8、The converter is essentially a highly over-sampling 1-bit ADC (the
comparator) followed by digital filtering and decimation to realize the
processing gain. The effective performance of the converter is greatly enhanced by the addition of circuitry to shape the quantization noise such that, instead of being uniformly spread throughout the 0 to fs/2 band, it is minimized in the band of interest (Figure 2. 9).
这个转换器实质上是一个后跟数字滤波和抽取、高过采样率的1位模数转换器（即比较器），数字滤波和抽取用来实现处理增益。由于增加了噪声整形电路，该转换器的有效性能获得了极大地提高。噪声整形电路将原来在0~1/2fs频带均匀存在的噪声最大限度地从有用频带中出去（见图2.9）。
9、DSPs are available in two major classes: fixed point and floating point. The fixed point class represents real numbers in a fixed number of bits. The position of the binary point (similar to the decimal point) can be controlled by the programmer, and determines the range of numbers that can be represented. As the range increases, though, the available precision goes down, since fewer bits lie to the right of the binary point. In 16 bits, the formats 16.0, 15.1, 14.2, 13.3, 12.4, 11.5, 10.6, 9.7, 8.8, 7.9, 6.10, 5.11, 4.12, 3.13, 2.14, and 1.15 are possible. The dynamic range, calculated as 20log (Full Scale Range/Smallest Resolvable Difference), remains the same for all 16-bit formats,20log = 96.3 dB.
数字信号处理器分为定点和浮点两大类，定点数字信号处理器是用固定比特数来代表实数，二进制小数点的位置可以由编程人员决定，这个位置决定了可以表示的实数范围，可用精度随着表示范围的增加而下降，因而二进制小数点的位数减少了，在16位数据中，可能出现的格式有16.0, 15.1, 14.2, 13.3, 12.4, 11.5, 10.6, 9.7, 8.8, 7.9, 6.10, 5.11, 4.12, 3.13, 2.14。所有16位定点格式的动态范围都是一样的，都是20lg（2的16次方）=96.3db.动态范围的计数方法为20lg（满量程范围/最小可分辨差别）。
10、Floating point DSPs represent real numbers using a mantissa and an
exponent, similar to scientific notation: Many combine mantissa and exponent into a 32-bit number. The dynamic range for floating point devices is calculated from the largest and smallest multipliers, where E is the exponent. Thus, for a representation that
uses 24 bits for the mantissa and 8 bits for the signed exponent, the dynamic range is 20 log ( ) = 1535.3 dB. A large dynamic range means the system has great power to represent a wide range of input signals, from very small to very large.

22、The flip-flop A flip-flop is basically a bi-state circuit in which either a 0 or 1 state can resides. Because of its simplicity, the flip-flop is extremely fast. As a basic element, the flip-flop is used in digital circuits and ICs. A flip-flop will lose its state when the supply voltage is removed. Therefore, it is volatile.The register A register is a set of flip-flops in parallel. Typically a register is 8, 16, 32 or 64 bits wide. Often a register is used to hold data, address pointers, etc. A register is volatile and very fast just like the flip-flop.触发器　触发器主要是一种能保持０或１状态的两状态电路，由于简单，它的运行速度极其迅速，作为一种基本元件，触发器在数字电路和集成电路中应用。当电源电压消失时触发器的状态将会失去，因此触发器是不稳定的。寄存器　寄存器是由一系列触发器并联组成。典型的寄存器有８位１６位，３２位或者６４位的。寄存器常用来保存数据，地址指针等。寄存器和触发器一样运行速度快但不稳定。23.SRAM (Static Random Access Memory) An SRAM is an array of addressable flip-flops. The array can be configured as such that the data comes out in single bit, 4-bit, 8bit, and etc. format. SRAM is simple, fast and volatile just like the flip-flop, its basic memory cell SRAM can be found on microcontroller boards (either on or off the CPU chip), where the amount of memory required is small and it will not payoff to build the extra interface circuitry for DRAMs. In addition, SRAM is often used as cache because of its high speed.ＳＲＡＭ（随即静态存储器）是一列可设置地址的触发器，队列可以设定为１位，４位，８位等位数数据的输出格式，ＳＲＡＭ就像触发器一样很简单、快速但不稳定。它的基本单元SRAM能从微控制器板（CPU芯片内部或外部）上找到，那里所需记忆量较小并且不能偿清为ＤＲＡＭ建立额外接口电路所需记忆量。另外ＳＲＡＭ由于速度常被用作高速缓冲存储器使用。24.A special case of SRAM memory is Content Addressable Memory (CAM) . In this technology, the memory consists of an array of flip-flops, in which each row is connected to a data comparator. The memory is addressed by presenting data to it (not an address!). All comparators will then check simultaneously if their corresponding RAM register holds the same data. The CAM will respond with the address of the row (register) corresponding to the original data. The main application for this technology is fast look up tables. These are often used in network routers.内容寻址器就是静态存储器的一个特例，运用这种技术，存储器构成一个阵列的触发器，其中每一行连接一个数据比较器，（并非寻址），如果它们对应的只读存储器具有相同的数据，所有的比较器将会同步检查，内容寻址器将会对地质所对应的原始数据作出反应，这种技术主要用于快速查表，他往往被用于网络路由器。25.DRAM memory is, just like SRAM memory constructed as an array of memory cells. A major difference between SRAM and DRAM, however, lies in the addressing technique. With an SRAM, an address needs to be presented and the chip will respond with presenting the data of the memory cell at the output, or accepting the data at the input and write it into the addressed cell. With DRAM technology, this simple approach is impossible since addressing a row of data without rewriting it will destruct all data in the row because of the dynamic nature.就像静态随机存储器SRAM一样，动态随机存储器DRAM用来构成一个个的存储单元组。ＳＲＡＭ和ＤＲＡＭ的主要不同点在于寻址技术，对于ＳＲＡＭ，地址需要呈现出来，这样，芯片会对存储单元数据的输出显示或者是输入端口的数据接受作出反应，并将数据写入地址单元，而对于ＤＲＡＭ技术，这样简单的方法是不可能实现的，因为给没有改写的数据寻址将会由于动态特性而破坏数据组中的所有数据。26.DC machines are characterized by their versatility. By means of various combinations of shunt, series, and separately excited field windings they can be designed to display a wide variety of volt-ampere or speed-torque characteristics for both dynamic and steady-state operation. Because of the ease with which they can be controlled, systems of DC machines are often used in applications requiring a wide range of motor speeds or precise control of motor output.直流电机的多功能性显著，通过并励、串励和他励等多样的励磁组别，直流电机可以呈现较宽范围的伏安特性或者转速转矩特性。

