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直接数字合成
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  direct digital synthesis
    As a result, a dual admittance blood flow monitoring system was designed and implemented. In the hardware, silver chloride electrodes was adopted. The constant current exciting source was composed of direct digital synthesis sinusoidal (DDS) wave generator and operational amplifier.
    系统硬件部分采用氯化银贴片电极,由直接数字合成正弦信号发生器、运算放大器构成恒流正弦激励源,通过前置放大、检波整流以及低通放大电路完成对阻抗响应信号的解调,并将解调后的信号经过运算放大器滤波放大后由12位并行模数转换器(ADC)采集进入上位机。
短句来源
    This paper is to design a current-mode multi-frequency impedance exciting source which adopts direct digital synthesis technology.
    目的:设计一个采用直接数字合成技术的电流模式多频阻抗激励源。 方法:作者设计了基于DDS芯片AD9850的波形发生单元和基于AD844的电压电流转换单元的阻抗激励源系统。
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  “直接数字合成”译为未确定词的双语例句
    Following is the main content:1).
    1)、开发了基于直接数字合成技术的多频阻抗激励源。
短句来源
    Methods A brand new signal generator for the neuron\|threshold stimulator was designed based on DDS and other new technologies, such as photoelectric coupling, isolated power, and floating\|ground technology, which were applied to replace traditional technologies like transformer isolation, etc.
    方法 基于直接数字合成 (directdigitalsynthesis ,DDS)以及其它新技术 ,设计出全新的信号发生源 ,采用光电耦合、高隔离电源以及浮地等方法 ,摒弃了传统的变压器隔离等技术 ,使神经阈值刺激输出的刺激信号能量较强且稳定 ,失真度低。
短句来源
    Based on DDS technique, the signal generator can create the sine wave signals, and it's amplitude, frequency and phase can be continuously adjusted.
    采用直接数字合成(DDS)技术构建正弦波发生器,幅值、频率、相位等连续可调;
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  direct digital synthesis
The DAC is intended for applications using direct digital synthesis, and focus has been set on reducing dynamic nonlinearities to achieve a high spurious free dynamic range (SFDR) at high generated frequencies.
      
Four channels of high precision frequency signals are generated by DDS(Direct Digital Synthesis).
      
However, in this case the added complexity is so high that currently it makes more sense to employ Direct Digital Synthesis.
      
Other possible approaches include external phase locking of non-synthesized generators and direct digital synthesis techniques.
      
This circuit topology is of special interest for use in direct digital synthesis applications.
      
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AIM To develop a signal source for data collection system of electrical impedance parameter tomography. METHODS Based on direct digital synthetic technique, sweeping frequency technique combined with mixing fre quency technique was employed to establish the signal source. This signal source has four output modes and the maximum output frequency number is four. RESULTS The frequency range of signal source is 1.6~380 kHz. The minimum frequency interval between any two frequencies is less than 100 Hz. The...

AIM To develop a signal source for data collection system of electrical impedance parameter tomography. METHODS Based on direct digital synthetic technique, sweeping frequency technique combined with mixing fre quency technique was employed to establish the signal source. This signal source has four output modes and the maximum output frequency number is four. RESULTS The frequency range of signal source is 1.6~380 kHz. The minimum frequency interval between any two frequencies is less than 100 Hz. The noise level of output is about -80 dB, and the signal to noise ratio is up to 60 dB. CONCLUSION By combining sweeping frequency technique with mixing frequency technique, the measure flexibly frequency can be selected. And the signal precision as well as the measuring speed can also be controlled easily. These make it possible for high quality data to be acquired in electrical impedance parameter tomography.

目的 研制用于电阻抗参数成像数据采集系统的信号源 .方法 基于直接数字合成技术 ,以扫频和混频相结合的方式建立了具有 4种工作模式、最多可同时输出 4种频率成分的信号源 .结果 信号源的输出频率可以在 1.6~ 380k Hz的频带范围内以小于 10 0 Hz的跨度编程选择 ,输出的噪声水平在 - 80 d B左右 ,信噪比大于 6 0 d B.结论 用多频率组合与扫频相结合的方式可以灵活地改变测量频率 ,控制信号的精度及测量的速度 ,为高质量的数据采集提供了保障 .

