Research On Analog Circuit Of LADAR Based On Geiger-mode Avalanche Photodiode

In recent years,with the development of lasers,laser detection has gradually become a hot spot in scientific research.As a hot spot for laser detection,laser radar is the core of artificial intelligence and autonomous driving.Geiger mode laser radar shows strong vitality in practical system applications due to its high sensitivity,simple and easy integration of pixel circuits.This thesis is devoted to the research of laser radar analog signal readout circuit,and a readout circuit of array type laser radar detector based on Geiger mode APD and a TDC applied to vehicle laser radar detector have been designed.Firstly,in the thesis the system architecture and working principle of the laser radar have been expounded,and the receiving part of the laser radar front end has been selective analyzed.The parameters and circuit scheme of the APD quenching circuit AQC,the time-to-digital converter TDC,the decoding circuit and other modules are determined according to the requirements of the receiving system,then a single-channel pixel readout circuit is designed,improved and multiplexed according to the array-symmetry feature to achieve the layout of the pixel circuit array.In this thesis,a high-precision TDC applied to the laser radar readout circuit has been designed and tapeouted.In order to make the TDC has a large dynamic range and small measurement accuracy,a layered quantization strategy has been adopted,in order to make the TDC has good PVT characteristics and a short conversion time,DLL technology is used to generate the clock.In this thesis,the high-precision TDC circuit is realized by a three-layer structure.In the first-layer circuit design,a path selection method is proposed and applied to an integer period measurement circuit for the high-precision TDC;In the second and third-layer circuits according to the feature of sampling clock timing and the unique thermal code decoding,a sampling and decoding circuit has been proposed for TDC fractional measurement.In processing the signal between multi-layer structures,according to the signal timing characteristics,a signal extraction circuit with an picosecond error is proposed.The circuit adopts SMIC 0.18?m standard CMOS technology,Cadence and Modelsim tools have been used to simulate the main modules of the circuit,and multiple different inputs have been used to verify the function of the system.In this thesis the high precision TDC applied in the laser radar has been designed and tapeouted.The array circuit has a working voltage of 1.8V,a reference clock of 200 MHz,and an array size of 5×5.The simulation results show that the system functions normally under different input,and the core module TDC can achieve a measurement precision less than 660 ps and a dynamic range more than 20?s,as corresponding to the detection accuracy of 10 cm and the detection range of 3km.Simulating high precision TDC with a 200 MHz clock frequency and a wide range of 2?s input,TDC can work normally,and achieve a less than 50 ps measurement precision.Through transmission curve,we can see that the TDC achieves a good function,has a characteristics of good linearity stability and a short conversion time,and provides a good technical foundation for subsequent automotive laser radar applications.