一种采用四/五输入可配置查找表结构和优化进位链的新型FPGA

本文提出了一种FPGA可编程逻辑单元中新型的查找表结构和进位链结构。查找表被设计为同时支持四输入和五输入的结构,可根据用户需要进行配置,且不增加使用的互连资源;在新型的进位链中针对关键路径进行了优化。最后在可配置逻辑单元中插入了新设计的可配置扫描链。该可编程逻辑单元电路采用0.13μm 1P8M 1.2/2.5/3.3V Logic CMOS工艺制造。测试结果显示可正确实现四/五输入查找表功能,且进位链传播前级进位的速度在同一工艺下较传统进位链结构提高了约3倍,同时整个可编程逻辑单元的面积较之前增大了72.5%。结果还显示,本文设计的FPGA在仅使用四输入查找表时,逻辑资源利用率高于Virtex II/Virtex 4/Virtex 5/Virtex 6/Virtex 7系列FPGA;在仅使用五输入查找表时,逻辑资源利用率高于Virtex II/Virtex 4系列FPGA。     

Design of a memristor-based look-up table (LUT) for low-energy operation of FPGAs

This paper presents a scheme for designing a memristor-based look-up table (LUT) in which the memristors are connected in rows and columns. As the columns are isolated, the states of the unselected memristors in the proposed scheme are not affected by the WRITE/READ operations; therefore, the prevalent problems associated with nanocrossbars (such as the write half-select and the sneak path currents) are not encountered. Extensive simulation results of the proposed scheme are presented with respect to the WRITE and READ operations; its performance is compared with previous LUT schemes using memristors as well as SRAMs. It is shown that the proposed scheme is significantly better in terms of WRITE time and energy dissipation for both memory operations (i.e. WRITE and READ); moreover it is shown that the READ delay is nearly independent of the LUT dimension. Simulation using benchmark circuits for FPGA implementation show that the proposed LUT offers significant improvements also at this level.     

一种基于多值RRAM的快速逻辑电路

针对移动物联网设备,提出一种基于多值RRAM的快速逻辑电路,以实现非易失性存储与快速逻辑运算。利用RRAM多值存储特性,采用Crossbar结构,实现了简单快速的译码器与高存储密度查找表,使逻辑电路具有较快的运算速度和较小的面积。基于该结构实现了4位、8位和16位的乘法器,其外围电路采用SMIC 65 nm CMOS工艺实现,而其核心多值RRAM则采用Verilog-A 模型模拟。仿真结果表明,与传统CMOS逻辑电路相比,基于多值RRAM的16位乘法器的速度提高了35.7%,面积减少了14%。     

基于FPGA分布式算法的滤波器设计

设计了FPGA的分布式算法结构和具体的硬件环境。基于FPGA的分布式算法充分利用FPGA的并行处理特性设计算法,简化了滤波器系统设计。采用了分割查找表技术,节省了FPGA硬件资源。对查找表（LUT）中内容经过相应的修改即可方便地实现低通、高通、带通滤波。对基于FPGA分布式算法的滤波器进行了仿真及工况环境下的测试实验。实验结果表明,该算法不仅提高了系统运行速度,而且节省了大量的FPGA资源,还具有极大的灵活性。     

基于低定量取样的枯水频率分析

概述了枯水频率分析的研究进展,采用低定量取样,应用泊松和指数(Po-Ex)分布分别拟合低定量系列的年发生次数和量级,并与皮尔逊III型(P3)模型进行比较.实测枯水流量系列和统计试验的计算结果表明,Po-Ex模型的拟合和预测效果较好,要优于采用年最小流量取样和P3模型的枯水频率分析.基于低定量取样的模型可利用更多枯水流量信息,具有更强的物理相关性.为枯水频率分析提供了一条新的途径.     

Digital techniques to mitigate feedback impairment and noise of look‐up table digital predistortion

In this article, some new effects of feedback impairment and noise on look‐up table (LUT) digital predistortion (DPD) are presented. Several digital techniques are proposed to mitigate these effects. A smoothing filter (SMF) for LUTs is used to eliminate fluctuations of the transfer function of the overall DPD amplification system. By combining SMF method with iterative average (IA) method, the LUTs iterative process becomes stable and well converged. A postcompensator is established according to the proposed two‐box model for feedback impairment. For the demonstration, both simulation and experiments are carried out based on a Hammerstein‐type PA. Simulation results give some preliminary cognition of these new effects and the effectiveness of proposed techniques. Experimental tests are performed on an S‐band amplifier excited with single‐carrier WCDMA signal. The adjacent channel power ratio (ACPR) at 5‐MHz offset is ?48 dBc after DPD with SMF method and postcompensator. A total of 8 dB extra improvement of ACPR is obtained compared with that with neither SMF nor postcompensator. The result clearly shows that the proposed digital techniques are qualified for LUT DPD system, especially when it suffers significant feedback impairment and noise. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

应用信号概率分布的查找表预失真方法

传统的基于查找表的数字自适应预失真技术没有考虑功率放大器输入信号的统计特性。为此,在正交频分复用(OFDM)系统中,结合OFDM信号幅度概率分布的特性,提出一种新的查找表构建方法。仿真结果表明,与传统的基于查找表的预失真技术相比,该方法能够有效地抑制由功率放大器非线性特性引起的信号带外频谱扩展。     

一种适合于硬件实现的数字预失真算法

传统的数字基带预失真算法较复杂不易实现。为此,设计一种适合于硬件实现的数字预失真算法。考虑对模拟射频部分引入的环路延迟和相位偏转的补偿,采用2块大小为32×16的查找表作为预失真模块,存储针对不同输入幅度信号的调整系数,以预先抵消功率放大器的失真。用调制方式为64QAM OFDM信号进行测试,结果表明,该算法的预失真性能较好。     

A look-up table for fully developed film-boiling heat transfer

An improved look-up table for film-boiling heat-transfer coefficients has been derived for steam–water flow inside vertical tubes. Compared to earlier versions of the look-up table, the following improvements were made:

• The database has been expanded significantly. The present database contains 77,234 film-boiling data points obtained from 36 sources.

• The upper limit of the thermodynamic quality range was increased from 1.2 to 2.0. The wider range was needed as non-equilibrium effects at low flows can extend well beyond the point where the thermodynamic quality equals unity.

• The surface heat flux has been replaced by the surface temperature as an independent parameter.

• The new look-up table is based only on fully developed film-boiling data.

• The table entries at flow conditions for which no data are available is based on the best of five different film-boiling prediction methods.

The new film-boiling look-up table predicts the database for fully developed film-boiling data with an overall rms error in heat-transfer coefficient of 10.56% and an average error of 1.71%. A comparison of the prediction accuracy of the look-up table with other leading film-boiling prediction methods shows that the look-up table results in a significant improvement in prediction accuracy.     

滚筒扫描仪主控电路的设计

主控电路是控制滚筒扫描仪的关键部分，本文介绍了一种高分辨率滚筒扫描仪的主控电路的设计，包括整体设计、扫描接口控制与LUT查找表计算系统、外围控制及PLL芯片设计。