Smart Structures and Materials 2005: Smart Structures and Integrated Systems, 2005
Fatigue crack growth during the service of aging aircrafts has become an important issue and the ... more Fatigue crack growth during the service of aging aircrafts has become an important issue and the monitoring of such cracks in hot spots is desirable. A structural health monitoring system using an acoustic emission technique under development for monitoring safety of such structures is described in this paper. A "continuous sensor" formed by connecting multiple sensor nodes in series arrangement to form a single channel sensor is proposed to monitor acoustic emission signals. This paper describes the work in progress on developing sensors, instrumentation, and measurement technique applicable to on-board monitoring of fatigue cracks in 7075-T6 aluminum lap joints. The traditional AE sensors as well as bonded nodes of continuous sensors described above were used to monitor acoustic emission signals emanating from crack growth in aluminum 7075 T6 specimens. It was possible to differentiate the signals due to crack growth from noise signals arising from fretting as well as RF pickup. The sensitivity of the bonded sensor under development was comparable to commercial high sensitivity resonant frequency AE sensors. The relationship between acoustic emission parameters and the crack growth rate in the aluminum specimens is examined.
Many design techniques have been incorporated into modern CMOS design practices to improve radiat... more Many design techniques have been incorporated into modern CMOS design practices to improve radiation tolerance of integrated circuits. Annular-gate NMOS structures have been proven to be significantly more radiation tolerant than the standard, straight-gate variety. Many circuits can be designed using the annular-gate NMOS and the inherently radiation tolerant PMOS. Bandgap reference circuits, however, typically require p-n junction diodes. These p-n junction diodes are the dominating factor in radiation degradation in bandgap reference circuits. This paper proposes a different approach to bandgap reference design to alleviate the radiation susceptibility presented by the p-n junction diodes. Index Terms-Bandgap reference, CMOS, dynamic threshold MOSFET (DTMOS), radiation hardening by design (RHBD), total ionizing dose (TID) radiation. I. INTRODUCTION V OLTAGE reference design is a well-researched area of analog design. All data converters require an accurate, reliable reference voltage for proper conversion [1]. A faulty reference voltage can have devastating effects on data conversion and ultimately the entire system. Temperature-insensitive bandgap voltage references have been a staple of analog and mixed signal system design for decades [2]. In spite of the extensive attention they receive on many fronts, reliable, radiation-tolerant bandgap reference design has remained elusive. Radiation hardening by process (RHBP) using silicon-on-insulator (SOI), or similar technology, effectively eliminates single event latch-up (SEL) by isolating substrate connections, however total ionizing dose (TID) effects remain a significant problem in bandgap reference reliability [3]. A more Manuscript
Sigma-Delta modulators (SDMs) are ubiquitous for implementation of high resolution analog-to-digi... more Sigma-Delta modulators (SDMs) are ubiquitous for implementation of high resolution analog-to-digital converters (ADCs.) However, SDMs are applicable to other signal processing functions such as signal multiplication and filtering. This paper will introduce via-configurable array technology as a cost effective approach for developing circuits like SDMs and provide application examples using these techniques.
Smart Structures and Materials 2005: Smart Structures and Integrated Systems, 2005
Fatigue crack growth during the service of aging aircrafts has become an important issue and the ... more Fatigue crack growth during the service of aging aircrafts has become an important issue and the monitoring of such cracks in hot spots is desirable. A structural health monitoring system using an acoustic emission technique under development for monitoring safety of such structures is described in this paper. A "continuous sensor" formed by connecting multiple sensor nodes in series arrangement to form a single channel sensor is proposed to monitor acoustic emission signals. This paper describes the work in progress on developing sensors, instrumentation, and measurement technique applicable to on-board monitoring of fatigue cracks in 7075-T6 aluminum lap joints. The traditional AE sensors as well as bonded nodes of continuous sensors described above were used to monitor acoustic emission signals emanating from crack growth in aluminum 7075 T6 specimens. It was possible to differentiate the signals due to crack growth from noise signals arising from fretting as well as RF pickup. The sensitivity of the bonded sensor under development was comparable to commercial high sensitivity resonant frequency AE sensors. The relationship between acoustic emission parameters and the crack growth rate in the aluminum specimens is examined.
Many design techniques have been incorporated into modern CMOS design practices to improve radiat... more Many design techniques have been incorporated into modern CMOS design practices to improve radiation tolerance of integrated circuits. Annular-gate NMOS structures have been proven to be significantly more radiation tolerant than the standard, straight-gate variety. Many circuits can be designed using the annular-gate NMOS and the inherently radiation tolerant PMOS. Bandgap reference circuits, however, typically require p-n junction diodes. These p-n junction diodes are the dominating factor in radiation degradation in bandgap reference circuits. This paper proposes a different approach to bandgap reference design to alleviate the radiation susceptibility presented by the p-n junction diodes. Index Terms-Bandgap reference, CMOS, dynamic threshold MOSFET (DTMOS), radiation hardening by design (RHBD), total ionizing dose (TID) radiation. I. INTRODUCTION V OLTAGE reference design is a well-researched area of analog design. All data converters require an accurate, reliable reference voltage for proper conversion [1]. A faulty reference voltage can have devastating effects on data conversion and ultimately the entire system. Temperature-insensitive bandgap voltage references have been a staple of analog and mixed signal system design for decades [2]. In spite of the extensive attention they receive on many fronts, reliable, radiation-tolerant bandgap reference design has remained elusive. Radiation hardening by process (RHBP) using silicon-on-insulator (SOI), or similar technology, effectively eliminates single event latch-up (SEL) by isolating substrate connections, however total ionizing dose (TID) effects remain a significant problem in bandgap reference reliability [3]. A more Manuscript
Sigma-Delta modulators (SDMs) are ubiquitous for implementation of high resolution analog-to-digi... more Sigma-Delta modulators (SDMs) are ubiquitous for implementation of high resolution analog-to-digital converters (ADCs.) However, SDMs are applicable to other signal processing functions such as signal multiplication and filtering. This paper will introduce via-configurable array technology as a cost effective approach for developing circuits like SDMs and provide application examples using these techniques.
Uploads
Papers by Jim Kemerling