Sharif Digital Repository

Reduction of Time to Digital Converter (TDC) quantization related phase noise is one of the most important challenges in all digital frequency synthesizer design. In this paper, a new structure is proposed to shape the quantization noise of flash TDCs. To verify effectiveness of the proposed general noise shaping technique, it is employed on a single delay chain flash TDC. To compensate the process variation effects on the implemented circuits, a calibration technique is also proposed. The design is implemented in 0.18μm CMOS technology. Simulations show effective noise shaping of output quantization noise  

Limitations in operation of analog switches at very low voltages have caused many problems in design of these types of switched capacitor circuits and data converters. In this paper by modifying a recently proposed clock boosting circuit, we could obtain a new structure with better performance for very low voltage circuits. This method requires simpler digital circuits in comparison with previously reported structures, as well as less number of transistors and smaller chip area. This method can be used for sampling the full swing signals with supply voltages as low as 0.4 volt. © 2008 IEEE  

In this paper a new cell structure is introduced to reduce the rate of CdTe corrosion in quantum dot sensitized solar cells (QDSSCs) using I -/I- 3 electrolyte. In this cell, one electrode is a titania nanorod that was sensitized with CdTe quantum dots as the working electrode. A thin gold layer is sputtered on the electrode to act as a protective layer against the I-/I- 3 corrosive electrolyte and to passivate the CdTe surface traps which are the main recombination centres in a QDSSC. In addition, a Schottky barrier formed at the interface of Au and CdTe prevents direct electron recombination from the CdTe conduction band with I- 3 ions. The mechanism of charge transfer and quantum dot... 

Exact spread-spectrum code tracking in the presence of multipath is an important issue in distance and time measurement systems. Different tracking algorithms based on feedback, feedforward or a combination of them reduce multipath effects, however, the accuracy of the tracking in presence of short-delay multipath signals is still a problem. In this paper, we consider feedback delay lock loops (DLL) and gating function schemes that have shown better performance with lower complexity under multipath. We develop a shot-noise process model for the control signal of a DLL in the presence of multipath signals and determine the range of tracking errors they cause. Then, we propose a method based... 

With recent deregulation in electricity industry, price forecasting has become the basis for this competitive market. The precision of this forecasting is essential in bidding strategies. So far, the artificial neural networks which can find an accurate relation between the historical data and the price have been used for this purpose. One major problem is that, they usually need a large number of training data and neurons either for complex function approximation and data fitting or classification and pattern recognition. As a result, the network topology has a significant impact on the network computational time and ability to learn and also to generate unseen data from training data. To... 

Visibility is an important topic in computer graphics, motion planning, and computational geometry. To deal with the increasing complexity of the scenes considered, some research has been performed in visibility processing in order to accelerate the visibility determination. Two of the most studied such structures are visibility graph and visibility complex. Visibility graph is a fundamental geometric structure which is used in many applications, including illumination and rendering, motion planning, pattern recognition, and sensor networks. While the concept of visibility graph is widely studied for 2D scenes, there is no acceptable equivalence of visibility graph for 3D space. Similarly,... 

The field emission properties of MoO2 nanostars grown on a silicon substrate and their emission performance in various vacuum gaps are reported in this article. A new structure of molybdenum oxides, named a nanostar, is grown by thermal vapor deposition with a length of ̃1 μm, a thickness of ̃50 nm, and its width in the range of 500-700 nm. The morphology, structure, composition, and chemical states of the prepared nanostars were characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). According to XRD analysis, the grown nanostructures are composed of both crystalline Mo4O11 and...