||With the development of technology, information not only text but also imaging and multimedia need to transmit by air. If high communication quality is required, the transmission data rate increases farther more. Current radio frequency transceiver equipment cannot fulfill such a high data rate requirement, so a new wireless standard 802.15.3a is under discussion. One of the proposals is MB-OFDM ultra-wideband (UWB). Occupying from 3.1-10.6GHz, the system can transmit up to 480Mb/s, and due to the OFDM modulation characteristic, it is robust to interference. An up-conversion mixer based on this project is designed. In order to use for OFDM system, a topology of high linearity is employed. Since the mixer is used for the UWB "mode 1" transmitter, at the output of the mixer, the bandwidth is tuned to 3.1-4.8GHz. Reducing the parasitic capacitance and output resistance is used for realizing it. A vertical inductor is also used here for reduce the parasitic capacitance and enlarge the self-resonant frequency (SRF). The circuit is implemented by TSMC 0.18um process, and the supply voltage is 1.8V. After carefully layout the circuit, the IIP3 (input intercept point) is 17.8dBm, and the bandwidth is 2.75-4.9GHz.