Research And Desgin Of Ultra Wideband 6 Bit Digital Controlled Phased Shifter On SiGe BiCMOS

Phased arrays are commonly employed to obtain steerable,directional antenna patterns,thereby improving the link budget and ensuring robustness in channels with weak or blocked line-of-sight path,which makes the phased arrays one of the hottest research directions.The phase shifter is an extremely critical module in the phased array system,which enables phased arrays for beam scanning by changing the phase of the corresponding radiating element.An inexpensive silicon-based process can integreate the RF circuitry implemented in SiGe BiCMOS with the digital circuitry implemented in Si CMOS on a single chip,which can greatly reduce the cost of the radiating element chip in the phased array and create the economic conditions for the wide application of phased array in business.Therefore,it is very important to study the small-area,low-cost and high-performance RF phase shifters implemented in the SiGe BiCMOS process.In this paper,a 6-bit active digital phase shifter in the X-band is designed based on SiGe BiCMOS technology.The 6-bit active digital phase shifter designed in this paper is a kind of vector modulation phase shifter.The main modules of the circuit include a two-stage input active balun,Type-? RC orthogonal sihnal generator,vector synthesis circuit,output balun,digital-to-analog coversion current array,logic control circuit,and bias circuit.The two-stage input active balun provides 50? input matching and converts the input sigle-ended RF signal into double-ended fifferential signals.In the 8-12 GHz operation band,the phase error of the differential signal is less than 0.04,and the amplitude error is less than 12 md B.The type-? quadrature signal generator converts the differential signal generated by the two-stage active balun into two in-phase and two quadrature differential signals.In the case of a post-stage load at the 8-12 GHz operating band,the quadrature phase error does not exceed 1 and the amplitude error is less than 50 md B.The output signal of Type-? quadrature signal generator is synthesized by a vector synthesis circuit.Changing the magnitude of the cell current in the digital-to-analog conversion current array by controlling the logic circuit can realize the phase shift of 9 states with a step value of 5.625 in the range of 0-45.By controlling the logic circuit to change the state of the switch in the vector synthesis circuit,the phase can be expanded in each quadrant,and then 64 phase-shifted states can be achived,achiveing a 6-bit precision phase-shifting purpose.The output balun uses a two-stage structure.Compared with the traditional output balun structure,this circuit can increase the gain of the entire phase shifter circuit under the same power consumption.The bias circuit is implemented with the band gap reference technology as the core principle,and provides stable bias of each module of the phase shifter.In summary,the 6-bit active phase shifter in this thesis uses the Tower Jazz 0.18?m SiGe BiCMOS process and uses Cadence IC software to complete the overall circuit setup,simulation,layout design,and post-imitation verfication.The final post-imitation show that the RMS phase error of the 64 phase-shifted states of the phase shifter is less than 1.25 and the RMS gain error is less than 0.74 dB within the 8-12 GHz operating frequency,and the flatness of the gain is maintained throughout the operating frequency band.The input reflection coefficient S₁₁<-13 dB,output reflection coefficient S₂₂<-17.9dB.The most critical performance indicators of the phase shifter have reached very good performance and meet the design index requirements.