光接收机前端等效输入噪声电流谱密度与噪声系数间的关系

根据光接收机前端等效电路模型,建立了噪声系数与等效输入噪声电流谱密度的关系.提出通过测量光接收机前端电路噪声系数间接获得等效输入噪声电流谱密度的方法.155Mb/s高阻结构光接收机前置放大器的电路仿真与计算验证了推导公式的正确性.最后给出在芯片测试实例.     

低噪声、宽带调谐光接收机的分析与设计

通过对最优噪声匹配网络的分析,提出了光接收机的设计方法。它基于噪声系数概念和宽带匹配理论,同时引入了等效输入热噪声电流的概念。由于在分析过程中直接利用有源器件的噪声参数(最小噪声系数、噪声阻抗和最佳源阻抗),这种设计方法是很精确的。通过分析,确定了调谐网络噪声匹配的一般条件,其目标是使光接收机获得最小等效输入噪声电流。     

低噪声、宽带调谐光接收机的分析与设计

通过对最优噪声匹配网络的分析，提出了光接收机的设计方法。它基于噪声系数概念和宽带匹配理论，同时引入了等效输入热噪声电流的概念。由于在分析过程中直接利用有源器件的噪声参数(最小噪声系数、噪声阻抗和最佳源阻抗)，这种设计方法是很精确的。通过分析，确定了调谐网络噪声匹配的—般条件，其目标是使光接收机获得最小等效输入噪声电流。     

长波长PIN／HBT集成光接收机前端噪声分析

文章研究磷化铟(InP)基异质结双极晶体管(HBT)和PIN光电二极管(PIN-PD)单片集成技术,利用器件的小信号等效电路详细计算了长波长PIN/HBT光电子集成电路(OEIC)光接收机前端等效输入噪声电流均方根(RMS)功率谱密度.分析表明:对于高速光电器件,当频率在100 MHz～2 GHz范围内时,基极电流引起的散粒噪声和基极电阻引起的热噪声起主要作用;频率大于5 GHz时,集电极电流引起的散粒噪声和基极电阻引起的热噪声起主要作用.在上述结论的基础上,文章最后讨论了在集成前端设计的过程中减小噪声影响的基本方法.     

接收机射频前端噪声特性分析

噪声是影响接收机灵敏度的重要因素之一。接收机引入的噪声越小,接收机灵敏度就越高。分析了接收机噪声,给出了射频前端噪声系数与接收机灵敏度的关系,论述了几种改善射频前端噪声系数的方法。     

低噪声和高增益CMOS下变频混频器设计

设计并实现了一个用于GPS接收机射频前端的CMOS下变频混频器.基于对有源混频器的噪声机制的物理理解,电路中采用了噪声消除技术,以减少Gilbert型混频器中开关管的闪烁噪声,并引入一个额外的电感与开关对共源节点的寄生电容谐振,改善整个电路的噪声系数和转换增益等关键性能指标.电路采用TSMC 0.25 μm RF CMOS工艺实现,SSB噪声系数为7 dB,电压转换增益为10.4 dB,输入1 dB压缩点为-22 dBm,且输入阻抗匹配良好,输入反射系数为-17.8 dB.全差分电路在2.5 V供电电压下的功耗为10 mW,可满足GPS接收机射频前端对低噪声、高增益的要求.     

雪崩光电二极管最佳偏置电路

文中对雪崩光电二极管的温度影响因素作了一般性讨论,给出了几种稳定方式.文中简要介绍了雪崩光电二极管的倍增噪声电流谱密度与等效输入噪声电流谱密度推出的结果.根据结论进行最佳倍增稳定偏置电路设计,给出了参考电路.使用这种自动偏置最佳状态电路,使探测系统性能大为改善.     

155Mb/s光通信用CMOS自动增益控制跨阻前置放大器

采用华润上华的0.6μm标准CMOS工艺设计了一种应用于光纤通信系统STM-1速率级别的自动增益控制(AGC)跨阻前置放大器.为了扩展输入动态范围,采用自动增益控制技术监控输入电流中与电流幅度成正比的直流分量的变化.当输入信号过大时,降低电路的跨阻增益,从而避免输出波形出现严重失真.通过分析电路中几个主要元件对等效输入噪声电流的贡献,给出了噪声性能优化的方法.测试结果表明,在5V电源电压下,小信号时电路差分跨阻增益达到91.7dBΩ(38.5kΩ),-3dB带宽125MHz,最大输入光功率0dBm,平均等效输入噪声电流谱密度为4.8pA.功耗为180mW.芯片面积为0.7×0.4mm².     

结型场效应晶体管低频噪声测试方法研究

在深入研究JFET低频噪声特性及产生机理的基础上,提出了一种通过测试宽频带功率谱密度得到其规定频率处等效输入噪声电压功率谱密度和噪声系数的测试方法,并给出了低频噪声测试的偏置电路、测试设备和测试方法。结合3DJ4和3DJ6型JFET器件的测试结果表明,采用本文提出的方法可适用于JFET的低频噪声的测试。     

CMOS低功耗3-5GHz超宽带接收机射频前端

本文介绍了一种新的低功耗射频接收机前端, 适用于3-5GHz的超宽带系统. 基于0.13µm CMOS工艺实现, 该直接转换式接收机由宽带噪声抵消结构的跨导输入级, 正交无源混频器和跨阻负载放大器组成. 测试结果显示该接收机在整个3.1-4.7GHz 频带范围内的输入反射系数小于-8.5dB, 转换增益27dB, 噪声系数4dB, 输入三阶交调点-11.5dBm, 输入二阶交调点33dBm. 工作在1.2V电源电压下, 整个接收机共消耗18mA电流, 其中包括10mA用于片上正交本振信号产生和缓冲电路.芯片面积为1.1mm×1.5mm.     

