A 1.1GHz CMOS FractionalN Frequency Synthesizer with a 3b ThirdOrder ¿¿ Modulator

A 1.1-GHz fractional-N frequency synthesizer is implemented in 0.5-µm CMOS employing a 3-b third-order ¿¿ modulator. The in-band phase noise of -92 dBc/Hz at 10-kHz offset with a spur of less than - 95 dBc is measured at 900.03 MHz with a phase detector frequency of 7.994 MHz and a loop bandwidth of 40 kHz. Having less than 1-Hz frequency resolution and agile switching speed, the proposed system meets the requirements of most RF applications including multislot GSM, AMPS, IS-95, and PDC.