基于NIR-AOTF的超声换能器阻抗特性分析及驱动系统设计

摘要

从压电超声换能器的阻抗特性出发,在对换能器的输入阻抗及匹配网络进行了深入研究的基础上设计了一种基于高速单片机和直接数字频率合成器(DDS)的NIR-AOTF驱动系统.采用软件查表法将各个频段驱动信号所对应的电压幅值控制字做成表并保存在单片机中,实现了DDS在各个频段的恒功率输出,并采用新型的宽带阻抗变换网络加载在压电换能器,最终在30 MHz~80 MHz带宽范围内匹配网络S21>-0.276 dB,回波损耗S11<-10.173 dB.由于驱动电路提供功率为36 dBm,实验证明换能器获得功率高于35 dBm,达到超声换能器实际工作的3 W~4 W功率要求,NIR-AOTF的0级光谱衍射效率最高达73%.%Based on the impedance characteristics of the piezoelectric ultrasonic transducer,an NIR-AOTF drive system based on the high-speed single-chip microcomputer and the direct digital frequency synthesizer(DDS)was designed on the research basis of the input impedance and matching network of the transducer. Using the software look-up table method,the voltage amplitude control characters of each frequency drive signal were made into a table and stored in the single chip computer that realized the DDS in the various bands of constant power output. And a new broadband impedance matching network was applied to the piezoelectric transducer,Finally,the S21>-0.276 dB and the S11<-10.173 dB in the range of 30 MHz~80 MHz bandwidth.Because the driving circuit provided power at 36 dBm,experiments showed that the power of transducer is higher than 35 dBm,which achieves the 3 W~4 W power requirement of ultrasonic transducer in actual operation,and the maximum diffraction efficiency of the 0-stage spectrum of NIR-AOTF is up to 73%.