氢钟信号传输后的末端噪声过滤

Terminal noise filtration of hydrogen clock signal after transmission

低相位噪声、高频率稳定度的10 MHz氢钟信号(HCS)是精密测量物理实验中不可缺少的微波频率基准。HCS在经过一定距离的传输后,由于受到周围电磁噪声和振动的干扰,其相位噪声和短期频率稳定度会恶化.介绍了一种过滤HCS传输后的末端噪声的方案,用于改善HCS的相位噪声和短期稳定度。该方案基于将恒温高稳晶振(OCXO)相位锁定到HCS上,使氢钟1 s内的相位噪声和频率稳定度由OCXO决定,而长期稳定度跟随HCS。经过该过滤方案后,HCS的功率从-4.4 dBm放大到5 dBm,末端相位噪声本底降低约10 dB,且消除了所有高于1 Hz的干扰.该系统可在不对实验室氢钟及其信号传输网络做改动的情况下,有效提高HCS频率的纯度,进而提高精密测量实验的精度.

The low phase-noise and high frequency-stability 10 MHz hydrogen clock signal(HCS) is the indispensable microwave frequency reference for physics experiments of precision measurement.After transmitted over a certain distance,the phase noise and short-term stability of the HCS will be downgraded due to the disturbance of the external electromagnetic noise and vibration.A scheme to filter the terminal noise of the HCS after transmission is introduced,which reduces the phase noise and improves the short-term stability of the HCS.The scheme is based on phase-locking of an oven-controlled crystal oscillator(OCXO)to the HCS,the phase noise and frequency stability of the reference signal at shorter than 1 s is defined by the OCXO,while the long-term stability follows the HCS.After the filtering scheme,the power of the HCS is amplified from-4.4 dBm to 5 dBm,the terminal phase noise background of the HCS is reduced about10 dB,and all disturbance higher than 1 Hz are eliminated.The system can dramatically purify the HCS without changing the laboratory hydrogen clock and the HCS transmitting network,and then the accuracy of precision measurement experiment is improved.