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This paper presents a self-sustained soil electrical conductivity (soil-EC) sensing IC. The sensing system harvests energy and measures the conductivity of the soil simultaneously using the proposed wide-range DC-DC converter. The power management circuits must accommodate the wide variations of the soil conductivity at varying power levels. The time-domain current sensing mechanism, which is embedded in the DC-DC converter, is employed to measure conductivity. Also, the digital codes are recorded and control the converter for achieving maximal power extraction and maintaining high conversion efficiency. The self-sustained soil-EC monitoring IC was fabricated using 0.18-μm CMOS technology. The range of the input voltage from a soil cell is from 0.8 to 1 V when carbon and zinc electrodes are used. The design achieves a tracking efficiency of 98% over an input range of 416-5000 μW, a throughput power range from 150 μW to 4.32 mW, and a peak system conversion efficiency of 88%, while the regulated voltage is about 1.7-1.8 V. The design can also measure the soil EC from 0.114 to 0.744 mS/cm in a resolution of 0.00568 mS/cm per bit.

For wide-range deployment of wireless sensing nodes in power- and size-constrained Internet of Things applications, self-sustaining wireless sensors without batteries are needed. The energy supply for these ubiquitous sensing devices should harness environmental energy sources to avoid frequent battery replacement and pollution. This paper presents a new soil energy harvesting system with a power management integrated circuit (IC) for wide-range maximum power point tracking (MPPT). The output power of a soil energy cell varies widely according to the soil moisture and soil contents. To extract the maximum amount of energy from the soil, high-efficiency power management with adaptive dc–dc conversion ratios and an MPPT mechanism is essential. The proposed system is implemented with a high-efficiency dc–dc converter IC in a 0.18- ${\mu }\text{m}$ CMOS process. The design achieves a peak tracking efficiency of 90.5% in the throughput power range from 56 $\mu \text{W}$ to 1 mW at an output voltage of 3 V and system efficiency exceeding 65% over an input resistance range of the soil energy source; the peak system efficiency is 73.9%. A demonstration was undertaken of the soil energy harvesting system lighting an LED array without any chemical batteries.

Electrical impedance tomography (EIT), a noninvasive and radiation-free medical imaging technique, has been used for continuous real-time regional lung aeration. However, adhesive electrodes could cause discomfort and increase the risk of skin injury during prolonged measurement. Additionally, the conductive gel between the electrodes and skin could evaporate in long-term usage and deteriorate the signal quality. To address these issues, in this work, textile electrodes integrated with a clothing belt are proposed to achieve EIT lung imaging along with a custom portable EIT system. The simulation and experimental results have verified the validity of the proposed portable EIT system. Furthermore, the imaging results of using the proposed textile electrodes were compared with commercial electrocardiogram electrodes to evaluate their performance.

Nanohybrids which combine SWCNTs and Ni–Co–Mn layered double hydroxides are prepared by a facile hydrothermal process and investigated for the first time as electrode materials for hybrid energy storage devices. The nanohybrid made with a precursor weight ratio of SWCNTs and Ni–Co–Mn layered double hydroxide of 10:90 exhibits the highest capacity of 912 C g−1 at 1 A g−1, while the nanohybrid made with a precursor weight ratio of 30:70 shows the highest rate retention of 65% from 1 A g−1 (672 C g−1) to 50 A g−1 (435 C g−1) and the best capacity retention of 70% after 10000 cycles. Moreover, the charge transfer mechanism of the Ni–Co–Mn layered double hydroxides during charge/discharge is investigated through in-situ X-ray absorption near-edge spectra. To demonstrate practical hybrid energy storage applications, two nanohybrid//SWCNTs asymmetric energy storage devices are assembled and tested in pouch cell configuration. Their performances under folded condition are also evaluated, revealing great potential for flexible hybrid energy storage applications.

