基于DDS和单片机数字控制信号发生器的设计外文翻译文献Word格式文档下载.docx

1、Keywords: DDS; MCU; Signal generator; Phase Accumulator; DACAbstract. Its advantage to use DDS chip is output signal frequency bigger, and precision higher, But users cant change the output signal waveforms. The MCU can produce the required arbitrary waveforms, but its program execution of the order

2、 limit the speed.So we use their Synergy to design the digital controlled signal generator. The System has the advantage of output good quality waveform, frequency of precision and stability ,and high frequency, empty, amplitude and phase is to step into the need.IntroductionThe digitally synthesize

3、d sine waveform （Direct Digital Synthesis, DDS） is a well-known method and has been applied to many embedded applications 1. This technique can be used to create a positive digital sine waveform. Compared to other frequency composing method, Direct Digital Frequency Synthesis（DDS） has been the most

4、popular trend in modern frequency synthetic technique for its excellent characteristics. The signal source that the DDS technology realizes can carry out accurate controlling on DDS frequency , extent , phase exporting wave forms etc. by numerical control circuit, the system making use of this metho

5、d has many merits such as stability, reliably and accuracy.The commercial DDS chip can only export a sine wave for the data in the ROM form already has been solidified. If needing to come into being any wave form, it may come true by the way that FPGA adopts DDS IP core or hardware describe language

6、 etc, however,the cost of This way cost is high; on the other hand, any wave form can be achieved by making use of micro controller unit （MCU） to carry out figure frequency combining and DA converting. The experiment and applying testing have shown that the numerical control signal source composed o

7、f STM32 micro controller and DDS chip can work well.DDS and wave form programming patternThe core of DDS system is phase accumulator carriage, and it is composed of a ADR and oneunit phase register. When any clock comes, the phase register increases by with the step length, phase register output and

8、 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 one-period sine wave, each address corresponds to the phase dot of 0360 degrees of the sine wave. The mapping digital signal drives DAC an

9、d outputs analog value. The output sine circle and frequency areThe 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

10、 wave circle, unit: s; TC -external referenced clock circle, unit: M -accumulated step length of phase register, constant; f out -output sine wave frequency, unit: Hz; f c -external referenced clock frequency, unit: N -phase accumulator digit, constant.The relationship among the frequency control wo

11、rd, and the output signal frequency and the referenced clock frequency are:Frequency control word is directly proportional to the output signal frequency. In order to describe clearly, the sine wave form is as one vector turns around phase circle, the phase circle matches along with a cycle sine wav

12、e. Every sampling pots in wave form corresponds to a phase dot of the phase circle.To synthesis the required frequency signal, it needs to accomplish the following steps1. Controlling every sampling increment of phase and accumulating them （frequency control word K）, output 2 pi cumulated phase （usi

13、ng phase accumulator）.2. Converting 2 pi accumulating phase into the corresponding sine amplitude, use ROM to store the corresponding phase-extent form of sine function in general.3. Use DAC to change extent code into the signal simulating voltage.4. The voltage signal that DAC exports is ladder wav

14、e form , the required simulation voltage out is achieved after LPF smoothing.Numerical control DDS signal source system designs analysisSystem uses the STM32 as control core and the AD9850 as generator. STM32 is 32-bit ARM-based micro controller with 128 K byte flash memory.The two signal output of

15、STM32 can be achieved by controlling AD9850 and DAC0832 output simultaneously. The system designs block diagram is shown in Fig. 1. One signal output can generate 30 MHz sine wave and rectangular wave by controlling AD9850, the other output generate any wave form with its frequency less than 10 KHz by numerical frequency mixture of DAC0832.Fig. 1 System designs block diagramHardware designAD9850 moduleAD9850 contains the DDS sy