A Fully Integrated 2 $\times$ 1 Dual-Band Direct-Conversion Mobile WiMAX Transceiver With Dual-Mode Fractional Divider and Noise-Shaping Transimpedance Amplifier in 65 nm CMOS

This paper presents a fully integrated 2 RX × 1 TX dual-band direct-conversion mobile WiMAX transceiver in a 65 nm CMOS technology. The frequency division ratios of 4 for the low band (2.3-2.7 GHz) and 8/3 for the high band (3.3-3.8 GHz) are employed to provide high immunity to the VCO pulling and to cover the entire frequency range with a single VCO. A "distribute-then-fractional" frequency plan is proposed to provide the frequency division ratios without degrading the LO signal integrity in the LO distribution path. The proposed plan is achieved by an inductor-less LO distribution with a novel compact dual-mode fractional divider. A noise-shaping transimpedance amplifier (TIA) is also proposed to mitigate the flicker noise of scaled CMOS devices. The two receivers consume 214.1 mW and 247.7 mW in the low-band and the high-band operations, which are lower than the power consumption of the mobile WiMAX transceivers reported previously. In spite of the low power consumption, the receivers achieve the total noise figure of 3.8 dB and 4.5 dB in the low-band and the high-band operations by virtue of the proposed noise-shaping TIA.