12 research outputs found
A SiGe 8-Channel Comparator for Application in a Synthetic Aperture Radiometer
We present a high-speed low-power 8-channel comparator tailored for the application of sampling antenna signals in a cross-correlator system for space-borne synthetic aperture radiometer instruments. Features like clock return path, per-channel offset calibration and bias current tuning make the comparator adaptable and gives the possibility to adjust the comparator for low power consumption, while keeping performance within the requirements of the cross-correlator system. The comparator has been implemented and fabricated in a 130-nm SiGe BiCMOS process. Measurements show that the comparator can perform sampling at a rate of 4.5 GS/s with a power consumption of 48 mW/channel or 1 GS/s with a power consumption of 17 mW/channel
1.6 GHz Low-Power Cross-Correlator System Enabling Geostationary Earth Orbit Aperture Synthesis
We present a 64-channel cross-correlator system for space-borne synthetic aperture imaging. Two different types of ASICs were developed to fit into this system: An 8-channel comparator ASIC implemented in a 130 nm SiGe BiCMOS process technology performs A/D conversion, while a single 64-channel digital cross-correlator ASIC implemented in a 65 nm CMOS process performs the signal processing. The digital ASIC handles 2016 cross-correlations at up to 3.6 GS/s and has a power dissipation of only 0.13 mW/correlation/GHz at a supply voltage of 1 V. The comparator ASIC can handle sample rates of at least 4.5 GS/s with a power dissipation of 47 mW/channel or 1 GS/s with a power dissipation of 17 mW/channel. The assembled system consists of a single board measuring a mere 136 x 136 mm(2) and weighing only 135 g. The assembled system demonstrates crosstalk of 0.04% between neighboring channels and stability of 800 s. We provide ASIC and system-board measurement results that demonstrate that aperture synthesis can be a viable approach for Earth observation from a geostationary Earth orbit
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Radiation effects in III-V compound semiconductor heterostructure devices
The radiation effects in III-V heterojunction devices are investigated in this thesis. Two types of heterojunction devices studied are InGaP/GaAs single heterojunction bipolar transistors (SHBTs) and GaN-based heterojunction light emitting diodes (LEDs). InGaP/GaAS HBTs are investigated for high energy (67 and 105 MeV) proton irradiation effects while GaN heterojunction LEDs are studied for neutron irradiation effects. A compact model and the parameter extraction procedures for HBTs are developed, and hence the I[subscript C]--V[subscript CE] characteristics of pre- and post-irradiation HBTs can be simulated by employing the developed model. HBTs are electrically characterized before and after proton irradiation. Overall, the studied HBT devices are quite robust against high energy proton irradiation. The most pronounced radiation effect shown in SHBTs is gain degradation. Displacement damage in the bulk of base-emitter space-charge region, leading to excess base current, is the responsible mechanism for the proton-induced gain degradation. The performance degradation depends on the operating current and is generally less at higher currents. Compared to the MBE grown devices, the MOVPE grown HBTs show superior characteristics both in initial performance and in proton irradiation hardness. The 67 MeV protons cause more damage than 105 MeV protons due to their higher value of NIEL (non-ionizing energy loss). The HBT I-V characteristics of pre- and post-irradiated samples can be simulated successfully by employing the developed model. GaN heterojunction LEDs are electrically and optically characterized before and after neutron irradiation. Neutron irradiation causes changes in both the I-V characteristic and the light output. Atomic displacement is responsible for both electrical and optical degradation. Both electrical and optical properties degrade steadily with neutron fluence producing severe degradation after the highest fluence neutron irradiation. The light output degrades by more than 99% after 1.6x10¹⁵ n/cm² neutron irradiation, and the radiation damage depends on the operating current and is generally less at higher currents
Silicon-Germanium Bipolar Technology for Enabling Cold-Capable, Radiation-Tolerant Electronics for Spacecraft
The objective of this research is to investigate the effect that low temperature has on the
radiation effects on advanced silicon-germanium (SiGe) heterojunction bipolar transistor
(HBT) for the application of deep-space exploration missions that are specifically classified
as extreme low-temperature and highly radiation active environments, such as Jovian
exploration missions. We designed a unique experimental testbed that enabled DC and RF
measurements to be taken in situ at various temperature and radiation points. The experiment
was conducted at the Jet Propulsion Laboratory (JPL) where low-temperature and
radiation environments can be mimicked. We showed that while there is some radiation
damage in base leakage current on the single transistor level, there is no observed damage
due to total-ionizing dose (TID) in noise figure, linearity, or gain for a 2.4 GHz low-noise
amplifier (LNA) that was irradiated at an ambient temperature of about 100 K up to 1 Mrad
(Si). Furthermore, we confirmed the notion that radiation at lower temperatures yields less
damage and showed why it is important to separate temperature-dependent performance
with measurable radiation damage at different temperatures.
