To focus ultrasonic energy by using electromagnetic ultrasonic phased array technology in a buried steel pipeline, and improve detection accuracy on the pipe wall, this paper presented a method of high frequency and high power multi-channel exciting source based on radio frenquency ( RF) theory and class-DE power amplifier technology. Multi-channel pulse sequence of time sequence and phase delay was realized by using filed-programmalbe gate array ( FPGA) and digital delay method. High frequency"floating gate" problem of the exciting source was effectively solved by optical fiber isolated pulse signal and power isolation transformed reference potential. Based on operating characteristics of the class-DE switch tube and power amplifying circuit, a class-DE power amplifier simulation model was established by using Pspice software. Experimental data shows that when it is working in the operation frequency of 1. 1 MHz and voltage of 300 V, the design of exciting source can output 1 ns delay pulse sequence, the output power of electromagnetic ultrasonic array element is 1. 5 kW, and Ip-p is 20 A of alternating current, which meet the requirements of inspection technology of electromagnetic ultrasonic phased array.%为实现电磁超声相控阵在埋地钢质管道内超声波能量聚焦,增强管壁缺陷检测精确度,基于射频理论及DE类功率放大器技术,提出了一种电磁超声相控阵多通道大功率高频激励源设计方法.通过现场可编程门阵列(field-programmable gate array,FPGA)数字延迟方式对采样时钟进行精确控制,以实现激励源多通道脉冲序列时序和相位的延迟.采用光纤隔离脉冲信号以及电源隔离转换参考电位,有效解决了激励源高频"浮栅"驱动问题.研究了DE类功率放大器开关管和放大电路的工作特性,并基于Pspice软件建立了DE类功率放大器仿真模型,实现了对放大电路元件参数的优化和性能指标的验证.实验结果表明:设计开发的激励源能够实现1 ns延时精度的脉冲序列,当工作频率为1.1 MHz以及工作电压为300 V时,电磁超声阵元输出的交变电流峰峰值为20 A,输出功率为1.5 kW,从而满足电磁超声相控阵检测技术的要求.
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