A Novel Cascode Mixer for NB-IoT Transceiver System in 65nm CMOS

Abstract

NB-IoT is a FDD system. Its TX & RX are operated at a fixed frequency offset at the same time. Conventional architecture builds 2 PLLs to support FDD. This paper presents a new architecture which only needs one PLL. Its receiver introduces a novel cascode-mixer structure (Cascaded by two current-mode passive mixers driven by 25% duty-cycle quadrature clocks). The cascode mixer makes two times mixing of RF signals using the LO1 produced by the PLL and the LO2 from the crystal reference. It achieves 18.7dB noise figure and +8.13 dBm IP1dB in simulation with a commercial 65nm RFCMOS process. It consumes 2.8mA from a 1.2V supply. IQ phase mismatch correction is also implemented in this design.