【正文】 fter connecting to the accurate clock source and writing the frequency phase control word, AD9850 can generate the frequencyprogrammable and phaseprogrammable output of analog sine wave, which can be used as the direct frequency signal source or be transferred into rectangular wave through highspeed parator. With the 125 MHz clock, 32bit frequency control word can carry out the output frequency resolution ratio of AD9850 with Hz[4]. DAC0832 module The circuit exports the phase data sheet to DAC0832 from STM32 and gets corresponding wave form by DA converting. The stepbystep adjusting phase amounts can create arbitrary frequency, the PWM signal from the STM32 transfers into the corresponding voltage by lowpass filter, therefore, the referenced voltage of DAC0832 is controlled, furthermore, the output wave form extent is tuned appropriately. The digital to analog conversion circuit is shown in Fig. 2 DAC circuit PWM converting DA circuit The lowpass filtered PWM signal from STM32 is then stable using the voltage follower, which will yield a stable output voltage。 TC external referenced clock circle, unit: s。 DAC Abstract. Its advantage to use DDS chip is output signal frequency bigger, and precision higher, But users can39。Design of Digital Controlled Signal Generator Based on DDS and MCU Yinjun Chena, Zehuai Yuan Faculty of Electronic Information and Mechanical Electrical Engineering, Zhaoqing University, Zhaoqing 526061, China Keywords: DDS。 Phase Accumulator。 on the other hand, any wave form can be achieved by making use of micro controller unit (MCU) to carry out figure frequency bining and DA converting. The experiment and applying testing have shown that the numerical control signal source posed of STM32 micro controller and DDS chip can work well. DDS and wave form programming pattern The core of DDS system is phase accumulator carriage, and it is posed of a ADR and one unit phase register. When any clock es, the phase register increases by with the step length, phase register output and phase control word add together, and then the output is imported to sine inquiry form address. The sine inquiring form includes the numeral extent information of oneperiod sine wave, each address corresponds to the phase dot of 0~360 degrees of the sine wave. The mapping digital signal drives DAC and outputs analog value. The output sine circle and frequency are The phase register will return to the original state when the 2N/M fc clock is finished. Accordingly, the DDS system output a sine wave when the sine inquiring form finish a circle. The output sine circle and frequency is TO output sine wave circle, unit: s。 f c external referenced clock frequency, unit: Hz。 (b) 1 MHz wave form output。信號發(fā)生器 。因此，我們利用它們之間的協(xié)同設(shè)計數(shù)字控制信號發(fā)生器。其它頻率合成方法相比 , 直接數(shù)字頻率合成器（ DDS）一直以其優(yōu)良的特性在現(xiàn)代頻率合成技術(shù)中最流行的趨勢。另一方面，可以任意波形通過開展數(shù)字頻率結(jié)合使用的微控制器單元（ MCU）和 DA轉(zhuǎn)換實現(xiàn)。 正弦查詢表格包含一個周期正弦波，每個數(shù)字幅度信息地址對應(yīng)于 0? 360度的正弦波的相位點。輸出正弦波的周期和頻率為 TO 輸出正弦波周期，單位：秒 。 N 相位累加器的位數(shù)，不變。 合成所需的頻率信號，它需要完成以下步驟： （頻率控制字 K），輸出 2 pi累計相位（使用相位累加器）。 數(shù)控 DDS 信號源系統(tǒng)設(shè)計分析 系統(tǒng)使用 STM32 作為控制核心和 AD9850作為發(fā)生器。一個信號輸出通過控制 AD9850，可產(chǎn)生 30 MHz正弦波和矩形波，其他輸出的任意波形及其頻率低于 10千赫是通過頻率數(shù)值混合器 DAC0832 產(chǎn)生的。 連接到精確的時鐘源和寫入頻率相位控制字后， AD9850的可以產(chǎn)生可編程頻率和相位可編程的模擬正弦波輸出波，這可以用來作為直接的高頻信號源，或者通過高速比較器被轉(zhuǎn)移到矩形波。數(shù)字到模擬轉(zhuǎn)換電路，如圖 2所示 : 圖 2 DAC 電路 PWM轉(zhuǎn)換 DA電路 低通濾波器的 PWM信號從 STM32到穩(wěn)定使用電壓跟隨器，然后穩(wěn)定將產(chǎn)生一個穩(wěn)定的輸出電壓，通過調(diào)整 PWM占空比可調(diào)節(jié)電壓。一個很好的平滑的輸出波形，可以通過使用低通有源功率濾波實現(xiàn)。系統(tǒng)軟件的設(shè)計過程如圖 5所示。這兩個模塊可以通過外側(cè)中斷和定時中斷被控制。 然后 8位數(shù)據(jù)被加載在 WCLK上升沿，將指針設(shè)置到下一個輸入注冊。 此功能是基于數(shù)字頻率合成原則，它把輸入頻率傳送到相應(yīng)的控制字，然后一步一步結(jié)合相位預計，在記憶體中輸出波形數(shù)據(jù)表。圖 6給出了相應(yīng)的實驗波形。占空比： 10％ ? 100％，差異≤ 1％。 五、一步一步的自動化，定義：最高值，最低值，一步一步的速度， 一步一步的計算，按升序或下降，循環(huán)或不循環(huán)。 結(jié)論 使 DDS和 MCU控制器組合使用，系統(tǒng)可以導出的數(shù)值控制消費者的需要的信號源，它具有的優(yōu)點，如良好的輸出的波形，頻率準確，可靠的穩(wěn)定性和高占空