A Direct Digital Frequency Modulation PLL with All Digital On-line Self-calibration for Quad-band GSM/GPRS Transmitter

The quad-band GSM/GPRS transmitter is implemented by using a PLL with an all-digital on-line self-calibration. Based on the all-digital self-calibration algorithm, all RF impairments including VCO gain and loop filter variations call totally be calibrated and repaired all digitally within 1% error. The calibration time is only 50usec by using digital adaptive gain algorithm so that the RF impairments are calibrated for every burst to track temperature, voltage, and process (PVT) variations. The measurement results show that the typical RMS phase error < 0.7 degrees and 0.8 degrees, 400kHz ORFS are < -69 and -66dBc, and the receive-band phase noise is 165 dBc/Hz and 158 dBc/Hz for the low and high bands, respectively. It demonstrates that exceeds 4 degrees margin to phase error and 6dBc margin to ORFS requirements for GSM/GPRS SAWless application.