Hong Kong Applied Science and Technology Research Institute Company, Limited

Wang Chi Cheng

Tat Fu Chan

Shiyuan Zheng

Yunlong Li

A Phase-Locked Loop (PLL) has a multi-curve voltage-controlled oscillator (VCO) with a curve-select input that adjusts the capacitance within the VCO and thus the VCO gain. A calibration unit generates a curve-select value to the VCO. Coarse calibration selects a Center Curve CC value using binary search of the curve-select bits. During fine calibration, the number of pulses of the VCO output are counted and stored for all curves in a target window around the center curve. The stored pulse counts are compared to an ideal pulse count for a specified frequency, and the curve-select value for the closest-matching pulse count is applied to the VCO. The target window is much smaller than all possible curves, so calibration is performed only on a few curves, reducing calibration time. A switch before the VCO opens the loop for faster open-loop calibration. Pulses are counted digitally without expensive analog comparators.

Fast coarse tune and fine tune calibration for a synthesizer by multi-curve calibration within a target window

A two-point modulation Phase-Locked Loop (PLL) has a gain-adjustable voltage-controlled oscillator (VCO). A digital data modulation signal is combined with a carrier and input to a feedback divider. The data modulation signal is also input to a Digital-to-Analog Converter (DAC) to generate an analog voltage to a second input of the VCO. A calibration unit divides the VCO output and counts pulses. During calibration, the data modulation signal is set to minimum and then maximum values and VCO output pulses counted. A count difference for the data modulation signal at maximum and minimum values is input to a Look-Up Table (LUT) to read out a gain calibration value. During normal operation mode, the gain calibration value from the LUT is applied to a second input of the DAC, which drives the VCO to adjust VCO gain. A switch before the VCO opens the loop for faster open-loop calibration.

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Hong Kong, China

Wang Chi Cheng