Transistor voltage-controlled oscillator and frequency synthesizer having the same

A frequency synthesizer, comprising:

• a reference signal source for providing a reference signal;
• a voltage-controller oscillator (VCO) for generating an oscillating signal and a first analog signal identical to the oscillating signal;
• an injection-locked frequency divider including a five-stage inverter ring oscillating frequency dividing circuit, the five-stage inverter ring oscillating frequency dividing circuit receives the first analog signal from the VCO and divides the frequency of the first analog signal by five, to generate a first frequency-divided signal;
• a pulse-swallow frequency divider for receiving the first frequency-divided signal and generating a second frequency-divided signal;
• a phase frequency detector (PFD) for receiving the second frequency-divided signal and comparing the second frequency-divided signal with the reference signal to output two digital signals;
• a charge pump for receiving and comparing the two digital signals sent by the PFD to output a second analog signal;
• and
• a loop filter for receiving the second analog signal and generating a third analog signal to the VCO.