Dynamic noise-feedback and mode-coupling mechanism silences the VCXOS phase noise

Frequency reference standards are essential to achieving frequency accuracy and phase stability in electronic systems. Such reference standards require the chief characteristics of low phase noise and good frequency stability. The best oscillator performance can be expensive. The novel approach (noise-feedback and mode-coupling mechanism) reported in this paper optimizes the performance of voltage-controlled crystal oscillators (VCXOs), even those with relative low Q resonators, for low phase noise and good frequency stability. The typical measured phase noise for 120 MHz VCXO is typically -138 dBc/Hz at 100 Hz offset from the carrier, and to author knowledge, this is the best phase noise performance for this class of VCXO so far reported.