For more than ten years, I have been studying passive location technology. More than 200 related academic papers have been published. The academic monograph "Passive Detection and Location Technology" funded by the National Key Publishing Fund has been published by the National Defense Industry Press in 2017. In 2022, Bentham Press published an English monograph on passive location methods based on phase difference measurement. In addition, three English monographs have been published so far. More than ten invention patents have been applied for and authorized.
Some research results with great breakthrough significance are as follows:
1. Linear solutions and inherent characteristics of the double-basic path difference location equation on the two-dimensional plane 
2. Doppler navigation system based on beacon signal
3. Fuzzy-free passive location method based on phase difference measurement
4. Airborne single-station Doppler ranging solution and accuracy correction method
5. A method for real-time detection of the position and motion parameters of maneuvering targets using dual aircraft
6. A method of passive location by using external emitter with unknown location
7. Two-station passive location solution independent of baseline length
8. Doppler direction finding method based on one-dimensional linear array