Aiming at the technical requirements of the complex electromagnetic environment adaptability test and evaluation for the spectrum-dependent equipment

starting from the linear coupling of field with circuit and the nonlinear response mechanism of circuit

the third-order intermodulation blocking effect model is established by introducing the third-order intermodulation blocking interference factor. Combining theoretical derivation and experimental measurement

the method of determining model parameters and the process of modeling and evaluation of third-order intermodulation blocking effect are given

and the experimental verification is carried out using the communication radio as the equipment under test. The results show that

using the third-order intermodulation blocking interference factor of the spectrum-dependent equipment tested at a specific working frequency

assuming that it does not change with the frequency offset of the radiated interference

according to the variation curve of the critical interference field strength of the single frequency electromagnetic radiation blocking for the spectrum-dependent equipment and the distribution parameters of environmental electromagnetic field spectrum

the third-order intermodulation blocking effect of the spectrum-dependent equipment can be accurately evaluated

and the tested error is less than 1dB.