A master - slave data acquisition system based on DSP is designed. Based on DDS technique, the signal generator can create two channels of the sinewave and the square wave signals, and its amplitude, frequency and phase can be continuously adjusted. The measured signal is demodulated by an analog multiplier, and the information of real and imaginary components is obtained, then the image can be reconstructed by sensitivity coefficient algorithm. The test and image construction results show that the MEIT system...

A master - slave data acquisition system based on DSP is designed. Based on DDS technique, the signal generator can create two channels of the sinewave and the square wave signals, and its amplitude, frequency and phase can be continuously adjusted. The measured signal is demodulated by an analog multiplier, and the information of real and imaginary components is obtained, then the image can be reconstructed by sensitivity coefficient algorithm. The test and image construction results show that the MEIT system has high data acquisition speed and image resolution.

文中设计基于DSP的主从式MEIT数据采集系统。采用直接数字合成(DDS)技术构建双路正弦波及同步方波发生器,实现幅值、频率、相位等连续调节:调制信号经同相与正交解调,获取实部与虚部信息,利用灵敏度系数算法进行图像重建,试验测试与成像结果表明,本系统不仅采集速度快而且图像分辨率高。

Objectives To resolve the difficult problems when carrying out animal experiment and clinical application of neuron\|threshold analog stimulator, a simulator based on direct digital synthesis (DDS) technology was designed for the project of “the mapping of neuron\|threshold in human brain and its clinical application”.Methods A brand new signal generator for the neuron\|threshold stimulator was designed based on DDS and other new technologies, such as photoelectric coupling, isolated power, and floating\|ground...

Objectives To resolve the difficult problems when carrying out animal experiment and clinical application of neuron\|threshold analog stimulator, a simulator based on direct digital synthesis (DDS) technology was designed for the project of “the mapping of neuron\|threshold in human brain and its clinical application”.Methods A brand new signal generator for the neuron\|threshold stimulator was designed based on DDS and other new technologies, such as photoelectric coupling, isolated power, and floating\|ground technology, which were applied to replace traditional technologies like transformer isolation, etc.Results The signal generated by the neuron\|threshold stimulator based on DDS was observed and the output sine wave FFT was done with oscilloscope (TDS 3034B).The total distortion was less than 1\0%.Conclusion The newly designed neuron\|threshold stimulator based on DDS is good to meet the requirements of the project of “the mapping of neuron\|threshold in human brain and its clinical application.”In respect of non\|distortion of output signals, stability and strength of stimulating energy, reliability of the entire machine, safety, etc.,there are great improvements, compared with the analog stimulator.

目的 针对基于模拟函数信号发生器的神经阈值刺激仪在动物实验和临床应用过程中遇到的实际困难和问题 ,为了满足科研项目“神经阈值图谱绘制及其临床应用研究”对神经阈值刺激仪各项指标的要求 ,重新设计、调试、改进神经阈值刺激仪。方法 基于直接数字合成 (directdigitalsynthesis ,DDS)以及其它新技术 ,设计出全新的信号发生源 ,采用光电耦合、高隔离电源以及浮地等方法 ,摒弃了传统的变压器隔离等技术 ,使神经阈值刺激输出的刺激信号能量较强且稳定 ,失真度低。结果 仪器整机安装调试后 ,就仪器输出的正弦波信号 ,用TDS30 34B数字存贮示波器对其观察并进行FFT处理 ,经计算可知 ,信号总波形失真度小于 1 0 %。结论 重新设计的神经阈值刺激仪无论从输出信号失真度上还是从刺激能量的强度和稳定度上 ,以及整机的可靠性、安全性等诸方面 ,都基于模拟函数信号发生器的神经阈值刺激仪有重大进步或改善 ,完全满足科研项目“神经阈值图谱绘制及其临床应用研究”对神经阈值刺激仪各项指标的要求。

 
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