∑—△调制噪声整形的研究

介绍∑－△调制器的基本结构，分析∑－△调制技术对噪声进行整形的基本原理及过采样率、∑－△调制器的级数对整形效果的影响，从中获得了一些有用的结论。     

过采样∑－△A／D调制器

过采样∑－△Ａ／Ｄ调制器洪志良（复旦大学电子工程系，上海，２００４３３）１引言过采样∑－△Ａ／Ｄ变换器通过过采样以时间来交换精度，从而避免实现高精度Ａ／Ｄ变换器所需要的复杂性。∑－△调制器结构是迄今为止在数字ＶＬＳＩ技术中执行高精度Ａ／Ｄ变换最吸引人...     

过取样△∑调制技术（五）──△∑调制器的电路实现──

前面讨论了△∑调制器的基本原理，本文将介绍△∑调制器的电路实现与分析，以及二阶、ＭＡＳＨ结构中的△∑调制器实际电路。     

高阶∑△调制器的稳定性分析与设计

本文将量化器等效为增益可变的加性噪块模型，研究了１ｂｉｓ高阶∑△调制器的稳定性，提出了一种设计１ｂｉｓ稳定高阶（＞２）∑△调制器的方法，该方法简单有效。     

以DSP为核心的超高精度信号发生器

本文介绍了一种产生高精度信号的新方法，它采用∑－△调制器技术，与DSP相结合，仅需一位的D／A转换器就可获得极高精度的模拟信号。文章介绍了∑－△码中的应用，讨论了采用C31时所能产生的正弦信号的最高频率，最后给出了实验结果。     

基于高阶单比特∑△调制器的频率综合器

本文介绍了高阶单比特∑△调制器在小数分频频率综合器中的应用。普通小数分频频率综合器容易产生很大的杂散频率，采用∑△调制器可以有效消除杂散频率降低相位噪声。由于多比特MASH结构的非线性，这里采用单比特高阶∑△调制器（CIFB），最后提出实现电路。     

16位数字二阶∑-△调制器的分析与设计

文章阐述了∑-△调制器的基本工作原理,构建了二阶∑-△调制器的基本结构,提出了一种用Verilog HDL语言描述二阶∑-△调制器的实现方法,其中采用了简单的移位方法来描述调制器的四个增益系数,以实现乘法操作,进而减小了芯片的面积。在此基础上,运用MATLAB系统工具建立了二阶∑-△调制器系统的模型,并完成了系统仿真验证。在电路级完成了它的Verilog语言描述,同时运用modelsim仿真工具对电路进行仿真验证,对数据进行FFT分析,最终证明了MATLAB系统模型和Verilog代码的一致性。     

低电压∑-△调制器关键技术及设计实例

介绍了低电压开关电容∑-△调制器的实现难点及解决方案,并设计了一种1V工作电压的∑-△调制器。在0．18μm CMOS工艺下,该∑-△调制器采样频率为6．25MHz,过采样比为156,信号带宽为20kHz;在输入信号为5．149kHz时,仿真得到∑-△调制器的峰值信号噪声失真比达到102dB,功耗约为5mW。     

∑-△调制器在SIMULINK下的噪声模型

为了满足在行为级对∑-△调制器进行完整仿真的需要，提出了在SIMULINK环境下∑-△调制器的噪声模型，包括采样时钟抖动、开关热噪声(kT／C噪声)、运算放大器的有限增益、有限带宽、压摆及饱和电压等非理想因素。在给出具体噪声模型的基础上，构造出二阶∑-△调制器模型。通过仿真，验证了噪声模型的正确性。     

∑-Δ调制噪声整形的研究

介绍∑-△调制器的基本结构,分析∑-△调制技术对噪声进行整形的基本原理及过采样率、∑-△调制器的级数对整形效果的影响,从中获得了一些有用的结论.     

雷达数字接收机中的中频带通采样和数字I/Q解调及其实现

带通采样技术是实现微字接收机的关键技术。数字接收机的载频和带宽影响其采样和处理的形式.本文首先较为详细地讨论了带通采样理论,然后在此基础上提出了两种采样形式的数字接收机的设计方案.     

On the Numerical Reconstruction of Images from a Microwave Hologram

A new technique for the numerical reconstruction of images from a long-wavelength hologram is proposed. The technique is to calculate images by the fast Fourier transform (FFT) algorithm with the hologram data sampled by a straight line approximation. This sampling technique is convenient to reduce the number of the sampling points, and the image can be reconstructed with less data than the conventional equally spaced sampling method. A one-dimensional hologram is constructed at S band and an image is reconstructed by the proposed method. These results are discussed and compared with the results of the conventional numerical reconstruction.     

