Abstract: Various embodiments of the invention relate to calibrate a wideband segmented Voltage Controlled Oscillator (VCO). Upon initial calibration, information of frequency spanning ranges of each segment in the VCO may be saved into a memory. When the VCO is used or activated, a microcontroller reads data from the memory and applied selected information accordingly. The initial calibration involves a frequency sweep process beginning from a first segment with an initial frequency and records any lock detection (LD) signal to the MCU when a frequency/phase lock is engaged from an unlock status or interrupted from a lock status. With the LD signals, frequency bands of the segments may be calibrated, adjusted for temperature compensated, and finalized after associating adjacent segment frequency overlap zone. A frequency band for a segment may be further segmented into multiple sub-bands with corresponding charge pump currents designated respectively for improved phase lock loop phase noise performance.