Oscillating device

An oscillating device comprising:

• a first quartz crystal resonator having a resonant frequency;
• a driving circuit coupled to the first quartz crystal resonator and configured to drive the first quartz crystal resonator to generate a first oscillating signal with the resonant frequency;
• a first buffer coupled to the driving circuit and configured to receive the first oscillating signal and isolate from a load variation behind the first quartz crystal resonator and the driving circuit to generate a first clock signal in response to the first oscillating signal;
• a bandpass filter, coupled to the first buffer, having a passband, wherein the bandpass filter is configured to receive and allow only the first clock signal with a harmonic frequency of the resonant frequency within the passband to pass through, thereby generating a filtered signal;
• a second quartz crystal resonator, having a frequency equal to the harmonic frequency, coupled to the bandpass filter and configured to receive the filtered signal to generate a second oscillating signal having the harmonic frequency;
• and
• a second buffer coupled to the second quartz crystal resonator and configured to receive the second oscillating signal and isolate from a load variation behind the first quartz crystal resonator, the driving circuit, the first buffer, the bandpass filter, and the second quartz crystal resonator to generate a second clock signal in response to the second oscillating signal.