A design of active mixer intended for the "mode 1" of ultra wideband multi-band OFDM receivers is presented. It is based on a doubly-balanced Gilbert cell type in which bleeding current sources are added in order to improve linearity and gain. Using an adequate input matching network and optimized device size, it was possible to obtain a good operation of the proposed mixer all over the 3.1-4.8 GHz band with AMS 0.35 μm CMOS process parameters. The simulated results show a conversion gain of 14.0 dBm. a noise figure of 7.7 dB and an input IP3 above 0 dBm. when the power consumption is 18 mW under 3 V supply voltage.