Design Of An Active Phase Shifter For X-band Phased Array System Based On Vector Modulation Technology

With the development and mature of the phased array technology,people take more and more attention to its importance,especially in military and communication.As the key part of phased array system,phase shifter directly determine the performance of the phased array system.The research focus and difficulty of the phase shifter lies in the development requirements of high bandwidth,low insertion loss and high level integration.Using IBM 0.18?m SiGe BiCMOS technology,an active phase shifter has designed in this paper,which is based on the vector modulation technology,applied in X-band phased array system.The designed active phase shifter include the orthogonal signal generator,the vector adder,the DAC gain control circuit and the on-chip Balun.The orthogonal signal generator circuit has designed by orthogonal all-pass filter structure.The vector adder consists of two gilbert gain control units,each unit contains a single pole double throw switch to get the output phase quadrant by changing the switch state.The DAC gain control circuit include five cascode current mirror arrays,and each array is controlled by a single pole double throw switch.Then,by changing the state of each switch to change the current ratio of I and Q path,the output phase is obtained.To complete the conversion of single-ended signal and differential signal and realize impedance matching function,the on-chip Balun has designed by the HFSS software.The on-chip Balun uses cascading winding structure,which is the main innovation of this paper.Completed the layout design and simulation of the active phase shifter,the simulation result shows that the active phase shifter achieved good performance,in Xband frequency range.The insertion loss is less than-1.75 dB,the phase error is less than 5.35°,the least input 1dB compression point is 2.96 dBm,the input VSWR is less than 1.59,the output VSWR is less than 1.26.The phase shifter has low insertion loss,good flatness and stability while saving the chip area.