IFM （instantaneous frequency measurement） system is an important reconnaissance resource in electronic reconnaissance. It can quickly determine the frequency of the signal to be measured， has good real-time performance， wide frequency range and high frequency resolution， and can also indicate the signals of simultaneous arrival in the case of multiple signals. It's very widely used. Based on the characteristic that IFM microwave phase discriminator can only respond to one signal at a certain instant， combining with the working principle of IFM， a new （more than 2 signals） interference strategy to IFM is investigated and the interference mechanism is analyzed， and the interference effect of IFM is evaluated through analog simulation. The simulation results show that the overlapping of multiple signals can produce obvious jamming effect on the IFM system， which can make it unable to measure the correct frequency， and the wrong output reaches the signal indication at the same time.

Multi-baseline interferometer （MBI） receiver is a kind of important sensor for electronic reconnaissance， which is widely used in radio direction finding （RDF） with the advantages of high accuracy of angle measurement and fast processing speed. A jamming strategy of multiple overlapping signals is proposed according to the working principle of the interferometer direction finding， and the jamming mechanism of multiple signals on interferometer direction finding is studied. Modeling and simulation are carried out to evaluate the jamming strategy. The simulation results show that the multiple overlapping signals can significantly jam the interferometer direction finding and make the interferometer fail to obtain the true direction of the radio frequency （RF） target and output the wrong indication of simultaneous arrival signals at the same time.

For a long time， hostile close-in reconnaissance （HCR） against China by foreign countries has become increasingly fierce， and has been upgraded to the theoretical level of "deterrence by detection"， showing a systematic and intelligent development trend. The threat， efficiency mechanism， technical theory， cognitive limitations of HCR are analyzed， limitations and cognitive misunderstandings of traditional DHCR （denial of hostile approaching reconnaissance） operations are analyzed. Taking electronic reconnaissance and radar counter-reconnaissance in electronic warfare as examples， regaining the electromagnetic right in DHCR is focused both with denying the tasks of HCR operations， a new theory of active defense in electromagnetic domain is proposed， and combined with the DHCR， a new tactical operation type is proposed with name of CRJ， laying a theoretical foundation for the systematization of DHCR.