Clock generator

A clock generator, comprising:

• a phase frequency detector configured to compare a phase and a frequency of a reference clock signal with a phase and a frequency of a first output clock signal and generate a detection signal based on a difference in the phases and frequencies of the clock signals;
• a loop filter configured to generate a first control voltage signal based on the detection signal;
• a first voltage controlled oscillator configured to generate and output a first output clock signal based on the first control voltage signal;
• a modulation filter configured to generate a modulation voltage signal based on the reference clock signal and generate a second control voltage signal by combining the modulation voltage signal and the first control voltage signal;
• and
• a second voltage controlled oscillator configured to generate and output a second output clock signal based on the second control voltage signal,
• wherein the modulation filter is a high-pass filter (“HPF”) consisting of a resistor and a capacitor, and wherein the modulation filter removes a direct current (DC) component and a lower-frequency harmonic component from the reference clock signal, and wherein the first control voltage signal is input to the resistor and the modulation voltage signal is input to the capacitor.