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  北暖29 2011-03-27 00:00:00

  這個你可以到ADI的官方去找AD9954的技術資料，里面有講DDS原理的。那個公司的技術文章一般都是英文的。

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  小布阿TvT 2011-03-28 00:00:00

  你去360文庫看看有沒有

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  *月蝴蝶谷 2011-03-25 00:00:00

  【DDS信號發(fā)生器】 【 spurious signal generator 】 DDS的基本工作原理 The basic principle of DDS 直接數(shù)字頻率合成是采用數(shù)字化技術，通過控制相位的變化速度，直接產(chǎn)生各種不同頻率信號的一種頻率合成方法。 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的基本結(jié)構(gòu)如圖1所示，它主要由相位累加器、正弦ROM表、D/A轉(zhuǎn)換器和低通濾波器構(gòu)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. 參考時鐘fr由一個穩(wěn)定的晶體振蕩器產(chǎn)生。 Reference clock by a stable fr produced crystal oscillator. 相位累加器由N位加法器與N位相位寄存器級聯(lián)構(gòu)成，類似于一個簡單的加法器。 Phase by N a accumulator adder and N a phase registers cascade constitute， similar to a simple adder. 每來一個時鐘脈沖，加法器將頻率控制數(shù)據(jù)與相位寄存器輸出的累積相位數(shù)據(jù)相加，把相加后的結(jié)果送至相位寄存器的數(shù)據(jù)輸入端。 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. 相位寄存器將加法器在上一個時鐘作用后所產(chǎn)生的新相位數(shù)據(jù)反饋到加法器的輸入端，以使加法器在下一個時鐘的作用下繼續(xù)與頻率控制數(shù)據(jù)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. 這樣，相位累加器在參考時鐘的作用下，進行線性相位累加，當相位累加器累積滿量時就會產(chǎn)生一次溢出，完成一個周期性的動作，這個周期就是DDS合成信號的一個頻率周期，累加器的溢出頻率就是DDS輸出的信號頻率。 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. 在參考時鐘fr的控制下，頻率控制字由累加器累加以得到相應的相位數(shù)據(jù)，把此數(shù)據(jù)作為取樣地址，來尋址正弦ROM表進行相位－幅度變換，即可在給定的時間上確定輸出的波形幅值。 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將數(shù)字量形式的波形幅值轉(zhuǎn)換成所要求合成頻率的模擬量形式信號，低通濾波器用于濾除不需要的取樣分量，這樣即可得到由頻率控制字決定的連續(xù)變化的輸出正弦波。 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的輸出頻率f0和參考時鐘fr、相位累加器長度N以及頻率控制字FSW的關系為： ; The output of spurious frequency f0 and reference clock fr， phase accumulators length N and frequency control word for: the relationship FSW; DDS的頻率分辨率為： ； Spurious frequency resolution for the:; 由于DDS的輸出Z大頻率受奈奎斯特抽樣定理限制，所以DDS 的Z高輸出頻率為fr/2，但在實際設計的DDS系統(tǒng)中，由于輸出濾波器的非理想性，一般輸出信號的Z大頻率只能達到參考時鐘頻率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. 【傳統(tǒng)信號發(fā)生器】 【 traditional signal generator 】 信號發(fā)生器又稱信號源或振蕩器，在生產(chǎn)實踐和科技領域中有著廣泛的應用。 Signal generator also called source or oscillators， in production practice and science and technology has been widely used in the field. 各種波形曲線均可以用三角函數(shù)方程式來表示。 Various waveform curve all can by trigonometric function equation. 能夠產(chǎn)生多種波形，如三角波、鋸齒波、矩形波（含方波）、正弦波的電路被稱為函數(shù)信號發(fā)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. 函數(shù)信號發(fā)生器在電路實驗和設備檢測中具有十分廣泛的用途。 Function signal generator in circuit experiment and test equipment in a very wide range of purposes. 例如在通信、廣播、電視系統(tǒng)中，都需要射頻（高頻）發(fā)射，這里的射頻波就是載波，把音頻（低頻）、視頻信號或脈沖信號運載出去，就需要能夠產(chǎn)生高頻的振蕩器。 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. 在工業(yè)、農(nóng)業(yè)、生物醫(yī)學等領域內(nèi)，如高頻感應加熱、熔煉、淬火、超聲診斷、核磁共振成像等，都需要功率或大或小、頻率或高或低的振蕩器。 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. 函數(shù)信號發(fā)生器的實現(xiàn)方法通常有以下幾種： The realization of the function signal generator method usually have the following kinds: （1）用分立元件組成的函數(shù)發(fā)生器：通常是單函數(shù)發(fā)生器且頻率不高，其工作不很穩(wěn)定，不易調(diào)試。 (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）可以由晶體管、運放IC等通用器件制作，更多的則是用專門的函數(shù)信號發(fā)生器IC產(chǎn)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. 早期的函數(shù)信號發(fā)生器IC，如L8038、BA205、XR2207/2209等，它們的功能較少，精度不高，頻率上限只有300kHz，無法產(chǎn)生更高頻率的信號，調(diào)節(jié)方式也不夠靈活，頻率和占空比不能獨立調(diào)節(jié)，二者互相影響。 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）利用單片集成芯片的函數(shù)發(fā)生器：能產(chǎn)生多種波形，達到較高的頻率，且易于調(diào)試。 (3) use monolithic integrated chip function generator: can produce various waveform， achieve the high frequency， and easy to debug. 鑒于此，美國美信公司開發(fā)了新一代函數(shù)信號發(fā)生器ICMAX038，它克服了（2）中芯片的缺點，可以達到更高的技術指標，是上述芯片望塵莫及的。 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頻率高、精度好，因此它被稱為高頻精密函數(shù)信號發(fā)生器IC。 MAX038 frequency and high accuracy， good， therefore it is called a high-frequency precision function signal generator IC. 在鎖相環(huán)、壓控振蕩器、頻率合成器、脈寬調(diào)制器等電路的設計上，MAX038都是優(yōu)選的器件。 In PLL， vco， frequency synthesizer， pulse width omdulatros etc circuit design， selection of devices are MAX038.

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