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Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,*,*,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,Unit 9 Digital Signal Processing,Passage C Comparison of DSP and ASP,9,单元 数字信号处理,C,篇 比较,DSP,和,ASP,学号：,7600,姓名：章太元,1/22,Passage C Comparison of DSP and ASP,Signals may be processed using analog techniques(analog signal processing,or ASP),digital techniques(digital signal processing,or DSP),or a combination of analog and digital techniques(mixed signal processing,or MSP).In some cases,the choice of techniques is clear;in others,there is no clear cut choice,and second-order considerations may be used to make the final decision.,With respect to DSP,the factor that distinguishes it from traditional computer analysis of data is its speed and efficiency in performing sophisticated digital processing functions such as filtering,FFT analysis,and data compression in real time.,2/22,信号能够用模拟技术处理（模拟信号处理，数字技术（或,ASP,），数字信号处理，或,DSP,），或一个组合模拟和数字技术（混合信号处理，或,MSP,）。在一些情况下，技术选择是明确；在其它情况下，没有明确选择，和二阶考虑能够用来做最终决定。,对于,DSP,，使得它与传统计算机数据分析是它速度和效率，进行复杂数字处理功效，如滤波，,FFT,分析，数据实时压缩,3/22,The term mixed signal processing implies that both analog and digital processing is done as part of the system.The system may be implemented in the form of a printed circuit board or a single integrated circuit chip.In the context of this broad definition,ADCs and DACs are considered to be mixed signal processors,since both analog and digital functions are implemented in each.Recent advances in Very Large Scale Integration(VLSI)processing technology allow complex digital processing as well as analog processing to be performed on the same chip.The very nature of DSP itself implies that these functions can be performed in real-time.,4/22,术语混合信号处理意味着，模拟和数字处理系统一部分。该系统可在印刷电路板或一个单一集成电路芯片形式实现。在这个广泛定义下，,ADC,和,DAC,被认为是混合信号处理器，因为模拟和数字功效实现在每个。在超大规模集成电路（,VLSI,）处理技术进展使得复杂数字信号处理和模拟处理是在同一芯片上进行。,DSP,本身性质意味着，这些功效能够在实时执行。,5/22,ASP vs.DSP Todays engineer faces a challenge in selecting the proper mix of analog and digital techniques to solve the signal processing task at hand.It is impossible to process real-world analog signals using purely digital techniques,since all sensors(microphones,thermocouples,strain gages,piezoelectric crystals,disk drive heads,etc.)are analog sensors.Therefore,some sort of signal conditioning circuitry is required in order to prepare the sensor output for further signal processing,whether it be analog or digital.Signal conditioning circuits are,in reality,analog signal processors,performing such functions as multiplication(gain),isolation(instrumentation amplifiers and isolation amplifiers),6/22,detection in the presence of noise(high common-mode instrumentation amplifiers etc.),dynamic range compression(log amps,LOGDACs,and programmable gain amplifiers),and filtering(both passive and active).Several methods of accomplishing signal processing are shown in Figure 9.5.The top portion of the figure shows the purely analog approach.The latter parts of the figure show the DSP approach.Note that once the decision has been made to use DSP techniques,the next decision must be where to place the ADC in the signal path.,7/22,ASP,与,DSP,今天工程师在选择适当混合模拟和数字技术来处理手头信号处理任务所面临挑战。这是不可能真实世界模拟信号处理采取纯数字技术，因为全部传感器（麦克风，热电偶，应变计，压电晶体，磁盘驱动器磁头，等）是模拟传感器。所以，某种形式信号调理电路是为了准备传感器输出信号深入处理，不论是模拟或数字。信号调理电路，在现实中，模拟信号处理器，如乘法执行这些功效（增益），隔离（仪表放大器和隔离放大器），在存在噪声检测（高共模仪表放大器等），动态范围压缩（对数放大器，,logdacs,，和可编程增益放大器），和过滤（包含被动和主动）。完成信号处理几个方法，如图,9.5,所表示。图中顶部显示纯模拟方法。图中一部分显示数字信号处理方法。请注意，一旦决定已经做出，采取,DSP,技术，未来决定必须在什么地方,ADC,信号路径。,8/22,Figure 9.5 Some Methods of Accomplishing Signal Processing,9/22,In general,as the ADC is moved closer to the actual sensor,more of the analog signal conditioning burden is now placed on the ADC.The added ADC complexity may take the form of increased sampling rate,wider dynamic range,higher resolution,input noise rejection,input filtering and programmable gain amplifiers(PGAs),on-chip voltage references,etc.,all of which add functionality and simplify the system.With todays high-resolution/high sampling rate data converter technology,significant progress has been made in integrating more and more of the conditioning circuitry within the ADC/DAC itself.,10/22,In the measurement area,for instance,24-bit ADCs are available with built-in programmable gain amplifiers(PGAs)which allow full-scale bridge signals of 10 mV to be digitized directly with no further conditioning.At voiceband and audio frequencies,complete coder-decoders(Codecs or Analog Front Ends)are available which have sufficient on-chip analog circuitry to minimize the requirement for external conditioning components.At video speeds,analog front ends are also available for such applications as CCD image processing and others.,11/22,在普通情况下，作为,ADC,靠近实际传感器，更多模拟信号调理负担，现在放在,ADC,。