Research And Design Of High-Precision Silicon-based Amplitude-Phase Control Unit

Due to its flexible and fast beamforming and beam scanning,phased array system has become one of the most potential solutions in the field of millimeter wave radar and wireless communication.At the same time,with the development of process and the update of the technology,silicon-based RF circuits have attracted more and more attention in the microwave field because of its advantages of low cost,low power depletion and high integration.Therefore,silicon-based on-chip phased array transceiver system has become a hot topic in academia and industry.As the crux of control module in the phased array system,this paper makes an intensive study on the amplitude and phase control circuit and does some designs,hoping to bring some reference to the performance improvement of RF front-end chip.First of all,this paper introduces the basic knowledge of phased array system,analyzes the working principle and performance index of amplitude and phase control circuit.Then it introduces the main structure of passive attenuator and phase shifter and their advantages and disadvantages,analyzes the causes of additional phase shift of various structures of attenuator,and gives corresponding compensation circuit to reduce the additional phase shift;at the same time,it also focuses on the topology of switchtype phase shifter,which lays a theoretical foundation for the following specific chip circuit design.Then,starting from the parasitic parameters and switch selection of silicon-based process transistors,a Ku-band 5-bit passive attenuator is designed using the traditional switch-type attenuator structure.By adopting the 0.18-um CMOS process,the attenuator adjusts the amplitude range of 32 states from 0dB to 31 dB.The RMS attenuation error is less than 0.35 dB.Although the additional phase shift is reduced by using the compensation structure of increasing capacitance in parallel branch,the phase performance can still improve further.To solve the phase shift problem in the previous attenuator,this paper analyzes the origin of the error in the multi-stage attenuator circuit,and puts forward a targeted method to improve the circuit accuracy and reduce the additional phase shift by optimizing the single-stage impedance.Based on the 0.13-um SiGe BiCMOS process,a Ka-band 5-bit attenuator with high accuracy and low phase imbalance is designed inthis paper.The attenuation step is 0.5dB and the maximum attenuation range is 15.5dB.The test results show that the RMS attenuation error is less than 0.3dB and the RMS phase error is less than 2.5° in the frequency band from 31 GHz to 41 GHz,which verifies the reliability of the optimized impedance design method.Finally,based on the 65-nm CMOS technology,a separate 6-bit passive phase shifter is designed which is used in the transceiver system of 94 GHz FMCW radar,and the impedance optimization method is also used in this design.As the first attempt to design a high frequency chip,the simulation and test results of the phase shifter show that the RMS phase error is less than 3.6° and the absolute amplitude error is less than±2dB in the frequency range of 92 GHz to 96 GHz.Two successful designs fully prove the superiority of this design method.