搜索到441650篇“ FREQUENCY“的相关文章
用于激光频率参数测量的飞秒光学频率梳
2024年
近年来随着光纤制造技术和飞秒激光技术的成熟,以掺铒(Er)光纤光学频率梳为代表的频率梳技术,逐步突破了光学频率测量领域,在长度测量、精密光谱分析、超低相位噪声微波频率产生、精密时间频率传递、温度测量等领域发挥出越来越重要的作用,已成为许多高端科研领域的基础性工具。但飞秒光学频率梳所解决的重要问题是对激光频率进行测量。本文主要面向激光频率参数测量的需求,研制基于掺Er光纤飞秒激光器的光学频率梳,在实现光学频率梳稳定运转的前提下,通过非线性光学频率变换技术,实现光谱范围从掺Er光纤光学频率梳的中心波长向各个待测激光波长的转换,并完成与多个不同波长激光的拍频信号探测。目前已验证的飞秒光梳可测频率范围为500~2000 nm;频率稳定度和准确度为10^(-16)量级;线宽为Hz量级。该指标满足了激光频率特性参数测量的需求,为激光绝对频率、频率漂移、线宽等参数的测量提供了基础性的测量工具。
韩羿曹士英宋文霞左娅妮房芳
关键词:频率测量拍频稳定度线宽
High Sensitivity Digital Instantaneous Frequency Measurement Receiver for Precise Frequency Analysis
2024年
There are numerous applications, such as Radar, that leverage wideband technology. However, the presence of noise introduces certain limitations and challenges. It is crucial to harness wideband technology for applications demanding the rapid and precise transmission of diverse information from one point to another within a short timeframe. The ability to report a signal without tuning within the input bandwidth stands out as one of the advantages of employing a digital wideband receiver. As indicated, a digital wideband receiver plays a pivotal role in achieving high precision and accuracy. The primary distinction between Analog and Digital Instantaneous Frequency Measurement lies in the fact that analog Instantaneous Frequency Measurement (IFM) receivers have traditionally covered extensive input bandwidths, reporting one accurate frequency per short pulse. In the contemporary landscape, digital IFM systems utilize high-sampling-rate Analog-to-Digital Converters (ADC) along with Hilbert transforms to generate two output channels featuring a 90-degree phase shift. This paper explores the improvement of sensitivity in current digital IFM receivers. The optimization efforts target the Hilbert transform and autocorrelations architectures, aiming to refine the system’s ability to report fine frequencies within a noisy wide bandwidth environment, thereby elevating its overall sensitivity.
Bilal AbdulhamedChien-In Henry Chen
Enhanced Wideband Frequency Estimation via FFT: Leveraging Polynomial Interpolation and Array Indexing
2024年
Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pose computational demands, and estimating non-integer multiples of frequency resolution proves exceptionally challenging. This paper introduces two novel methods for enhanced frequency precision: polynomial interpolation and array indexing, comparing their results with super-resolution and scalloping loss. Simulation results demonstrate the effectiveness of the proposed methods in contemporary radar systems, with array indexing providing the best frequency estimation despite utilizing maximum hardware resources. The paper demonstrates a trade-off between accurate frequency estimation and hardware resources when comparing polynomial interpolation and array indexing.
Kiran JayaramaChien-In Henry Chen
关键词:SUPER-RESOLUTION
基于渐进可控频偏范围的多频实信号频率估计器
2024年
多频实信号的频率估计是应用面广的基础信号处理问题,其精度受限于难以降低各频率成分的谱间干扰。为根本解决该问题,提出可自动抑制谱间干扰的多频实信号频率估计器,具体以频偏范围可控的单频估计器为基础,通过迭代构造两种残差信号(即降序残差和排它残差)并将其馈入单频估计器,从而获得各成分频率估计结果。其特色在于,在迭代过程中,可渐进设置频偏范围参数,从而保证各频率成分可稳步地获得高精度估计结果。数值结果表明,该研究提出的多频估计器精度高于现有的多频估计器精度,具有宽广的应用前景。
黄翔东吕冲李燕平王晓雷
关键词:频率估计
基于图像处理与时频分析的跳频信号频率估计算法
2024年
针对电子侦察领域,复杂电磁环境中跳频信号频率估计的问题,结合图像处理技术提出一种基于时频分析的频率估计算法。首先基于干扰噪声与跳频信号时频特性的差异,通过BM3D与形态滤波的方法对时频图像中含有的高斯白噪声及扫频干扰进行滤除,其次组合采用灰度化、Roberts边缘检测、Hough变换等图像处理手段对信号的时频图像进行处理以突出目标信息,最后通过像素点搜索、阈值处理等方式定位时频脊线的确切位置,估计信号频率。仿真结果表明,该算法能够初步实现信噪比≥-8 dB且在低信噪比条件下保持估计均方误差处于10-5量级范围的信号频率估计,可完成对于低信噪比条件下跳频信号频率的估计。
王欣怡刘满国李柯达陈立功
关键词:电子侦察跳频信号频率估计图像处理时频分析
最大化电力系统频率最低点的并网风电机组频率支撑控制
2024年
为提高电力系统遭受大扰动后的频率稳定性,风电机组需具有主动频率支撑的能力。然而,现有的风机频率支撑控制大多直接模仿同步发电机的惯量及调频特性,未能充分发挥风机控制的灵活性。针对这一问题,从提升系统频率最低点这一核心需求出发,提出一种考虑系统一次调频特性的风机最优频率支撑控制。首先,以最大化频率最低点为控制目标,提出并严格证明了系统频率最优轨迹的通用形态。然后,构建了风机能量回收特性的定量表达,并以此为基础,结合系统频率响应模型逆向推导了风机的最优频率支撑控制。最后,仿真和对比验证表明,所提方法通过与系统原有的调频特性协同,从而显著提升了频率最低点,且对不同运行工况和扰动水平均具有较好的鲁棒性。
张宇博杨松浩郝治国
关键词:频率稳定风机
Frequency-Self-Adaptive Radio Frequency Power Harvester Enabled by Shape-Reconfigurable Liquid Metal
2024年
Radio frequency(RF)energy harvester as an efficient tool for capturing and converting the flourishing ambient RF energy provides a promising solution for long-term powering the wireless sensor networks and the Internet of things(IoTs).However,the actual distribution of the environmental RF signals is dynamically frequency-dependent due to the diverse wireless terminals only interacting with specified frequencies.To take full advantage of the RF energy carrying this characteristic,an intelligent RF energy harvester is in demand to automatically sense the frequency information of an incident signal and conduct the corresponding RF-to-direct current transformation process.Here,to the best of my knowledge,a frequency-self-adaptive RF harvester is first presented with the help of the shape-reconfigurable liquid metal,which can precisely identify and efficiently convert an arbitrary signal from the frequency span of 1.8 to 2.6 GHz.Companied with a microcontroller unit and a tensile system,the dynamic functionality of the entire system is comprehensively demonstrated,showing promising potential to significantly advance various fields,including sustainable IoT applications,green wearable technologies,and self-powered devices.
