共查询到19条相似文献,搜索用时 62 毫秒
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DDS技术在高频石英晶体测试系统中的应用 总被引:1,自引:1,他引:0
在此介绍了一种以DDS芯片AD9912作为信号源的高频石英晶体测试系统。AD9912是一款直接数字频率合成芯片。一方面,AD9912内部时钟速度可高达1GSPS,并集成了14位数/模转换器,可以直接输出400MHz信号;另一方面,AD9912的频率控制字为48位,可以小于4μHz的分辨率输出信号。由于采用了DDS芯片AD9912作为信号源,所设计的石英晶体测试系统能够在20kHz~400MHz范围内测试石英晶体的串联谐振频率。与国内目前普遍使用的基于振荡器和阻抗计测试方法的测试仪相比,该测试系统具有测试频率范围宽、重复精度高等优点。 相似文献
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目前国内石英晶体谐振器的测试仪器主要分为阻抗型的晶体测试仪(如广州电子仪器厂的CZ-8A型晶体阻抗计)和PI网络测试系统(如:美国SAUNDERS公司的250A晶体测试仪)两大类,其中阻抗型的晶体测试仪的测量准确度低、测试范围窄、测试项目少。而PI网络测试系统无论从准确度和测试项目上都要比阻抗型的晶体测试仪好的多,所以PI网络测试系统将起着越来越重要的作用;晶体的谐振频率作为晶体的关键参数,它的测试不确定度也越来越引起人们的重视,本文将对PI网络测试系统的代表产品美国SAUNDERS公司的250A晶体测试仪测试晶体频率的不确定度进行分析。 相似文献
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为了研究常温状态下石英旋光晶体透射谱线,根据石英旋光晶体透射比的理论分析,采用UV-3101PC分光光度计实际测试,得到了300nm~1500nm波长范围特定厚度石英旋光晶体的连续透射谱线,并对所得谱线与理论结果进行了对比分析。结果表明,400nm以内由于石英晶体吸收比较明显,从而峰值透射比低于50%,由于旋光率随波长变化率很大,谱线周期很小;400nm~800nm之间峰值透射比60%,透射谱线的周期性及峰值个数受晶体厚度影响明显;波长大于1000nm时,由于旋光率随波长变化率很小从而谱线周期很大,并且谱线不规则,与石英材料波长选择吸收有关。 相似文献
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微波鉴相器的鉴相误差分析 总被引:2,自引:0,他引:2
分析了微波鉴相器的鉴相原理,并用散射矩阵的方法分析了微波鉴相器的鉴相误差与微波相关器的幅度、相位及检波器的检波系数之间的关系,给出误差函数及图表,明确了鉴相误差与鉴相角相关这一事实. 相似文献
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通过对设计出的一维掺杂光子晶体的数值计算和理论分析,得出:双通道透射峰的波长随杂质光学厚度呈线性变化和双通道透射峰的半高宽随光子晶体折射率n2的增加而减小.以此为基础,设计出可调波长范围达140 nm、滤波通道半高宽的可调范围在1~5 nm、滤波通道透射峰值大于0.98的一维光子晶体双通道可调谐滤波器. 相似文献
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相位法激光测距广泛应用于距离测量,尤其是短距离测量领域,测距系统的测量精度和速度主要取决于鉴相器的设计,为提高鉴相器的测量精度和速度,本文给出了一种新型数字鉴相器。通过加入反馈电路控制信号调制器,只需一组鉴相器即可实现激光发射信号与接收信号相位差的测量。调整CIC滤波器的参数,最大限度地提高滤波器输出信号的信噪比。对CORDIC算法进行优化,不仅扩展了测量范围,而且提高了测量精度和速度。本文使用Matlab对该数字鉴相器进行了性能评估,并在FPGA上实现了该数字鉴相器,与传统的数字鉴相器相比,测量精度和速度都有较大的提高,同时也降低了设计成本。 相似文献
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V. N. Bondarenko 《Journal of Communications Technology and Electronics》2007,52(3):339-342
An optimal phase discrimination algorithm for phase tracking of a spread-spectrum signal with minimum frequency-shift keying is proposed. The noise immunity of the algorithm is analyzed. 相似文献
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抗高过载石英晶体元件的研制 总被引:1,自引:0,他引:1
使用一种简单实用的设计方法,采用特殊的结构设计,研制出的石英晶体元件具有抗高过载的能力.这种产品可制作的频率范围是3~60MHz,具有抗冲击力在1000~20000g,结合试验验证,这种石英晶体元件在经受高冲击后,仍然能够稳定的工作,所以充分证明了石英晶体元件通过采用这种特殊的结构,完全可以达到具有抗高过载(冲击力在1000~20000g)的能力.解决的关键问题是石英晶体元件晶片的设计、结构的设计及加工过程中应注意的问题. 相似文献
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《Vehicular Technology, IEEE Transactions on》1986,35(3):106-117
