Research On Silicon-based Millimeter-wave Integrated Attenuator Circuits

The fast development of the wireless technology has enabled phased-array technology and 5G communication technology a hot research point.As an indispensable module in the wireless technology,the radio frequency front-end chip influences the performance of the wireless system.Silicon-based integrated circuit has been attracting increasing attention in the micrometer and millimeter wave filed,because it has many advantages,such as low cost,low power consumption and high integration.In order to achieve amplitude control with large range and high precision,this paper has done deep research in silicon-based attenuators.Firstly,this paper introduces the basic structures of traditional attenuators,and analyzes their operation principal.Furthermore,the critical techniques of attenuators are studied,including reducing insertion loss,alleviating phase shift and improving linearity.Based on the model of the CMOS transistor parasitic components,this paper analyzes the cuases of phase shift,and points out the limitation of the existing technique,thus putting forward the tail capacitor to decrease the phase shift.The tail capacitor in the attenuation branch forms a low pass filter,which compensates the transmission phase of the attenuation state.For purpose of verifying the effect of the proposed tail capacitor,this paper designs a K-band 6-bit attenuator with low phase shift based on standard CMOS 180 nm process.The attenuation range is 31.5 dB and the step is 0.5 dB with 64 working states.In measurement,the rms phase shift is bleow 3.8° from 19 GHz-21 GHz.Next,to realize amplitude control in a Ku-band four-channel phased-array chip,this paper designs a 4-bit differential attenuator with tail capacitor in standard standard CMOS 180 nm process.The designed step is 1 d B,and the attenuation range is 15 dB with 16 working states.In measurement,the rms phase shift is below 3.7°.Last,in the 5G communication system,amplitude control is also necessary in the radio frequency front-end chip.Therefore,this paper designs a 5-bit differential attenuator with low phase shift at 39 GHz in standard CMOS 65-nm process.With the help of tail capacitors,the measured rms phase shift is below 2.8°.