Noise minimization techniques for voltage controlled crystal oscillator (VCXO) circuits

Crystal oscillators are commonly used as reference frequency standards for synthesis of the harmonic signal required for their operation. The phase noise of these standards limits the noise floor and interference susceptibility that affects directly the system performance. The novel approach reported in this paper optimizes the dynamic noise factor and frequency drive sensitivity for achieving ultra low phase noise VCXO circuits. An example of 100 MHz mode feedbacks and differential coupled crystal oscillators are demonstrated for the validation of this inventive approach.