共查询到17条相似文献,搜索用时 156 毫秒
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输入信号的占空比对异或门混频器差频输出的影响 总被引:1,自引:0,他引:1
在基于频率输出的传感器测量电路设计中,经常碰到的一个问题是如何高精度测量由测量参数引起的小频率增量。将测量信号和参考信号经过混频器混频,通过低通滤波获得两信号差频输出的方法可解决这个问题。与其他数字混频器相比,异或门混频器在处理两准数字信号差频时有无可比拟的优势。通过理论分析、仿真和实际电路实验,考察了输入信号占空比的变化对异或门混频器差频输出性能的影响。结果表明:两输入信号为占空比50%的方波时,并或门混频器的差频输出性能最佳,滤波电路相对简单;随占空比的变化,异或门混频器的差频输出性能逐渐变差,需要辅以比较复杂的滤波电路。 相似文献
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单向液压脉动疲劳试验机负荷频率测量新方法 总被引:1,自引:0,他引:1
有效利用单向液压脉动疲劳试验机载荷信号特点,不使用专用频率传感器,采用同步等精度测频法,实现了试验机负荷频率的快速测量。为改善因被测信号周期变化导致测频精度下降的问题,提出周期自适应法;为克服在测量过程中由±1标准时钟脉冲产生的计数误差,采用了多路时延技术。通过在国产PMS-500试验机上实际测试,验证了该方法的有效性。 相似文献
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《仪表技术与传感器》2016,(8)
文中主要介绍一种以FPGA器件为控制核心的高精度数字频率计,其中待测信号经过输入缓冲电路,由FPGA采集并计数处理,最终测量结果显示在触摸彩屏液晶上。设计基于NiosⅡ,把采集部分和控制部分很好地融合在一起,辅之等精度测频法、多周期测时间间隔法和多周期测占空比法,从而达到精确、实时测量的目的。经试验验证,该系统能实现对输入频率从1 Hz~200 MHz周期信号的周期、频率、占空比和时间间隔的测量,测量精度优于10-7,稳定性和实时性好。 相似文献
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基于单片机和CPLD的高精度频率计设计 总被引:1,自引:0,他引:1
介绍了利用CPLD进行测频计数,单片机实施控制实现多功能频率计的设计电路的方法.利用等精度的设计方法,克服了基于传统测频原理的频率计的测量精度随被测信号频率的下降而降低的缺点,利用CPLD来实现频率、周期、脉宽和占空比的测量计数,利用单片机完成整个测量电路的测试控制、数据处理;显示输出部分也由CPLD来完成. 相似文献
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《仪表技术与传感器》2017,(4)
在工业现场利用应变传感器进行形变测量时,被测物在小负荷作用下使得传感器输出的应变信号十分微弱。微弱信号有时甚至会被现场的强噪声信号完全淹没,这时提取有效的微弱信号将变得非常困难。针对这种实际问题,应用相关检测法设计了基于正交锁相放大器的微弱应变信号检测系统。在设计中,待测微弱应变信号通过信号调理、低噪声放大和带通滤波后与严格正交的两路参考信号进行相乘。然后,将乘法器输出信号进行低通滤波得到与待测信号幅值成正比的直流信号。对直流信号经过A/D采集和计算实现微弱应变信号的检测。经过Simulink仿真、现场实验与运行,结果表明系统能有效地抑制噪声信号,准确测量出微弱的应变信号。 相似文献
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针对现有混沌振子难以检测频率未知微弱信号这一难点,提出利用Duffing振子输出值的方差峰值结合遗传算法检测淹没在强噪声背景中频率未知微弱信号的一种新方法。从分析混沌系统结构参数的阈值入手,讨论了周期策动力的频率、初始相位和噪声对系统运行状态的影响;研究系统输出值方差与系统状态的对应关系,探讨待测信号频率以及与周期策动力之间相位差对状态变量方差和状态转换时间的影响。由此,提出采用具有相位偏移的Duffing振子阵列覆盖全相位,并结合遗传算法,优化求解不同频率输入信号下系统输出值方差的极值,以此得到待测信号频率的方法。该方法解决了现有混沌振子类检测方法必须已知信号频率的限制。实验结果证明了本方法能准确、快速地检测待测信号频率。新方法的状态判定简便、检测精度高、更为灵活、适应性强,为微弱信号的检测提供了新的手段。 相似文献
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《现代制造技术与装备》2017,(7)
在泵站监测监控系统中,需要读取振动加速度传感器的频率信号。本文设计了一种基于PLC的频率测量接口电路,可用于泵站监测监控系统中振动加速度传感器频率及周期的测量。该电路具有测频、测周两种测量方式自动选择功能,并且具有较高的测量精度。 相似文献
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Cherednichenko S Drakinskiy V Berg T Khosropanah P Kollberg E 《The Review of scientific instruments》2008,79(3):034501
We report on low noise terahertz mixers (1.4-1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performance was characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K [double sideband (DSB)] at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4-4.8 GHz, the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEB stability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200-500 nW range. 相似文献
