A 3.1–4.8-GHz direct-conversion mixer in 0.35-μm CMOS for mode-1 MB-OFDM UWB systems

This paper presents a CMOS direct-conversion mixer for TFI-OFDM receiver of UWB group #1 bands, providing a 110 Mbits/s rate and optimized for 0.35-μm technology. The proposed mixer uses the current-bleeding technique in both the driver and switching stages with wideband impedance matching, consisting of a bandpass filter embedding the RF stage. The 1/f noise of the switching pairs dominates the noise performance for down-converted frequencies below 1 MHz. Above 1 MHz, the insertion of an inductor at the tail of switching pairs reduces uniformly the noise figure by 2.2 dB. Over 3.1–4.8 GHz, the circuit drawing 6 mA from 3-V supply, shows a conversion gain of 14.0 ± 1.0 dB, IIP3 of 0 ± 2 dBm, double-sideband noise figure of 4.5–4.8 dB, and port-to-port isolation above 61.0 dB. The mixer output bandwidth is 460 MHz. The RF power and LO amplitude marginally affect these performances within, respectively, the FCC-power limits and 2.5–3.4 V range.