This paper presents a capacitive DC-DC converter with adaptive DC-DC conversion ratios and maximum power point tracking (MPPT) for soil and solar energy extraction. To overcome the varying input power ranges of the soil/solar energy sources, a two-dimension power tracking loop with time-based current slope detection was employed. The design was fabricated in a 0.18-μm CMOS process, achieving >80% efficiency in a throughput power range of 360μW to 25mW in the soil mode and from 400 μW to l0mW in the solar mode while the peak system efficiency is 89.5%.

This paper presents a self-sustainable landslide surveillance system that detects hazardous water content level in soils and provides real-time landslide warnings to residents, without requiring wired electricity transmission. A self-powered soil water content sensor was applied as the trigger of alert event. It solves the energy supply problem by an environmental interrupt mechanism, which wakes up the sensor and communication circuits in a sensing node only when the water content in monitored soils exceeds a certain threshold, and thus completely eliminates the need for an ALS node to periodically wake up, sense and communicate. By tightly integrating energy harvesting, environment sensing and circuit wake-up, it may well be the most energy-efficient landslide surveillance system designed to monitor water content in soils in the world.

Thermal solution and thermal management are critical issues in either 2.5D or 3D stacking design, especially when the hotspots are not located next to the heat sink. On the other hand, chip and package designers are eager to know the realtime temperature performance of the stacked chips therefore the workload can be assigned to the proper domain. Hence, a thermal test chip for evaluating the package is proposed in this paper. The thermal sensor network based on a ring oscillator is implemented in this work. Infrared radiation microscopic is employed for inspecting the real-time temperature performance of the chip and package. Four types of package are implemented and experimented by inspection of infrared radiation thermography. The experimental results show that one of proposed design provides good temperature consistency within difference of 0.6°C with the thermal sensors. Meanwhile, the proposed package has excellent capability for evaluating thermal management of the stacked dies by providing good thermal non-uniformity by 0.035 °C/mm.

Different from traditional static thermal solutions (STS) or dynamic thermal management (DTM), we propose a design of metallic thermal skeletons in order to conduct the heat generated by the virtual core array in this paper. Not only the proposed design can lower the maximum temperature of the hotspot, but improve the thermal uniformity of the test chip. Furthermore, the presented metallic thermal skeletons are composed of the BEOL metallization for connection with the on-chip heat sink. Virtual cores with temperature sensors are also designed to construct a 126-core array and, as the role of the virtual many-core system. The thermal sensor network is based on a ring oscillator whose oscillation frequency is sensitive to temperature. Simulations and theoretical computations have been performed to see the effectiveness of the proposed metallic thermal skeletons. Finally, the infrared radiation thermal images are employed for monitoring the temperature of the virtual cores and that of the metallic thermal skeletons. The experimental results show that the proposed type γ design provides excellent capability for enhancement of thermal conduction and largely enhances the thermal uniformity of the test chip.

Based on differential properties of the received preamble, a novel start of packet (SoP) detection and synchronization approach is developed for the IEEE802.11n MIMO-OFDM WLAN system to obtain better mean and variance of timing estimates and lower missing packet and false alarm rates.

A novel strategy codeword selection (called partial channel precoding) for channel state information (CSI) in a limited feedback scenario is proposed. Consider as an example the CSI codebook in the 3GPP LTE system of a 4×4 MIMO structure. Rather than using the traditional method of selecting the nearest codebook to the right singular vectors of the entire channel matrix, a partial match that aims to place the third and fourth signal streams near the null space of the first two receive antennas is presented. Combined with the successive interference cancellation scheme, this novel codeword selection strategy is shown to improve SINR and subsequently the frame error rate performance of a MIMO-OFDM system.

Effects of improved channel estimation are studied for a proposed IEEE 802.11n OFDM MIMO system. Three channel estimation methods are considered: maximum likelihood (ML), time-domain truncation (TDT) and model-based (MB). TDT and MB are particularly useful when the channel delay spread is short. For an MMSE receiver, MB shows a 1-2.5 dB improvement over ML on the packet error rate performance for TGn channels B and D for various modulation and coding schemes. TDT is a simplified version of MB and shows a 1-2 dB improvement over ML at low SNRs. But improvements diminish when transmit beamforming is also employed.