共查询到16条相似文献,搜索用时 156 毫秒
1.
本文分析了高频换能器接电缆后产生谐振频率漂移及阻抗改变的原因,并利用电路理论提出了电容匹配方案。计算了匹配电容抵消谐振频率漂移及阻抗改变的效果。实践证明方案切实可行。为高频基阵解决此类问题提供了理论依据。 相似文献
2.
3.
文章主要研究了一种低旁瓣圆形活塞高频换能器,采用去环非均匀分布方法实现低旁瓣,推导了去环非均匀圆形活塞换能器的指向性函数表达式,建立了指向性仿真模型,并采用Matlab软件进行仿真优化,对不同去环位置和不同去环宽度的圆形活塞换能器旁瓣级变化规律进行了分析,并通过添加匹配层拓展带宽。制作了一款低旁瓣圆形活塞宽带高频换能器,并进行测量。实测结果与仿真基本一致,换能器实测最大旁瓣级为-22.4 dB,较均匀圆形活塞换能器旁瓣级降低了4.8 dB,中心频率为325 kHz,-3 dB带宽为150 kHz。 相似文献
4.
匹配层厚度振动换能器研究 总被引:2,自引:0,他引:2
随着水声信号处理技术的发展,对宽带信号的需求日益增长。换能器的带宽是宽带信号处理的基础,而匹配层技术是拓宽厚度振动换能器频带最有效的方法。研究了多匹配层厚度振动换能器的设计方法,建立了复数形式的多匹配层厚度振动换能器等效网络模型,仿真研究了匹配层参数对换能器响应带宽的影响,指出了单、双匹配层在拓宽换能器带宽方面的限制,还指出匹配层的最佳厚度并非一定就是四分之一波长。在此基础上,制作了单、双匹配层换能器样品,对仿真结果进行了试验验证。测试结果和仿真结果符合得很好。 相似文献
5.
6.
7.
采用等效电路变换和多物理场有限元仿真计算进行压电水声换能器宽带匹配特性研究,得出不同匹配电路下的换能器电声性能的变化规律,合理选择电感电容值和串并联方式进行调谐匹配实现双峰谐振,一方面提高换能器的工作带宽,另一方面提高工作频率范围内的发送电压响应值并减小工作频带内响应值的起伏,依照仿真数据设计制作了一款球形换能器,采用串联电感进行调谐匹配,并测试调谐匹配前后的水中电声性能,对比匹配前后换能器性能的差异。结果表明,测试结果和仿真计算吻合,运用多物理场仿真计算手段对于预测分析水声换能器电声性能具有较好的指导意义。 相似文献
8.
匹配层对超声换能器的性能起着至关重要的作用,寻找合适的匹配层材料是换能器设计中的关键步骤。提出了一种基于环氧树脂-氧化铝复合材料的匹配层材料。首先,测试了不同配比的环氧树脂-氧化铝复合材料的声学性能,对比了其声学特性,并确定了材料的最佳配比。其次,研制了相应的换能器,分析该匹配层对换能器性能的影响,通过脉冲-回波方法测试了其性能参数。最后,基于四分之一波长匹配层原理对匹配层的厚度进行了优化。结果显示,环氧树脂中加入质量分数为 60%的氧化铝粉末的匹配层对换能器的改善效果最佳,该方案减小了换能器接收回波的拖尾,接收回波的幅值提高至 1 136 mV(+104%),-6 dB带宽达到 49.679%(+107%)。结果表明,氧化铝-环氧树脂混合材料可以提升换能器的声学性能,是较为理想的匹配层材料,在高频超声换能器的设计与应用中具有很好的应用前景。 相似文献
9.
10.
以160 kHz的超声果蔬清洗机为研究对象,设计了静态匹配电路。该电路由高频变压器实现阻抗匹配,串联电感实现调谐匹配。考虑到静态匹配只适合于换能器的一个谐振点,提出通过动态模拟换能器的工作状态来设计适合的匹配电感,使换能器在一定频率范围内,都可以维持在最佳状态。此外,为保证换能器参数变化后,仍能工作良好,设计了较实用的频率跟踪电路。 相似文献
11.
