利用数模转换器R-2R梯形网络

数模转换器的核心是一个精密R－2R梯形网络，根据电路理论灵活运用DAC中的梯形网络，可以用DAC实现新的功能。给出了灵活运用DAC梯形网络的两种方法。     

电压型R-2R梯形网络DAC线性误差分析方法

根据节点电阻模型和分析方法,设计了一个12位电压型R-2R梯形网络D/A转换器(DAC)。仿真结果表明,该D/A转换器的积分线性误差(INL)可低至0.21 LSB;该模型和分析方法能够有效地估计和用于减小由R-2R梯形网络各电阻之间的差值导致的DAC线性误差。     

多相位改进型R-2R梯形DAC电路

介绍一种多相位改进型R－2R梯形DAC电路，它适合于ASIC或混合设计的梯形DAC电路，使许多应用电路中所使用的传统的CMOS多相DAC电路中元件更少，微调程序更简单。     

An On-Line Calibration Technique for Mismatch Errors in High-Speed DACs

In this paper a novel online calibration technique for high-speed DACs is presented. The approach consists of two elements. The first element is the use of a redundant signed digit (RSD) scheme for the selection of the current sources. This enables a fully digital correction. The second element consists of an adaptive estimation of the correction terms by an LMS algorithm. For this purpose the DAC output signal is low-pass filtered and digitized by an accurate but low-speed calibration ADC. By replicating this analog signal path in the digital domain, the errors can be calculated and used to update the correction weights. The dynamic behavior and the accuracy of the adaptive calibration loop are analyzed both theoretically and through computer simulations, and it is shown that this way a greatly improved accuracy can be obtained.      

一种新颖的R-2R电阻网络

设计了一种新颖的“5+7”分段式结构的R-2R电阻网络。与典型12位R-2R电阻型D/A转换器相比,采用该电阻网络的12位D/A转换器所需并联的MOS开关管数量大为减少,约为前者的1/8,提高了MOS开关管的匹配性。基于2 μm SOI CMOS工艺,采用该R-2R电阻网络结构设计了一款±15 V电压供电、双基准、12位四通道的D/A转换器,修调后,该D/A转换器DNL和INL典型值分别为0.15 LSB和0.27 LSB。     

Area Allocation Strategies for Enhancing Yield of R-2R Ladders

A new strategy for allocating area, at layout, for enhancing the soft yield of R-2R ladders is introduced. In contrast to the conventional and convenient approach of allocating equal area to each R/2R bit-slice, the new strategy allocates progressively larger areas to higher-order bits. With this strategy, the INL yield for a fixed total resistor area as determined by local random variations in the sheet resistance is optimized. Simulation results show that the new area allocation strategy provides significant improvements in INL yield compared to what is achievable with the conventional area allocation strategy.     

一种改进的反馈制两级交换结构FTSA-2-SS

基于反馈的两级交换结构FTSA (Feedback-based Two-stage Switch Architecture)在仿真中表现出极其优异的时延性能,但该结构对调度算法的时间限制使其理论性能无法实现。针对这一问题,该文基于2-错列对称的crossbar连接模式提出一种改进的反馈制两级交换结构FTSA-2-SS (FTSA using the 2-Staggered Symmetry connection pattern),应用该连接模式可使信元传输与调度算法并行工作,从而将算法的时域空间拓展到一个时槽。此外,该文还利用双信元缓冲模式和RB (Re-sequencing Buffer)来解决由此而带来的信元冲突和失序问题。理论分析表明FTSA-2-SS和FTSA具有相同的稳定性,仿真结果显示FTSA-2-SS的时延性能优于其他非反馈负载均衡结构。     

一种可以提高热光开关阵列可靠性的驱动电路的设计

分析了加热器对热光开关阵列可靠性的影响并在此基础上提出了一种改进的驱动电路,使4×4简化树形结构的光开关的阵列的可靠性从78.87%提高到97.04%.模拟及实验结果表明该控制和驱动电路可以为热光开关阵列提供适当的驱动电流.     

一种带双极性基准的双R-2R电阻网络结构

介绍了一种带双极性基准(±10 V)的双R-2R电阻网络结构。该结构充分利用双极性基准的优势,减少了双极性输出所需运算放大器的数量,提高了D/A转换器的精度;同时又降低了电路对工艺绝对精度的要求。经过理论推算和电路模拟仿真,在相同工艺精度条件下,采用该结构的12位D/A转换器,其精度优于其他两种采用常规双极性输出结构的D/A转换器。     

一种改进的空间平滑算法

空间平滑是一种有效的解相干算法。但是当相干信源相距很近时,传统的空间平滑算法性能明显下降。该文提出一种改进的空间平滑算法。该算法首先将子阵输出的自相关矩阵进行互相关,然后将前后向互相关矩阵平均后的协方差矩阵作为修正后的空间平滑矩阵进行空间谱估计。文中给出了该算法的表达式,分析了算法的性能。仿真结果证明该算法与传统算法及利用子阵协方差算法相比具有更高的分辨能力和更低的信噪比门限。     

基于加窗隐马尔可夫模型的窄带干扰抑制技术研究

针对基于隐马尔可夫模型的窄带干扰抑制技术在直接序列扩频系统中存在频谱泄漏和收敛速度较慢的问题,提出增加窗函数并选择合适的HMM训练估计时隙数的改进算法,该方法在减弱"频谱泄漏"效应的同时,加快了算法的收敛速度.仿真实验表明改进算法对快变的强窄带干扰具有较好的抑制效果.     

