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五、拍频振荡器另一种被广泛作为低频信号发生器的是拍频振荡器.拍频振荡器的方框图如图1所示.高频可变振荡器和高频固定振荡器的工作频率,均较输出的低频高很多,经混频后,取其差频,不需要的和频及其他频率 相似文献
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针对传统时延控制波束形成器无法适应宽带信号接收的问题,提出一种宽带波束域频率聚焦自适应波束形成算法。首先,通过时延控制方法在空间预设方位形成多个独立波束,利用傅里叶变换将多波束数据变换到频域,针对每个频点构造聚焦矩阵,通过聚焦变换将宽带信号对齐到同一参考频率;然后,估计子带聚焦后的协方差矩阵,并进行特征分解得到信号子空间;最后,利用基于特征子空间(ESB)的波束形成方法得到权矢量,实现自适应波束形成。仿真结果表明,该算法能够实现对宽带信号的自适应接收,具有良好的抗干扰能力和稳健性。 相似文献
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本系统主要由电源、锁相环振荡器和稳幅电路三部分组成。实现了题目给定的基本要求,并出色地完成了设计任务的发挥部分。电路采用单片集成振荡器(MC1648)、变容二极管等组成压控振荡器产生正弦波;利用单片机(89C51)控制集成锁相环(BU2614)进而控制压控振荡器得到高频率稳定度的输出信号;利用振荡器内部AGC电路自动控制振荡器增益,稳定输出幅度;采集并显示输出信号幅度。键盘预置频率值以及振荡频率步进值,能根据需要设置不同的步进值。采用液晶显示输出频率、峰峰值,界面友好并有效降低系统功耗。多路输出的电源装置供给系统稳定运行所需各类电源。制作工艺特点是高频及部分低频电路采用印刷电路板,减小分布参数以及介质损耗对系统工作稳定性的影响。采用集成锁相环芯片进行振荡频率闭环控制,频率输出稳定度大大提高。 相似文献
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<正> 变频级是超外差式收音机的关键电路,其主要任务是把调谐回路选出来的某一频率的高频信号,转变为固定频率(465kHz)的中频信号,送到中频放大级进行放大。 变频级电路结构与原理 为了将高频信号转变成固定中频信号,就要在变频级电路中设置本机振荡器和混频器,并且要把由天线接收的输入信号和本机振荡器产生的本振信号同时加至混频器进行混频,然后通过调谐回路选择出所需要的固定中频信号,其电 相似文献
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本文介绍一种浅调频方案,它利用高频晶振和低中心频率的LC调频振荡器(VCO)混频得到70MH2调频信号,使频偏、非线性失真和频率稳定度三项互相矛盾的主要指标均满足要求。 相似文献
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用线性化近似方法计算了单模激光损失模型在输入偏置调幅波信号后的稳态平均光强相对涨落C(0)和输出功率S(ω),得到稳态平均光强相对涨落C(0)与载波信号振幅B、高频载波信号频率ω以及量子噪声强度Q的变化规律,发现在低频调制信号频率增大、高频载波信号频率减小、量子噪声实虚部关联越强和远离阈值时,激光系统的统计涨落较小。通过对系统功率谱S(ω)与a0/A、低频调制信号频率Ω、高频载波信号频率ω以及量子噪声实虚部间的关联系数λq的研究,也发现了一些特殊的现象。 相似文献
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单片机软件产生DTMF信号 总被引:2,自引:0,他引:2
1. DTMF信号的基本特征CCITT规定DTMF双音多频信号的标准频率如表1,频率误差小于±1.5%。8种频率分成高频群和低频群。从高频群和低频群中各抽出一种频率进行组合,共有16种组合,代表16个的数据,或代表通信领域中16个按键功能,如表2。通用发码电路采用3.579545Hz振荡器,分频后产 相似文献
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Canolty RT Cadieu CF Koepsell K Knight RT Carmena JM 《IEEE transactions on bio-medical engineering》2012,59(1):8-11
Phase-amplitude cross-frequency coupling (CFC)-where the phase of a low-frequency signal modulates the amplitude or power of a high-frequency signal-is a topic of increasing interest in neuroscience. However, existing methods of assessing CFC are inherently bivariate and cannot estimate CFC between more than two signals at a time. Given the increase in multielectrode recordings, this is a strong limitation. Furthermore, the phase coupling between multiple low-frequency signals is likely to produce a high rate of false positives when CFC is evaluated using bivariate methods. Here, we present a novel method for estimating the statistical dependence between one high-frequency signal and N low-frequency signals, termed multivariate phase-coupling estimation (PCE). Compared to bivariate methods, the PCE produces sparser estimates of CFC and can distinguish between direct and indirect coupling between neurophysiological signals-critical for accurately estimating coupling within multiscale brain networks. 相似文献
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微波信号调制电路设计与实现 总被引:1,自引:0,他引:1
在智能微波开关的发射电路中,对高频微波信号采用了低频和中频两级调制的方法。为避免现场多对智能微波开关之间的相互干扰,首先用37~51 Hz分8级可调的低频高占空比方波信号调制21 kHz固定频率的中频信号,再用该信号调制10 GHz的高频微波信号。在信号调制的同时,用低频信号控制MOS管对高频微波模块的DC-DC供电电源反馈回路进行干预,使DC-DC电路工作于最佳状态,输出电压峰值平稳,避免了高频发射模块间歇式工作对电源电路输出的影响,提高了智能微波开关的测量精度和工作的可靠性。设计结果与理论分析结果比较接近,达到了设计要求。 相似文献
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Multi-focus image fusion aims to produce an all-in-focus image by merging multiple partially focused images of the same scene. The main work is identifying the focused region and then composing all the focused regions. In this paper, a novel efficient multi-focus image fusion method based on distributed compressed sensing (DCS) is proposed. Firstly, the low-frequency and high-frequency images are obtained by comparing the variance of the source images, which are further utilized to get the low-frequency and high-frequency dictionaries. Secondly, DCS using joint sparsity model-1 (JSM-1) is applied to reconstruct the precise high-frequency images. Thirdly, the decision map is obtained based on all the high-frequency images and then improved by the morphological processing. Finally, the focused pixels are chosen from the source images through the decision map. Experimental results indicate that the proposed DCS-based method can be competitive with or even outperform some state-of-the-art methods in terms of both visual and quantitative metric evaluations. 相似文献
