lesson16 翻译

2024年4月3日发(作者：大众捷达2019款报价)

不能第16课DSP的基本概念

We don\'t speak in a digital signal. A digital signal is a language of 1s and 0s that can

be processed by mathematics. We speak in real-world, analog signals. Analog signals

are real world signals that we experience everyday-sound, light, temperature,and

pressure. A digital signal is a numerical representation of the analog signal. It may be

easier and more cost effective to process these signals in the digital world. In the real

world,we can convert these signals into digital signals through the analog-to-digital

converter, process the signals,and if needed, bring the signals back out to the analog

world through the digital-to-analog converter.

我们说话时不用数字信号。一个数字信号是1和0的语言，可以通过数学处理。在现实世界

中说话我们用模拟信号。模拟信号是现实世界中的信号，我们日常的经验，声，光，温度和

压力。数字信号是模拟信号的数字表示。在世界上的这些数字信号，可能是更简单，更符合

成本效益的过程。在现实世界中，我们可以通过模数转换器将模拟信号转换成数字信号，对

信号进行处理时，如果需要，将通过数模转换器转换成模拟信号。

The essentials of analog-to -digital and analog-to -digital conversion

The first essential step in analog-to-digital (A/D) conversion is to sample an analog signal.

This step is performed by a sample and hold circuit, which samples at regular intervals called

sampling length of the sampling interval is the same as the sampling period, and

the reciprocal of the sampling is the sampling frequency fs. According to the Nyquist theorem, a

signal with a maximun frequency of W Hz (called a band-limited signal ) must be sampled at

least 2W samples per second to ensure accurate recording. When this minimun is not respected,

distortion called aliasing occurs. Aliasing causes high frequency signals to appear as lower

frequency signals. To be sure aliasing will not occur, sampling is always preceded by low pass

filtering. The low pass filter, called the anti-aliading filter, removes all frequencies above half

the selected sampling rate.

模数 数模转换概要

在模数转换（A / D）中，第一个重要步骤，是模拟信号的采样。这一步是由采样保持电

路完成的，它每隔一定时间采样称为采样间隔。

采样长度和采样周期是一样的，和采样频率成反比。

根据奈奎斯特定理，对于一个最长W赫兹频率的信号（称为一个频带有限的信号）必须至

少要有2W每秒的采样速率才能保证不失真的采样。如果最小采样速率没有达到就会出现混

叠失真。

混叠现象导致高频率信号变成低频率信号出现。为了保证混叠现象不出现，采样都在低通滤

波之前进行。

低通滤波器，称为反 aliading过滤器，删除所有频率的一半以上选定的采样率。

A/D转换器为每一个模拟样本选择一个量化水平。一个N位的转换器选择更多的量化水

平。

The larger the number of levels,the smaller the quantization errors,calculated as the difference

between the quantized level and the true sample level.

采样数量越大 量化误差越小 被认为量化数量和真实的采样数量之间的不同。

Most quantization errors are limited in size to half a quantizaion step Q.

大多数的量化错误被限制在量化步长Q里。

The quantization step size is calculated as Q=R/,where R is the full scale range of the analog

signal and N is the number of bits used by the converter

量化步长被定义为Q=R /

2

，其中R是模拟信号的全部量程范围。N是被转化器使用的比

N

特数。

The strength of the signal compared to that of the quantization errors is measured by dynamic

range and signal-to-noise ratio.

信号的强度和量化错误的比是被动态量程测量的以及信噪比。

Once digital signal processing is compete,digital-to-analog(D/A) conversion must occur.

一旦数字信号处理完成，数模转换将要发生。

This process begins by converting each digital code into an analog voltage that is proportional in

size to the number represented by the code.

这个过程由每一个数字码元转换成码元代表的比例的大小的模拟电压开始的

This voltage is held steady through zero order hold until the next code is available,one sampling

interval later.

