Research On And Design Optimization Of Phase Shift Variation In Ultra Wideband Variable Gain Amplifier

The constantly increasing number of Internet users and Internet of things has pushed Radio Frequency toward faster data rates and lower costs.This growth in data traffic has been extremely challenging for wireless and fiber communications.The microwave millimeter-wave frequency bands allocated to wireless multi-Gb/s point-to-point communication are attractive solutions to accommodate higher data-rates and evolve future communications.The highly integrated microwave phased array has been an active re-search field in 5G communication systems for its high scanning resolution,all-weather communication and moderate detection distance.As the crucial component in the phased-array systems,the performance of variable gain amplifiers has a significant impact on scanning resolution,beam steering,and signal-to-noise ratio of the received signal.The silicon germanium process has a low cost,a high yield and high frequency performance comparable to that of the?-?compound process with the development of the semiconductor manufacturing process,and hence a very broad application prospect.The research on variable gain amplifiers with low phase-shift variation in this paper is based on Tower Jazz 0.18?m BiCMOS technology.This paper introduces the basic performance parameters of the variable gain amplifiers,including the control characteristic of dB-linear,bandwidth,linearity and phase-shift varia-tion,etc.And the optimization of various performances is analyzed in detail from the cir-cuit level.Ultra-wideband systems have high requirements for the performances of RF circuits.As the gain control cell of a phased array system,its phase-shift variation has an important influence on scanning resolution of beam-steering.Therefore,this paper analyzes and summarizes the optimum designs of phase-shift variation by consulting a large number of literatures,and proposes a new compensation circuit suitable for the cir-cuit.The two variable gain amplifiers designed in this paper are based on the current steer-ing to achieve the control of dB-linear.A pre-distortion circuit is introduced to broaden the gain dynamic range and the peak inductor is employed to expand the bandwidth.In order to meet the test requirements,a shunt feedback and source degeneration inductor are used in the UWB system and a fourth-order LC-ladder band-pass filter is used in the Ku^K band for input matching of the two variable gain amplifier and both the output matching are accomplished by emitter followers to achieve 50?impedance matching.The two designs achieve corresponding zero-pole compensation currents based on different pre-distortion circuits to optimize the phase-shift variation,and their effects on the gain control characteristic and dynamic range are analyzed.Theoretical analysis of gain,phase-shift variation,bandwidth,matching and linearity were considered,and the circuit simulation is performed for verification.Based on profound understanding of layout design points,layout design is achieved.Finally,the circuit design works are completed by the constant optimization of the schematics and layouts,and the post-simulation results are analyzed and discussed.The post-simulation results of the two VGAs with low phase-shift variation designed in this paper are as follows:The phase-shift variation of the VGA for ultra wideband in worst case is 1.2°with a gain dynamic range of 32dB and a bandwidth of 3¹0GHz.Furthermore,it shows that the input and output return loss are less than-10dB in the whole work fre-quency band and entire gain range,an IP_1dB of-15dBm@7GHz and an IIP3 of-8.2dBm@7GHz are achieved at maximum gain mode;The variable gain amplifier for Ku^K band shows that the input and output return loss are less than-10dB and a linear-in-dB gain range of-25dB⁵dB in the whole work frequency band.It has an IP_1dB of-12dBm@19GHz and an IIP3 of-3dBm@19GHz at maximum gain mode.The phase-shift variation is lower than 4°?within 31dB gain range?in the desired band.