An ultra low phase noise GSM local oscillator in a 0.09 μm standard digital CMOS process with no high-Q inductors

A design approach is presented for realizing a fully integrated local oscillator, covering all 4 GSM bands, and fulfilling the stringent phase noise requirement of -162 dBc/Hz at a 20-MHz offset from a 915-MHz carrier in a 1.4-V 0.09-μm digital CMOS process. By operating a digitally-controlled oscillator at a 4× frequency followed by ÷ 4 frequency dividers, the requirements of on-chip inductor Q and the amount of gate oxide stress are relaxed. Both dynamic and SCL dividers are also studied for their phase noise performance. It was found that a dynamic divider is needed for stringent TX outputs while an SCL divider can be used for RX to save power. Both dividers are capable of producing a tight relation between 4 quadrature output phases at low voltage and low power.