Recently, bandwidth efficient constant-amplitude digital modulation schemes have also been shown to be power efficient when coherent detection is used. Partial-response continuous phase modulation (CPM) schemes are within this class. In some applications noncoherent detection is preferred. The performance of CPM systems is analyzed for differential and discriminator detection. An additive white Gaussian channel is assumed. The detectors make symbol-by-symbol decisions. The considered schemes are M-ary with an arbitrary modulation index and pulse shaping over several symbol intervals. The performance is analyzed by means of error probability expressions. The IF filter for the detectors is optimized within a special class of filters to give good performance. The differential detector is also analyzed on a Rayleigh fading channel. The fading is assumed to be slow. The IF filter is also optimized on this channel. Simulated error probabilities for discriminator detection with a Viterbi detector are also presented both for the Gaussian and the Rayleigh fading channel. The discriminator detector making symbol-by-symbol decisions is simulated on the Rayleigh fading channel. It is shown that partial-response CPM schemes with good performance can also be obtained with noncoherent detectors. 相似文献
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A technique for the analysis of two-channel high-definition television (HDTV) transmission systems is presented. Design methods based on limitations due to the combined spatial and temporal characteristics of the human visual system (HVS) are developed. The concepts of resolution imbalance, recognizability, and spatial-temporal multiplexing are explained. The design and analysis of two-channel NTSC-compatible HDTV systems having an aspect ratio of 16:9 with double the vertical and horizontal resolution of the present NTSC system is described. It is shown that such a system requires more than two channels for transmission. Signal processing techniques are suggested to improve the quality of the images without using any extra channels. Time multiplexing of different frequency bands are used to exploit the psychovisual redundancies of the HVS to reduce the number of pels to be transmitted. Finally, comparing the spatial resolutions of the reconstructed images by a two-channel HDTV system with that of the HVS, it is found that the spatial resolution are not yet as good as that of the HVS 相似文献
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为了研究SMD石英晶体的抗高过载能力,采用自由式霍普金森压杆对7050、6035、5032、3225、3225(一级加固)、3225(二级加固)六种型号SMD石英晶体进行高过载环境下的动态加载测试。结果表明,在高过载条件下,SMD石英晶体的抗高过载性能随尺寸减小而不断提高,并且产品经历高过载环境后电气参数的不良率逐步降低。未经过加固处理的各型号SMD石英晶体(7050、6035、5032、3225)经过高过载试验(50 000~80 000 g)后,电气参数均出现超差,不能满足武器系统的要求。经过加固处理的SMD石英晶体样品(3225一级加固、3225二级加固)经过高过载试验可以正常工作。 相似文献
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A new method has been developed to drive a single quartz crystal in both of its modes. Using a modulator and a demodulator the oscillator provides a C mode frequency output directly as well as the difference frequency between the C and B modes. Results concerning this dual-mode oscillator used in a digital temperature compensated quartz crystal oscillator (DTCXO) are reported. 相似文献