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本文讨论了原子钟内部的3种噪声即白色调相噪声,白色调频噪声和随机游走调频噪声对相位和频率估计的影响,分析表明,这3种噪声对相位估计和频率估计的影响完全不同,在相位估计中,选择适当的平滑长度和取样间隔可以控制估计误差,而在频率估计中,估计精度不能通过[估计器或测量设备的改进而任意提高,存在一个极限,这个极限由原子钟的内部噪声来决定。 相似文献
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对基于相干布居囚禁(CPT)态原子的芯片级原子钟技术进行了综述,包括CPT原子钟的基本原理、Ramsey?CPT原子钟技术、CPT原子钟的微小型化方案、CPT芯片原子钟的发展等,对其中的关键技术:激光频率调制、Ramsey技术、左右旋圆偏振光泵浦(push?pull)、激光和微波稳频以及微光机电加工系统(MOEMS)等技术进行分析讨论,最终总结出CPT原子钟向着低功耗、芯片化和时钟精度高的方向发展。 相似文献
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通过对LC压控振荡器原理的分析,设计了一种新型CMOS集成压控振荡器.该电路通过利用振荡器的输出产生高电压来控制开关电容阵列的开启来实现输出频率在不同频段中转换,从而提高输出频率范围和降低相位噪声.电路采用TsMc18rf工艺,用cadence的spectre工具进行仿真.结果表明:在0.6V的电源电压下,频率覆盖了2.07GHz到2.78GHz,可调控范围约为29%,总功耗约为1.8mw,1MHz频偏处相位噪声约为一120dB/Hz,满足了设计要求. 相似文献
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《振动与冲击》2017,(16)
频率估计和相位估计是物理学中的两个基本的测量问题。现有的估计器难以对这两个参数实现高精度的联合测量。为实现联合测量,对已有前后向子分段频率估计器做如下两方面改进:(1)对前、后向子分段快速傅里叶变换(Fast Fourier Transform,FFT)谱峰相位值做平均,获得中心样点的瞬时相位估计;(2)引入频移补偿措施,使得前、后向子分段的峰值谱能量更为集中,增强了估计器抵御噪声的能力,同时提升了估计器的频率和相位估计精度。理论分析和仿真实验表明,该联合估计器性能高于原有前后向子分段估计器和全相位FFT/FFT相位差估计器,对于频率偏离情况,其频率估计方差为克拉美-罗限的4/3倍,其相位估计方差可达到克拉美-罗限。 相似文献
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研制了基于单锥TEM室的短电磁脉冲标准场实验装置,并联合清华大学工程物理系、俄罗斯全俄光学与物理测量研究院,以D-dot传感器为传递标准,分别在中国和俄罗斯开展了短电磁脉冲标准场实验装置的实验室联合比对。比对结果表明,在单锥TEM室内θ=70°、 r=0.6m位置处,三方实验室测量的D-dot传感器响应波形与激励波形基本一致,传感器等效面积差异小于2%。比对结果进一步检验了单锥TEM室作为短电磁脉冲标准场装置的有效性,并验证了其用于短脉冲测量天线参数时域标定的技术可行性。 相似文献
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电磁干扰是通信系统在可靠性及设备安全性中必须考虑的因素,近些年迅速发展的高功率电磁脉冲对雷达天线等通信设备造成严重的威胁.提出一种新型电磁能量选择表面(ESS),该表面在十字形ESS的基础上增加了4个金属枝节,通过单元间加载PIN二极管获得自适应特性.在枝节处加载二极管可以在金属网格结构中引入栅格结构,有效增加屏蔽带宽,而且在透波模式下,枝节形成的二维狭缝阵列结构会在高频产生透射共振,使得表面在高频有一个频带使工作信号通过.仿真结果表明,提出的ESS在高功率电磁脉冲作用下会处于防护模式,其-20 dB带宽可达3.4 GHz;正常工作信号作用下ESS处于透波模式,此时表面为频率选择表面(FSS),其在低频和高频各有一个工作频带,低频部分带宽为0 GHz~1.3 GHz,高频谐振频率为5.36 GHz,带宽可达150 MHz. 相似文献
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脉冲磁场传感器的时域标定 总被引:9,自引:0,他引:9
针对脉冲磁场测量的要求,对传感器的时域标定问题进行了研究,组建基于高压脉冲源,TEM传输室,数字存贮示波器及计算机的时域标定系统,提出了基于输出误差模型的时域定数据处理方法,利用该模型可方便地获得的传感器的灵敏度,转折频率等参数,成功地利用所建立的误差修正模型对传感器造成的测量失真进行了恢复。 相似文献
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Lukacs M Yin J Pang G Garcia RC Cherin E Williams R Mehi J Foster FS 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(10):1719-1729
A new approach for fabricating high frequency (> 20 MHz) linear array transducers, based on laser micromachining, has been developed. A 30 MHz, 64-element, 74-microm pitch, linear array design is presented. The performance of the device is demonstrated by comparing electrical and acoustic measurements with analytical, equivalent circuit, and finite-element analysis (FEA) simulations. All FEA results for array performance have been generated using one global set of material parameters. Each fabricated array has been integrated onto a flex circuit for ease of handling, and the flex has been integrated onto a custom printed circuit board test card for ease of testing. For a fully assembled array, with an acoustic lens, the center frequency was 28.7 MHz with a one-way -3 dB and -6 dB bandwidth of 59% and 83%, respectively, and a -20 dB pulse width of -99 ns. The per-element peak acoustic power, for a +/- 30 V single cycle pulse, measured at the 10 mm focal length of the lens was 590 kPa with a -6 dB directivity span of about 30 degrees. The worst-case total cross talk of the combined array and flex assembly is for nearest neighboring elements and was measured to have an average level -40 dB across the -6 dB bandwidth of the device. Any significant deviation from simulation can be explained through limitations in apparatus calibration and in device packaging. 相似文献
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A. F. G. Wyatt I. N. Adamenko K. E. Nemchenko 《Journal of Low Temperature Physics》2002,126(1-2):609-614
We calculate the energy density of high energy phonons created from a pulse of low energy phonons spatially confined to a narrow cone. We include the tangential expansion of the propagating pulse and the interactions between high energy phonons within the pulse as well with low energy phonons. The expansion of the pulse causes it to cool so much that the creation of high energy phonons stops within 3 mm of the heater. The decay rate of high energy phonons governs the dynamic equilibrium inside the pulse. The magnitude of the high energy phonons, emitted by the pulse into the cold liquid helium, is calculated for different length pulses. It is found that small heaters can produce short pulses of high energy phonons from relatively long injected pulses. 相似文献
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The boundary element/exponential approximation technique for calculating the loaded straight wire horizontally located above a dissipative half-space is presented. The influence of a lossy ground is taken into account via Sommerfeld integrals appearing within the kernel of the electric field integral equation for thin wire. These integrals are computed by means of the exponential approximation technique. The resulting integral equation for loaded wire above an imperfect earth is solved by the boundary element method. Numerical results are obtained for current distribution along a resistively loaded dipole antenna and along a transmission line of a finite length. 相似文献