对相对论速调管放大器（RKA）锁相特性进行了粒子模拟与实验研究。在2.5维粒子模拟中，研究了电子束电压波形特征对RKA锁相特性的影响，结果表明：电子束电压波形上冲对RKA锁相特性有正面影响，即能够减小相位差达到锁定状态的时间，幅度为20%的上冲导致大约23的相位差变化；波形顶降则对RKA锁相特性有负面影响，可使相位差过早地偏离稳定值，幅度为5%的顶降大约能引起50的相位差偏离；电压波形的上升时间对RKA相位锁定特性也有影响，但规律不明显。在三维粒子模拟和实验中，研究了导引磁场大小对RKA锁相特性的影响，结果表明，在1.6 T以下，RKA输出微波与种子源微波之间的相位差锁定值总体上随导引磁场的增大而减小，在细节上，呈现阶跃形式，即一定范围内导引磁场大小变化不会导致相位差的改变。实验研究表明，在导引磁场范围为0.6~1.2 T时，RKA锁定相位差随导引磁场的增大而减小，阶跃现象不明显。
The phase-locking properties of an S-band relativistic klystron amplifier (RKA) are investigated. In 2.5-dimensional particle-in-cell simulations, the influences of the electron beam voltage waveform on RKA phase-locking are studied. The results show that the spike in the voltage waveform of the electron beam has a positive effect on the RKA phase-locking properties, and it can reduce the time spent to achieve the locked state. A spike of 20% over the original voltage amplitude can cause a change of about 23 in the phase difference. Waveform flat-drops have negative impacts on the phase-locking of the RKA, which make the phase prematurely depart from the steady state. A flat-drop of 5% off the original voltage amplitude can cause a deviation of 50 in the phase difference. The rise time of the voltage waveform influences the RKA phase locked state either, but the trend is not obvious. The influence of the guiding magnetic fields on the phase is studied in a three-dimensional PIC simulation. The results show that the phase differences decrease when the guiding magnetic fields increase in the overall trend when the magnetic fields are below 1.6 T. In detail, the step form is shown, i.e. within a certain range, the changing of the guiding magnetic fields does not result in the changing of the phase differences. Experimental studies show that the phase differences decrease when the guiding magnetic fields increase. In the experiments, the guiding magnetic fields are between 0.6 T and 1.1 T, and the step form of the phase differences is not obvious.