[1] [1] Jia Shanghu. D flip-flop and a 555 timer make an orthogonal and pulse generator ［J］. Electronics and Automation, 2000, (5): 46-47(in Chinese).

[2] [2] Luo Xiaoqiao, Liao Xiaofang. Design of PWM signal generator based on CPLD ［J］. Electronic Measurement Technology, 2007, 30(12): 87-89(in Chinese).

[3] [3] Sun Qun, Song Qing. Portable signal generator based on direct digital synthesis ［J］. Instrument Technique and Sensor, 2009, (4): 67-70(in Chinese).

[4] [4] Microchip Technology Inc. PIC16F87XA Data Sheet ［OL］. 2013, http://www. microchip.com.

[5] [5] Wang Feng, Xia Wei, Wang Ming. Design of signal generator based on MCU and AD 9833 ［J］. Journal of Nanjing Normal University (Engineering and Technology), 2012, 12(1): 76-79(in Chinese).

[6] [6] Chen L, Liu G, Gao B, et al. Development of digital-controlled measuring instrument for hearing ［J］. Journal of Signal & Information Processing, 2012, 3(4): 421-426.

[7] [7] Analog Devices. AD9833-EP: Enhanced Product Data Sheet ［OL］. 2013, http://www.analog.com.

[8] [8] Hu Yu. Application of MAX038 in precision frequency synthesized waveform generators ［J］. Modern Electronic Technique, 2007, 30(1): 68-70(in Chinese).

[9] [9] He Jin. Talking about the selection and application of digital isolation device ［J］. Electronic Design Applicaton, 2008(2): 57-59(in Chinese).

[10] [10] NVE Corporation. High Speed Digital Isolators IL710 Data Sheet ［OL］. 2013, http:// www.nve.com.