A high linearity current mode mixer for IEEE 802.11 b/g/n/ax standard WLAN receivers is designed to meet the cus-tomized requirements of low cost and linearity for wireless LAN receivers.Adopting a zero intermediate frequency receiver architec-ture,the circuit structure of the current mode mixer mainly includes a transconductance stage amplifier,a mixing switch stage,and atransimpedance amplifier.By switching between two operating states of the transconductance stage and changing the feedback resist-ance of the transimpedance amplifier,the four level gain of the mixer can be adjusted.The mixing switch stage adopts a dual balanced passive mixing circuit to provide high linearity.In order to solve the DC offset problem in zero intermediate frequency receivers,a cur-rent injection DC offset calibration circuit has been added to further improve the linearity of the mixer.Optimize the design of the transconductance operational amplifier circuit in the transimpedance amplifier to increase its bandwidth,ensuring that the input imped-ance of the transimpedance amplifier is small enough to ensure the linearity of the mixer;Based on the 180 nm RF CMOS process,the mixer is simulated.When the local oscillator frequency is 2.4GHz,the four gain levels are 38dB,32dB,27dB,and 21dB,respective-ly.The intermediate frequency bandwidth can reach 20MHz;The noise figure is 8.46dB under high gain conditions,and the input third-order intermodulation point can reach 13.72dBm under low gain conditions;The simulation results show that the current mode mixer achieves good linearity performance under a wide intermediate frequency bandwidth,meeting the customization requirements of WLAN receivers.
关键词
电流模式混频器/线性度/跨导放大器/跨阻放大器/零中频接收机/直流失调校准
Key words
current mode mixer/linearity/transconductance amplifier/transimpedance amplifier/zero intermediate frequency re-ceiver/DC offset calibration
维普
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