Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for a microwave cavity resonator stabilized oscillator, are described. The oscillator can include a cavity resonator configured to resonate at least at one predetermined resonant frequency in a GHz frequency range. The oscillator can include circuitry including a microwave amplifier, a low pass filter and a phase shifter. The circuitry may be arranged in a feedback loop configuration, and may be at least partially mounted above a first surface of the cavity resonator. The circuitry may be electrically coupled to the cavity resonator to form an oscillator. The circuitry can include a first delay line segment that is selected instead of at least one other delay line segments for wire-bond connection to complete the feedback loop configuration at zero degree phase.

Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for a microwave cavity resonator stabilized oscillator, are described. The oscillator can include a cavity resonator configured to resonate at least at one predetermined resonant frequency in a GHz frequency range. The oscillator can include circuitry including a microwave amplifier, a low pass filter and a phase shifter. The circuitry may be arranged in a feedback loop configuration, and may be at least partially mounted above a first surface of the cavity resonator. The circuitry may be electrically coupled to the cavity resonator to form an oscillator. The circuitry can include a first delay line segment that is selected instead of at least one other delay line segments for wire-bond connection to complete the feedback loop configuration at zero degree phase.

A structure of an integrated crystal oscillator package has a first quartz crystal resonator, a second quartz crystal resonator, and application-specific integrated circuit chip (ASIC) combined in a package. The ASIC has a switch control for receiving audio formats of 44.1 kHz and 48 kHz with different hi-fidelity (hi-fi). The first quartz crystal resonator has a first clock rate corresponding to the 44.1 kHz frequency and the second quartz crystal resonator has a second clock rate corresponding to the 48 kHz frequency to be switched by the present invention in operation.