求一篇“基于DDS技术信号源”的英文文献

【DDS信号发生器】
【 spurious signal generator 】

DDS的基本工作原理
The basic principle of DDS

直接数字频率合成是采用数字化技术，通过控制相位的变化速度，直接产生各种不同频率信号的一种频率合成方法。
Direct digital frequency synthesis is using digital technology， through the phase change speed control， directly to produce all sorts of different frequency signal a frequency synthesis method.

DDS的基本结构如图1所示，它主要由相位累加器、正弦ROM表、D/A转换器和低通滤波器构成。
The basic structure of DDS is shown in figure 1 shows， it mainly consists of phase accumulators， sine ROM table， D/A converter and low-pass filter composition.

参考时钟fr由一个稳定的晶体振荡器产生。
Reference clock by a stable fr produced crystal oscillator.

相位累加器由N位加法器与N位相位寄存器级联构成，类似于一个简单的加法器。
Phase by N a accumulator adder and N a phase registers cascade constitute， similar to a simple adder.

每来一个时钟脉冲，加法器将频率控制数据与相位寄存器输出的累积相位数据相加，把相加后的结果送至相位寄存器的数据输入端。
Each to a clock pulse， the adder will frequency control data with the accumulation of the phase registers output data addition， the addition phase results of the data sent to phase register input.

相位寄存器将加法器在上一个时钟作用后所产生的新相位数据反馈到加法器的输入端，以使加法器在下一个时钟的作用下继续与频率控制数据相加。
Phase registers adder on will be produced when the clock function of the new phase data feedback to adder input， in order to make adder next clock under the effect of frequency control data to continue with added.

这样，相位累加器在参考时钟的作用下，进行线性相位累加，当相位累加器累积满量时就会产生一次溢出，完成一个周期性的动作，这个周期就是DDS合成信号的一个频率周期，累加器的溢出频率就是DDS输出的信号频率。
So， phase accumulators in reference clock， under the action of linear phase accumulate， when phase accumulators when accumulated full amount can produce a spill， completing a cyclical movements， this cycle is a frequency signal DDS synthesis， accumulators spillover periodic frequency is the signal frequency DDS output.

在参考时钟fr的控制下，频率控制字由累加器累加以得到相应的相位数据，把此数据作为取样地址，来寻址正弦ROM表进行相位－幅度变换，即可在给定的时间上确定输出的波形幅值。
In reference to the clock fr under the control of frequency control word of accumulators tired to get the corresponding phase data， put this data as sampling address to addressing sine ROM table phase - amplitude transform at a given time， can determine the output waveform amplitude.

DAC将数字量形式的波形幅值转换成所要求合成频率的模拟量形式信号，低通滤波器用于滤除不需要的取样分量，这样即可得到由频率控制字决定的连续变化的输出正弦波。
DAC will digital quantity forms of wave amplitude frequency convert the required forms an analog synthesis， low-pass filter used in signal sampling filter doesn't need to get weight， so determined by frequency control word continuous variation of the output sine wave.

DDS的输出频率f0和参考时钟fr、相位累加器长度N以及频率控制字FSW的关系为： ;
The output of spurious frequency f0 and reference clock fr， phase accumulators length N and frequency control word for: the relationship FSW;

DDS的频率分辨率为：；
Spurious frequency resolution for the:;

由于DDS的输出Z大频率受奈奎斯特抽样定理限制，所以DDS 的Z高输出频率为fr/2，但在实际设计的DDS系统中，由于输出滤波器的非理想性，一般输出信号的Z大频率只能达到参考时钟频率fr的40%左右。
Because the output by spurious frequency largest Nyquist sampling theorem limit， so the highest output frequency DDS for fr / 2， but in actual design DDS system， because the output filter non-ideal sex， general output signal can only be the biggest frequency reference around 40% of the clock frequency fr.

【传统信号发生器】
【 traditional signal generator 】

信号发生器又称信号源或振荡器，在生产实践和科技领域中有着广泛的应用。
Signal generator also called source or oscillators， in production practice and science and technology has been widely used in the field.

各种波形曲线均可以用三角函数方程式来表示。
Various waveform curve all can by trigonometric function equation.

能够产生多种波形，如三角波、锯齿波、矩形波（含方波）、正弦波的电路被称为函数信号发生器。
Can produce various waveform， such as triangle wave， sawtooth wave， rectangle wave (including square wave)， the circuit is called sine wave function signal generator.

函数信号发生器在电路实验和设备检测中具有十分广泛的用途。
Function signal generator in circuit experiment and test equipment in a very wide range of purposes.

例如在通信、广播、电视系统中，都需要射频（高频）发射，这里的射频波就是载波，把音频（低频）、视频信号或脉冲信号运载出去，就需要能够产生高频的振荡器。
For example in communication， radio， and television systems， all need rf (high frequency) launch the rf waves， here is the carrier， audio (low frequency)， video signals or pulse signal carry out， just need to be able to produce high-frequency vibe.

在工业、农业、生物医学等领域内，如高频感应加热、熔炼、淬火、超声诊断、核磁共振成像等，都需要功率或大或小、频率或高或低的振荡器。
In industry， agriculture， biomedical in fields， such as high-frequency heating， melting， quenching， ultrasonic diagnosis， nuclear magnetic resonance imaging， etc， all need power or big or small， frequency or high or low oscillators.

函数信号发生器的实现方法通常有以下几种：
The realization of the function signal generator method usually have the following kinds:

（1）用分立元件组成的函数发生器：通常是单函数发生器且频率不高，其工作不很稳定，不易调试。
(1) the components with division: it is usually function generator single function generator and frequency is not high， its work is not very stable， not easy debugging.

（2）可以由晶体管、运放IC等通用器件制作，更多的则是用专门的函数信号发生器IC产生。
(2) can be made by the transistor， the op-amp IC etc， more universal device is made with special function signal generator IC produce.

早期的函数信号发生器IC，如L8038、BA205、XR2207/2209等，它们的功能较少，精度不高，频率上限只有300kHz，无法产生更高频率的信号，调节方式也不够灵活，频率和占空比不能独立调节，二者互相影响。
Early function signal generator IC， such as L8038， BA205， XR2207/2209 etc， the functions of them less， precision， frequency cap 300kHz， unable to produce only higher frequency of signal， adjust the way also not enough flexibility， frequency and occupies emptiescompared to cannot independent regulation， both affecting each other.

（3）利用单片集成芯片的函数发生器：能产生多种波形，达到较高的频率，且易于调试。
(3) use monolithic integrated chip function generator: can produce various waveform， achieve the high frequency， and easy to debug.

鉴于此，美国美信公司开发了新一代函数信号发生器ICMAX038，它克服了（2）中芯片的缺点，可以达到更高的技术指标，是上述芯片望尘莫及的。
In view of this， the American beauty developed a new generation letter ICMAX038 function signal generator， it overcomes the (2) chip shortcomings， can achieve higher technical index， is the chip deficits.

MAX038频率高、精度好，因此它被称为高频精密函数信号发生器IC。
MAX038 frequency and high accuracy， good， therefore it is called a high-frequency precision function signal generator IC.

在锁相环、压控振荡器、频率合成器、脉宽调制器等电路的设计上，MAX038都是优选的器件。
In PLL， vco， frequency synthesizer， pulse width omdulatros etc circuit design， selection of devices are MAX038.

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