The World’s Smallest Quartz-Based OCXO for 5G Synchronization Applications

In this work we successfully developed an ultra-miniature Oven Controlled Crystal Oscillator (OCXO) with the size of 5.0 mm 3.2 mm. A heater-embedded crystal package is demonstrated to establish a thermally symmetry oven structure, thus improving the oven stability and reliability. By using a three layer in series heater resistor design, an ultra-miniature size of 2.5 mm 2.0 mm crystal can be realized. In addition, a SC minus cut is considered to further improve the temperature stability, phase noise, drive level sensitivity, gravity sensitivity, aging, and longer holdover performance. Moreover, the SC minus cut has a lower inflection temperature at 83°C comparing to the traditional SC-cut crystal with higher inflection temperature at 89°C, thus a better aging and lower power consumption is achieved by setting a lower oven controlled temperature. As a result, the temperature stability has achieved ±20 ppb across the ambient temperature from -40 to 95°C, indicating that the result satisfies the requirement for 5G synchronization applications, such as IEEE1588 V2 and enhanced synchronous Ethernet equipment clock (eEEC).