Noise in distributed MESFET preamplifiers

The theory of noise in a distributed MESFET preamplifier is developed. From this, it is shown that the equivalent input noise current density of a distributed preamplifier of an optical receiver can be improved by using large gate line matching impedance and appropriate scaling of the MESFET width. A front-end tuning circuit was designed using filter theory to further improve the noise performance of the preamplifier. A monolithic GaAs MESFET distributed preamplifier was fabricated with on chip front-end tuning components. Using a 35 μm InGaAs p-i-n photodiode, the preamplifier was shown to have an equivalent input noise current density of 8 pA/√Hz and an 8 GHz bandwidth. To date, this is the best known result for a 0.8 μm GaAs MESFET process     

Noise performance of optical receivers: comparison of directional coupler and resistive feedback based front ends

Noise properties of a directional-coupler-based optical receiver (DCOR) and the resistive-feedback optical receiver (RFOR) topologies are compared. For the DCOR the authors have both simulated and subsequently measured an input equivalent noise current of 3 pA/ square root (Hz) for a bandwidth of up to 2.5 GHz. By using the same noise modelling approach the simulation results for the RFOR topology gave a noise current of 10 pA/ square root (Hz) over the same bandwidth thus verifying the superiority of the DCOR over the resistive feedback optical receiver.<>     

Fiber-optic multigigabit GaAs MIC front-end circuit with inductorpeaking

The design and performance of a multigigabit optical front-end circuit are discussed. Inductor peaking is applied to the GaAs MIC preamplifiers and a 3-dB down bandwidth of 6.5 GHz, 15.5-pA/√Hz averaged input equivalent noise current density from 10 MHz to 6.5 GHz, and transimpedance gain of 57 dB are achieved. A 3-dB down bandwidth of 6.1 GHz is achieved in an optical front-end circuit with a InGaAs p-i-n photodiode. This performance indicates that the optical front-end circuit with inductor peaking is promising for multigigabit optical receivers     

Using High Frequency Operational Amplifiers for Low Noise Design

In this paper we present a comprehensive noise and stability analysis of both the current feedback and the voltage feedback op-amp when connected as transimpedance amplifiers with capacitive current sources. It is generally assumed that the current feedback op-amp is noisier than the voltage feedback op-amp; we show how external component values play an important role in determining the total equivalent input noise current spectral density and show that the voltage feedback op-amp may, in certain cases, be noisier than the current feedback op-amp. Both amplifier types are compared in terms of stability, noise and bandwidth; we find that the current feedback op-amp is particularly suited for operation as a transimpedance amplifier. Theoretical analysis is confirmed by simulations of equivalent circuits of the current feedback op-amp and the voltage feedback op-amp, and simulations of the macro models of two high performance commercially available op-amps, namely the Elantec EL2260 current feedback op-amp and the Elantec EL2244 voltage feedback op-amp.     

High-performance monolithically integratedIn0.53Ga0.47As/InP p-i-n /JFET optical receiverfront-end with adaptive feedback control

An optical transimpedance receiver front-end that is adaptable to a wide range of bit-rates up to 3 Gb/s has been realized by monolithically integrating high efficiency p-i-n photodiodes with low noise InGaAs junction field effect transistors. The transimpedance-bandwidth product of the receiver is 2.8 THz Ω. The average equivalent input noise current for full circuit bandwidth is 4.0 pA/√Hz. The preamplifier for nonreturn to zero data transmission without equalization of the frequency response at 1.55 μm offers a sensitivity of -41.5 dBm and -29.5 dBm at 140 Mb/s and 2.4 Gb/s, respectively. The dynamic range is 17 dB at 2.4 Gb/s and exceeds 30 dB at 500 Mb/s     

Design and anaylsis of a 2.5-Gbps optical receiver analog front-end in a 0.35-/spl mu/m digital CMOS technology

This paper presents the design of an optical receiver analog front-end circuit capable of operating at 2.5 Gbit/s. Fabricated in a low-cost 0.35-/spl mu/m digital CMOS process, this integrated circuit integrates both transimpedance amplifier and post limiting amplifier on a single chip. In order to facilitate high-speed operations in a low-cost CMOS technology, the receiver front-end has been designed utilizing several enhanced bandwidth techniques, including inductive peaking and current injection. Moreover, a power optimization methodology for a multistage wide band amplifier has been proposed. The measured input-referred noise of the optical receiver is about 0.8 /spl mu/A/sub rms/. The input sensitivity of the receiver front-end is 16 /spl mu/A for 2.5-Gbps operation with bit-error rate less than 10/sup -12/, and the output swing is about 250 mV (single-ended). The front-end circuit drains a total current of 33 mA from a 3-V supply. Chip size is 1650 /spl mu/m/spl times/1500 /spl mu/m.     

Analysis of the transistor-related noise in integrated p-i-n-HBToptical receiver front-ends

The equivalent-input-noise-current spectral density for a monolithically integrated optical receiver front-end using InP/InGaAs heterojunction bipolar transistors and a p-i-n photodiode is computed from a small-signal model. Particular attention is paid to the contributions to the noise from the HBT in the first stage of the amplifier. It is shown that with transistors designed for 1-10-Gb/s receivers the base current shot noise dominates in the frequency range from 10 MHz to 1 GHz, and both the base resistance thermal noise and the collector current shot noise are important at higher frequencies. Device features which determine the extent of these noise sources are identified, and ways to improve the noise performance are discussed