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混响效果器的冲激响应常常具有很长的长度,应用目前常规滤波器的设计方法很难在实时处理的条件下使误差、存储量和延迟较小.根据冲激响应的频谱能量基本上集中在低频这一特点,本文提出一种将高低频段分别处理的设计方法.首先对冲激响应和信号的低频段进行抽取,抽取后的冲激响应构成FIR滤波器,抽取后的信号通过这个滤波器后再进行零值内插,然后通过一个低通滤波器输出.冲激响应的高频部分在时间较长时渐趋于零.因而将其截断后再采用变换域处理方法获得信号高频部分的输出.这一方法对于TMS320C5402 DSP芯片来说,能够在使误差、存储量和延迟较小的条件下达到实时处理. 相似文献
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基于NSCT域压缩感知模型的路面病害图像滤波算法 总被引:2,自引:2,他引:0
针对目前路面图像滤波算法复杂度高且难以耦合噪声抑制和信号平衡的缺点,提出一种基于非下采样Contourlet变换(NSCT)域压缩采样的滤波算法。首先,使用NSCT对含噪路面病害图像进行分解,得到变换后的低频子带系数和高频子带系数;然后,对高频子带系数建立压缩感知(CS)去噪模型,并采用伪随机傅里叶矩阵对系数进行观测,之后使用分裂Bregman迭代方法对系数进行重构,得到去噪模型重建后的高频子带系数;最后,采用逆NSCT对低频子带系数和高频子带系数进行重构,得到滤波后的图像。实验结果分析表明了本文算法的有效性。 相似文献
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G. G. Denisov A. V. Smorgonsky V. P. Gubanov S. D. Korovin V. V. Rostov M. I. Yalandin 《Journal of Infrared, Millimeter and Terahertz Waves》1984,5(10):1389-1403
The stimulated scattering of electromagnetic waves in microwave generators, in which a high-current electron beam excites either a backward wave (BWO) or a quasi-critical frequency wave (orotron) is investigated experimentally. The scattering occurs at the same electron beam and the high-frequency feedback is provided by the inhomogeneities of the electrodynamic system of the microwave generator itself. A power of several tens of megawatts has been achieved in the 3-mm range. The mode selection permitted to obtain single-mode scattering. 相似文献
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Min Wang 《International Journal of Electronics》2013,100(9):1215-1227
An integrated circuit capable of generating very low-frequency signals for biomedical applications is presented in this article. By employing microwave circuit design concepts and techniques, the chip can produce very low frequency signals starting from a pair of 4?GHz signal generators. Measurements reveal that a continuous set of frequencies between 0.03?Hz and 185?Hz are generated, which represents a tuning range of 6167:1. The chip was fabricated using a standard 0.13-µm CMOS process and the circuit core measures 0.49?mm2. 相似文献
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提出一种采用小波变换(WT)及双字典协作稀疏表示分类(CSRC)的人脸识别方法-WT-CSRC.WT-CSRC首先利用PCA(主成分分析)将小波分解后的人脸高频细节子图融合成高频细节图像;然后用PCA分别对人脸低频图像和高频细节图像进行特征提取,构造低频和高频特征空间,并用训练样本在两种特征空间上的投影集构造低频字典和高频字典;最后将测试样本在两种字典上进行稀疏表示,并引入互相关系数以增强人脸识别的可靠性,实现了人脸的协作分类.实验结果表明,提出的方法提高了人脸识别率,对光照变化及表情变化具有较强的顽健性,并且具有较高的时间效率. 相似文献
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Bibey M.-B. Deborgies F. Krakowski M. Mongardien D. 《Microwave Theory and Techniques》1999,47(12):2257-2262
Additive phase noise is studied in directly modulated optical links (1.55-μm distributed-feedback laser and p-i-n photodiode). Up-conversion close to the microwave carrier, of the very low-frequency noise of the laser, is calculated. The phase-noise conversion factor is derived from the laser rate equations, as a function of laser parameters and modulation frequency. Noise sources are identified and included into the model to evaluate the microwave phase noise and then the noise-to-signal ratio in terms of phase fluctuations. Very low- and high-frequency relative intensity noise (RIN) laser measurements are performed. Theoretical RIN curves are calculated and laser parameters needed for the phase-noise model are deduced. Additive phase-noise measurements are performed. Good agreement is obtained between calculations and measurements. Very good additive phase-noise values have been obtained at 10-kHz offset: -148 and -139 dBc/Hz at 3 and 9 GHz, respectively 相似文献