 times higher than that of the conventional envelope detector with the same current and load. The proposed RF-to-DC conversion circuit (WuRx) achieves a sensitivity of about −65.4 dBm based on 45% to 55% duty, dissipating a power of 22 µW from a 1.2 V supply voltage. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.1

Carbon-free high-performance cathode for solid-state Li-O-2 battery

The development of a cathode for solid-state lithium-oxygen batteries has been hindered in practice by a low capacity and limited cycle life despite their potential for high energy density. Here, a previously unexplored strategy is proposed wherein the cathode delivers a specific capacity of 200 milliampere hour per gram over 665 discharge/charge cycles, while existing cathodes achieve only similar to 50 milliampere hour per gram and similar to 100 cycles. A highly conductive ruthenium-based composite is designed as a carbon-free cathode by first-principles calculations to avoid the degradation associated with carbonaceous materials, implying an improvement in stability during the electrochemical cycling. In addition, water vapor is added into the main oxygen gas as an additive to change the discharge product from growth-restricted lithium peroxide to easily grown lithium hydroxide, resulting in a notable increase in capacity. Thus, the proposed strategy is effective for developing reversible solid-state lithium-oxygen batteries with high energy density

High-energy and durable lithium metal batteries using garnet-type solid electrolytes with tailored lithium-metal compatibility

Lithium metal batteries using solid electrolytes are considered to be the next-generation lithium batteries due to their enhanced energy density and safety. However, interfacial instabilities between Li-metal and solid electrolytes limit their implementation in practical batteries. Herein, Li-metal batteries using tailored garnet-type Li7-xLa3-aZr2-bO12 (LLZO) solid electrolytes is reported, which shows remarkable stability and energy density, meeting the lifespan requirements of commercial applications. We demonstrate that the compatibility between LLZO and lithium metal is crucial for long-term stability, which is accomplished by bulk dopant regulating and dopant-specific interfacial treatment using protonation/etching. An all-solid-state with 5 mAh cm(-2) cathode delivers a cumulative capacity of over 4000 mAh cm(-2) at 3 mA cm(-2), which to the best of our knowledge, is the highest cycling parameter reported for Li-metal batteries with LLZOs. These findings are expected to promote the development of solid-state Li-metal batteries by highlighting the efficacy of the coupled bulk and interface doping of solid electrolytes. Lithium-metal batteries (LMBs) have attracted intense interest but the instability issues limit its practical deployment. Here, the authors report a durable LMB with high energy density using a garnet-type solid electrolyte with a tailored Li-metal compatibility

Manganese oxide cathodes for rechargeable batteries

textManganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol or hydrogen in various solvents followed by firing at moderate temperatures. The samples have been characterized by wet-chemical analyses, thermal methods, spectroscopic methods, and electron microscopy. It has been found that chemical residues in the oxides such as carboxylates and hydroxyl groups, which could be controlled by varying the reaction medium, reducing agents, and additives, make a significant influence on the electrochemical properties. The Li/Mn ratio in the material has also been found to be a critical factor in determining the rechargeability of the cathodes. The optimized samples exhibit a high capacity of close to 300 mAh/g with good cyclability and charge efficiency. The high capacity with a lower discharge voltage may make these nanostructured oxides particularly attractive for lithium polymer batteries. The research on the manganese oxide cathodes for alkaline batteries is focused on an analysis of the reaction products generated during the charge/discharge processes or by some designed chemical reactions mimicking the electrochemical processes. The factors influencing the formation of Mn3O4 in the two-electron redox process of d-MnO2 have been studied with linear sweep voltammetry combined with X-ray diffraction. The presence of bismuth, the discharge rate, and the microstructure of the electrodes are found to affect the formation of Mn3O4, which is known to be electrochemically inactive. A faster voltage sweep and a more intimate mixing of the manganese oxide and carbon in the cathode are found to suppress the formation of Mn3O4. Bismuth has also been found to be beneficial in the one-electron process of gMnO2 when incorporated into the cathode. The results of a series of chemical reactions reveal that bismuth is blocking some reaction paths leading to the unwanted birnessite or Mn3O4. Barium is also found to play a similar role, but it is less effective than bismuth for the same amount of additive. Optimization of the additives has the potential to make the rechargeable alkaline cells based on manganese oxides to successfully compete with other rechargeable systems due to their low cost, environmental friendliness, and excellent safety features.Materials Science and Engineerin

A Broadband PVT-Insensitive All-nMOS Noise-Canceling Balun-LNA for Subgigahertz Wireless Communication Applications

A broadband process, voltage, and temperature (PVT)-insensitive noise-canceling balun-low-noise amplifier (LNA) was implemented in the 0.13-μm CMOS process for subgigahertz wireless communication applications. The proposed LNA is based on the traditional common-gate common-source (CGCS) balun-LNA topology, and it adopts the diode-connected loads to reduce the noise contribution originated from CGCS transistors and enhance the linearity due to post linearization. The auxiliary common-source (CS) amplifier with a diode-connected is added to reduce the overall noise figure (NF) of the LNA by sharing an input signal with CGCS transistors and applying its output signal to the diode-connected load of CS transistor. Because the voltage gain of the LNA is determined by the transconductance (gₘ) ratio of the same types of nMOS transistors, its power gain (S₂₁) and NF are quite roust over PVT variations. In experiments, it showed S₂₁ of 14 dB and NF of 4 dB with an input return loss (S₁₁) of greater than 10 dB at 450 MHz. Concerning voltage variation (1.08-1.32 V) and temperature variation (-20 °C ~ +80 °C), the worst variations in S₂₁ and NF were approximately 1.4 and 1.1 dB, respectively. IEEE1

