CATV干线放大器的选择

ＣＡＴＶ干线放大器的选择广西田东县广播电视局黄宪伟引言如果说有线电视前端是整个有线电视系统的“心脏”的话，那么可以毫不夸张地认为干线是整个ＣＡＴＶ系统的“动脉”，因而干线的建设是整个系统建设不可忽视的问题。干线质量的好坏最大限度地取决于干线电缆和放大...     

谈谈AGC放大器在CATV干线上的使用

谈谈ＡＧＣ放大器在ＣＡＴＶ干线上的使用浙江省广播电视科研所张江鑫随着有线电视（ＣＡＴＶ）事业的发展，区域性有线电视网越来越大，从而对干线放大器提出了更高的要求。干线放大器的作用，就是补偿传输电缆对射频信号的衰减，高质量地把射频信号传的更远。为了补偿干...     

不同增益干线放大器的合理选用

不同增益干线放大器的合理选用２２４１００江苏大丰市广播电视局顾俊华近几年，我国城乡有线电视发展迅速，除超干线采用光缆传输外，同轴电缆干线传输在有线电视系统中还占有相当大的比重。目前市场上提供的干线放大器有增益为２０～２４ｄＢ的低增益放大器，也有增益为...     

传输干线设计中放大器级连与输入电平及增益的关系分析

要保证有线电视系统有高性能指标，除了各种器件具有优良的性能以外，必须对系统进行优化设计。大中型ＣＡＴＶ系统，放大器是传输干线的重要器件。在特定的系统中，接入的放大器数量是有限的。如果串接的放大器级数越多，则带入的噪声和失真就越大，从而会降低系统的指标...     

干线放大器输入,输出电平设计

１前言ＣＡＴＶ系统（即有线电视系统）包括前端、干线传输和用户分配三部分。其中,干线传输部分是整个系统的大动脉,它关系到整个系统的用户收看电视节目的质量。衡量干线传输信号质量的关键性指标主要有载噪比、交扰调制比、相互调制比。而干线放大器的输入、输出电平...     

干线放大器的维护与维修

在电缆传输系统中,为了远距离大容量传输有线电视信号,必须加接多级干线放大器,以补偿电缆对电视信号的传输损耗。 干线放大器有分立元件和集成电路两种,由于集成电路的放大器可靠性高,设计维修方便,现一般都采用集成电路的干线放大器。 有线电视干线放大器的维护分定期检查保养和一般性检查维护,维修指发生故障后去排除。 对有线电视干线放大器的保养维护一般采用手摸、眼看、鼻闻和用万用表、场强仪测量等方法进行。现以LTF/4200A/B放大器为例,简介其维护与维修。     

CATV干线放大器的选择

如果说有线电视前端是整个有线的“心脏”的话，那么毫不夸张地认为干线是整个ＣＡＴＶ系统的“动脉”。因而干线的建设是整个系统建设不可忽视 问题。而干线质量的好坏最大限度地取决于干线电缆和放大器的选择。     

前置运算放大器的噪声分析与设计

D类音频功率放大器设计系统中,前置运算放大器大多采用全差分设计,为实现较好的THD性能及噪声特性,要求其具有较宽的输入输出电压范围,高SNR,高PSRR,高CMRR。本文运用标准的电路理论和噪声模型,详细分析了运算放大器电路的噪声及应用在D类功放中引起的整体噪声特性,并给出改善放大器噪声性能的设计方法及设计结果。     

Noise in free-electron laser amplifier

The equations of the free-electron laser amplifier are generalized to include higher order modes. The density and velocity fluctuations in the entering electron beam cause noise excitation in the amplifier. The electron beam fluctuations have been studied extensively, both theoretically and experimentally, in traveling wave tubes, and hence the well-tested formalism developed for this purpose is conveniently applied to the present problem. It is found that the fluctuations put a severe constraint on the achievable exponential gain in a proposed Raman-type free-electron laser operating at optical frequencies. A1/lambda^{3}scaling law is derived.     

Noise properties of a Raman amplifier

We present the first measurements of the noise properties of a Raman optical amplifier. Measurements on CW Raman amplified optical signals from a 1.5-μm single frequency laser in 32 km of silica fiber, pumped by a 1.45-μm color center laser, reveals that the main noise source is the shot noise generated in the receiver due to the spontaneous Raman radiation. For signal levels down to -50 dBm, no excess noise due to the Raman process could be detected.     

