Design Of CMOS Ultra-wideband Switch Circuit

With the rapid development of modern wireless communication systems,the low cost,high integration RF front-end has been constantly refurbished and improved.The utilization of commercial complementary metal oxide semiconductor(CMOS)in microwave transceiver system design is the general trend,and today’s communication system has been unable to satisfy operating in single frequency band,and the multi band and ultra-wideband(UWB)system came into being.The CMOS process is difficult to integrate large power devices such as microwave switch and amplifier,which is harder to realize UWB operation and integration simultaneously.This paper is devoted to research the silicon based CMOS UWB switch,hoping to promote the development of UWB microwave systems.In this paper,the main performance parameters of microwave switch are analyzed theoretically,and the improvement methods of insertion loss,isolation and power handling capacity are proposed.The passive inductors and on-chip passive balun for microwave switches are also analyzed.The wideband transformer balun is designed and simulated.The simulation results show that the insertion loss is 1.844dB at 16.5GHz,and the ldB bandwidth is 13.5GHz.The amplitude balance in the 1GHZ-25GHz band is less than 0.6dB,and the phase equilibrium in the 4GHz-25GHz band is within the range of±50.Bandwidth,insertion loss,isolation and power handling capacity always trade off between each other during design process of switch circuit.Two UWB switches are designed based on classic series-shunt structure,differential UWB switch can connect differential module and single-end module while single end UWB switch has wider application scope itself.The differential switch used the negative bias voltage technique,the leakage elimination technique and the AC floating technique to improve the isolation and power handling capability.The single-end switch used a unique matching network to improve the performance of the switching circuit at high frequency.Through the simulation of UWB differential microwave switch,it is found that the return loss of the switch is less than-10dB before the 27.5 GHz.The insertion loss is less than 2dB before 15GHz,before the 20GHz,the insertion loss is less than 2.5dB.The isolation is less than-22.5dB before 20GHz.At 15GHz,the input ldB compression point of the transmit mode is 13.6dBm.The simulation results of UWB single ended microwave switch show that the return loss of the switch in the transmit mode and receive mode are both less than-10dB in the DC-30GHz,and the insertion loss is 2.4dB at 20GHz and 1.95dB at 15GHz,and the isolation are both less than-23dB in DC-30GHz.At 15GHz,the input 1dB compression point of the transmit mode is 7.5dBm.The simulation results show that the UWB switch designed in this paper accords with the expected effect,and has some significance for researching CMOS UWB microwave switch.