增加,ADC,复杂性能够增加采样率形式，更宽动态范围，高分辨率，输入噪声排斥，输入滤波和可编程增益放大器（,PGA,），片上参考电压，等等，全部这些新增功效和简化系统。今天高分辨率、高采样率数据转换技术，在集成越来越多调理电路内,ADC/DAC,本身取得了显著进展。在测量领域，比如，,24,位,ADC,提供内置可编程增益放大器（,PGA,）允许,10 MV,全桥被数字化信号直接没有深入调整。在音频和音频解码器（编解码器或编码器，完整模拟前端）可有足够片上模拟电路，以尽可能降低对外部条件要求。在视频速度，模拟前端也可用于,CCD,图像处理和其它应用程序。,12/22,A practical example,As a practical example of the power of DSP,consider the comparison between an analog and a digital lowpass filter,each with a cutoff frequency of 1 kHz.The digital filter is implemented in a typical sampled data system shown in Figure 9.6.Note that thereare several implicit requirements in the diagram.First,it is assumed that an ADC/DAC combination is available with sufficient sampling frequency,resolution,and dynamic range to accurately process the signal.Second,the DSP must be fast enough to complete all its calculations within the sampling interval,1/,f,s,.Third,analog filters are still required at the ADC input and DAC output for anti-aliasing and anti-imaging,but the performance demands are not as great.Assuming these conditions have been met,the following offers a comparison between the digital and analog filters.,13/22,一个实际例子作为一个实用,DSP,电源例子，考虑一个模拟和数字低通滤波器之间比较，各有一个截止频率为,1,千赫。,The digital filter is implemented in a typical sampled data system shown in Figure 9.6.,注意，图中一些隐含要求,thereare,。,First,it is assumed that an ADC/DAC combination is available with sufficient sampling frequency,resolution,and dynamic range to accurately process the signal.,第二，,DSP,必须足够快采样间隔内完成全部计算，,1/FS,。第三，模拟滤波器仍在,ADC,输入和抗混叠和反成像,DAC,输出所需，但性能要求是不一样大。,Assuming these conditions have been met,the following offers a comparison between the digital and analog filters.,14/22,Figure 9.6 A Typical Sampled Data System,15/22,The required cutoff frequency of both filters is 1 kHz.The analog filter is realized as a 6-pole Chebyshev Type 1 filter(ripple in passband,no ripple in stopband),and the response is shown in Figure 9.7.In practice,this filter would probably be realized using three 2-pole stages,each of which requires an op amp,and several resistors and capacitors.Modern filter design CAD packages make the 6-pole design relatively straightforward,but maintaining the 0.5 dB ripple specification requires accurate component selection and matching.,16/22,两个滤波器截止频率是,1,千赫要求。模拟滤波器实现为,6,极切比雪夫型滤波器（,1,通带阻带纹波，无纹波），和响应如图,9.7,所表示。在实践中，该过滤器可能会使用三极阶段实现，每一个都需要一个运算放大器，和几个电阻和电容器。当代,CAD,软件包过滤器设计使六极设计相对简单，但保持,0.5 dB,纹波规格要求准确组件选择与匹配。,17/22,Figure 9.7 The Magnitude Response in dB,18/22,On the other hand,the 129-tap digital FIR filter shown has only 0.002 dB passband ripple,linear phase,and a much sharper roll off.In fact,it could not be realized using analog techniques!Another obvious advantage is that the digital filter requires no component matching,and it is not sensitive to drift since the clock frequencies are crystal controlled.The 129-tap filter requires 129 MACs in order to compute an output sample.This processing must be completed within the sampling interval,1/,f,s,in order to maintain real-time operation.In this example,the sampling frequency is 10 kSPS,therefore 100 s is available for processing,assuming no significant additional overhead requirement.Most DSPs can complete the entire multiply-accumulate process(and other functions necessary for the filter)in a single instruction cycle.,19/22,另首先，,129,个抽头,FIR,数字滤波器含有,0.002 dB,通带纹波，线性相位，和一个更清楚滚。实际上，它不可能使用模拟技术实现！另一个显著优势是，数字滤波器不需要匹配，它是不敏感漂移因为时钟频率晶体控制。,129,抽头滤波器需要,129,个苹果来计算输出样本。这么处理必须在采样间隔内完成，,1/FS,，为了保持实时操作。在本例中，采样频率为,10 kSPS,，所以,100,有效处理，假设没有显着额外开销要求。大多数,DSP,能够完成整个乘法累加过程（和其它必要过滤功效）在一个单一指令周期。,20/22,Therefore,a 129-tap filter requires that the instruction rate be greater than 129/100 s=1.3 million instructions per second(MIPS),DSPs are available with instruction rates much greater than this,so the DSP certainly is not the limiting factor in this application,In a practical application,there are certainly many other factors to consider when evaluating analog versus digital filters,or analog versus digital signal processing in general.Most modern signal processing systems use a combination of analog and digital techniques in order to accomplish the desired function and take advantage of the best of both the analog and the digital world.,21/22,所以，一个,129,抽头滤波器要讨教学率应大于,129/100S=1300000,指令每秒（,MIPS,）。,DSP,可与指令率比这大得多，所以,DSP,当然不是在该应用程序中限制原因。,在实际应用中，有一定评定时，模拟与数字滤波器考虑各种原因影响，或模拟与数字信号处理普通。大多数当代信号处理系统，用来模拟和数字技术组合来完成预期功效，利用最好模拟和数字世界。,22/22,
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