1,511 research outputs found
Prevalence and identification of alcohol use disorders among nonpsychiatric inpatients in one general hospital
No full textPsychosocial and psychiatric risk factors for suicide: case-control psychological autopsy study
No full text
Design and Implementation of a Low-Jitter 6GHz Spread Spectrum Clock Generator for Serial-ATA
No full textEMI (Electro-Magnetic Interference) causes more destruction to the transmitting signal since the operating frequency is higher than before. Spread spectrum clocking (SSC) is a method that can reduce the EMI effectively. This method is more and more popular since it is easy to design and suitable for integrated IC. Serial ATA is a high speed external mass storage device having the SSC specifications as following: a triangular modulation profile with down spread, a 5000 ppm frequency deviation, a 30~33KHz modulation frequency, an EMI reduction larger than 7dB, and a 3ps RMS jitter @ 250 cycles.
Our research is stressed on low-jitter design. Due to the higher operating frequency requirement, design with low-jitter performance becomes more and more important and thus more difficult to realize. VCO phase noise dominates the jitter performance of PLLs. Therefore, we proposed a LC tank VCO with low phase noise characteristic. The simulation results show that the phase noise is -119.8dBc/Hz @1MHz offset voltage and FoM is -190.8.
In this Thesis, a spread spectrum clock generator (SSCG) modulated by a divider is presented. The PLL is fabricated in a 0.18μm CMOS process and the whole SSCG system is integrated and tested on an FPGA board. The simulation results show that all specifications of the Serial ATA have been achieved in our system and the jitter measurement shows that the RMS jitter is 0.4ps @ 250 cycles.TABLE OF CONTENTS
ABSTRACT i
LIST OF FIGURES v
LIST OF TABLES ix
CHAPTER 1 INTRODUCTION 1
1.1 Motivation 1
1.2 Thesis Organization 2
CHAPTER 2 BASIC OF SPREAD SPECTRUM CLOCKING 5
2.1 Specification of Serial ATA for SSC 5
2.2 Fundamental Theory of SSC 6
2.3 Types of SSC Implementation 8
2.4 Jitter Performance 10
CHAPTER 3 FRACTIONAL-N PLL USING Δ-Σ MODULATOR 13
3.1 Principle of Phase-Locked Loop 13
3.2 Analysis of Phase-Locked Loop 14
3.2.1 Voltage Controlled Oscillator 14
3.2.2 PFD with Charge Pump and Loop Filter 15
3.2.3 Linear Model of PLL 17
3.2.4 Phase Noise in PLL 19
3.3 Fractional-N Frequency Synthesis 21
3.3.1 Pulse Swallow 22
3.3.2 Fractional Spurs 24
3.4 Δ-Σ Modulator 26
3.5 Third-Order MASH Δ-Σ Modulator 29
CHAPTER 4 DESIGN OF SPREAD SPECTRUM CLOCK GENERATOR 33
4.1 System Architecture 33
4.2 Voltage Controlled Oscillator 34
4.2.1 LC-VCO Versus Ring-VCO 35
4.2.2 VCO Phase Noise 35
4.2.3 LC-VCO Technique 37
4.2.4 A New LC-VCO with Back-Gate Tuning Technique 39
4.3 Phase/Frequency Detector 40
4.4 Charge Pump 41
4.5 Programmable Charge Pump 43
4.6 Multi-Modulus Divider 44
4.7 Loop Filter 45
4.8 MASH 1-1-1 Δ-Σ Modulator 49
4.9 Triangular Generator 52
CHAPTER 5 SIMULATION RESULTS OF SPREAD SPECTRUM CLOCK GENERATOR 55
5.1 SSCG Behavior Simulation 55
5.2 Circuit Level Simulation 58
5.2.1 Voltage Controlled Oscillator 59
5.2.2 Phase/Frequency Detector and Charge Pump 62
5.2.3 Prescaler 64
5.2.4 Multi-Modulus Divider 64
5.2.5 Closed-Loop Simulation of PLL 65
5.2.6 PLL Implementation 67
5.3 MASH 1-1-1 and Triangular Generator 69
5.4 Closed-Loop Simulation of SSCG 71
CHAPTER 6 CONCLUSION 75
REFERENCE 7
Analysis of Technical Approaches (ATA)
No full textStudies & Prototyping This JSB ATA Study Paper is the author's work product and does not reflec
Psychiatric and psychosocial predictors of substance use disorders among adolescents - Longitudinal study
No full text[[abstract]]Background Few studies have prospectively examined psychosocial and psychiatric predictors of adolescent substance use disorders simultaneously. Aims To identify psychosocial and psychiatric predictors of substance use disorders in adolescence. Method School children aged 12 years (s.d.=0.3) free from any substance use disorder at grade 7 (n=428) were assessed in three consecutive years, using a standardised psychiatric interview. Their baseline psychosocial information was also collected. The outcome was the onset age of a substance use disorder. The Cox regression model was used for data analysis. Results The most significant predictive factors for adolescent substance use disorder included male gender, attention-deficit hyperactivity disorder, conduct disorder and sibling use of tobacco. Three protective factors against such morbidity included living in a household with two parents, a good academic grade at grade 7 and objection to the use of substances. Conclusions Early intervention for disruptive behaviour disorders and specific psychosocial risk factors might prevent substance use disorders in early adolescence
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