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The exact input-output relationship is derived for a firstorder automatic gain control loop wherein the variable gain is an exponential function of the gain control voltage. The exact solution is compared to the linearized solution, and the condition for valid linearization is given. 相似文献
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A loop gain measurement technique for switching regulators using a digital modulator is introduced. While the conventional technique injects and measures the analog signals, the proposed digital modulator injects a digital perturbation and measures the resultant duty cycle modulation. Since the duty cycle signal, derived from all feedback loops, provides the ultimate control of a switching regulator, the loop gain defined at the duty cycle modulator is unique. Employing the digital modulator, this loop gain can be measured even with a switching regulator employing the current injected control. Furthermore, this new technique overcomes false measurement problems found in the conventional technique when the feedback signal at the point where the loop gain is measured contains a pulsating nature. 相似文献
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变增益控制是导弹控制中的常用方法.根据一个理想的瞬态响应,用优化计算的方法反求增益的变化规律,以达到计算控制增益的目的,并能最终很好地抑制干扰的影响.仿真实验表明,这种最优变增益控制至少与有角速度反馈的倾斜角控制系统的变增益控制方式效果相当,在大过载机动时比后者更好. 相似文献
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文献[1]根据|1+|来判断放大电路反馈极性和负反馈放大电路产生自激振荡的条件有不当之处,容易给学生造成误解.本文利用环路增益AF来判断放大电路反馈极性、反馈深度并讨论稳定性.首次采用环路增益的奈奎斯特图来分析反馈极性、反馈深度和稳定性.实验结果表明环路增益奈奎斯特图的成功引入,非常简单直观的解决了文献[1]中的不当之... 相似文献
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Smyth F. Kilper D.C. Chandrasekhar S. Barry L.P. 《Lightwave Technology, Journal of》2009,27(21):4686-4696
The reconfiguration of channel or wavelength routes in optically transparent mesh networks can lead to deviations in channel power that may impact transmission performance. A new experimental approach, applied constant gain, is used to maintain constant gain in a circulating loop enabling the study of gain error effects on long-haul transmission under reconfigured channel loading. Using this technique we examine a number of channel configurations and system tuning operations for both full-span dispersion-compensated and optimized dispersion-managed systems. For each system design, large power divergence was observed with a maximum of 15 dB at 2240 km, when switching was implemented without additional system tuning. For a bit error rate of 10-3, the maximum number of loop circulations was reduced by up to 33%. 相似文献
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This letter derives new gain control schemes for an amplify-and-forward single-frequency relay link in which loop interference from the relay transmit antenna to the relay receive antenna has to be tolerated. The proposed gain control schemes take into account the effect of residual loop interference that remains after imperfect loop interference cancellation. As a result of our gain control strategy, the signal-to-interference and noise ratio can be maximized while, at the same time, transmit power is decreased. Finally, we evaluate system performance by deriving closed-form outage probability expressions for the gain control schemes. 相似文献
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利用SMIC0.18μm COMS混合工艺,针对无线通信系统中的信号接收机,设计了一个能够工作在40MHz频带内的中频闭环可变增益放大器VGA,它包括可编程的输出电压和数字化的自动增益控制AGC电路。可编程的输出电压使得该VGA能够很好的适应不同应用方案下的动态范围要求,通常情况下,AGC电路依靠DSP基带芯片实现,然而,这里重点讨论从DSP芯片分离出来的数字AGC电路,独立的AGC电路使得VGA和DSP可以各自集中精力于自己的工作,降低部件相关性。该闭环VGA具有20dB增益调整范围。可编程输出AC电压峰峰值Vp-p,能够以每50mV为一档从100mV编程到300mV。 相似文献
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Călin Vlădeanu 《Circuits, Systems, and Signal Processing》2013,32(2):919-929