CO2 concentration and its spatiotemporal variation in the troposphere using multi-sensor satellite data, carbon tracker, and aircraft observations

Satellite-based atmospheric CO2 observations have provided a great opportunity to improve our understanding of the global carbon cycle. However, thermal infrared (TIR)-based satellite observations, which are useful for the investigation of vertical distribution and the transport of CO2, have not yet been studied as much as the column amount products derived from shortwave infrared data. In this study, TIR-based satellite CO2 products ??? from Atmospheric Infrared Sounder, Tropospheric Emission Spectrometer (TES), and Thermal And Near infrared Sensor for carbon Observation ??? and carbon tracker mole fraction data were compared with in situ Comprehensive Observation Network for Trace gases by AIrLiner (CONTRAIL) data for different locations. The TES CO2 product showed the best agreement with CONTRAIL CO2 data resulting in R2 ~ 0.87 and root-mean-square error ~0.9. The vertical distribution of CO2 derived by TES strongly depends on the geophysical characteristics of an area. Two different climate regions (i.e., southeastern Japan and southeastern Australia) were examined in terms of the vertical distribution and transport of CO2. Results show that while vertical distribution of CO2 around southeastern Japan was mainly controlled by horizontal and vertical winds, horizontal wind might be a major factor to control the CO2 transport around southeastern Australia. In addition, the vertical transport of CO2 also varies by region, which is mainly controlled by anthropogenic CO2, and horizontal and omega winds. This study improves our understanding of vertical distribution and the transport of CO2, both of which vary by region, using TIR-based satellite CO2 observations and meteorological variables.clos

Interface Properties between Lithium Metal and a Composite Polymer Electrolyte of PEO18Li(CF3SO2)2N-Tetraethylene Glycol Dimethyl Ether

The electrochemical properties of a composite solid polymer electrolyte, consisting of poly(ethylene oxide) (PEO)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and tetraethylene glycol dimethyl ether (TEGDME) was examined as a protective layer between lithium metal and a water-stable lithium ion-conducting glass ceramic of Li1+x+y(Ti,Ge)2−xAlxP3−ySiyO12 (LTAP). The lithium ion conductivity and salt diffusion coefficient of PEO18LiTFSI were dramatically enhanced by the addition of TEGDME. The water-stable lithium electrode with PEO18LiTFSI-2TEGDME, as the protective layer, exhibited a low and stable electrode resistance of 85 Ω·cm2 at 60 °C, after 28 days, and low overpotentials of 0.3 V for lithium plating and 0.4 V for lithium stripping at 4.0 mA·cm−2 and 60 °C. A Li/PEO18LiTFSI-2TEGDME/LTAP/saturated LiCl aqueous solution/Pt, air cell showed excellent cyclability up to 100 cycles at 2.0 mAh·cm−2

Intercomparison of Terrestrial Carbon Fluxes and Carbon Use Efficiency Simulated by CMIP5 Earth System Models

This study compares historical simulations of the terrestrial carbon cycle produced by 10 Earth System Models (ESMs) that participated in the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Using MODIS satellite estimates, this study validates the simulation of gross primary production (GPP), net primary production (NPP), and carbon use efficiency (CUE), which depend on plant function types (PFTs). The models show noticeable deficiencies compared to the MODIS data in the simulation of the spatial patterns of GPP and NPP and large differences among the simulations, although the multi-model ensemble (MME) mean provides a realistic global mean value and spatial distributions. The larger model spreads in GPP and NPP compared to those of surface temperature and precipitation suggest that the differences among simulations in terms of the terrestrial carbon cycle are largely due to uncertainties in the parameterization of terrestrial carbon fluxes by vegetation. The models also exhibit large spatial differences in their simulated CUE values and at locations where the dominant PFT changes, primarily due to differences in the parameterizations. While the MME-simulated CUE values show a strong dependence on surface temperatures, the observed CUE values from MODIS show greater complexity, as well as non-linear sensitivity. This leads to the overall underestimation of CUE using most of the PFTs incorporated into current ESMs. The results of this comparison suggest that more careful and extensive validation is needed to improve the terrestrial carbon cycle in terms of ecosystem-level processes

Synergistic Composite Coating for Separators in Lithium Metal Batteries

Despite their conspicuous advantages in energy density, lithium metal batteries (LMBs) are still in the research stage owing to uncontrolled lithium dendrite growth, which deteriorates their cycle life and safety. In this study, we aim to formulate a separator coating and identify the optimal coating conditions that are scalable with the ultimate goal of fabricating separators that largely address the chronic issues of LMBs. For this purpose, a mixture of an ionic liquid, a block copolymer, and microspheres was applied to a conventional polyethylene separator. While the polymeric microspheres mechanically strengthen the coating layer against lithium dendrite growth, the ionic liquid and block copolymer support lithium ion conduction and provide robust connections among the composite components, all jointly resulting in a uniform lithium ion flux, which in turn results in plated lithium metal with a highly compact morphology. Alongside improved thermal stability, this composite coating enables superior cyclability in Li parallel to Li symmetric and Li parallel to Cu asymmetric cells as well as pouch-type full cells. The simple, scalable nature of the present coating approach renders it useful not only for lithium metal batteries currently in development but also for common commercial lithium ion batteries, which suffer from severe lithium plating upon fast charging.