A Low Phase Noise 4.596GHz VCO for Chip-scale Cesium Atomic Clocks

Abstract

The chip-scale cesium atomic clock can provide various devices a high accuracy and high stability frequency reference. According to its operating mechanism, a 4.596GHz voltage-controlled oscillator (VCO) with small volume, low power consumption and low phase noise is vital, serving as a microwave signal source to achieve the closed-loop clocking of the whole system. Based on this, an applicative 4.596GHz VCO is designed by using a coaxial resonator with high quality factor. Firstly, the Short-Open-Line-Thru (SOLT) calibration standards for the network analyzer are designed to extract the parameters of the used coaxial resonator and its equivalent circuit model is built. Secondly, the VCO is designed with the modified Clapp circuit topology and then the transient simulation and the harmonic balance simulation are both run to evaluate the oscillation frequency and the phase noise performance of the designed VCO. Finally, the VCO is tested and the test results show that the phase noises are -44.66dBc/Hz@300Hz and -61.12dBc/Hz@1KHz, the output power is 0.006dBm and the voltage-controlled tuning sensitivity is about 50MHz/V, well meeting the application requirements of the chip-scale cesium atomic clocks.