Design of an output-capacitorless low-dropout regulator for power management applications

This article aims to present the design of a 4.5-V, 450-mA low drop-out (LDO) voltage linear regulator based on a twostage cascoded operational transconductance amplifier (OTA) as error amplifier. The aforementioned two-stage OTA is designed with cascoded current mirroring technique to boost up the output impedance. The proposed OTA has a DC gain of 101 dB under no load condition. The designed reference voltage included in the LDO regulator is provided by a band gap reference with the temperature coefficient (T¿) of 0.025 mV/ºC. The proposed LDO regulator has a maximum drop-out voltage of 0.5 V @ 450 mA of load current, and has the worst case power supply rejection ratio (PSRR) of [54.5 dB, 34.3 dB] @ [100 Hz, 10 kHz] in full load condition. All the proposed circuits are designed using a 0.35 µm CMOS technology. The design is checked in order to corroborate its performance for wide range of input voltage, founding that the circuit design works fine meeting all the initial specification requirements.Postprint (published version

Output-capacitorless low-dropout regulator for power management applications

This article aims to present the design of a 4.5-V, 450-mA low drop-out (LDO) voltage linear regulator based on a two-stage cascoded operational transconductance amplifier (OTA) as error amplifier. The aforementioned two-stage OTA is designed with cascoded current mirroring technique to boost up the output impedance. The proposed OTA has a DC gain of 101 dB under no load condition. The designed reference voltage included in the LDO regulator is provided by a band gap reference with the temperature coefficient (T¿) of 0.025 mV/ºC. The proposed LDO regulator has a maximum drop-out voltage of 0.5 V @ 450 mA of load current, and has the worst case power supply rejection ratio (PSRR) of [54.5 dB, 34.3 dB] @ [100 Hz, 10 kHz] in full load condition. All the proposed circuits are designed using a 0.35 µm CMOS technology. The design is checked in order to corroborate its performance for wide range of input voltage, founding that the circuit design works fine meeting all the initial specification requirements.Postprint (published version

An ultra-fast digital diffuse optical spectroscopic imaging system for neoadjuvant chemotherapy monitoring

Up to 20% of breast cancer patients who undergo presurgical (neoadjuvant) chemotherapy have no response to treatment. Standard-of-care imaging modalities, including MRI, CT, mammography, and ultrasound, measure anatomical features and tumor size that reveal response only after months of treatment. Recently, non-invasive, near-infrared optical markers have shown promise in indicating the efficacy of treatment at the outset of the chemotherapy treatment. For example, frequency domain Diffuse Optical Spectroscopic Imaging (DOSI) can be used to characterize the optical scattering and absorption properties of thick tissue, including breast tumors. These parameters can then be used to calculate tissue concentrations of chromophores, including oxyhemoglobin, deoxyhemoglobin, water, and lipids. Tumors differ in hemoglobin concentration, as compared with healthy background tissue, and changes in hemoglobin concentration during neoadjuvant chemotherapy have been shown to correlate with efficacy of treatment. Using DOSI early in treatment to measure chromophore concentrations may be a powerful tool for guiding neoadjuvant chemotherapy treatment. Previous frequency-domain DOSI systems have been limited by large device footprints, complex electronics, high costs, and slow acquisition speeds, all of which complicate access to patients in the clinical setting. In this work a new digital DOSI (dDOSI) system has been developed, which is relatively inexpensive and compact, allowing for use at the bedside, while providing unprecedented measurement speeds. The system builds on, and significantly advances, previous dDOSI setups developed by our group and, for the first time, utilizes hardware-integrated custom board-level direct digital synthesizers (DDS) and analog to digital converters (ADC) to generate and directly measure signals utilizing undersampling techniques. The dDOSI system takes high-speed optical measurements by utilizing wavelength multiplexing while sweeping through hundreds of modulation frequencies in tens of milliseconds. The new dDOSI system is fast, inexpensive, and compact without compromising accuracy and precision

