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1.
Ahmed Helmy Khaled Sharaf Hani Ragai 《Analog Integrated Circuits and Signal Processing》2003,37(3):139-148
A noise analysis of bipolar harmonic mixers (BHM) used for direct-conversion receivers is presented in this paper. Analytical and simulated results for the transfer function of the mixer are presented. Simple analytical expressions describing noise contribution from all sources are derived. Estimation of flicker noise quite agrees with harmonic-balance simulation results. Based on the derived expressions, total time average noise power spectral density (PSD) at the output is compared with simulation results. For the recommended regions of operation, error is less than 20%. The overall BHM noise figure (NF) is calculated and optimized based on a simple extracted formula. Errors introduced by analysis remain within a 1.5-dB margin with respect to simulation results. The validity of analysis for high frequencies is justified. The effect of flicker noise coefficient on the overall mixer NF is compared for different available processes. 相似文献
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谢伟 《数字社区&智能家居》2014,(8):5303-5306
基于视频的火焰检测算法为解决传统感烟感温火焰检测方法受环境制约的问题提供了一条新的路径。通常的视频火焰检测算法主要利用火焰的颜色、形状、频域特征等信息来进行检测,计算较为复杂,往往不能达到实时性。文中结合火焰的颜色、运动特性以及频闪特性,提出一种简单高效的视频火焰检测方法。首先使用ViBe算法提取出视频中的运动区域作为火焰候选区域,以降低计算量,再通过火焰的颜色模型筛选出疑似火焰区域,最后根据火焰的频闪特性建立一个简单的频闪模型,进一步滤除与火焰颜色相似的非火焰运动区域。通过实验证明,该文提出的算法能够检测出不同环境下火焰的发生,且执行效果较高。 相似文献
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时频联合分析评判火焰燃烧稳定性的实验研究 总被引:1,自引:0,他引:1
通过改变燃气量和一级空气量完成一系列燃烧工况。采用低成本的火焰检测装置采集得到各个工况火焰辐射的脉动信息,利用快速傅里叶变换算法将获得的时域信号衍生出频域上的功率谱信号。从时域信号的周期性能和频域信号中主峰频率的波动情况提取出反应火焰脉动性能的参数:火焰强度比方差和火焰闪烁频率,通过联合分析得到其随时间和燃烧状态变化的规律,实现对燃烧稳定性能的评判。 相似文献
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Fei‐Bo Duan Peng‐Fei Bai Alex Henzen Ling‐Ling Shui Biao Tang Guo‐Fu Zhou 《Journal of the Society for Information Display》2016,24(11):676-685
Electrophoretic display (EPD) technology is attractive when used for reading devices such as e‐paper because of its paper‐like appearance. EPD driving is more complex than other display technologies such as liquid crystal display or organic light emission diode because the driving result of a pixel strongly depends on the initial display state. The particle size and distribution in the EPD film may vary, even if the initial state is the same. Therefore, the display devices vary between different manufacturing batches. Furthermore, different display modes such as videos, pictures or documents need different driving waveforms to achieve an optimal result. EPD manufacturers need to build a customized driving waveform for every manufacturing batch. This is very inconvenient if new applications on EPD are to be developed. And the workload is huge. In this work, an adaptive method is described for automatically creating EPD driving waveforms to fit different conditions. The central idea of this method is generally adjusting the driving time and the voltage state after getting the feedback from a measurement model. In this method, a new driving waveform is used to reduce refresh time and visual flicker. The experimental results show that the proposed approach can automatically and adaptively generate an EPD driving waveform with reasonable quality. 相似文献
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Abstract— In this paper, the perception of flicker in time‐sequential or field‐sequential 3‐D LC TVs driven by LED backlights is described. The seriousness of the perceived flicker and its influence on visual discomfort is investigated for various backlight operational modes. Results show that display backlights presenting different temporal light distribution have significant contribution to flicker visibility and visual discomfort. The display dimension, 2‐D or 3‐D, affects visual discomfort but not flicker visibility. The relationship between visual discomfort and flicker visibility is proportional when rendering 2‐D images, but not in the case of 3‐D images. Finally, a simple model is presented to evaluate visual discomfort related to flicker in 2‐D rendering. 相似文献
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A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven
light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method.
Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics
problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage.
Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer.
The experimental result shows that the proposed PWM dimmer has good performances. 相似文献
10.
论荧光灯频闪效应及其电子镇流器的设计误区 总被引:1,自引:0,他引:1
荧光灯(含CFL节能灯)均存在不同程度的频闪,客观上长期危害人的健康和损害人的视觉系统,而解决和降低办公场地、工厂企业、教学科研、生活居住等环境大面积照明时荧光灯频闪效应的有效和重要的途径之一是采用符合电磁兼容(EMC)标准要求的电子镇流器,并同时大幅提高电子镇流器的工作频率(≥40KHz)。本文就此作了较详细的阐述。 相似文献