对非整周期正弦波形信噪比计算方法的研究

以双音多频信号为例,通过运用快速傅里叶变换和Hanning窗等数学方法,分析了信号频率,电平和相位之间的关系,推导出了计算非整周期正弦波形信噪比的算法,解决了数字信号处理中非整周期正弦波形信噪比计算精度低下的问题。以C编程语言进行实验,证明了算法的正确性和可重用性,并可极大的提高工作效率。     

直接数字波形合成中的镜频干扰分析

该文针对数字波形合成信号中的镜频干扰问题展开讨论,着重分析了镜频的形成机理及分布特点,说明了采样率对镜频干扰的影响。在此基础上定量分析了产生镜频干扰的采样率条件,并通过实验结果验证。该分析结果为数字波形合成中的采样率选取提供了新的理论依据。     

用线性电路模拟非正弦周期函数信号的波形

简要说明了如何利用EWB模／数混合模拟软件为工作平台，设计出用线性电路模拟非正弦周期函数信号波形的电路。     

应用于数字阵列的多通道波形产生系统设计

直接数字频率合成（DDS）是数字阵列雷达（DAR）实现收发数字波束形成的关键技术之一。给出了一种基于DDS技术的多通道波形产生系统的设计方案,该方案在25cm×12cm的PCB板上实现了波形产生、波形捷变与幅相控制的系统集成设计。该系统能同时产生16路频率、幅度和相位独立控制的中频雷达信号,满足数字阵列雷达对收发阵列单元的高集成度、小型化、低成本和多功能的要求;系统实现的主要技术指标为：信号带宽1～120MHz可变,通道隔离度大于60dBc,窄带脉内信噪比大于65dBc,满足数字阵列雷达技术指标的要求。     

数字波形产生器的设计

所设计的数字波形产生器是基于数字波形存储直读法来产生多模式、多波形脉冲压缩信号的。本文从硬件的实现、软件的编程以及数字基带信号数据的生成等几个方面对该产生器进行了介绍，最后给出了从频谱仪上观察到的实验结果。     

复杂波形雷达接收机的带宽选择

处理复杂雷达波形往往采用数字信号处理的方式。此时接收机带宽的选择会影响到系统的性能和信号处理机的设备量，本文针对几种特定的雷达波形，分析了采用复杂波形情况下雷达接收机带宽的选择问题。     

便携式数字示波器的波形后处理

介绍一种简单实用便携式数字示波器的波形后处理方法,即将波形获取软件Wavestar与数据分析软件Origin结合起来对数字示波器的输出波形进行处理。同时,以一台逆变器的测量分析为例,分析单独使用波形获取软件进行波形处理的局限性,介绍Origin的数据分析处理能力,说明两种软件如何很好地配合以发挥各自的特长。     

宽带数字波形产生中的广义多相滤波

提出了一种"广义多相滤波"的概念,将多相滤波推广至多相合成的阶数与内插比不一致的情形,使得设计者在构建宽带数字波形产生系统时可以按照实际情况进行速度与面积的平衡。从时域对广义多相滤波进行了推导,并给出了其具体实施步骤。基于广义多相滤波算法,构建了一个宽带数字波形产生系统,使用测试信号对该系统的功能进行了仿真,给出了广义多相滤波在实际硬件中所使用的资源。结果表明,该算法对宽带数字波形产生系统的研制有一定的实际意义。     

波形对数字信道化接收机测频性能影响分析

对于典型的数字信道化接收机之后级联相位差分法测频的处理架构,现有的测频精度表达式未考虑波形复包络对测量精度的影响。该文针对这一问题,推导了考虑波形复包络影响的新的测频精度表达式,并进行了仿真。仿真分析的结果与推导的精度表达式一致,表明改进的测频精度表达式能够有效反映信号波形对测频性能的影响。     

数字瞬时测频——波形拟合法测频

在本节中,我们将给出一种叫做波形拟合法的测频算法。所谓波形拟合法就是用一个理想的正余弦函数去近似给定的信号波形,我们努力的方向是使拟合尽可能地逼近信号,这时理想函数的频率将可以最接近地表示信号的频率。我们很清楚,一个单频信号具有三个参数,那就是它的频率、初始相     

Novel four quadrant DC-link soft switching inverter generating sinusoidal waveforms

A novel high frequency resonant link inverter using zero-voltage switching (except for one device where zero-current switching is used) operable in four quadrants is proposed. It provides several excellent advantages over the conventional resonant link inverters, such as low VA ratings, low acoustic noise and low harmonic distortion.<>     

Predictive digital filtering of sinusoidal signals

The p-step ahead predictive filters for narrowband waveforms with m distinct spectral peaks are considered. By minimization of the noise gain, the coefficients of the optimal Lth order FIR predictor is derived, where L>2m-1. The minimum-length FIR predictor is given by L=2m-1, and the feedback extension of this predictor is studied. Design of feedback gains subject to different optimization criteria is studied in detail. The generalization to complex-valued signals, cascaded predictors, and adaptive predictors are also included. Several design and simulation examples are presented     

Probability distributions of noiselike waveforms generated by a digital technique

This letter discusses the probability distributions of waveforms obtained by a weighted summation of digits stored in an n stage feedback shift register which is generating a binary sequence of periodic length 2n or 2n?1.     

