A wide-bandwidth 2.4 GHz ISM band fractional-N PLL with adaptive phase noise cancellation

A fast-settling adaptive calibration technique is presented that makes phase noise cancelling Delta E fractional-N PLLs practical for the low reference frequencies commonly used in wireless communication systems. The technique is demonstrated as an enabling component of a 2.4 GHz; ISM band CMOS PLL IC with a 730 kHz bandwidth, a 12 MHz reference, and an on-chip loop filter. In addition to the adaptive calibration technique, the IC incorporates a dynamic charge pump biasing technique to reduce power dissipation. The worst-case phase noise of the IC is -101 dBc/Hz and -124 dBc/Hz at 100 kHz and 3 MHz offsets, respectively, and the adaptive phase noise cancellation technique has a worst-case settling time of 35 mu s. The IC is implemented in 0.18 mu m CMOS technology. It measures 2.2 x 2.2 mm(2), and its core circuitry consumes 20.9 mA from a 1.8 V supply.