这个电压是稳定的通过零阶保持稳定的直到下一个码元是可用的一个采样间隔之后。

This creates a staircase-like signal that contains frequencies above W signals are

removed with a smoothing low pass filter,the last step in D/A conversion.

它创造了一个 信号包含了WHz的频率。 这些信号被一个平滑的低通滤波器过滤了，最

后一步就是D/A转换了。

The images of each frequency f present in a sampled signal appear,through sampling,at the

infinite number of frequencies kfs

?

fHz.

通过采样而出现的存在于采样信号中每一个频率f的图像出现在无限的频率数量之中。

When the sampling rate is lower than the required Nyquist rate,that is fs<2W,images of high

frequency signals erroneously appear in the baseband(or Nyquist range) due to aliasing.

当采样速率低于奈奎斯特率时，就是f<2W高频信号由于混叠在基带信号中出现

错误。

While this undersampling is normally avoided,it can be exploited. For example, signals whose

frequencies are restricted to a narrow band of high frequencies can be sampled at a rate similar

to twice the width of the band instead of twice the maximum frequency.

然而欠采样通常是可以避免的，它可以被利用。例如，信号的频率限制在高频窄带内，就

能以类似2倍的带宽速率去采样 而不是2倍的最大的频率

All of the important signal characteristics can be deduced from the copy of the spectrum that

appears in the baseband through sampling.

所有信号重要的规格参数能够从出现的基带采样频谱中推断出来。

Depending on the relationship between the signal frequencies and the sampling rate,spectral

inversion may cause the shape of the spectrum in the baseband to be inverted from the true

spectrum of the signal.

依赖于信号的频率和采样速率之间的关系， 频谱的倒置可能导致频谱在基带中的外形

从信号的频谱中反转。

Technologies for digital signal processing

数字信号处理技术

If a universal microprocessor solution existed with which every design could be

realized,the electronics industry wouldn\'t be a very competitive place

如果存在着普遍的微处理器解决方案的每一个设计可以实现，电子产业将不是一个非常有竞

争力地方。

.However,typically in most electronic designs,more than one processor technology

can be used to implement the required functions.

然而最典型的电子设计，有多种处理技术能够被用于实现需要的功能。

The trick is,of course,to choose the one that best delivers the performance,size,power

consumption,features,software and tools to get the job done fast---without breaking

the budget.

那个诀窍当然是去选着一个最先进性能，最好的尺寸，最小的功耗，特性，软件

及工具去做，同时不超过预算。

After almost two decades of development,digital signal processors continue to take

the place of competitive l signal processors are,after all,at the center

of signal processing.

将近20年的发展，数字信号处理继续保持着竞争地位。毕竟数字信号处理是信号处理的关

键。

A digital signal processor (DSP) is a type of microprocessor----one that is incredibly

fast and powerful.

数字信号处理器（DSP）是微处理器的一中----是一个令人难以置信的快速和强大。

A DSP is unique because it processes data in real real-time capability makes

a DSP perfect for applications that cannot tolerate any delays.

DSP是独一无二的，因为它的数据处理是及时的，这个没有延时的能力使得它完

美的应用于不能容忍任何的延时。

For example, did you ever talk on a cell phone where two people couldn\'t talk at

once? You had to wait until the other person finished you both spoke

simultaneously, the signal was cut-you didn\'t hear the other person.

例如，你曾经打电话时有过2个人不能同时说话的经历么？你不得不等到其他的

人说完了。如果你们同时说话，信号就被掐断了，这样你不能听到其他的人说什

么。

With today\'s digital cell phones,which use DSP, you can talk DSP

processors inside cell phones process sounds so rapidly you hear them as quickly as

you can speak-in real are just some of the advantages of designing with

DSPs over other microprocessors:

当今使用DSP技术的数字手机，你能够正常的说话。手机中的DSP处理技术

处理声音信号如此的快，以至于你听到对方说话就像面对面说话一样。这里有一

些对比与其他的微处理器的DSP技术的优点。

The FPGA Alternative Field-Programmable Gate Arrays have the capability of

being reconfigurable within a system,which can be a big advantage in applications

that need multiple trial versions within development,offering reasonably fast time to

market.

