Design Of CMOS RF Switch

With the rapid development of wireless communication technology,various new transceiver systems are continuously expedited.At the same time,requirements for radio frequency systems or components are getting higher and higher.And low cost,low power consumption,and high integration are the goal that researchers are constantly pursuing.The increasingly mature complementary metal oxide semiconductor technology has exactly these three characteristics.The RF switch is one of the important components of the transceiver system.The traditional high-performance RF switch chip is mostly realized by the PIN diode and III-V compound process.There are relatively few studies on the CMOS process.This thesis will conduct in-depth research on CMOS high-performance single-pole double-throw switch.The key performance indicators of RF switch are insertion loss,isolation,linearity,and return loss.Owing to the fact that there are some mutual constraints between the four performance indicators,they must to be considered in the actual circuit design,systematically.Starting from the basic theory of RF and the principle of switch,this thesis discusses the insertion loss,isolation,linearity and return loss in detail,and proposes optimization methods.Finally,based on the basic transistor series-shunt circuit structure,two high-performance CMOS RF switches applied in different scenarios are purposed.The first switch adopts the symmetric structure,uses the body-floating technology.Impedance transformation network,aiming at switch's ports,is performed to achieve low insertion loss and high linearity.The second switch adds a variable-impedance module to one of the branches of the basic series-shunt structure.This asymmetric structure can satisfy high power-handling capacity requirements in the transmission mode.The single-pole double-throw switch designed in this thesis is obtained by simulation.The symmetric SPDT switch exhibits a 1.2-dB insertion loss,a 28-dB isolation,a 25-dBm input power 1-dB compression point,and the return loss S11 and S22 are-26dB and-21dB at 5.4GHz.The asymmetric switch achieves 1.9-dB insertion loss and 21-dB isolation,and the return loss S11 and S22 are-21dB and-18dB in the TX mode at 15GHz.Meanwhile,the switch exhibits a 1.4-dB insertion loss,a 21-dB isolation,a 7.6-dBm output power 1-dB compression point,and the return loss S11 and S22 are-28dB and-18dB in the RX mode.