函数信号发生器外文文献翻译(3)

Fixed output voltage regulator part selects three-terminal integrated voltage regulator. The use of three terminal regulator can be easily integrated form of fixed output power supply.

4.Software

The software design adopts C programming language and programs different functional modules by the modularization program design idea. This structured approach enables program-level clarity, ease of use, maintenance, and debugging. The software design completes management of all the features of the signal generator, the initialization module, and the function modules of two parts. Initialization module is for the various hardware registers, data registers, and display device initialization.

Initialization module design is composed of four parts-the microprocessor initialization, AD9850 chip initialization, AD7520 chip initialization and LCD1602 initialization.

Function module is a display module, keyboard input module and signal conditioning modules and amplitude components. The keyboard module is mainly used to set the frequency, phase and amplitude.

The main system software programming method uses the structural method. The function modules separate from the main program and subprograms generated waveforms. Delay can be inserted to change the frequency.

Firstly, we perform the initialization of the micro controller, AD9850, AD7520 and LCD displays. Then we choose waveform by keyboard. The frequency adjustment is done through the AD9850 chip and the waveform amplitude modulation can be accomplished

through the AD7520 chip.

The entire process to achieve the following functions: plug in the power, the liquid crystal display, and then loop. If a key is detected, it is implied that data transmission circuit begins. The program continues to detect the keyboard and the control of different keys have different functions.

As long as the signal generation module outputs a few basic waveforms through the keyboard control, AD9850 chip can produce different waveforms with different frequencies through the linear combination. The amplitudes are relatively stable.

5.Conclusion

The designed signal generator is mainly composed of AT89S52 single chip microcomputer, AD9850 DDS chip, AD7520 chip, display circuit and filter circuit. The single chip microcomputer controls the whole circuit, the signal frequency generated by the AD9850 chip. The signal is filtered through the filter circuit. The AD7520 chip adjusts the signal amplitude under the control of the AT89S52 single chip microcomputer. We can observe frequency and amplitude of the signal through display circuit. By using the AD9850 chip, it is relatively high stability and the wave generated by the nonlinear distortion factor is relatively small. The system is not only simple in structure, easy to implement, but also convenient and cheap. It has a theoretical and practical value. Acknowledgements

This work is supported by National Natural Science Foundation of China (No. 10904073).

References

[1] Yong lun Wan, Qiang Si, You xin Lu, Xue gang Wang. Ultra-wideband radar signals generated technology with two-channel.

Signal Processing, Volume 87, Issue 12, 2007, Pages 3101-3107.

[2] Walt Kester. Direct Digital Synthesis (DDS). Data Conversion Handbook, 2005, Pages 677-691.

[3] Y. SUN, The new ATMEL's AT89S52 and its applications, 2004 - Beijing: Tsinghua University Press.

[4] CMOS 125MHz complete DDS synthesizerAD9850.

[5] Geoff Walker , Gerard Ledwich. Bandwidth Considerations for Multilevel Converters. IEEE Transactions on Power Electronics, 1999, 14 (1): 110221105