The Experts below are selected from a list of 59613 Experts worldwide ranked by ideXlab platform
Johanna Nieminen - One of the best experts on this subject based on the ideXlab platform.
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how low energy is bluetooth low energy comparative measurements with zigbee 802 15 4
Wireless Communications and Networking Conference, 2012Co-Authors: Matti Siekkinen, Markus Hiienkari, Jukka K Nurminen, Johanna NieminenAbstract:Ultra low Power communication mechanisms are essential for future Internet of Things deployments. Bluetooth Low Energy (BLE) is one promising candidate for such deployments. We study the energy consumption of BLE by measuring real devices with a Power Monitor and derive models of the basic energy consumption behavior observed from the measurement results. We investigate also the overhead of Ipv6-based communication over BLE, which is relevant for future IoT scenarios. We contrast our results by performing similar measurements with ZigBee/802.15.4 devices. Our results show that when compared to ZigBee, BLE is indeed very energy efficient in terms of number of bytes transferred per Joule spent. In addition, IPv6 communication energy overhead remains reasonable. We also point out a few specific limitations with current stack implementations and explain that removing those limitations could improve energy utility significantly.
Dinesh K Agrawal - One of the best experts on this subject based on the ideXlab platform.
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experimental proof of major role of magnetic field losses in microwave heating of metal and metallic composites
Journal of Materials Science Letters, 2001Co-Authors: Jiping Cheng, Dinesh K AgrawalAbstract:In 1999 we found that powdered metal samples including very complex shaped and large size (100 mm diameter, 1 kilograms) could be fully sintered in 30 min in a 2.45 GHz multi-mode microwave cavity [1]. Moreover, these samples had properties at least as good as, and usually better than, those sintered in conventional furnaces. This finding was outside the experience of a very large number of scientists whose extensive work has been covered in many reviews [2–4]. This achievement was as puzzling to us as to colleagues and efforts to explain this by skin depth absorption etc. did not work. The well known extensive theoretical treatment of microwave-material interaction by many workers (see e.g. Varadan and Varadan [5], Booske et al. [6] and others) have in common that they always treat the energy absorption mechanism as due to the dielectric loss factor. In 1994 Cherradi et al. [7] reported their preliminary work in which they showed that the magnetic field must make substantial contributions to the heating of alumina (at high temperature) and semiconductors, and metallic copper. But in their work, the experimental design of using samples of 120 mm length, where in some cases, the sample was exposed to both magnetic and electric field simultaneously, caused a complicated interplay of the different absorption. In present work, a finely tuned microwave cavity with a cross section dimension of 86 mm by 43 mm which works in TE103 single mode was used to investigate the microwave heating behaviors of various materials in different microwave fields. Fig. 1 shows the scheme of the microwave system, and the distribution of the microwave field within the cavity is sketched in Fig. 2. In the L/2 location along the length of the cavity, the maximum electric (E) field is in the center of the cross section, where the magnetic (H ) field is minimum; and the maximum magnetic field is near the wall, where the electric field is minimum. A quartz tube was introduced in this location to hold the sample and also to enable us to control the atmosphere. A 2.45 GHz, 1.2 kW microwave generator (Toshiba, Japan) with Power Monitor was used as microwave source. A small cylindrical sample (5 mm diameter and 3 mm thick) was placed inside at two different locations, the maximum electric field area where the magnetic field is minimum, and the maximum magnetic field area where the electric field is minimum, respectively. Sample temperatures were measured using an infrared pyrometer (Mikron Instrument Co., Model M90-BT, temperature range −50 ◦C–1000 ◦C). During the experiments, atmospheric pressure nitrogen gas was passed through the quartz tube to avoid oxidation of metal samples at high temperature. Initially, we tried to use a fixed microwave Power for all samples during heating, but for some samples, the temperature increase was too fast and the highest temperature exceeded the measuring range of the pyrometer, and in some cases, discharging and arcing occurred. So we set different microwave Powers for different samples to get more stable heating results. Fig. 3a shows the heating observed for a typical commercial powdered metal sample (Keystone Powdered-metal Company, Saint Marys, PA, USA. The