We also took a simulation approach to determine whether single-event transients (SETs)
get worse as a result of the device being in low ambient temperatures. For a single standalone
device, the results show that the transient gets larger in magnitude but shorter in
duration. However, the circuit results show that the effects of an SET get worse in some
cases with low temperatures such as in the context of LNAs, but can also get better in other
cases such as current-mode logic (CML) D-flip-flops.M.S
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Radiation effects in III-V semiconductors and heterojunction bipolar transistors
The electron, gamma and neutron radiation degradation of III-V semiconductors
and heterojunction bipolar transistors (HBTs) is investigated in this thesis.
Particular attention is paid to InP and InGaAs materials and InP/InGaAs
abrupt single HBTs (SHBTs). Complete process sequences for fabrication of
InP/InGaAs HBTs are developed and subsequently employed to produce the
devices, which are then electrically characterized and irradiated with the different
types of radiation. A comprehensive analytical HBT model is developed and radiation
damage calculations are performed to model the observed radiation-induced
degradation of SHBTs.
The most pronounced radiation effects found in SHBTs include reduction
of the common-emitter DC current gain, shift of the collector-emitter (CE) offset
voltage and increase of the emitter, base and collector parasitic resistances. Quantitative
analysis performed using the developed model demonstrates that increase
of the neutral bulk and base-emitter (BE) space charge region (SCR) components
of the base current are responsible for the observed current gain degradation. The
rise of the neutral bulk recombination is attributed to decrease in a Shockley-Read-Hall (SRH) carrier lifetime, while the SCR current increase is caused by rising SCR
SRH recombination and activation of a tunneling-recombination mechanism. On
the material level these effects are explained by displacement defects produced
in a semiconductor by the incident radiation. The second primary change of the
SHBT characteristics, CE offset voltage shift, is induced by degradation of the
base-collector (BC) junction. The observed rise of the BC current is brought on
by diffusion and recombination currents which increase as more defects are introduced
in a semiconductor. Finally, the resistance degradation is attributed to
deterioration of low-doped layers of a transistor, and to degradation of the device
metal contacts
DESIGN OF RF RECEIVER COMPONENTS FOR SPACE APPLICATION SUSING SIGE BICMOS
The objective of the proposed research is to understand the behavior of components in SiGe BiCMOS technologies to the radiation environment present in space, and use such understanding to inform the design and testing of RF receiver components for space-flight applications. To evaluate the response of SiGe HBTs to various types of radiation, exposure to X-rays is performed to emulate operation in the space environment. Degradation in relevant device performance characteristics is considered as it changes with longer exposures. Then, implications of impaired device performance are demonstrated for circuit components commonly present in RF receivers for both radar and communications, and design considerations for operation in space are discussed.M.S
Investigation of radiation-hardened design of electronic systems with applications to post-accident monitoring for nuclear power plants
This research aims at improving the robustness of electronic systems used-in high level radiation environments by combining with radiation-hardened (rad-hardened) design and fault-tolerant techniques based on commercial off-the-shelf (COTS) components. A specific of the research is to use such systems for wireless post-accident monitoring in nuclear power plants (NPPs). More specifically, the following methods and systems are developed and investigated to accomplish expected research objectives: analysis of radiation responses, design of a radiation-tolerant system, implementation of a wireless post-accident monitoring system for NPPs, performance evaluation without repeat physical tests, and experimental validation in a radiation environment.
A method is developed to analyze ionizing radiation responses of COTS-based devices and circuits in various radiation conditions, which can be applied to design circuits robust to ionizing radiation effects without repeated destructive tests in a physical radiation environment. Some mathematical models of semiconductor devices for post-irradiation conditions are investigated, and their radiation responses are analyzed using Technology Computer Aided Design (TCAD) simulator. Those models are then used in the analysis of circuits and systems under radiation condition. Based on the simulation results, method of rapid power off may be effectively to protect electronic systems under ionizing radiation. It can be a potential solution to mitigate damages of electronic components caused by radiation.
