Design And Implementation Of An Ultra-wideband Six-bit MMIC Digital Phase Shifter

As an important information acquisition device in modern military equipment,phased array radar occupies a pivotal position in ECM.Phased array radars are developing towards miniaturisation,ultra-wideband and high performance,while phase shifters,as the core components of phased array radars,are difficult to improve their effective bandwidth and phase shift accuracy while maintaining miniaturisation.The aim of this paper is to design an ultrawideband six-bit MMIC digital phase shifter with both miniaturisation and high phase shift accuracy based on a 0.25 um GaAs pHEMT process to extend the effective bandwidth of the phase shifter based on X-band.This paper compares the CMOS and GaAs processes,analyses their advantages and disadvantages,and explains why the GaAs process was used for the phase shifter design.Afterwards,the phase shifter principle and the classification of phase shifters are introduced,and the advantages and disadvantages of each type of phase shifter are summarised.Finally,the working principle of the p HEMT switch,the core device in phase shifter,and the commonly used SPDT switch topology are introduced.Based on the phase shifter design specifications,this paper analyses various MMIC digital phase shifters and their switching topologies,studies and elaborates on the cascading process of two-stage cascaded high-pass and low-pass structures,investigates the optimal selection method of components and the phase shifter simulation test method,and finally determines the?-type high-pass structure for 5.625° and 11.25° phase shifters,the embedded T-type high-pass and low-pass structure for 22.5° and 45° phase shifters.The 90° phase shifter uses a two-stage cascaded T-shaped embedded high-pass and low-pass structure,and the 180° phase shifter uses a modified reflective structure.The whole layout is designed to reduce the impact on the RF signal by suppressing the DC bias,meanwhile the optimal cascade is used to expand the bandwidth and improve the phase shifting accuracy.After return of the tape out,measured results are in error with the simulation,and by correcting the errors and optimizing the chip design,the results were obtained to meet the design specifications.The corrected simulation results show that: in the frequency range of 7-13 GHz,the typical value of insertion loss is 10 d B,the voltage VSWR at both input and output is less than 1.9,the RMS phase shift error is less than 2.8°,and the chip size is 2.25mm*2.25 mm.The phase shifter design meets the specification requirements and verifies the correctness of the design,which is a reference value for subsequent designs of miniaturisation,high phase shifting accuracy and ultra-wide bandwidth of phase shifters.