A multi-band phase-locked loop frequency synthesizer

Abstract

A phase-locked loop (PLL) frequency synthesizer suitable for multi-band transceivers is proposed. The multi-band PLL frequency synthesizer uses a switched tuning voltage- controlled oscillator (VCO) that covers a frequency range of 111 to 297MHz with a low average conversion gain of 41 .71 MHZ/V. A key design feature of the multi-band PLL frequency synthesizer is that the VCO tuning switches are controlled only by the normal loop dynamics. No external control is needed for the synthesizer to switch to different bands of operation. The multi-band PLL frequency synthesizer is implemented in a standard 1.2[]m CMOS technology using a 2.7V supply. The frequency synthesizer has a measured frequency range of 111 to 290MHz with phase noise up to -96dBc/Hz at a 50kHz carrier offset. Experimental comparisons of the multi-band PLL frequency synthesizer with a similar classic digital PLL frequency synthesizer show the multi-band synthesizer to have a 20% greater frequency range, an average 7.3dB superior phase noise performance, and similar acquisition time.