With simulation studies of photocurrent responses of semiconductor devices, two methods are presented to mitigate the damages of total ionizing dose: component selection and radiation shielding protection. According to the investigation of radiation-tolerance of regular COTS components, most COTS-based semiconductor components may experience performance degradation and radiation damages when the total dose is greater than 20 K Rad (Si). A principle of component selection is given to obtain the suitable components, as well as a method is proposed to assess the component reliability under radiation environments, which uses radiation degradation factors, instead of the usual failure rate data in the reliability model. Radiation degradation factor is as the input to describe the radiation response of a component under a total radiation dose. In addition, a number of typical semiconductor components are also selected as the candidate components for the application of wireless monitoring in nuclear power plants.
On the other hand, a multi-layer shielding protection is used to reduce the total dose to be less than 20 K Rad (Si) for a given radiation condition; the selected semiconductor devices can then survive in the radiation condition with the reduced total dose. The calculation method of required shielding thickness is also proposed to achieve the design objectives. Several shielding solutions are also developed and compared for applications in wireless monitoring system in nuclear power plants.
A radiation-tolerant architecture is proposed to allow COTS-based electronic systems to be used in high-level radiation environments without using rad-hardened components. Regular COTS components are used with some fault-tolerant techniques to mitigate damages of the system through redundancy, online fault detection, real-time preventive remedial actions, and rapid power off. The functions of measurement, processing, communication, and fault-tolerance are integrated locally within all channels without additional detection units. A hardware emulation bench with redundant channels is constructed to verify the effectiveness of the developed radiation-tolerant architecture. Experimental results have shown that the developed architecture works effectively and redundant channels can switch smoothly in 500 milliseconds or less when a single fault or multiple faults occur.
An online mechanism is also investigated to timely detect and diagnose radiation damages in the developed redundant architecture for its radiation tolerance enhancement. This is implemented by the built-in-test technique. A number of tests by using fault injection techniques have been carried out in the developed hardware emulation bench to validate the proposed detection mechanism. The test results have shown that faults and errors can be effectively detected and diagnosed. For the developed redundant wireless devices under given radiation dose (20 K Rad (Si)), the fault detection coverage is about 62.11%. This level of protection could be improved further by putting more resources (CPU consumption, etc.) into the function of fault detection, but the cost will increase.
To apply the above investigated techniques and systems, under a severe accident condition in a nuclear power plant, a prototype of wireless post-accident monitoring system (WPAMS) is designed and constructed. Specifically, the radiation-tolerant wireless device is implemented with redundant and diversified channels. The developed system operates effectively to measure up-to-date information from a specific area/process and to transmit that information to remote monitoring station wirelessly. Hence, the correctness of the proposed architecture and approaches in this research has been successfully validated.
In the design phase, an assessment method without performing repeated destructive physical tests is investigated to evaluate the radiation-tolerance of electronic systems by combining the evaluation of radiation protection and the analysis of the system reliability under the given radiation conditions. The results of the assessment studies have shown that, under given radiation conditions, the reliability of the developed radiation-tolerant wireless system can be much higher than those of non-redundant channels; and it can work in high-level radiation environments with total dose up to 1 M Rad (Si).
Finally, a number of total dose tests are performed to investigate radiation effects induced by gamma radiation on distinct modern wireless monitoring devices. An experimental setup is developed to monitor the performance of signal measurement online and transmission of the developed distinct wireless electronic devices directly under gamma radiator at The Ohio State University Nuclear Reactor Lab (OSU-NRL). The gamma irradiator generates dose rates of 20 K Rad/h and 200 Rad/h on the samples, respectively. It was found that both measurement and transmission functions of distinct wireless measurement and transmission devices work well under gamma radiation conditions before the devices permanently damage. The experimental results have also shown that the developed radiation-tolerant design can be applied to effectively extend the lifespan of COTS-based electronic systems in the high-level radiation environment, as well as to improve the performance of wireless communication systems. According to testing results, the developed radiation-tolerant wireless device with a shielding protection can work at least 21 hours under the highest dose rate (20 K Rad/h).
In summary, this research has addressed important issues on the design of radiation-tolerant systems without using rad-hardened electronic components. The proposed methods and systems provide an effective and economical solution to implement monitoring systems for obtaining up-to-date information in high-level radiation environments. The reported contributions are of significance both academically and in practice
Topical Workshop on Electronics for Particle Physics
The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities