A 0.56-2.92 GHz Wideband and Low Phase Noise Quadrature LO-Generator Using a Single LC-VCO for 2G-4G Multistandard Cellular Transceivers

Abstract

A wideband and low phase noise quadrature local oscillation (LO) signal generator for multi-standard cellular transceivers was proposed. Using the new LO-plan consisting of divide-by-6, divide-by-4, and divide-by-12 frequency dividers, the required frequency tuning range (FTR) of a VCO was reduced to 39%, which can be easily covered by a single LC-VCO. Due to the reduced FTR, the VCO can retain a high Q-factor and achieve low phase noise. The key building block of the new LO-plan is a quadrature divide-by-6 divider, capable of generating precise I/Q signals. To implement the quadrature divide-by-6 divider, we proposed a fully differential divide-by-3 divider with 50% duty cycle. Using the same idea, a fully differential divide-by-2 circuit was also proposed for divide-by-4 and divide-by-12 dividers. The proposed LO-generator was fabricated in a 40-nm CMOS process, and covered LO-frequencies of 0.56 - 2.92 GHz for multi-standard cellular transceivers. The LO-generator occupied a small silicon area of 0.15 mm2 and achieved an excellent phase noise performance of -141.02 dBc/Hz at a 1-MHz offset from a 709-MHz LO-frequency.