Lockwood G.R. Foster F.S. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1994,41(2):225-230
Obtaining an accurate transducer model for a high-frequency transducer can be troublesome using traditional models, such as the KLM model, since it is often difficult to measure precisely the piezoelectric, dielectric, and mechanical properties of the transducer. This paper describes an alternative method of modeling transducers using network theory. The network theory model for a transducer is determined from a measurement of the transducer impedance in water and the pulse-echo response of the system for a given electrical source and load. A discussion of how this model can be used to optimize the design of an electrical matching circuit is given. This method is illustrated by designing a two-element transmission line matching circuit for a miniature 53 MHz transducer. Excellent agreement between the network model prediction and the experimental response is obtained 相似文献
12.
针对声波测井压电换能器的多频点阻抗匹配技术展开研究,首先采用多模态等效电路精确描述了换能器的导纳特性;然后通过分析多模态阻抗匹配理论,设计电感-电容复合阻抗匹配网络,并结合换能器等效电路进行参数优化和电路仿真。实验表明,相比于换能器没有阻抗匹配的测试结果,该阻抗匹配技术可大幅提高换能器在谐振频率附近多个频率处的有功功率,频带内的有功功率平均提高了30倍,从而改善换能器的激励带宽和激励效率,提高测井仪器的适应性、探测深度和分辨率。 相似文献
13.
Son KT Lee CC 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2010,57(12):2784-2794
The input impedance matching technique of acoustic transducers at off-resonant frequencies is reported. It uses an inherent impedance property of transducers and thus does not need an external electric matching circuit or extra acoustic matching section. The input electrical equivalent circuit includes a radiation component and a dielectric capacitor. The radiation component consists of a radiation resistance and a radiation reactance. The total reactance is the sum of the radiation reactance and the dielectric capacitive reactance. This reactance becomes zero at two frequencies where the impedance is real. The transducer size can be properly chosen so that the impedance at one of the zero-crossing frequencies is close to 50 Ω, the output impedance of signal generators. At this off-resonant operating frequency, the reflection coefficient of the transducer is minimized without using any matching circuit. Other than the size, the impedance can also be fine tuned by adjusting the thickness of material that bonds the transducer plate to the substrates. The acoustic impedance of the substrate and that of the bonding material can also be used as design elements in the transducer structure to achieve better transducer matching. Lead titanate piezoelectric plates were bonded on Lucite, liquid crystal polymer (LCP), and bismuth (Bi) substrates to produce various transducer structures. Their input impedance was simulated using a transducer model and compared with measured values to illustrate the matching principle. 相似文献
14.
Huang SW Li PC 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2007,54(5):947-956
This paper proposes an approach to designing binary codes suitable for high-frequency applications of coded excitation in medical ultrasound. For a high-frequency ultrasound system, transmitting well-designed binary codes with a low sampling ratio (i.e., the bit rate divided by the transducer center frequency) is a practical way to improve the signal-to-noise ratio (SNR) because the challenge of implementing arbitrary-waveform generators for transmitting nonbinary codes increases with the frequency and the switching speed of square-wave pulsers are limited. One conventional approach designs codes using a base sequence that modulates wideband sequences up to the transducer passband. Because a major portion of codes is excluded as a candidate, codes designed using this approach typically need long compression filters for restoring the axial resolution, and they do not improve the SNR efficiently. In contrast, the approach proposed here searches all the codes that match the transducer passband; hence, the resultant codes exhibit better performance. The technique was tested using a bit rate of 50 MHz and a sampling ratio of 2. For a transducer with an ideal Gaussian frequency response with a center frequency of 25 MHz and a -6 dB bandwidth of 15 MHz, the SNR for the same side-lobe extent was 1 to 6 dB higher for the codes designed using the proposed approach compared with those designed using the conventional approach. When a real transducer response with a center frequency of 26.4 MHz and a one-way -6 dB bandwidth of 20.7 MHz was considered, the codes designed using the proposed approach were superior by 0.5 to 5 dB. Therefore, our approach is better than the conventional approach for designing binary codes for high-frequency ultrasound, with the results indicating that the moderate bit rate of 50 MHz will suffice when the ultrasonic center frequency is 25 MHz. 相似文献
15.
16.
Sleva M.Z. Hunt W.D. Connuck D.M. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(4):626-627
A novel ultrasound tissue characterization system is described which utilizes a network analyzer, S-parameter test set, 180° hybrid junction, and a mock transducer circuit to exploit the wide-band potential of a commercial piezoelectric polymer transducer. The relatively short round-trip pulselength achieved using the system (70 ns in water) is compared to that obtained using a high-frequency pulser/receiver and the same transducer (130 ns in water). Finally, the in vitro acoustic response of a section of neonate porcine carotid artery obtained using the network analyzer-based system is reported, along with histologic results for the same vessel 相似文献