A digital calibration enhanced GSM/GPRS transmitter

This paper presents a GSM/GPRS transmitter which performance is enhanced by the proposed all digital self-calibration technique. Also, the non-ideal effects for realizing the technique including current mismatch, static phase error and VCO gain non-linearity in a conventional charge pump PLL can be self-diagnosed by the self-calibration. The measurement results shows 0.5 degree phase error and -68dBc ORFS for GMSK modulation, which prove that the accuracy of the loop gain calibration and VCO gain linearity is within 1%, and two times reduction compared to all digital and analog transmitters. The silicon prototype is implemented in 65nm process and with a 1.2V supply. The area overhead for the full custom design to enable the technique is only 0.005mm².