This article presents an analysis of spurious signals’ influence on automatic frequency control (AFC) in EPR spectrometers. The primary source of spurious signals is leakage across the circulator in the microwave bridge. Additionally, the signals reflected from connectors in the line between the circulator and the resonator modify that signal. Spurious signals may degrade the performance of AFC, significantly offsetting lock points from the center frequency of the resonator. The offset’s size depends on the parameters of the resonator and the amount of the circulator isolation. It can be minimized by the appropriate use of a phase shifter located in the line between the circulator and the resonator. Another way to avoid these problems is to introduce a leakage compensation arm to the microwave bridge.

本文分析了杂散信号对 EPR 光谱仪中自动频率控制 (AFC) 的影响。杂散信号的主要来源是微波桥中环行器的泄漏。此外，从环行器和谐振器之间线路中的连接器反射的信号会修改该信号。杂散信号可能会降低 AFC 的性能，显着抵消谐振器中心频率的锁定点。偏移量的大小取决于谐振器的参数和环行器的隔离量。通过适当使用位于环行器和谐振器之间的线路中的移相器，可以将其最小化。避免这些问题的另一种方法是在微波桥中引入泄漏补偿臂。