Research And Design Of Frequency Source Of K-band Automotive Collision Avoidance Radar

Frequency source is the key component of automotive collision avoidance radar system,and its performance is directly related to many indexes of automotive collision avoidance radar.This is mainly because the type of waveform generated by the frequency source and the performance of the output frequency directly determine the intermediate frequency signal obtained from the mixing of the transceiver signal and then affect the accuracy of the range and velocity measurement of the automotive collision avoidance radar.Therefore,the research and design of automotive collision avoidance radar frequency source has scientific research value and engineering significance.In this thesis,the working principle and frequency source of automotive collision avoidance radar ranging and velocimetry are studied,the realization scheme of automotive collision avoidance radar frequency source is designed,and its verification simulation and PCB board processing test are carried out.The main work is as follows:Firstly,the principle of ranging and velocity measurement based on Frequency-Modulated Continuous Wave(FMCW)radar is introduced in this thesis,and the performance index of frequency source system in automotive collision avoidance radar is analyzed.Secondly,the frequency synthesizer schemes commonly used in frequency source system are studied in this thesis,which are Direct Digital Synthesis(DDS)scheme,Phase-Locked Loop(PLL)frequency synthesis scheme and their combination scheme.By comparing these three frequency synthesis schemes,A frequency source scheme suitable for automotive collision avoidance radar is designed,and the feasibility of the scheme is analyzed and verified.Compared with the traditional frequency source scheme,this scheme has the advantages of simple circuit structure,easy program control,low cost and low phase noise.Thirdly,the circuit of frequency source system is designed in this thesis.This design adopts the modular design idea,divides the frequency source system into:the PLL circuit module,the control circuit module and the steady voltage power supply circuit module according to the function,thus simplifies the circuit structure,reduces the debugging difficulty.The design of active loop filter and the simulation optimization of frequency source system are accomplished with ADIsimPLL4.10 software.The loop bandwidth is426kHz,the phase margin is46~o,the locking time is 9?s,and the phase noise is-90.625dBc/Hz@10kHz when the system is stable.The circuit design of three modules is completed based on the consideration of various device data sheets,electromagnetic compatibility and product performance.Finally,the design and fabrication of the frequency source PCB layout are completed in this thiesis,and the physical objects are processed and tested.The test results show that the output power of the frequency source system is 8.32 dBm at the center frequency of24.125GHz,and the phase noise is-79.94 dBc/Hz@lkHz,-86.99dBc/Hz@10kHz,-90.93dBc/Hz@100kHz,-99.97dBc/Hz@1MHz,and the spur is lower than-50dBc.The all of parameters meet the design requirements,and have the advantage of low phase noise.