Research And Design On Wideband Digital Phase Shifter And Digital Attenuator

With the rapid development of microwave and radio frequency technology,microwave monolithic integrated circuit(MMIC)is widely used in military electronic countermeasures and civil communication systems because of its small size,low cost,high reliability and perfect performance consistency.The 10?18 GHz wideband digital phase shifter and digital attenuator designed in this paper are important parts of transmit/receive(T/R)module in the active phased array radar,whose performance directly determines the overall radar.This paper first summarizes the research status of digital phase shifter and digital attenuator at home and abroad,and analyses the relevant knowledge of MMIC,including Ga As process substrate,passive and active device model,and the principle and model of p HEMT as switch control device.Then the design of MMIC digital phase shifter and attenuator is deeply studied from the aspects of working principle,technical index and circuit topology.According to the optimal topology selection theory,the high-low pass phase shifting network and switch-path-type attenuation topology are employed in order to achieve high-precision phase and amplitude performance.The optimal cascading order is determined based on the port impedance characteristics of six basic bits,which reduces the performance deterioration.Finally,considering the coupling effect,the whole layout of phase shifter and attenuaor is verified by electromagnetic simulation to ensure that the performance meets the design requirements.Based on the 0.15 ?m Ga As p HEMT process,the 6 bit digital phase shifter and 6 bit digital attenuator are designed and fabricated,and the on-chip test is carried out.The mearsured results of 6 bit digital phase shifter show that the input/output VSWR of 64-state phase shift is less than 1.8:1,the insertion loss in reference state is less than 8.6 d B,the rms phase and amplitude error of 64-state phase shifter is 4.4° and 0.6 d B max over the 10?18 GHz frequency band.The chip size is 3.5 mm×1.4 mm including the test pads.The mearsured results of 6 bit digital attenuator show that the input/output VSWR of 64-state attenuation is less than 1.7:1,the insertion loss in reference state is less than 4.2 d B,the rms amplitude and phase error of 64-state attenuation is 0.5 d B and 4.2° max over the 10?18 GHz frequency band.The chip size is 2.7 mm×0.8 mm including the test pads.The 10?18 GHz wideband digital phase shifter and digital attenuator designed in this paper both have wideband performance,low insertion loss,and high-precision phase and amplitude characteristics,it can be widely used in T/R module of microwave phased array radar.