A High Dynamic Range Digitally-Controlled Oscillator (DCO) for All-Digital PLL Systems

In this paper, a new high dynamic range Digitally-Controlled Oscillator (DCO) for All-DPLL systems is proposed. The proposed DCO is based on using a ΔΣ modulator as a Digital-to-Analog converter. Using ΔΣ DAC can provide a very high resolution (۱۸-bit) control on the DCO. The ΔΣ DAC output is a ۲-level pulse signal that needs to be filtered for cancelling the out of band shaped noise. The used ΔΣ modulator is a ۴th order MASH ΔΣ modulator working with the OSR of ۱۲۸ and the sampling frequency of ۴۵۰MHz. the proposed DCO is used in a PLL to synthesize the frequency in the range of ۱۷۰۰MHz to ۱۸۰۰MHz for GSM-۱۸۰۰ application. The achieved phase noise for this PLL based synthesizer in whole the range is -۱۱۵ dBc/Hz at the offset frequency of ۵۰۰ kHz. The designed ADPLL including the DCO is simulated in ADS with ۰.۱۸µm CMOS technology.

کلیدواژه ها:

ADPLL ، DCO ، ΔΣ DAC ، OSR ، phase noise ، OSR ، اسیلاتور کنترلشونده ی دیجیتال ، حلقه ی قفل فاز تمام دیجیتال ، مدولاتور دلتا سیگما ، نویز فاز