Study on the Law and Mechanism of the Third-Order Intermodulation False Alarm Effect of the Stepped Frequency Ranging Radar

Abstract

In order to improve the radar’s electromagnetic protection ability, it is essential to master the law of the false alarm effect of the radar’s out-of-band third-order intermodulation electromagnetic radiation, starting from the circuit field-circuit coupling mechanism, and the mechanism of the third-order intermodulation false alarm effect is analyzed. Taking a stepped frequency ranging radar as the research object, the absolute level value of the false alarm signal is selected as the sensitive criterion of the false alarm effect. The dual-frequency electromagnetic false alarm interference effect is carried out by using the method of the differential mode injection equivalent substitution electromagnetic radiation. The results show that the dual-frequency electromagnetic interference will cause the radar to generate the third-order intermodulation false alarm signal with the random position and waveform spreading. Under a certain interference intensity, the level of the third-order intermodulation false alarm signal increases with the increase of the interference field strength. With the continuous increase of the interference field strength, the fifth-order intermodulation false alarm signal gradually appears. The imaging mechanism, the waveform characteristics, and the level change law of the fifth-order intermodulation false alarm target, are similar to the third-order intermodulation false alarm target, and its position is also random. The maximum third-order intermodulation false alarm signal can reach 18 dBmV, indicating that the radar is sensitive to the out-of-band intermodulation electromagnetic interference.