基于dds和單片機數(shù)字控制信號發(fā)生器的設(shè)計外文翻譯、中英對照、英漢互譯-文庫吧
2024-10-21 16:04 本頁面
【正文】 ing steps 1. Controlling every sampling increment of phase and accumulating them (frequency control word K), output 2 pi cumulated phase (using phase accumulator). 2. Converting 2 pi accumulating phase into the corresponding sine amplitude, use ROM to store the corresponding phaseextent 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 wave form , the required simulation voltage out is achieved after LPF smoothing. Numerical control DDS signal source system designs analysis System uses the STM32 as control core and the AD9850 as generator. STM32 is 32bit ARMbased micro controller with 128 K byte flash memory. The two signal output of 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 diagram Hardware design AD9850 module AD9850 contains the DDS system and highspeed parator. The AD9850 can realize the entire numerical frequency bining. The core of the programmable DDS is the phase accumulator, it is posed of a ADR and a N bit phase register, N is for 24 ~ 32. After 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。 the voltage can be adjusted by tuning the PWM dutyfactor. The system output three PWM signals, which controls AD9850 output extent, dutyfactor and the output extent of DAC0832, respectively,. Fig. 3 shows the PWM controls DA transferring circuit. Fig. 3 PWM controlled DA converting circuit Fig. 4 Export amplification and the wave filtering circuit. (a) amplification circuit。 (b) filtering circuit Amplification and wave filtering circuit The amplification circuit will export amplified wave form and modify the factor of amplification. An excellent smooth output waveform can be achieved by using the lowpass active power filtering. The amplification circuit and the filtering circuit is showed in Fig. 4. Software design And the system software mainly include AD9850 driving module, DAC0832 driving module, the stepbystep automation module, PWMconvertingDA module and uC/GUI figure supporting system implanted in procedure. The operation interface is full of humanization for the multiwindow pattern is adopted. The design process of the system software is shown in Fig. 5. Implanted uC/GUI The numerical control signal source has used the uC/GUI software sufficiently to establish many windows and control buttons. By means of invoking the corresponding windows and control with the feedback information, the p
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