A 900 MHz local oscillator using a DLL-based frequency multiplier technique for PCS applications

One approach to implementation of low-phase-noise integrated fixed-frequency local oscillators (LOs) for use as the RF LO in a blockdown-convert receiver architecture for PCS wireless communications down-converts the entire RF band to a lower frequency using a fixed-frequency LO. This allows new approaches to the implementation of low-phase-noise oscillators with low-Q components. The technique uses a DLL-based frequency multiplier to synthesize a RF LO whose phase noise is closely related to that of the reference crystal and not dependent on the phase noise of a VCO. An experimental prototype generates a 900 MHz signal and is designed to meet the requirements of the IS-137 standard. The device achieves a phase noise of -123dBc/Hz at a 60 kHz offset frequency with 39 mA overall current consumption from a 3.3 V supply. This prototype was fabricated in 0.35 /spl mu/m double-poly five-metal CMOS.