High resolution and low distortion digital look-up-table sinusoidal oscillators

We propose two new methods to reduce the spurious harmonic distortion of a digital sinusoidal signal generated using the look-up-table (LUT) method. Spurious harmonic distortion arises when we try to interpolate the value of a sample that is not present in the LUT. The first proposed method depends on a real time evaluation of the missing sample value without the need for any additional LUT length. The second proposed method requires an additional table and some real time processing to calculate the value of the interpolated sample. The two proposed methods are simulated and their performance is compared with that of the existing methods; namely direct LUT, linear interpolation and trigonometric interpolation. The simulation results show that our proposed methods are superior to both direct LUT and linear interpolation methods. Moreover, for practical table lengths, the performance of our proposed methods is of the same order as that of the trigonometric interpolation method.     

A new digital approach to design 3D CAP waveforms

A minimax optimization approach has previously been contributed to extend the conventional two-dimensional (2D) carrierless amplitude/phase modulation (CAP) scheme to three-dimensional (3D) (see Shalash, A. and Parhi, K.K., IEEE Trans. Commun., vol.47, p.1655-67, 1999; Proc. IEEE ISCAS '97, p.2136-9, 1997). We show that there is no guarantee of spectral efficiency by this approach. This is a potentially fatal design flaw which results in the 3D CAP system being exceptionally susceptible to noise, even if it is of very small magnitude, for example, quantization noise. A new minimax approach is, thus, contributed to design bandwidth-efficient 3D CAP waveforms which are more robust and useful for very high-speed digital subscriber loop applications and high-speed LAN systems. Some design examples are provided.     

Performance of a practical digital system for the learning of signal waveforms

Results are presented for the asymptotic performance and convergence of a practical parametric learning system which is capable of estimating and recognising initially unknown waveforms. It is shown that the system performs almost as well as an ideal system in which all signal parameters are known.     

On-chip oscilloscopes for noninvasive time-domain measurement of waveforms in digital integrated circuits

High-speed digital design is becoming increasingly analog. In particular, interconnect response at high frequencies can be nonmonotonic with "porch steps" and ringing. Crosstalk (both capacitive and inductive) can result in glitches on wires that can produce functional failures in receiving circuits. Most of these important effects are not addressed with traditional automatic test pattern generation (ATPG) and built-in self-test (BIST) techniques, which are limited to the binary abstraction. In this work, we explore the feasibility of integrating primitive sampling oscilloscopes on-chip to provide waveforms on selective critical nets for test and diagnosis. The oscilloscopes rely on subsampling techniques to achieve 10-ps timing accuracy. High-speed samplers are combined with delay-locked loops (DLLs) and a simple 8-bit analog-to-digital converter (ADC) to convert the waveforms into digital data that can be incorporated as part of the chip scan chain. We will describe the design and measurement of a chip we have fabricated to incorporate these oscilloscopes with a high-frequency interconnect structure in a TSMC 0.25-/spl mu/m process. The layout was extracted using Cadence's Assura RCX-PL extraction engine, enabling a comparison between simulated and measured results.     

Digital sinusoidal PWMs for a micro-controller based single-phase inverter,Part 1: Principles of digital sinusoidal PWM generation