CMOS图像传感器固定模式噪声抑制新技术。

针对有源像素(APS)CMOS图像传感器中的固定模式噪声(FPN),设计了一种动态数字双采样的噪声抑制新技术;该技术比普通双采样技术具有更佳的抑制效果,其电路结构简单,适合于像素尺寸不断缩小的CMOS图像传感器发展趋势。通过MPW计划,采用Chartered0.35μmCMOS工艺制作了测试ASIC芯片,试验结果表明动态数字双采样技术有效抑制了FPN噪声。     

Pulsewidth modulation technique for sampling electrostatic forcemicroscopy

A new sampling electrostatic force microscopy technique for noninvasive measurement of microelectronic circuits is presented. The technique utilises a pulsewidth modulated sampling signal at the probe end to enable internal voltage measurement. Unlike previous sampling methods, the presented technique does not require broadband elements     

Optical down-sampling of wide-band microwave signals

Phase-encoded optical sampling allows radio-frequency and microwave signals to be directly down-converted and digitized with high linearity and greater than 60-dB (10-effective-bit) signal-to-noise ratio. Wide-band electrical signals can be processed using relatively low optical sampling rates provided that the instantaneous signal bandwidth is less than the Nyquist sampling bandwidth. We demonstrate the capabilities of this technique by using a 60-MS/s system to down-sample two different FM chirp signals: 1) a baseband (0-250 MHz) linear-chirp waveform and 2) a nonlinear-chirp waveform having a 10-GHz center frequency and a frequency excursion of 1 GHz. We characterize the frequency response of the technique and quantify the analog bandwidth limitation due to the optical pulse width. The 3-dB bandwidth imposed by a 30-ps sampling pulse is shown to be 10.4 GHz. We also investigate the impact of the pulse width on the linearity of the phase-encoded optical sampling technique when it is used to sample high-frequency signals.     

New continuous dynamic focusing technique in ultrasound imaging

A new continuous dynamic focusing technique for ultrasound imaging is proposed. The conventional delay-sum-sampling process can be replaced by a sampling-sum process if the maximum delay time is less than the sampling interval. To extend the sampling interval effectively, second-order sampling is adopted.     

Progressive Random Sampling With Stratification

A number of applications, including claims made under federal social welfare programs, requires retrospective sampling over multiple time periods. A common characteristic of such samples is that population members could appear in multiple time periods. When this occurs, and when the marginal cost of obtaining multiperiod information is minimum for a member appearing in the sample of the period being actively sampled, the progressive random sampling (PRS) method developed by the authors earlier can be applied. This paper enhances the progressive random sampling method by combining it with stratification schemes; the resultant stratified progressive random sampling (SPRS) technique is shown to provide significant improvement over traditional sampling techniques whenever stratification is appropriate. An empirical example based on a data transformation of a real-world application is provided to illustrate the practical application of the technique.     

Overview of Energy-Efficient Successive-Approximation Analog-to-Digital Converters： State-of-the-Art and a Design Example

This paper makes a review of state-of-the- arts designs of successive-approximation register analog-to-digital converters （SAR ADCs）. Methods and technique specifications are collected in view of innovative ideas. At the end of this paper, a design example is given to illustrate the procedure to design an SAR ADC. A new method, which extends the width of the internal clock, is also proposed to facilitate different sampling frequencies, which provides more time for the digital-to-analog convert （DAC） and comparator to settle. The 10 bit ADC is simulated in 0.13 μm CMOS process technology. The signal-to-noise and distortion ratio （SNDR） is 54.41 dB at a 10 MHz input with a 50 MS/s sampling rate, and the power is 330 μW.     

Low sampling rate technique based frequency-domain random demodulation for broadband digital predistortion

This paper proposes a combination technique of the frequency-domain random demodulation (FRD) and the broadband digital predistorter (DPD). This technique can linearize the power amplifiers (PAs) at a low sampling rate in the feedback loop. Based on the theory of compressed sensing (CS), the FRD method preprocesses the original signal using the frequency domain sampling signal with different stages through multiple parallel channels. Then the FRD method is applied to the broadband DPD system to restrict the sampling process in the feedback loop. The proposed technique is assessed using a 30 W Class-F wideband PA driven by a 20 MHz orthogonal frequency division multiplexing (OFDM) signal, and a 40 W GaN Doherty PA driven by a 40 MHz 4-carrier long-term evolution (LTE) signal. The simulation and experimental results show that good linearization performance can be achieved at a lower sampling rate with about 24 dBc adjacent channel power ratio (ACPR) improvement by applying the proposed combination technique FRD-DPD. Furthermore, the performance of normalized mean square error (NMSE) and error vector magnitude (EVM) also has been much improved compared with the conventional technique.     

Corrections for nonuniform sampling distortions in magnetic resonance imagery

A technique for estimating and correcting nonuniform sampling distortions in magnetic resonance imagery is presented. The technique consists of first estimating the sampling grid distortion using a parametric model, and then estimating the uniformly sampled data by interpolation on the nonuniform grid. Parameterized models for two particular sampling grid distortion are presented. Maximum likelihood and maximum a posteriori estimators are developed for these distortions. Using computer simulated data, these estimators are shown to perform well.