S-band antenna phased array communications system

The development of an S-band antenna phased array for spacecraft to spacecraft communication is discussed. The system requirements, antenna array subsystem design, and hardware implementation are examined. It is stated that the phased array approach offers the greatest simplicity and lowest cost. The objectives of the development contract are defined as: (1) design of a medium gain active phased array S-band communications antenna, (2) development and test of a model of a seven element planar array of radiating elements mounted in the appropriate cavity matrix, and (3) development and test of a breadboard transmit/receive microelectronics module

Operating Point Optimization of a Hydrogen Fueled Hybrid Solid Oxide Fuel Cell-Steam Turbine (SOFC-ST) Plant

This paper presents a hydrogen powered hybrid solid oxide fuel cell-steam turbine (SOFC-ST) system and studies its optimal operating conditions. This type of installation can be very appropriate to complement the intermittent generation of renewable energies, such as wind generation. A dynamic model of an alternative hybrid SOFC-ST configuration that is especially suited to work with hydrogen is developed. The proposed system recuperates the waste heat of the high temperature fuel cell, to feed a bottoming cycle (BC) based on a steam turbine (ST). In order to optimize the behavior and performance of the system, a two-level control structure is proposed. Two controllers have been implemented for the stack temperature and fuel utilization factor. An upper supervisor generates optimal set-points in order to reach a maximal hydrogen efficiency. The simulation results obtained show that the proposed system allows one to reach high efficiencies at rated power levels.This work has been carried out in the Intelligent Systems and Energy research group of the University of the Basque Country (UPV/EHU) and has been supported by the UFI11/28 research grant of the UPV/EHU and by the IT677-13 research grant of the Basque Government (Spain) and by DPI2012-37363-CO2-01 research grant of the Spanish Ministry of Economy and Competitiveness

SIRU development. Volume 1: System development

A complete description of the development and initial evaluation of the Strapdown Inertial Reference Unit (SIRU) system is reported. System development documents the system mechanization with the analytic formulation for fault detection and isolation processing structure; the hardware redundancy design and the individual modularity features; the computational structure and facilities; and the initial subsystem evaluation results

Practical quantum realization of the ampere from the electron charge

One major change of the future revision of the International System of Units (SI) is a new definition of the ampere based on the elementary charge \emph{e}. Replacing the former definition based on Amp\`ere's force law will allow one to fully benefit from quantum physics to realize the ampere. However, a quantum realization of the ampere from \emph{e}, accurate to within $10^{-8}$ in relative value and fulfilling traceability needs, is still missing despite many efforts have been spent for the development of single-electron tunneling devices. Starting again with Ohm's law, applied here in a quantum circuit combining the quantum Hall resistance and Josephson voltage standards with a superconducting cryogenic amplifier, we report on a practical and universal programmable quantum current generator. We demonstrate that currents generated in the milliampere range are quantized in terms of $ef_\mathrm{J}$ ($f_\mathrm{J}$ is the Josephson frequency) with a measurement uncertainty of $10^{-8}$. This new quantum current source, able to deliver such accurate currents down to the microampere range, can greatly improve the current measurement traceability, as demonstrated with the calibrations of digital ammeters. Beyond, it opens the way to further developments in metrology and in fundamental physics, such as a quantum multimeter or new accurate comparisons to single electron pumps.Comment: 15 pages, 4 figure

Overview and evolution of the LeRC PMAD DC Testbed

Since the beginning of the Space Station Freedom Program (SSFP), the Lewis Research Center (LeRC) has been developed electrical power system test beds to support the overall design effort. Through this time, the SSFP has changed the design baseline numerous times, however, the test bed effort has endeavored to track these changes. Beginning in August 1989 with the baseline and an all DC system, a test bed was developed to support the design baseline. The LeRC power measurement and distribution (PMAD) DC test bed and the changes in the restructure are described. The changes includeed the size reduction of primary power channel and various power processing elements. A substantial reduction was also made in the amount of flight software with the subsequent migration of these functions to ground control centers. The impact of these changes on the design of the power hardware, the controller algorithms, the control software, and a description of their current status is presented. An overview of the testing using the test bed is described, which includes investigation of stability and source impedance, primary and secondary fault protection, and performance of a rotary utility transfer device. Finally, information is presented on the evolution of the test bed to support the verification and operational phases of the SSFP in light of these restructure scrubs