Research On Optical Receiver With Auto Gain Control Based On SiGe BiCMOS Technology

The development of information and communication technology has advanced the digital and intelligent transformation of human society.Future technology such as driverless,telemedicine,and AI are developing rapidly.The demand for data communication is growing dramatically in these areas.The copper interconnect technology has become hard to meet the needs of today's technological developments.As an optical communication scheme,optical interconnect has the advantages of high bandwidth,low loss and no crosstalk,et al.Therefore,it is an ideal solution of future interconnection.As an important part of optical communication system,the optical receiver needsto transform optical signals into electrical signals.Under the actual working conditions,the input signal of the optical receiver will fluctuate due to the factors such as intermediate loss.However,the optical receiver with automatic gain control module can adapt to the large input dynamic range.The common auto gain control method using the DC offset cancellation circuit to detect the peak voltage.But this solution requires precise capacitance to control the sampling time.In addition,although the CMOS technology is the most popular technology today,it is still insufficient in the design of high-speed optical receivers.Yet,the SiGe BiCMOS technology has the advantages of high performance photo detectors and high transconductance heterojunction bipolar transistor.Therefore,it is more suitable for OEIC optical receiver design.To achieve the high bandwidth and auto gain control opto-electronic integrated optical receiver based on the SiGe BiCMOS technologies,the research works carried out in this thesis are as following:1.Based on UMC 0.18?m CMOS technology,a novel RGC transimpedance amplifier was designed using pole migration method.By applying a cascode assisted amplifier and a parallel feedback PMOS transistor,the input impedance was successfully reduced.At the same time,the ?-type matching network and the source follower reduced the influence of post capacitance.All of these let the main pole move to high frequency,which finally led to a transmission rate of 8Gb/s.2.Based on IHP SiGe BiCMOS 0.25?m technology,a pseudo differential optoelectronic integrated circuit optical receiver was designed.The overall optical receiver includes photodetectors,transimpedance amplifier,gain amplifier,output buffer and DC offset cancellation circuit.By introducing a pseudo detector,the DC operating point of the differential circuit is guaranteed to be stable.The post layout simulation results showed that the designed optical receiver had a gain of 74.4 dB? and a-3dB bandwidth of 22.8GHz.3.Based on the design of the pseudo difference optical receiver,an automatic gain control module with reset function and a sleek DC offset circuit are introduced to design a fully differential OEIC optical receiver with auto gain control.The beam splitter provided by the IHP 0.25 ?m SiGe BiCMOS technology is used to evenly distribute the incident light signal energy to the Ge waveguide coupled detectors on both sides of the differential circuit.The circuit bandwidth is extended by a cascode transimpedance amplifier with emitter follower feedback and a capacitor-degenerate Cherry-Hooper gain amplifier.The post layout simulation results showed that the designed optical receiver had a gain of 80 dB? and a-3dB bandwidth of 35GHz with a-10dBm optical power.Besides,the average input-referred noise current spectral density within the interesting bandwidth was less than 35 pA/?(Hz).The gain automatic control feature could be guaranteed when the input optical power was in the range from-15dBm to-3dBm.The output voltage was about 500mV and the fluctuation was less than 10%.