资 源 简 介
The focus of this monograph is the development of a low power, radiofrequency transmitter architecture. Specifically, a technique for in serviceautomaTIc calibraTIon of a modulated phase locked loop (PLL) frequencysynthesizer is presented and examined in detail. Phase/frequencymodulaTIon is accomplished by modulaTIng the feedback divide value in aphase locked loop frequency synthesizer [1]. A digital pre-compensationfilter is used to extend the modulation bandwidth by canceling the lowpasstransfer function of the PLL [2]. The automatic calibration circuitmaintains accurate matching between the digital precompensation filterand the analog PLL transfer function across process and temperaturevariations. The automatic calibration circuit, which is the main contributionof this work, has been designed to operate while the transmitteris in service. This online calibration eliminates the need for productioncalibration and periodic down time for calibration cycles.Key features of the new calibration system include the following:High data rate Gaussian Frequency Shift Keying (GFSK) and GaussianMinimum Shift Keying (GMSK) modulation.Support for M-ary FSK modulation.No required manufacturing calibration.Potential for low power operation.Key features of the implemented system include:RF output carrier center frequency in the 1.88 GHz range.GMSK/GFSK modulation at 2.5 Mb/s.4-GFSK modulation at 5.0 Mb/s.Low power (78 mW) operation.