轨到轨输入输出范围运算放大器的噪声分析和优化

这篇文章设计了一个轨到轨（Rail-to-Rail）输入输出范围的低噪声运算放大器,在输入级采用电流补偿的方法来稳定该运算放大器在整个输入共模范围内的跨导,在输出级使用了AB类的输出方法来提高运算放大器的输出范围,且详细分析了该运算放大器的噪声性能,在此基础上给出了改善该运算放大器噪声性能的方法,以此来提高该运算放大器的动态范围。     

Noise performance of an overloaded maser amplifier

The noise output and noise factor F of a simplified model of a maser is studied as a function of the ratio g/G of small-signal gain g to actual gain G. The noise output drops rather sharply as g/G is increased. The noise factor, however, increases only very slowly from its value of F = 1 at g/G = 1 to F = 1 + ½ ln g for a totally overloaded maser (G = 1).     

Noise in an AlGaAs semiconductor laser amplifier

The noise characteristics in a Fabry-Perot (FP) cavity type semiconductor laser amplifier, biased at just below its oscillation threshold current, have been studied theoretically and experimentally. Quantum mechanical multimode rate equations containing a Langevin shot noise source and an input signal term were numerically solved for an exponential band-tail model with nok-selection rule. Noise power calculated using this rate equation was compared with a simpler photon statistic master equation method. The experimental results on noise power for an AlGaAs laser amplifier are in reasonable agreement with the two different theoretical predictions. Dominant noise powers in a semiconductor laser amplifier are beat noise powers between signal and spontaneous emission, and between spontaneous emission components. Noise characteristics in a Fabry-Perot cavity type laser amplifier can be improved both by the reduction of the facet mirror reflectivities and by use of an asymmetric cavity configuration with low-input and high-output mirror reflectivities. Two beat noise powers are expressed in simple analytic form by introducing an equivalent noise bandwidth and an excess noise coefficient as figures of merit in an optical amplifier.     

Noise analysis of a photoreceiver using a P-I-N and GaAs HBT distributed amplifier combination

A noise analysis for a common-collector-cascode traveling wave HBT preamplifier is developed. The photoreceiver, consisting of a P-I-N and GaAs HBT MMIC distributed amplifier, was implemented using Nortel's f/sub T/=70 GHz GaAs HBT process, is the first to have a P-I-N mounted on the MMIC chip. The P-I-N preamplifier, having a measured bandwidth of 22 GHz, displayed a measured average equivalent input noise current density of 24 pA//spl radic/Hz. Good agreement was obtained between the predicted and measured noise performance.     

IL型半导体激光放大器的噪声

IL型激光放大器(LA)可以用做光功率放大器,也可以用做中继放大器代替复杂的光-电中继器.IL型LA的噪声性能对相干光通信系统的性能至关重要,它直接影响到系统的误码率.我们对IL型LA的强度噪声谱和频率飘移谱,进行了数值计算,并讨论了注入光的噪声谱、注入光功率和锁定相位等对噪声谱的影响.     

Noise analysis for optical frequency conversion using nearlydegenerate four wave mixing in semiconductor optical amplifier

For future wavelength-division-multiplexed (WDM) networks, optical frequency conversion will enable the flexible and efficient use of optical frequency bandwidth. However, the signal degradation at frequency converters limits the maximum size of the network. Noise due to optical frequency conversion using nearly degenerate four wave mixing in a semiconductor optical amplifier is investigated, and it is found that the crosstalk from one of the two pump lasers can impose the power penalty on the bit error rate (BER) characteristics after optical frequency conversion. Analytical expressions for BER are developed and used to evaluate the receiver sensitivity penalty caused by optical frequency conversion. On the basis of these results the optimal setting of the frequency difference between the signal and pump lasers and the power ratio of the two pump lasers are discussed. A 155-Mb/s frequency-shift keying (FSK) transmission with 1750-GHz (14 nm) optical frequency conversion has been carried out, using a novel phase noise cancellation method. The BER performance is in good agreement with the calculated results