## 1 Introduction  
The weak working signal of the navigation system is extremely susceptible to various types of electromagnetic radiation. Therefore, more and more attention is drawn to its anti-jamming performance research. At present, the research on navigation receivers mainly focuses on three aspects. Firstly, the influence of all kinds of electromagnetic interference signals on the performance parameters of commercial navigation receivers [1] is studied, where the C/N0 [2; 3; 4], interference rejection level, and interference recovery time [5] are used as effect parameters to evaluate the influence of electromagnetic interference on the performance of navigation receivers. Secondly, anti-interference methods and algorithms [6; 7] are proposed to improve the anti-interference performance of navigation receivers by inhibiting interference signals. Finally, the interference prediction models based on the interference mechanism are established by studying the interference prediction methods [8; 9; 10]. Whatever the research perspective is, the sensitivity criterion needs to be defined at first. Both the GJB-4405A-2006 [11] and GJB-6741-2009 [12] have defined the assessment rule of the jamming effect for speech communication and digital communication, respectively. The interference to speech and digital communication equipment is divided into five levels for these two. The subjective method is adopted to evaluate the speech signal in the speech communication system, i.e., no interference, very weak interference, weak interference, strong interference, very strong interference, while the objective method of the increment of bit error rate(BER) is employed to assess the digital signal in digital communication system, i.e., \(\Delta P_{e}\leq 1\%\), \(1\%<\Delta P_{e}\leq 5\%\), \(5\%<\Delta P_{e}\leq 7.5\%\), \(7.5\%<\Delta P_{e}\leq 10\%\) and \(10\%<\Delta P_{e}\). The sensitivity criterion of a certain type of communication equipment could be more easily defined based on the above two standards. The sensitivity threshold level testing method in GJB-151B-2013 [13] or MIL-STD-461G [14] could be appropriate for general electronic equipment to obtain the electromagnetic sensitivity threshold. However, the relevant materials on the sensitivity criterion of navigation receivers was not provided in current studies. Meanwhile, the signal intensity of the navigation receiver is relatively weak, and the measurement error is bound to be too large by adopting the conventional measurement methods, which is worthy of further study.  
In this context, the electromagnetic interference mechanism of non-linear equipment is analyzed firstly. Furthermore, the sensitivity criterion of equipment in current studies is analyzed to draw the application of the sensitivity criterion on a navigation receiver. After defining the sensitivity criterion of the navigation receiver based on the effect sensitivity phenomenon and establishing the measurement method, which includes the variable interference power step size and the requirement of a system recovery state after each interference, the single-frequency continuous wave electromagnetic radiation effects experiment is carried out on a certain type of navigation receiver. The repeatability and accuracy of the critical interference power/field intensity testing data adopting the proposed measurement method will be validated, and the sensitivity law of the navigation receiver will be explored.