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Flip chips are widely used in microelectronics packaging owing to the high demand of integration in IC fabrication. Solder bump defects on flip chips are difficult to detect, because the solder bumps are obscured by the chip and substrate. In this paper a nondestructive detection method combining ultrasonic excitation with vibration analysis is presented for detecting missing solder bumps, which is a typical defect in flip chip packaging. The flip chip analytical model is revised by considering the influence of spring mass on mechanical energy of the system. This revised model is then applied to estimate the flip chip resonance frequencies. We use an integrated signal generator and power amplifier together with an air-coupled ultrasonic transducer to excite the flip chips. The vibrations are measured by a laser scanning vibrometer to detect the resonance frequencies. A sensitivity coefficient is proposed to select the sensitive resonance frequency order for defect detection. Finite element simulation is also implemented for further investigation. The results of analytical computation, experiment, and simulation prove the efficacy of the revised flip chip analytical model and verify the effectiveness of this detection method. Therefore, it may provide a guide for the improvement and innovation of the flip chip on-line inspection systems. 相似文献
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A quasi-optical diplexer for injection of signal and local oscillator frequencies into a mixer at millimeter wave-lengths is described. The diplexer accepts both image and signal bands, presents low loss at both the signal and local oscillator frequencies and rejects local oscillator noise at the signal frequency. The configuration of the device makes it particularly useful for Cassegrain receivers using a cooled mixer and a lens corrected feed system. The diplexer has been tested at 150 GHz on the 11-m radio telescope operated by The National Radio Astronomy Observatory in Tucson, Arizona. 相似文献
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Akash Kumar Anindya Debnath Antar Banik Kabirul Islam Mondal Partha Pratim Biswas Rik Bhattacharyya T K Maiti 《测试科学与仪器》2017,8(1)
研制了基于定时器的压频转换器, 电路主要由工作于非稳态多谐振荡器模式下的定时器LM555和两个光敏电阻构成. 由于数字存储振荡器测得的定时器输出波频率与所施加的输入电压基本呈线性比例关系, 所研制的转换器为类数字输出, 因此具有线性输入/输出关系、 体积小、 易携带和高性价比等优点. 此外, 定时器输出波可以直接与PC机、 微处理器或微控制器相连, 不需要模/数转换器就能完成对输入电压信号的进一步处理. 相似文献
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Yao JianjunWu ZhenshunHan JunweiYue DonghaiSchool of Mechanical andElectrical Engineering Harbin Institute of Technology Harbin China 《机械工程学报(英文版)》2004,17(4):628-630
The method for harmonic cancellation based on artificial neural network (ANN) is proposed. The task is accomplished by generating reference signal with frequency that should be eliminated from the output. The reference input is weighted by the ANN in such a way that it closely matches the harmonic. The weighted reference signal is added to the fundamental signal such that the output harmonic is cancelled leaving the desired signal alone. The weights of ANN are adjusted by output harmonic, which is isolated by a bandpass filter. The above concept is used as a basis for the development of adaptive harmonic cancellation (AHC) algorithm. Simulation results performed with a hydraulic system demonstrate the efficiency and validity of the proposed AHC control scheme. 相似文献