【作者】 肖林荣；

【导师】 陈偕雄；

【作者基本信息】 浙江大学 ， 电路与系统， 2012， 博士

【摘要】 在过去的半个多世纪里,集成电路技术遵循着Moore定律取得了惊人的进展,而缩小器件特征尺寸是提高芯片集成度和性能的主要途径。但随着特征尺寸的不断缩小,以CMOS技术为主导的集成电路发展遇到了前所未有的挑战,特别是低功耗设计及互连线问题。当器件的特征尺寸进入纳米级,量子效应将逐渐占据主导地位并可能使器件失效,从而使特征尺寸的缩小达到其物理极限。有鉴于此,近年来一方面科研人员从理论上、材料上和工艺上加以修正,以延续Moore定律引领的CMOS技术的生命；另一方面提出了各种可能的替代MOS器件的新型纳米电子器件,以发展新一代集成电路技术。其中的量子细胞自动机(Quantum-Dot Cellular Automata, QCA),因其提供了一种全新的信息存储和计算方式,由其组成的数字逻辑电路与CMOS相比具有功耗更低、集成度更高和速度更快等固有特点,被认为是新一代的纳电子器件强有力的竞争者。在介绍QCA原理及QCA数字逻辑电路设计和仿真方法的基础上,本文聚焦于QCA通用逻辑门、通用阂值逻辑门、双边沿触发器以及三值QCA逻辑电路的设计和仿真。具体工作和创新之处如下：1、QCA通用逻辑门和通用阈值逻辑门的设计和应用。提出了基于模块化技术的QCA通用逻辑门ULG.2,并应用该ULG.2设计了全加/全减器、全比较器和4选1数据选择器。与已有的QCA通用逻辑门及其应用电路相比,在细胞数、QCA信号线交叉数等方面电路的性能均有较大的改善。随后提出了QCA通用逻辑门ULG3和三变量通用阈值逻辑门UTLG,并分别提出了基于QCA通用逻辑门ULG.3和三变量通用阂值逻辑门UTLG的任意三变量逻辑函数的查表综合。利用所提出的ULG3和UTLG可实现3变量全部256个逻辑函数。所设计的电路经QCADesigner软件仿真,验证了其逻辑功能的正确性。2、QCA双边沿触发器的设计。触发器是数字系统的关键部件,但相对QCA门电路及组合逻辑电路的研究而言,QCA触发器及时序逻辑电路的研究还很不充分,尤其是高性能的触发器及其应用电路。本文提出了两种基于QCA的新型高性能触发器——双边沿D触发器和双边沿JK触发器。通过QCADesigner仿真,结果表明所设计的两种双边沿触发器均具有正确的逻辑功能。若保持原有的时钟频率不变,所提出的双边沿触发器比相应的QCA单边沿触发器处理数据的速度将提高一倍,从而为设计高性能数字电路和系统提供了坚实的基础。3、三值QCA (tQCA)基本逻辑电路的Matlab仿真。现行计算机系统采用二值逻辑电路,主要受限于电路元件只有开关两种状态的技术条件限制。其实多值逻辑电路(MVL)由于信号线能传输多值信号,可携带比二值信号更多的信息量,从而有效地提高电路的信息密度,减少互连线,提高系统工作速度。在介绍tQCA细胞的基础上,循着二值QCA逻辑电路的研究思路,提出了基于Matlab的tQCA基本逻辑电路的半经典模型的仿真算法。随后分别对tQCA信号线、非门和多数门进行了编程仿真。结果表明,三值QCA逻辑电路并不是二值QCA逻辑电路的简单推广,其电路设计理论和设计规则有待进一步研究和探索。更多还原

【Abstract】 Over the past half-century, a series of significant achievements in IC technology have been gained following Moore’s low. Downscaling of device feature sizes is a main approach to increase ICs’integration density and improve their performance. However, with device scaling into nanometer regime, quantum effects begin to be dominant and may cause device failure. As a mainstream technology for ICs, CMOS technology is approaching its physical limits and facing serious challenges especially in power consumption and interconnection. Therefore, a great deal of attention has been paid to overcome these obstacles by amending CMOS theory and improving its fabrication processes. Meanwhile extensive research on nanometre alternatives to CMOS has also been carried out. One of the alternatives is known as Quantum-Dot Cellular Automata (QCA), which implements a unique computational paradigm and overcomes some limitations of current technologies, with the potential for faster speed, smaller size and lower power consumption than CMOS.Since introduction of QCA, a number of interesting QCA-based logic circuits have been proposed. Howeve, there is still much work to be done to the design of QCA-based logic circuits. Based on investigation of QCA’s basic principles, this thesis focuses on the study of QCA-based digital logic circuit design and proposes some novel QCA-based logic circuits. The detailed contents and main innovations in this work are summerized as follows.1. Design and application of QCA-based optimal universal logic gate (ULG) and universal threshold logic gate (UTLG). As novel fundamental logic elements for future ICs, two novel QCA-based ULGs and one UTLG have been proposed. As examples, full adder/subtraction, full comparator and 4-to-1 multiplexer are implemented with proposed modular ULG.2. Compared with traditional design based on majority gates and inverters, their performance has been improved dramatically. Then, examples showing how to realize three-variable logic functions with a QCA-based ULG.3 or UTLG is given, respectively. All 256 three-variable logic functions can be realized using tabular design method. Simulation results obtained by using QCADesigner tool for all proposed QCA-based circuits show that the proposed circuits have correct logic function.2. Design of QCA-based dual-edge triggered (DET) flip-flops. Flip-flops are critical for the performance of digital systems. QCA is limited in its sequential circuit design with high performance flip-flops while a number of combinational logic circuits have been presented. Based on a brief introduction of DET flip-flop, two original QCA-based D and JK DET flip-flops are proposed, offering the same data throughput of corresponding single-edge triggered (SET) flip-flops at half of the clock pulse frequency. The logic functionality of the two proposed flip-flops is verified with QCADesigner tool. All the proposed QCA-based DET flip-flops show higher performance than their SET counterparts in terms of data throughput. By using lower clock pulse frequency, the proposed DET flip-flops are promising for constructing QCA-based sequential circuits and systems with high performance.3. Simulation of ternary quantum-dot cellular automata (tQCA) basic logic circuits using Matlab. The use of binary logic in computer structures was historically necessary only due to technological limitations. The benefits of using multi-valued processing are obvious and range from higher data storage capabilities to faster and more sophisticated processing. Based on an introduction of ternary QCA cell which allows for the representation of three logic values, a simulation algorithm with tQCA’s semiclassical model is presented. Then simulations about three tQCA basic logic circuits such as tQCA wire, inverter and majority voter followed with corresponding counterparts have been performed by using Matlab. The simulations show that the behavior of above tQCA-based structures agrees with the ternary truth table raised by ALukasiewicz except the majority gate. The majority gate structure does not behave as intended. So it should be noted that this initial work represents only a step forward in developing a more basic circuits of tQCA-based ternary logic circuits.更多还原