A Model for Predicting Second-Order Intermodulation Low-Frequency Blocking Effects

To identify and improve the electromagnetic compatibility of a global navigation satellite system (GNSS) receiver under a complex electromagnetic environment, the blocking effects of single-frequency and out-of-band dual-frequency electromagnetic radiation (EMR) on a GNSS receiver were experimentally analyzed. This study is the first to investigate second-order intermodulation second-order intermodulation low-frequency blocking (SILB) interference which was newly discovered in our tests. The mechanism of the SILB effect was analyzed, and two key parameters were identified. The SILB interference factor and the relative value of the low-frequency interference level were introduced to establish a model predicting SILB effects. The method of determining the parameters, the modeling process, and the results are discussed in this article on the basis of both theoretical derivations and experimental measurements. A GNSS receiver was used as the equipment under test to verify the model. Notably, the results demonstrated that the threshold for SILB was approximately 30 dB lower than that for out-of-band single-frequency interference. The model proposed in this article accurately evaluated and predicted the SILB interference.