Frequency synthesizer and high-speed automatic calibration device therefor

An automatic calibration device for a phase-locked loop based frequency synthesizer, the automatic calibration device comprising:

• a frequency-to-digital converter configured to convert frequencies of a first signal and a second signal outputted from a voltage controlled oscillator into a first digital value and a second digital value, respectively;
• a frequency difference detector configured to calculate a difference between the first digital value and the second digital value;
• and
• a loop bandwidth calibration logic configured to tune a charge pump gain using a difference between the first digital value and the second digital value such that a loop bandwidth is kept constant within a range of output frequency bands of the voltage controlled oscillator,
• wherein the first signal is a signal outputted by the voltage controlled oscillator for a minimum voltage within a segment displaying linear frequency characteristics in an optimal control code for a capacitor bank of the voltage controlled oscillator, and the second signal is a signal outputted by the voltage controlled oscillator for a maximum voltage within the segment.

An RF frequency synthesizer comprising:

• a phase-locked loop, the phase-locked loop comprising a voltage controlled oscillator, a frequency divider, a reference frequency generator, a phase/frequency detector, and a pulse-voltage converter;
• and
• an automatic calibration loop, the automatic calibration loop comprising the voltage controlled oscillator and an automatic calibration device,
• wherein the automatic calibration device comprises:
• a frequency-to-digital converter configured to convert a frequency of a signal outputted from a voltage controlled oscillator into a first digital value, a frequency difference detector configured to calculate a difference between the first digital value outputted from the frequency-to-digital converter and a second digital value corresponding to a target frequency, an automatic frequency calibration logic configured to select an optimal control code for a capacitor bank such that an output frequency of the voltage controlled oscillator is closer to the target frequency, and a loop bandwidth calibration logic configured to tune a charge pump gain such that a loop bandwidth is kept constant at the optimal control code using the frequency-to-digital converter.