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

A wideband and low phase noise quadrature local oscillation (LO) signal generator for multistandard 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 voltage-controlled oscillator (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 multistandard cellular transceivers. The LO-generator occupied a small silicon area of
$0.15\;\text{mm}^{2}$
and achieved an excellent phase noise performance of
$- {141}.{02}\;\text{dBc}/\text{Hz}$
at a 1 MHz offset from a 709 MHz LO-frequency.