一种改进的THz-SAR高频振动误差补偿方法

将太赫兹波用于SAR成像可以解决常规SAR成像帧速低、慢动目标检测困难等问题。太赫兹合成孔径雷达(THz-SAR)与传统微波SAR成像最重要的区别在于运动补偿。因为THz-SAR的工作波长比传统微波SAR要短得多,平台的微小振动会影响成像质量,尤其是高频振动误差。平台的高频振动会在成像结果中引入成对回波,传统SAR成像算法无法实现成对回波的聚焦,也就无法准确估计振动参数,进而构造参考函数补偿高频振动带来的正弦调制相位。首先基于多普勒Keystone变换(DKT)的THz-SAR成像算法实现成对回波的聚焦成像;然后提出小波多分辨分析的方法估计高频振动频率,结合参数空间投影法完成振动幅相的估计,并实现高频振动误差的补偿;最后采用点目标的回波数据仿真验证了所提方法的有效性。     

一种速度优化的流水线模数转换电容误差平均技术

无源电容误差平均技术是一种本质线性(Inherently Linear)的流水线模数转换电容失配校准技术,但其转换速度是传统技术的一半.为了提高速度,本文提出了一种改进的电容误差平均技术.该技术从减少一个转换周期所需的时钟相数目和减少每个时钟相的时间两个方面来优化速度.电路分析和MATLAB仿真表明,在两种典型的情况下,改进的技术能将速度提高52%(跨导放大器为开关电容共模反馈)和64%(跨导放大器为非开关电容共模反馈)以上.改进的技术更适用于高速高精度及连续工作的应用场合.     

Digitally tuned analogue integrated filters using R-2R ladder

A new technique for designing digitally tuned frequency selective analogue integrated circuits is proposed. The technique incorporates the R-2R ladder as a circuit element into the circuit design to provide precise frequency characteristics that can be tuned over a wide range. Two filters are described to illustrate the proposed approach. The proposed filters are used to implement the lowpass channel-select filter of a multi-standard direct conversion wireless receiver and the bandpass filter of a low IF frequency-hopping receiver     

基于阵列技术的MEMS陀螺温度补偿方法

为了减少温度对MEMS陀螺测量精度的影响,提出了一种采用阵列技术的MEMS陀螺仪温度误差补偿新方法。该方法不需要进行温度测量,通过对多陀螺输出进行数据融合以消除温度对陀螺仪输出的影响,达到正确检测角速率的目的,简化了系统结构。采用遗传算法优化的BP神经网络来进行陀螺阵列数据的融合,抛开通常把零偏和标度因数分开建模补偿的思想,将两者统一进行补偿。实验结果表明,该方法能够大幅度降低温度造成的陀螺误差,从而满足工程应用需要。     

直接调制DFB激光器调制特性的温度补偿技术研究

分析了直接调制DFB激光器的调制特性对温度的依赖特性,提出在具有背光检测功能的光发射模块中对 DFB激光器的调制电流进行温度补偿,使模块的消光比和输出光功率在器件工作温度范围内保持稳定。     

Extending the R-2R lens to 360°

The R.2R lens is a remarkable microwave device that provides perfect focusing, giving multiple simultaneous antenna beams from a circular or cylindrical array. However, the perfect focusing of the R-2R brings with it a serious limitation on angular coverage as a result of the angular doubling that enters when the array elements in the antenna are connected to the launcher elements on the lens periphery. We have now found a way to modify the R-2R concept so that a full circle of array elements can be mapped onto a full circle of beam ports. The new mapping makes use of hybrid junctions and either four or six physical lenses. The interconnections result in360degof simultaneous antenna beams, each of which can be used both for transmission and for reception.     

A Generalized Design Technique for Practical Distributed Reciprocal Ladder Networks

A generalized design approach is presented for ladder networks consisting of a cascade of constituent two-port networks connected by short lengths of transmission lines. The design is made possible by the derivation of simple equations which define the inverter impedance and associated reference planes of any passive lossless reciprocal two-port. This enables the general ladder network to be equated to a prototype network at a reference frequency. An example is given of the design of a coaxial low-pass filter where fringing capacitances are compensated automatically.     

An Internally-Matched High-Isolation CMOS SPDT Switch Using Leakage Cancellation Technique

An internally-matched single-pole double-throw (SPDT) switch with high isolation is presented. The high isolation is resulted from the leakage cancellation by employing a compensation circuit, which also achieves impedance match for all ports. The SPDT chip, implemented in a 0.18-mum CMOS process, achieves a measured isolation of 72 dB, an insertion loss of 1.1 dB, return losses better than 10 dB at all ports and PidB of 19.3 dBm at 1.9 GHz.