A modified closed-loop auto frequency calibration technique for a 1.571-GHz integer-N PLL

作者：Liu, Jianghua; Jiang, Jinguang^*; Tang, Yanan

来源：International Journal of Electronics, 2017, 104(6): 898-912.

DOI：10.1080/00207217.2016.1253786

• Auto frequency calibration
• modified closed-loop
• coarse frequency band search
• start-up trap
• phase-locked loop (PLL)
• lock time

In this paper, a modified closed-loop auto frequency calibration technique (MCL-AFC) is adopted in an integer-N phase-locked loop (PLL) for GPS-L1 application. The ignorance of circuit initial conditions setting in the closed-loop AFC may cause the start-up trap and long frequency calibration time. To solve these problems, the MCL-AFC technique is introduced. The process of MCL-AFC is listed below: first, initialisation process is only used for start-up of PLL; second, closed-loop voltage comparison process and open-loop switching process will take place alternately until optimum frequency control words are obtained. Tuning voltage searching range is reduced by half during the voltage comparison process since VCO's tuning voltage is set to half of supply voltage through switching process. The MCL-AFC circuit is implemented in a 1-poly 6-metal 180nm CMOS process and its chip area is 0.0167mm(2). The measured locked output frequency of the PLL is 1.571GHz and the out-band phase noise is -131.9dBc/Hz at 1MHz. The calibration time of PLL with MCL-AFC circuit is reduced to only 5 mu s while whole locking time is about 10.2 mu s.

• 出版日期2017-6
• 单位武汉大学