在一个系统中另类的FPGA现场可编程门阵列有重构的能力，它在发展需要提供

快的产品上市时间 需要多种实验版本中应用中有一大优点

They also offer greater raw performance per specific operation because of the

resulting dedicated logic circuit.

他们也提供更多的原始的性能卫每一种特殊的产品，因为产生专用的逻辑电

路。

However, FPGAs are significantly more expensive and typically have much

higher power dissipation than DSPs with similar functionality.

然而FPGA明显的更贵和功耗更大，和DSP在相同的功能下相比。

As such,even when FPGAs are the chosen performance technology in designs

such as wireless infrastructure, DSPs are typically used in conjunction with FPGAs to

provide greater flexibility, better price/performance ratios,and lower system power.

本身即使FPGA被选中设计技术在设计技术中，如基础无线传输，DSP往往和

FPGA协同提供更大的灵活性，更好的性价比，和更低的系统功耗。

The ASIC Alternative Application-specific ICs can be tailored to perform

specific functions extremely well, and can be made quite power efficient.

ASIC的替代应用专用IC能够非常好满足其特定的功能，还可以做得相当的省

电。

However,since ASICS are not field-programmable,their functionality cannot be

iteratively changed or updated while in product development.

然而，由于ASIC是不是现场可编程，在产品开发中它们的功能不能改变或更新。

As such,every new version of the product requires a redesign and trips through

the foundry,an expensive proposition, and an impediment to rapid time-to-market.

因此每一个新的产品的更新，需要重新设计通过制造，一个昂贵的方案，和

一个缺陷去去产品快速上市。

Programmable DSPs, on the other hand, can be updated without changing the

silicon,merely change the software program, greatly reducing development cost, and

availing aftermarket feature enhancements with mere code downloads. Consequently,

more often than not, when you see ASICs in real time signal processing applications,

they are typically employed as bus interfaces, glue logic, and/or functional

accelerators for a programmable DSP-based system.

可编程的DSP，在另一方面，能够更新而不用改变芯片只用改变软件的程序，很

大程度上减少了更新的花费，同时有利于售后功能的增强通过单纯的程序的下

载。所以很多时候当你看到ASIC在实时信号处理应用中，他们通常采用总线接

口，逻辑电路和与或的功能加速器为一个可编程的DSP为基础的系统。

The GPP Alternative In contrast to ASICs that are optimised for specific

functions, general-purpose micoprocessors (GPPs) are best suited for performing a

broad array of tasks.

与特定用途的集成电路相比，The GPP Alternative对于完成特定的功能最优化，

一般功能的GPPs最适合做成阵列板

However, for applications in which the end product must process answers in

real time, or must do so while powered by consumer batteries,GPPs comparatively

poor real time performance and high power consumption all but rules them out.

然而，对于应用中的最终产品必须实时的处理答案，或必须这样做当采用商品电

池时，GPPS的比较差的实时性能和高能耗的，所以问题出来了。

More and more, these processors are being seen as the dinosaurs of the industry,

too encumbered with PC compatibility and desktop features to adapt to the changing

real time market place.

越来越多，这些处理器都被视为业界的恐龙，也堆满了做卖弄电脑的兼容性和功

能，以适应不断变化的实时市场。

As the world embraces tiny hand-held wireless-enabled products that require

power dissipation measured in milliwatts-not the watts that these processors

consume-DSPs are the programmable technology of trend is bound to

continue as digital Internet appliances get smaller, faster and more portable.

作为世界拥抱微型手持无线上网功能的产品，需要毫瓦的功耗测量，而不是瓦，

这些处理器的功耗，DSP是可编程技术的首选。这一趋势必将继续使互联网数字

家电变得更小，更快，更便于携带。