Space-time (ST) trellis coded modulation (TCM) represents a high spectral efficiency technique for multiple antennas transmissions over fading channels. In literature, it was shown that ST-TCM technique offers full diversity when the rank criterion is met. However, “brute force” methods were used in almost all previous work to search for full diversity ST-TCM codes. In the present paper, we aim to derive an exact expression for the minimum coding gain distance (CGD) in the case of full diversity ST-TCM codes with minimum memory size, for two transmit antennas. Therefore, we transpose the ST-TCM design rules into operations over the set of modulo-M integer numbers (Z M ), between the current trellis state and encoder’s input information symbol value, in order to derive the transmitted M-levels phase shift keying modulated (M-PSK) output values. In this context, a new design method is introduced to control the code’s minimum CGD value of full diversity ST-TCM schemes. 相似文献
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《Circuits and Systems Magazine, IEEE》2008,8(1):55-71
Introductory treatments of feedback amplifiers commonly contain inconsistencies, or present results as universal when in fact they need qualification. Loop gain, overall gain, input impedance and output impedance are instances. A case can therefore be made for rigorous development, even in a first course, provided mathematical rigor can be combined with physical insight. A feedback factor H is first defined for ideal circumstances. The corresponding forward-path gain G has an obvious physical interpretation: the amplifier without feedback, the external source and load impedances, and the feedback network are all involved, and the form of G is such as to suggest best practice for the various feedback configurations. Stability considerations, and precise values for overall gain, sensitivity, input impedance and output impedance follow directly from GH. 相似文献
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基于高双折射光纤环形镜L-band EDFA增益平坦实验 总被引:4,自引:4,他引:4
采用高双折射光纤环形镜进行了L bandEDFA的增益平坦实验。调节环内的偏振控制器,可以改变环的反射谱或透射谱的位置和深度;改变环内高双折射光纤的长度,可以改变环的反射谱或透射谱的波长响应周期。适当选取双折射光纤的长度和调节偏振控制器使环形镜的反射谱EDFA的增益谱相匹配。实现了L bandEDFA的增益平坦。双级结构的L bandEDFA经高双折射光纤环形镜平坦后,在1570~1595nm范围内,平均增益18.6dB,增益平坦度达±0.57dB。 相似文献
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基于光纤环形镜的L-波段掺铒光纤放大器增益的提高 总被引:3,自引:0,他引:3
提出了一种基于光纤环形镜作为反射器的反射式L-波段掺铒光纤放大器(EDFA)结构。光纤环形镜不但可以反射后向放大自发辐射(ASE)作为二次抽运源,而且还可以反射信号,使信号得到二次放大。当抽运功率为115mW时。在1570~1605nm波长范围内,反射式L-波段掺铒光纤放大器的平坦小信号增益达到29.14dB,与前向抽运方式L-波段掺铒光纤放大器相比(保持平坦性不变)。增益提高了5.33dB。分别输入波长为1580nm和1600nm的信号,反射式L-波段掺铒光纤放大器的饱和输出功率为7.63和7.6dBm.与前向抽运方式L-波段掺铒光纤放大器相比分别提高了2.98和3dB。 相似文献
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文章阐述变型电桥原理(MEBP)的创新思路,介绍射频信道变型电桥原理(MEBP)自动增益控制模型的传递函数、自动增益控制传递电压、自动增益控制的极限精度、增益控制算法和变型电桥平衡模型.然后阐述射频信道变型电桥原理(MEBP)自动增益控制方案,介绍自动增益控制传递电压的形成机理.最后列出S波段射频信道变型电桥原理(MEBP)闭环自动增益控制实验系统技术指标,利用温度实验数据绘制出增益控制精度的曲面.结果表明变型电桥原理(MEBP)自动增益控制的精度能够达到0.2dB. 相似文献
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总结了目前稳幅电路的一般形式和特点。提出了一种基于锁相环的新型自动增益控制电路结构,分析了电路特性,并对实际设计时一些重要参量的选取进行了较为详细的分析探讨。 相似文献
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L波段掺铒光纤放大器(EDFA)的增益介质具有本征增益平坦特性,但平坦增益值低,放大器实用性差,因此对放大器优化设计提高平坦增益有十分重要的意义。使用光纤环形镜(FLM)作为增益平坦滤波器进行L波段掺铒光纤放大器的增益平坦化实验,实现了高增益值的平坦输出。 相似文献
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The authors present a simple configuration of a gain-clamped semiconductor optical amplifier (GC-SOA) based on automatic intensity control of a feedback light generated by amplified spontaneous emission, using a narrow bandwidth thin-film-tunable filter. Experimental results show that the proposed amplifier has good gain clamping characteristics and the feedback light dramatically reduces steady and transient gain variations. The feedback light operates satisfactorily with the channel's add-drop frequency up to 20.9 kHz. We also examined the performance of the GC-SOA by employing the feedback light at different wavelengths. 相似文献