Nowadays, Digital Sinusoidal Pulse Width Modulation (DSPWM) is playing a major role in the generation of pure sinusoidal waveforms using micro-controller based inverters (Kawabata, Miyashita and Yamamoto 1991 Kawabata, T., Miyashita, T. and Yamamoto, Y. 1991. “Digital Control of Three-Phase PWM Inverter With LC Filter,”. IEEE Transactions on Power Electronics, 6: 62–72.  [Google Scholar]; Herrmann, Langer and Broeck 1993 Herrmann, U., Langer, H. G. and Broeck, H. V.D. 1993. “Low Cost DC to AC Converter for Photovoltaic Power Conversion in Residential Applications,”. 24th Annual IEEE Power Electronics Specialists Conference. 1993, Seattle, WA, USA.  [Google Scholar]; Ying-Yu 1995 Ying-Yu, T. “DSP-Based Fully Digital Control of a PWM DC-AC Converter for AC Voltage Regulation,”. 26th Annual IEEE Power Electronics Specialists Conference. Atlanta, GA.  [Google Scholar]; PICREF-1 1997 PICREF-1. 1997. Uninterruptible Power Supply Reference Design Vol. 2004. Microchip Technology [Google Scholar]; Shih-Liang, Meng-Yueh, Jin-Yi, Li-Chia and Ying-Y 1999 Shih-Liang, J., Meng-Yueh, C., Jin-Yi, J., Li-Chia, Y. and Ying-Yu, T. 1999. “Design and Implementation of an FPGA-Based Control IC for AC-Voltage Regulation,”. IEEE Transactions on Power Electronics, 14: 522–532.  [Google Scholar]; The Electrical Engineering Handbook 2000 The Electrical Engineering Handbook. 2000. , 2nd ed., New York: CRC Press LLC.  [Google Scholar]; Koutroulis, Chatzakis, Kalaitzakis and Voulgaris 2001 Koutroulis, E., Chatzakis, J., Kalaitzakis, K. and Voulgaris, N. C. 2001. “A Bidirectional, Sinusoidal, High-Frequency Inverter Design,”. IEE Proceedings-Electric Power Applications, 148: 315–321.  [Google Scholar]; Skvarenina 2002 Skvarenina, T. L. 2002. “The Power Electronics Handbook,”. In Industrial Electronics Series, Edited by: Irwin, J. D. New York: CRC.  [Google Scholar]; Pop, Chindris and Dulf 2004 Pop, O., Chindris, G. and Dulf, A. 2004. “Using DSP Technology for True Sine PWM Generators for Power Inverters,”. 27th International Spring Seminar on Electronics Technology: Meeting the Challenges of Electronics Technology Progress, 1: 141–146.  [Google Scholar]; Zhongyi, Mingzhu and Yan 2005 Zhongyi, H., Mingzhu, L. and Yan, X. “Core Techniques of Digital Control for UPS,”. IEEE International Conference on Industrial Technology.  [Google Scholar]). The types of DSPWM that can be generated depend on the micro-controller hardware resources and are therefore limited, but provide performance benefits not possible with an analogue controller. For instance, digital controllers offer a programmable solution and therefore more flexibility, as advanced algorithms and additional features can be added to the system in software instead of hardware (Monti, Santi, Dougal, and Riva 2003 Monti, A., Santi, E., Dougal, R. A. and Riva, M. M. 2003. “Rapid Prototyping of Digital Controls for Power Electronics,”. IEEE Transactions on Power Electronics, 18: 915–923.  [Google Scholar]; Brush 2005 Brush, L. “Trends in Digital Power Management: Power Converter and System Demand Characteristics,”. Twentieth Annual IEEE Applied Power Electronics Conference and Exposition. Austin, TX [Google Scholar]). Digital controllers are also less sensitive to environmental conditions and show precise behaviour compared with their analogue counterparts (Skvarenina 2002 Skvarenina, T. L. 2002. “The Power Electronics Handbook,”. In Industrial Electronics Series, Edited by: Irwin, J. D. New York: CRC.  [Google Scholar]). This two-part article looks at the benefits and limitations of three major DSPWMs for a single-phase full-bridge inverter and investigates their performance. In Part 1, the theory of the three major DSPWMs are presented, including mathematical models and simulation results. It looks at the PWM patterns required to generate these DSPWMs and the benefits and limitations of each. To evaluate the proposed mathematical models and simulation results, a 2kVA single-phase full-bridge inverter was developed and the DSPWMs implemented. In Part 2, experimental results from the implementation of the DSPWMs on the prototype 2kVA inverter are presented, which confirms the validity of the proposed analysis in Part 1. Moreover, the performance, including efficiency and losses (switching, conduction, and transformer) of the different DSPWMs implemented on the 2kVA inverter under different loads were examined and recommendations presented.     

用PC直接获取数字示波器波形和联机波形参数测量

数字存储示波器,顾名思义除了能实现一般的显示波形功能之外,更重要的是能将屏幕上显示的波形保存下来,以便作再次观察和其它用途,这是数字存储示波器和普通示波器的根本区别。据了解,一般的数字存储示波器用户,都会使用它进行测量和观察波形,对如何存储波形的方法并没有去研究或不太了解。本文提供了利用电脑与安捷伦数字存储示波器实现联机,并利用电脑直接将示波器的波形存储下来,和对存储下来的波形进行参数测量分析等方法,对数字存储示波器用户有一定的参考价值。     

Mathematical model of digital frequency-sampling filters with shiftable phase-frequency characteristic

The paper presents mathematical models of digital frequency-sampling filters with shiftable phase-frequency characteristic (PFC) and a generalized mathematical model taking into account the PFC shift introduced at the input. The conducted investigations made it possible to develop a class of narrow-band filters with the possibility of PFC shift and the real-time variation of instantaneous phase of the output signal.