Aiming at the shortcomings of complex broadband transmitter/receiver systems and inflexible bandwidth control in the existing inverse synthetic aperture radar (ISAR) imaging systems, in this paper, a novel two-dimensional imaging method based on frequency diverse ISAR (FDISAR) is proposed by combining frequency diversity technique with inverse synthetic aperture technique. In the imaging process, FDISAR is different from the stepped-frequency ISAR, which needs to transmit the same burst at different observation moments. Once the bandwidth is determined, the bandwidth of the subsequent burst synthesis cannot be changed, which reduces the flexibility of the radar system. In this method, single-frequency signals of different frequencies are transmitted to the target at different observation times, and the wideband signals are synthesized using the frequencies at different observation times to obtain the resolution capability in the range direction. In addition, the relative motion synthetic aperture of the target and radar is used to obtain the azimuth resolution capability, and finally the two-dimensional imaging capability of the moving target is formed. Specifically, we established an ISAR imaging model based on frequency diversity to synthesize a broadband signal, and used an improved backward projection algorithm (BP) to complete the two-dimensional imaging of the target. On this basis, the influence of the transmission signal frequency selection on the imaging quality is analyzed, and the half-power resolution in range and azimuth directions is derived. Furthermore, in order to eliminate side lobes and improve imaging quality, we combined compressive sensing (CS) theory with a BP imaging algorithm based on compressed sensing to obtain high-quality target 2D images. Simulation and actual measurement results show that FDISAR can achieve two-dimensional imaging of moving multi-scattering point targets. The application of this method is of great significance for reducing the complexity of the ISAR imaging system and improving the flexibility of the system's control bandwidth resources.
2. Kang, B. S., K. Lee, and K. T. Kim, "Image registration for 3-D interferometric-ISAR imaging through joint-channel phase difference functions," IEEE Transactions on Aerospace and Electronic Systems, Vol. 57, No. 1, 22-38, 2021.
3. Hu, C., L. Wang, Z. Li, and D. Zhu, "Inverse synthetic aperture radar imaging using a fully convolutional neural network," IEEE Geoscience and Remote Sensing Letters, Vol. 17, No. 7, 1203-1207, 2020.
4. Cheng, P., J. Cheng, X. Wang, and J. Zhao, "An ISAR imaging method based on improved CAMP algorithm," IEEE Sensors Journal, Vol. 21, No. 12, 13514-13521, 2021.
5. Stankovic, L., "ISAR image analysis and recovery with unavailable or heavily corrupted data," IEEE Transactions on Aerospace and Electronic Systems, Vol. 51, No. 3, 2093-2106, 2015.
6. Ji, B., Y. Wang, B. Zhao, X. Lu, and R. Xu, "Novel super-resolution ISAR imaging method via two-dimensional unitary matrix pencil algorithm," 2020 15th IEEE International Conference on Signal Processing (ICSP), Vol. 1, 600-604, 2020.
7. Zhang, S., Y. Liu, and X. Li, "Bayesian bistatic ISAR imaging for targets with complex motion under low SNR condition," IEEE Transactions on Image Processing, Vol. 27, No. 5, 2447-2460, 2018.
8. Zhang, S., Y. Liu, X. Li, and G. Bi, "Fast ISAR cross-range scaling using modified newton method," IEEE Transactions on Aerospace and Electronic Systems, Vol. 54, No. 3, 1355-1367, 2018.
9. Hu, J., J. Zhang, Q. Zhai, R. Zhan, and D. Lu, "ISAR imaging using a new stepped-frequency signal format," IEEE Transactions on Geoscience and Remote Sensing, Vol. 52, No. 7, 4291-4305, 2014.
10. Zhang, L., Z. Qiao, M. Xing, Y. Li, and Z. Bao, "High-resolution ISAR imaging with sparse stepped-frequency waveforms," IEEE Transactions on Geoscience and Remote Sensing, Vol. 49, No. 11, 4630-4651, 2011.
11. Yeh, C. M., et al., "Rotational motion estimation for ISAR via triangle pose difference on two range-Doppler images," IET Radar Sonar & Navigation, Vol. 4, No. 4, 528-536, 2010.
12. Berizzi, F., E. D. Mese, M. Diani, and M. Martorella, "High-resolution ISAR imaging of maneuvering targets by means of the range instantaneous Doppler technique: Modeling and performance analysis," IEEE Transactions on Image Processing, Vol. 10, No. 12, 1880-1890, 2001.
