谢 生 ,石岱泉 ,毛陆虹 ,周高磊
AuthorsHTML:谢 生 ^{1, 2}，石岱泉 ¹ ，毛陆虹 ³ ，周高磊 ³
AuthorsListE:Xie Sheng,Shi Daiquan,Mao Luhong,Zhou Gaolei
AuthorsHTMLE:Xie Sheng^{1, 2}，Shi Daiquan¹，Mao Luhong³，Zhou Gaolei³
Unit:1. 天津大学微电子学院，天津 300072；
2. 天津市成像与感知微电子技术重点实验室，天津 300072；
3. 天津大学电气自动化与信息工程学院，天津 300072

Unit_EngLish:1. School of Microelectronics，Tianjin University，Tianjin 300072，China；
2. Tianjin Key Laboratory of Imaging and Sensing Microelectronic Technology，Tianjin 300072，China；
3. School of Electrical and Information Engineering，Tianjin University，Tianjin 300072，China

Abstract_Chinese:基于 IHP 0.13 μm SiGe BiCMOS 工艺，设计了一款应用于超高速光通信的四级脉冲幅度调制(PAM4)光发 射机驱动电路．整体电路包括两路高速非归零码(NRZ)通道(最高有效位通道和最低有效位通道)、时钟缓冲级、电 流模式逻辑(CML)加法器和输出缓冲级．鉴于 PAM4 信号的高线性度要求，为解决传统设计中电平失配率(RLM) 较低的问题，设计了带有低压共源共栅电流镜的 CML 加法器，避免电流镜像不精确和输出阻抗随加法逻辑变化所 带来的非线性因素．同时，针对传统输出级带宽不足与摆幅过小的问题，设计了有源电感负载的 ft 倍频器结构，在 实现同等增益下更高电路带宽的同时，突破传统输出级设计中输出摆幅与阻抗匹配之间的矛盾．后仿真结果表明， 在电源电压 3.3 V、输入信号为两路 100 mV 的 25 Gb/s NRZ 信号的条件下，所设计的两路高速 NRZ 通道可实现约 18.3 dB 的增益和 19.65 GHz 的带宽，带宽范围内等效输入噪声电压小于 37.6 nV/ Hz ．整体电路可实现 50 Gb/s PAM4 输出信号，输出眼图清晰，且获得了 RLM 为 98.6%的高线性度，输出摆幅达 1.5 V．
Abstract_English:In this paper，a 0.13 μm SiGe BiCMOS-based four-level pulse amplitude modulation(PAM4)optical transmitter driving circuit was designed for ultra-high-speed optical communication application. Two high-speed non return-to-zero(NRZ)channels(the most significant bit channel and the least significant bit channel)，two clock buffers，a current mode logic(CML)adder，and an output buffer constituted the overall design. Due to the high linearity requirements of the PAM4 signal，a CML adder with a low-voltage cascode current mirror was designed to overcome the drawbacks of the low level mismatch ratio(RLM). This adder can avoid the nonlinear factors caused by the inaccuracy of the current mirror and the variation of the output impedance with the addition logic. A ft frequency multiplier with active inductance load was designed to avoid the narrow bandwidth and small swing，this design solves the tradeoff between output swing and impedance matching while achieving a wider circuit bandwidth with the same gain. The post simulation results showed that the two high-speed NRZ channels achieve a gain of about 18.3 dB，a bandwidth of 19.65 GHz，and an input-referred noise of less than 37.6 nV/ Hz within the-3 dB bandwidth at a power supply voltage of 3.3 V and 25 Gb/s input NRZ signals of 100 mV. The overall circuit achieved a 50 Gb/s PAM4 output with a clear output eye diagram. Moreover，a high linearity with an RLM of 98.6% was obtained，and the outputswing reached 1.5 V.
Keyword_Chinese:四级脉冲幅度调制；高线性度；大摆幅；SiGe BiCMOS；光发射机
Keywords_English:four-level pulse amplitude modulation；high linearity；large swing；SiGe BiCMOS；optical transmitter

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