Abstract: A novel 0.13 μm CMOS low-voltage folded-switching mixer for direct-conversion ultra wideband(UWB) receiver is presented.The topology of the mixer is given.A shunt resistor is used in the wideband input-matching network.A CMOS inverter with current-reuse technology is used in the transconductor stage.The transconductor stage and the switching stage are ac-coupled with capacitors.LC resonators take the place of traditional current sources.Methods of improvement of performances of linearity,gain and noise are analyzed.Die is fabricated with 0.13 μm CMOS technology of Semicondactor Mannfacturing International Co(SMIC). The measured results gave excellent linearity,IIP3 of 10.2 dB(mW),with power gain of-4.2 dB,single side band(SSB) noise figure of 12.8 dB,while dissipating 5.1 mW at 1.0 V power supply.