Cheng ZhangYuchao WangZebin ZhuHai LinKun WangXintong ShiYi DuChaoyun SongLong RenQiang Cheng
关键词:FREQUENCYPOWERHARVESTINGRECTIFICATION
Diagnosing ratio of electron density to collision frequency of plasma surrounding scaled model in a shock tube using low-frequency alternating magnetic field phase shift
2024年
A non-contact low-frequency(LF)method of diagnosing the plasma surrounding a scaled model in a shock tube is proposed.This method utilizes the phase shift occurring after the transmission of an LF alternating magnetic field through the plasma to directly measure the ratio of the plasma loop average electron density to collision frequency.An equivalent circuit model is used to analyze the relationship of the phase shift of the magnetic field component of LF electromagnetic waves with the plasma electron density and collision frequency.The applicable range of the LF method on a given plasma scale is analyzed.The upper diagnostic limit for the ratio of the electron density(unit:m^(-3))to collision frequency(unit:Hz)exceeds 1×10^(11),enabling an electron density to exceed 1×10^(20)m^(-3)and a collision frequency to be less than 1 GHz.In this work,the feasibility of using the LF phase shift to implement the plasma diagnosis is also assessed.Diagnosis experiments on shock tube equipment are conducted by using both the electrostatic probe method and LF method.By comparing the diagnostic results of the two methods,the inversion results are relatively consistent with each other,thereby preliminarily verifying the feasibility of the LF method.The ratio of the electron density to the collision frequency has a relatively uniform distribution during the plasma stabilization.The LF diagnostic path is a loop around the model,which is suitable for diagnosing the plasma that surrounds the model.Finally,the causes of diagnostic discrepancy between the two methods are analyzed.The proposed method provides a new avenue for diagnosing high-density enveloping plasma.
吴明兴谢楷刘艳徐晗张宝田得阳
The Planck Constant and Its Relation to the Compton Frequency
2024年
The Planck constant is considered one of the most important universal constants of physics, and despite all we know much about it, the physical nature of it has not been fully understood. Further investigation and new perspectives on the Planck constant should therefore be of interest. We demonstrate that the Planck constant also can be directly linked to the Compton frequency of one, which again is divided by the Compton frequency in one kg. If this is right, it means also the Planck constant is linked to quantization of matter, not only energy. However, as we will show the frequency of one when expressed in relation to kg will be observational time dependent. This means the missing mass gap surprisingly both is equal to the Planck mass, which is larger than any known particle and also it is linked to a very small mass that again is equal to what has been suggested as the photon mass in the existing literature. This new view could be an important step forward in understanding the physical nature of the Planck constant as well as the mass gap and even the rest mass of a photon.
Espen Gaarder Haug
关键词:ELECTRON
动态双频跳频电台接收端FPGA设计
2024年
为解决动态双频跳频电台跳频信号解跳频这一关键技术的硬件实现,依照动态双频跳频同步方案,设计了跳频电台接收端的整体结构,研究了跳频电台接收端解跳频的数学模型,采用Verilog HDL语言在EP4CE6F17C8芯片上实现了两种解跳频器设计方案,分别为IP核乘法器解混频+带通滤波+BPSK解调方案和加法树乘法器解混频+带通滤波+改进型DPSK解调方案。测试结果表明,两种方案都能实现跳频电台接收端解跳频器功能,后一方案消耗硬件资源更少,更符合跳频电台接收端多通道并行运算要求,为下一步研制动态双频跳频电台样机提供了技术参考。
张凤娟刘长水徐琨
关键词:跳频电台现场可编程门阵列

相关作者

姜仕仁
作品数:61被引量:429H指数:14
供职机构:浙江科技学院
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应怀樵
作品数:329被引量:656H指数:10
供职机构:北京东方振动和噪声技术研究所
研究主题:虚拟仪器 信号处理 模态分析 数据采集 DASP
刘进明
作品数:188被引量:237H指数:5
供职机构:北京东方振动和噪声技术研究所
研究主题:虚拟仪器 信号处理 频响函数 参数识别 DASP
李佳
作品数:15被引量:29H指数:2
供职机构:东南大学附属中大医院
研究主题:急性呼吸窘迫综合征 糖皮质激素 危重病 皮质醇 鲍氏不动杆菌
陈秋华
作品数:23被引量:48H指数:5
供职机构:东南大学附属中大医院
研究主题:急性呼吸窘迫综合征 肺复张 急性肺损伤 俯卧位通气 ARDS