可控增益光电集成光接收机设计

Optoelectronic Integrated Optical Receiver with Automatic Gain Control

基于IHP 0.25μm SiGe BiCMOS工艺,利用工艺库提供的分束器将入射光信号能量均分给差分电路两侧的Ge波导耦合型探测器,设计了一款应用于高速光通信和光互连领域的增益自动可控型光电集成光接收机.整体电路包括光电探测器、跨阻放大器、两级增益放大器、输出缓冲级、直流偏移消除模块和自动增益控制模块.为解除利用直流偏移消除电路检测峰值电压这种传统方案对消直流电容容值的限制,电路设计了同时具有峰值检测和增益控制功能的自动增益控制模块,并引入放电复位电容来控制采样时间.为了稳定差分电路的直流工作点,并避免引入过多功能模块对电路噪声的恶化,设计了结构灵巧的直流偏移消除电路.同时,为了提升电路带宽,还设计了带射随器反馈的共射跨阻放大器、带简并电容的Cherry-Hooper增益放大器以及可有效降低输入电容对级联电路带宽限制的f_T倍频器.仿真结果表明,在电源电压为3.3 V、输入光功率-10 d Bm的情况下,所设计的光接收机电路增益为80.2 dBΩ,-3 dB带宽为34.8 GHz,带宽范围内等效输入噪声电流小于35 pA/√Hz.输入光功率在-15^-3 dBm范围内,电路可实现对增益的自动控制,输出摆幅约500 mV,波动小于10%.在40 Gb/s的传输速率下,电路眼图清晰方正,无明显的欠冲与过冲,交叉点清晰,张开度良好,有望用于高速单片集成光接收机中.

An optoelectronic integrated optical receiver with automatic gain control based on IHP 0.25μm SiGe BiCMOS technology was designed for application in high-speed optical communication and interconnection.The beam splitter provided by the technology library was used to evenly distribute the incident light signal energy to the Ge waveguide-coupled detectors on both sides of the differential circuit.The overall circuit included photodetectors,transimpedance amplifier,two-stage gain amplifier,output buffer,DC offset cancellation circuit,and automatic gain control circuit.To eliminate the limitation of the DC offset cancellation capacitor in detecting the peak voltage using the DC offset cancellation circuit,the circuit was designed,including an automatic gain control module with peak detection and gain control functions,and a reset capacitor was introduced to control the sampling time.A sleek DC offset cancellation circuit was designed to prevent noise deterioration and stabilize the DC operating point.Meanwhile,the circuit bandwidth was extended by a cascode transimpedance amplifier with emitter follower feedback,a capacitive degeneration Cherry-Hooper gain amplifier,and an fT frequency multiplier.The post-layout simulation results showed that the designed optical receiver achieved a gain of 80.2 d BΩand 34.8 GHz of-3 d B bandwidth when using supply voltage of 3.3 V and optical power of-10 d Bm.Moreover,the average input-referred noise current spectral density within the bandwidth of interest was less than 35 pA/√Hz.The gain automatic control feature can be guaranteed when the input optical power is in the range of-15--3 d Bm.The output voltage was approximately 500m V,and the fluctuation was less than 10%.At a transmission rate of 40 Gb/s,the eye circuit diagram was clear and square and did not have obvious undershoot and overshoot.In addition,the intersection is clear and the opening degree was good.The proposed circuit was expected to be applied to a high-speed optoelectronic integrated optical receiver.