Research And Design Of Ka-Band CMOS Digital Phase Shifter

RF phase shifters are widely applied in military and civiliary equipment.Especially in the microwave and millimeter phased array,phase shifters can be used to change the direction of the atenna beam.It is of great significance to investigate the the microwave and millimeter phase shifters with high performance and low cost.In this dissertation,the Ka-band digital phase shifters is researched and designed using 40nm CMOS process.The design procedure of the 5-bit digital passive phase shifter and the 6-bit digital active phase shifter are presented.Both phase shifters improve phase shifting accuracy by adopting redundant bits.Firstly,the passive phase shifter consists of two 90°reflection-type phase shifters and a 180°phase shifte.And each 90°reflection phase shifter is composed of differential 3d B orthogonal directional coupler and LC series load network.The variable capacitance in the load network is realized by 6-bit digital switched capacitor array which is the key to phase shifting.The digital control signal for 180°phase shifter is 1-bit and the phase shifter totally has 7-bit digital control signals.Finally,the circuit-field co-simulation results show that the passive phase shifter can achieve a full 360°phase-shift range with a resolution of 11.25°.The RMS phase error is less than 3.79°,and the RMS gain error is less than 0.63d B over 19.5～23.5GHz.This chip occupies an area of 818×526μm~2.Secondly,the core circuit of active vector-sum phase shifter is composed of orthogonal signal generator,analog differential adder and buffer.The active phase shifter has a total of 9-bit digital control signals,including 2-bit for the analog differential adder to select polarity and 7-bit for DAC to change output current.Moreover,bandgap reference current source provides stable reference current for DAC.The co-simulation results show that the active phase shifter can achieve a full 360°phase-shift range with a resolution of 5.625°.The RMS phase error is less than 1.1°and the RMS gain error is less than 0.19d B over 19.5～23.5GHz.The power consumption is 30mW.This chip area is 745×514μm~2.