说明：  本系统介绍USB接口波形发生器的设计。它采用直接数字频率合成（DDFS）技术，实时将USB接收到的数据转换成各种频率的波形输出，所使用的USB传输方式为全速同步传输。
(The design of USB interface waveform generator is introduced in this paper. It uses the direct digital frequency synthesis (DDFS) technology, real-time data will be converted to USB into a variety of frequency waveform output, the use of the USB transmission mode for full speed synchronous transmission.)