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experimental proof of major role of magnetic field losses in microwave heating of metal and metallic composites
Journal of Materials Science Letters, 2001Co-Authors: Jiping Cheng, Dinesh K AgrawalAbstract:In 1999 we found that powdered metal samples including very complex shaped and large size (100 mm diameter, 1 kilograms) could be fully sintered in 30 min in a 2.45 GHz multi-mode microwave cavity [1]. Moreover, these samples had properties at least as good as, and usually better than, those sintered in conventional furnaces. This finding was outside the experience of a very large number of scientists whose extensive work has been covered in many reviews [2–4]. This achievement was as puzzling to us as to colleagues and efforts to explain this by skin depth absorption etc. did not work. The well known extensive theoretical treatment of microwave-material interaction by many workers (see e.g. Varadan and Varadan [5], Booske et al. [6] and others) have in common that they always treat the energy absorption mechanism as due to the dielectric loss factor. In 1994 Cherradi et al. [7] reported their preliminary work in which they showed that the magnetic field must make substantial contributions to the heating of alumina (at high temperature) and semiconductors, and metallic copper. But in their work, the experimental design of using samples of 120 mm length, where in some cases, the sample was exposed to both magnetic and electric field simultaneously, caused a complicated interplay of the different absorption. In present work, a finely tuned microwave cavity with a cross section dimension of 86 mm by 43 mm which works in TE103 single mode was used to investigate the microwave heating behaviors of various materials in different microwave fields. Fig. 1 shows the scheme of the microwave system, and the distribution of the microwave field within the cavity is sketched in Fig. 2. In the L/2 location along the length of the cavity, the maximum electric (E) field is in the center of the cross section, where the magnetic (H ) field is minimum; and the maximum magnetic field is near the wall, where the electric field is minimum. A quartz tube was introduced in this location to hold the sample and also to enable us to control the atmosphere. A 2.45 GHz, 1.2 kW microwave generator (Toshiba, Japan) with Power Monitor was used as microwave source. A small cylindrical sample (5 mm diameter and 3 mm thick) was placed inside at two different locations, the maximum electric field area where the magnetic field is minimum, and the maximum magnetic field area where the electric field is minimum, respectively. Sample temperatures were measured using an infrared pyrometer (Mikron Instrument Co., Model M90-BT, temperature range −50 ◦C–1000 ◦C). During the experiments, atmospheric pressure nitrogen gas was passed through the quartz tube to avoid oxidation of metal samples at high temperature. Initially, we tried to use a fixed microwave Power for all samples during heating, but for some samples, the temperature increase was too fast and the highest temperature exceeded the measuring range of the pyrometer, and in some cases, discharging and arcing occurred. So we set different microwave Powers for different samples to get more stable heating results. Fig. 3a shows the heating observed for a typical commercial powdered metal sample (Keystone Powdered-metal Company, Saint Marys, PA, USA. The
J J Laserna - One of the best experts on this subject based on the ideXlab platform.
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spectroscopic diagnostics on cw laser welding plasmas of aluminum alloys
Spectrochimica Acta Part B: Atomic Spectroscopy, 2001Co-Authors: S Palanco, M Klassen, J Skupin, K Hansen, E Schubert, G Sepold, J J LasernaAbstract:Abstract In-process diagnostics intended to correlate spectrometric measurements to the occurrence of laser welding defects such as notches and blowholes have been carried out. The plasma light emitted during high-Power CO2 laser welding of a 6013 aluminum alloy was guided to an imaging spectrograph and the dispersed light was detected with a CCD system. A transient recorder was used to record the signal from a fast laser-Power Monitor and the sync signals from the CCD and a fast speed video camera. Accuracy of the measurements are discussed in relation to the low and fast acquisition rate approaches (58 spectra s−1 and 4×103 spectra s−1, respectively) used in the experiments. Spectroscopic measurements at fast acquisition rates showed both an increase in the intensity of the overall spectral emission and the growth of lines corresponding to ionic aluminum species taking place right before the occurrence of weld defects.
Benton H Calhoun - One of the best experts on this subject based on the ideXlab platform.