这对于动态和稳态的运行设备都可以通过设计实验，由于直流电机的易控性，直流电机系统通常用在要求有较宽范围的电动速度或者要求电机输出控制精度要求较高的设备中。27.As we know, the AC voltage generated in each rotating armature coil is converted to DC in the external armature terminals by means of a rotating commutator and stationary brushes to which the armature leads are connected. The commutator-brush combination forms a mechanical rectifier, resulting in a DC armature voltage as well as an armature m.m.f. wave which is fixed, in space. The brushes are located so that commutation occurs when the coil sides are in the neutral zone, midway between the field poles. The axis of the armature m.m.f. wave then is 90 electrical degrees from the axis of the field poles, i.e., in the quadrature axis.我们知道，每一个旋转的电枢线圈产生的交流电压通过旋转的换向器和电枢连接的固定点的电刷在外部电枢终端转换成直流，换向器电刷总线形成了一个机械整流器，导致直流电枢电压和电枢磁动势在空间上是固定的。电刷是固定的位置，，这样当线圈的两端在磁极之间的中性区时发生换向。电枢磁动势领先于磁。28.The outstanding advantages of DC machines arise from the wide variety of operating characteristics which can be obtained by selection of the method of excitation of the field windings. The field windings may be separately excited from an external DC source, or they may be self-excited; i.e., the machine may supply its own excitation. The method of excitation profoundly influences not only the steady-state characteristics, but also the dynamic behavior of the machine in control systems.直流电机的突出优势源于广泛的多样性的运行方式特性，其特性可以有选择励磁绕组的励磁方法获得，励磁绕组可以通过外部的直流电机单独励磁，也可以自励，及电机给自身提供励磁，励磁方法不但可以深深的影响静态的特性，也可以影响控制系统里电机的动态特性。29.An outstanding advantage of the shunt motor is ease of speed control. With a rheostat in the shunt-field circuit, the field current and flux per pole can be varied at will, and variation of flux causes the inverse variation of speed to maintain counter e.m.f. approximately equal to the impressed terminal voltage. A maximum speed range of about 4 or 5 to 1 can be obtained by this method, the limitation again being commutating conditions. By variation of the impressed armature voltage, very wide speed ranges can be obtained.并励直流电机的一个突出的特点是容易对他进行速度调节。在他的并励回路中串联一个可调电阻，每极的电流和磁通就可以按照期望变化，并且磁通的变化以获得近似等于外加端电压的反电势。通过这种方式可以获得一个最大的大约4~5倍的速度变化范围，但他的局限性是电流额换向问题。通过改变外加端电压，可以获得一个较大的速度范围。30.The application advantages of DC machines lie in the variety of performance characteristics offered by the possibilities of shunt, series, and compound excitation. Some of these characteristics have been touched upon briefly in this article. Still greater possibilities exist if additional sets of brushes are added so that other voltages can be obtained from the commutator. Thus the versatility of DC machine systems and their adaptability to control, both manual and automatic, are their outstanding features.直流电机的应用优势在于由并励，串励和复励各种可能的方式所提供的各种各样的性能特征。在这篇文章中，一些特征已被简单触及。还存在更大可能性，如果添加额外的电刷装置可以从换向器获得别的电压。因此直流电机的突出特点是电机系统的多用性和他们同时适合人工和自动控制。

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