A current mode 2.4 GHz direct conversion receiver

A novel direct-conversion RF architecture is proposed that has a current mode interface between the low noise amplifier (LNA) and the down-conversion mixer, as well as the mixer and the base-band filter. The proposed architecture eliminates the voltage swing at the output of all the radiofrequency blocks. The voltage swing is seen only in the baseband after second order filtering, thus resulting in significant linearity improvements and robustness to adjacent channel interference. The current mode interface between filter and mixer also eliminates a redundant voltage-current conversion, giving significant noise advantages. A prototype wireless local area network (WLAN) receiver was designed and simulated in 0.13 μm technology, giving a third-order input-referred intercept point of 5 dBm and a noise figure of 2.7 dB for the receive chain. The circuit (including base-band) consumes 8 mA from a 1.2 V supply.