Numerical and theoretical analysis on voltage and time domain dynamic range of scaled CMOS circuits
It is believed that the time-domain resolution of a digital signal edge transition is superior to the voltage resolution of an analog signal in advanced CMOS processes[1], [2]. The reasoning behind this is that operating voltage has been reducing, making the signal more vulnerable to noise power due to scaling. On the other hand, in time domain, scaling has resulted to increase in frequency and therefore design of faster circuits, while also contributing to reduction of jitter. However, this is a concept that has not yet been quantitatively examined. This paper aims at verifying the effectiveness of the time-domain circuits over voltage-domain circuits in terms of their dynamic range performances by simulations as well as by theoretical analysis, especially in the scaled nano-meter processes. It has been shown that for a given technology the time domain dynamic range is superior to the voltage domain dynamic range by a factor of (ωT /B)2 where ωT is the unity gain frequency and B is the bandwidth.
Delay-Line-Based Analog-to-Digital Converters
We will introduce a design of analog-to-digital converters (ADCs) based on digital delay lines. Instead of voltage comparators, they convert the input voltage into a digital code by delay lines and are mainly built on digital blocks. This makes it compatible with process scaling. Two structures are proposed, and tradeoffs in the design are discussed. The effects of jitter and mismatch are also studied. We will present two 4 bit, 1 GS/s prototypes in 0.13 mum and 65 nm CMOS processes, which show a small area (0.015 mm2) and small power consumption (<2.4 mW).
Damage initiation and propagation in composite shells subjected to impact
Abstract The paper investigates the impact-induced damage initiation and propagation for laminated composite shells under low-velocity impact. A three-dimensional eight-node non-conforming element is described to analyze interlaminar stress distribution, and progressive failure. The damage analysis is performed by using Tsai–Wu quadratic failure criterion, Tsai’s damage modes and an additional delamination formula at all Gaussian points. The damage modes considered are matrix cracking, fiber breakage and delamination. The progressive failure is expressed by reducing stiffness of the material at all failed Gaussian points. Special attention is centered on curved laminates. Impact energy threshold for the onset of damage and transient damage size are predicted for composite shells. The analyses of the flat and curved laminates are compared for discussing their different damage mechanism. In addition, the influence of the stacking sequence, the thickness and the radius of curvature on damage behavior of composite shells are studied.