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 about 10 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.