**5. Conclusions**

The target detection and tracking performance of a bistatic compact HFSWR was investigated in this paper. An applicable target tracking method for bistatic compact HFSWR was proposed and its performance was verified using the field data collected simultaneously by a monostatic and a bistatic HFSWRs sharing the same transmitter. The experiment results demonstrate that the bistatic HFSWR can produce target tracks with acceptable errors. Moreover, the tracking results of the bistatic HFSWR were compared with those of a monostatic HFSWR. It is found that the range estimation accuracy, thus the tracking accuracy of a bistatic HFSWR is lower than that of a monostatic one based on the data in this work. The combination of a monostatic HFSWR and a bistatic HFSWR provides target observations from different perspectives, thus, the T/R-R configuration can obtain synchronous as well as complementary information for the same target. This configuration may be potentially exploited to increase the target detection probability, improve the target detection and tracking accuracy, and enhance the track continuity. Also, the T/R-R configuration can increase the detection range and extend the coverage area, thus more targets can be monitored.

In the future, more data should be collected by the T/R-R compact HFSWR so that enough statistical sample can be used to determine how long a track should be maintained based on predictions only. According to our experience, improper selection of the termination criteria will lead to track fragmentation. In our experiments, it is found that the fragmentation phenomenon appears more often for the bistatic radar than the monostatic radar. The effect of the parameters involved in the bistatic tracking algorithm on the tracking performance also needs to be studied. Moreover, new track association and fusion methods will be developed to associate and merge the track segments simultaneously obtained by the monostatic radar and bistatic radar into a longer track to improve the continuity as well as the accuracy of target tracking with compact HFSWR.

**Author Contributions:** Conceptualization, W.S. and W.H.; methodology, W.S. and M.J.; software, W.S.; validation, W.S., W.H., and Y.J.; formal analysis, W.S. and W.H.; investigation, M.J.; resources, Y.J. and Y.D.; data curation, Y.J.; writing—original draft preparation, W.S.; writing—review and editing, W.H.; visualization, M.J.; supervision, W.H. and Y.D.; project administration, W.S.; funding acquisition, W.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Key R&D Program of China with grant number 2017YFC1405202, National Natural Science Foundation of China with grant numbers 61501520, 61831010, 61671166, the Fundamental Research Funds for the Central Universities with grant numbers 19CX02046A, 17CX02079, and CSC scholarship for 1-year research abroad at Memorial University.

**Acknowledgments:** The authors would like to thank the anonymous reviewers for their comments and suggestions that helped to improve the quality of this article.

**Conflicts of Interest:** The authors declare no conflict of interest.