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Sub-microAmp Energy Harvesting and Power Management Units for Self-Powered IoT SoCs: Analog vs. Digital Implementations
2020 IEEE Custom Integrated Circuits Conference (CICC), 2020Co-Authors: Benton H CalhounAbstract:The Power consumption of ultra-low-Power (ULP) Internet-of-Things (IoT) SoCs and components has been scaling down from μW to pW levels over the past ten years. Designing energy harvesting and Power management units (EH-PMUs) that consume sub-μA quiescent current to efficiently provide such low load current is challenging. This paper reviews the trends and techniques for sub-μA EH-PMUs with a specific focus on the choice between analog and digital implementations. We first discuss ULP EH-PMU design trends based on recent published results and then analyze three design examples. The first example reviews a popular multiple-input multiple-output (MIMO) EH-PMU architecture with ultra-low quiescent current and compares tradeoffs for analog vs. digital zero-current detectors. The second example discusses the design of analog and digital low-dropout regulators (LDOs) with a performance comparison from silicon measurement results. The digital LDO can achieve faster settling time for step response than the analog structure, but the analog LDO has no ripple, making it ideal for noise-sensitive blocks like RF. Finally, an analog Power Monitor for maximum-Power-point tracking (MPPT) in a piezoelectric energy harvester utilizes subthreshold transistor characteristics to simply a complex algorithm and to maintain low Power consumption.
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a piezoelectric energy harvesting system with parallel sshi rectifier and integrated mppt achieving 417 energy extraction improvement and 97 tracking efficiency
Symposium on VLSI Circuits, 2019Co-Authors: Abhishek Roy, Benton H CalhounAbstract:This work presents an integrated maximum-Power-point tracking (MPPT) algorithm and its implementation for the high-performance parallel-synchronized-switch harvesting-on-inductor (SSHI) rectifier, which uses the Perturb and Observe (P&O) method and a proposed Power Monitor for output Power evaluation. Fabricated in 130nm, this piezoelectric energy-harvesting system implements a 417% FOM rectifier with 97% tracking efficiency MPPT, which makes it the first work demonstrating a parallel-SSHI rectifier and high tracking-efficiency MPPT simultaneously.
Abhishek Roy - One of the best experts on this subject based on the ideXlab platform.
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a piezoelectric energy harvesting system with parallel sshi rectifier and integrated mppt achieving 417 energy extraction improvement and 97 tracking efficiency
Symposium on VLSI Circuits, 2019Co-Authors: Abhishek Roy, Benton H CalhounAbstract:This work presents an integrated maximum-Power-point tracking (MPPT) algorithm and its implementation for the high-performance parallel-synchronized-switch harvesting-on-inductor (SSHI) rectifier, which uses the Perturb and Observe (P&O) method and a proposed Power Monitor for output Power evaluation. Fabricated in 130nm, this piezoelectric energy-harvesting system implements a 417% FOM rectifier with 97% tracking efficiency MPPT, which makes it the first work demonstrating a parallel-SSHI rectifier and high tracking-efficiency MPPT simultaneously.
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A battery-less 507nW SoC with integrated platform Power manager and SiP interfaces
2017 Symposium on VLSI Circuits, 2017Co-Authors: Farah B. Yahya, Christopher J. Lukas, Jacob Breiholz, Abhishek Roy, Harsh N. Patel, Ningxi Liu, Xing Chen, Avish Kosari, Divya AkellaAbstract:A 507nW self-Powered SoC is demonstrated for ultra-low Power (ULP) internet-of-things (IoT) applications. The SoC includes ULP system-in-package (SiP) interfaces that enable its harmonious integration with a radio transmitter (TX) and a non-volatile memory (NVM). The energy harvesting platform Power manager (EH-PPM) Powers the SoC as well as off-chip components and is optimized for low quiescent Power. It supplies the SoC with 0.5V, 1.0V, and 1.8V and can also Power ULP sensors and the SiP components while running an example shipping-integrity tracking algorithm. A Power Monitor (PM) cold-boots the SoC from NVM and adapts the system's Power consumption. The tight integration between the SoC's blocks enables sub-μW operation.