An all-factor modulation bandwidth extension technique for delta-sigma PLL transmitter

In this work, an all-factor modulation bandwidth extension technique for one-point delta-sigma (ΔΣ) phase locked loop (PLL) transmitter is presented. The factors that need to be calibrated have been discussed. Firstly, RC variation of the loop filter is compensated by using an RC tracking circuit. Secondly, variation of the loop gain of the modulator is calibrated by sensing the magnitude differences between its values at DC and high frequency. Since two critical factors of PLL are calibrated, the proposed technique can achieve higher calibration accuracy. Moreover, this technique has been proven to be valid for all PLL types and orders by theoretical analyses given in this paper. And one particular case has been verified by measurement results.