Compact Active Switch Design For Millimeter-wave Phased Array System

Millimeter-wave phased array systems play an important role in the future fifth generation mobile communications.The active switch is one of the vital modules to control the transmitted and received switching in the phased array system.The switch circuits include active and passive topology.The active switch could avoid the shortcomings of insertion loss and low integration,which is naturally existed in the passive switch.The active switch consists of switch module and driver amplifier.The former is composed of a cascaded common-gate(CCG)amplifier in transmitting channel and a common-drain(CD)amplifier in receiving channel.On one hand,the CCG amplifier is adopted to improve the power gain and switch isolation of transmitting channel.A stability compensation network is considered to improve the stability of CD amplifier,and a switched capacitance is added to realize the impedance matching multiplexed in common port of the switch.On the other hand,the cascode topology is adopted for driver amplifiers,which presents good performance on stability,power gain and bandwidth.The above modules are well integrated by capacitors and inductors and the transmission lines are widely used to connect these modules and the terminal of transmitting/receiving channels.The capacitors and inductors form the T and pi networks,which are fully optimized to ensure the low matching loss and broad bandwidth of the circuit.The inter-stages are compensated with each other to achieve the broadband and high gain performance.Fabricated in 65-nm CMOS technology,the chip size is about 0.52 mm~2,of which the active switch is about 0.2 mm~2.The measured results show that in transmitting mode,the circuit achieves the maximum gain of 16 d B and the bandwidth of 10 GHz(30 GHz-40 GHz).The maximum output power of 4.2 d Bm is delivered,and the DC power is only 11.8 m W.In receiving mode,the active switch provides the maximum gain of 12.8 d B throughout the bandwidth of 30 GHz to 40 GHz.The input power 1 d B compression point of about-12 d Bm and DC consumption is about 5.6 m W.The measurement of active switch shows comparable switch isolation and reverse isolation with passive switch,It provides additional power gain for the phased array and occupies smaller chip are,which presents wide application prospect.