13. Munoz-Ferreras, J. M. and F. Perez-Martinez, "On the Doppler spreading effect for the range-instantaneous-doppler technique in inverse synthetic aperture radar imagery," IEEE Geoscience and Remote Sensing Letters, Vol. 7, No. 1, 180-184, 2010.
14. Wang, Y. and Y. Lin, "ISAR imaging of non-uniformly rotating target via range-instantaneous-Doppler-derivatives algorithm," IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol. 7, No. 1, 167-176, 2014.
15. Liu, Q., A. Liu, Y. Wang, and H. Li, "A super-resolution sparse aperture ISAR sensors imaging algorithm via the MUSIC technique," IEEE Transactions on Geoscience and Remote Sensing, Vol. 57, No. 9, 7119-7134, 2019.
16. Zhang, S., et al., "High-resolution bistatic ISAR imaging based on two-dimensional compressed sensing," IEEE Transactions on Antennas and Propagation, Vol. 63, No. 5, 2098-2111, 2015.
17. Jiu, B., H. Liu, H. Liu, L. Zhang, Y. Cong, and Z. Bao, "Joint ISAR imaging and cross-range scaling method based on compressive sensing with adaptive dictionary," IEEE Transactions on Antennas and Propagation, Vol. 63, No. 5, 2112-2121, 2015.
18. Rodenbeck, C. T., et al., "Ultra-wideband low-cost phased-array radars," IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 12, 3697-3703, 2005.
19. Zhang, L., Z. Qiao, M. Xing, J. Sheng, R. Guo, and Z. Bao, "High-resolution ISAR imaging by exploiting sparse apertures," IEEE Transactions on Antennas and Propagation, Vol. 60, No. 2, 997-1008, 2012.
20. Zheng, J., T. Su, W. Zhu, L. Zhang, Z. Liu, and Q. H. Liu, "ISAR imaging of nonuniformly rotating target based on a fast parameter estimation algorithm of cubic phase signal," IEEE Transactions on Geoscience and Remote Sensing, Vol. 53, No. 9, 4727-4740, 2015.
21. Kang, M., S. Lee, S. Lee, and K. Kim, "ISAR imaging of high-speed maneuvering target using gapped stepped-frequency waveform and compressive sensing," IEEE Transactions on Image Processing, Vol. 26, No. 10, 5043-5056, 2017.
22. Fan, H., L. Ren, E. Mao, and Q. Liu, "A high-precision method of phase-derived velocity measurement and its application in motion compensation of ISAR imaging," IEEE Transactions on Geoscience and Remote Sensing, Vol. 56, No. 1, 60-77, 2018.
23. Chen, Y., et al., "An adaptive ISAR-imaging-considered task scheduling algorithm for multi-function phased array radars," IEEE Transactions on Signal Processing, Vol. 63, No. 19, 5096-5110, 2015.
24. Xiong, J., W. Wang, and K. Gao, "FDA-MIMO radar range-angle estimation: CRLB, MSE, and resolution analysis," IEEE Transactions on Aerospace and Electronic Systems, Vol. 54, No. 1, 284-294, 2018.
25. Xu, J., G. Liao, S. Zhu, L. Huang, and H. C. So, "Joint range and angle estimation using MIMO radar with frequency diverse array," IEEE Transactions on Signal Processing, Vol. 63, No. 13, 3396-3410, 2015.
26. Ma, Y., P. Wei, and H. Zhang, "General focusing beamformer for FDA: Mathematical model and resolution analysis," IEEE Transactions on Antennas and Propagation, Vol. 67, No. 5, 089-3100, 2019.
27. Donoho, D. L., "Compressed sensing," IEEE Transactions on Information Theory, Vol. 52, No. 4, 1289-1306, 2006.
28. Herman, M. A. and T. Strohmer, "High-resolution radar via compressed sensing," IEEE Transactions on Signal Processing, Vol. 57, No. 6, 2275-2284, 2009.
29. Potter, L. C., et al., "Sparsity and compressed sensing in radar imaging," Proceedings of the IEEE, Vol. 98, No. 6, 1006-1020, 2010.
30. Rong, J., Y. Wang, and T. Han, "Iterative optimization-based ISAR imaging with sparse aperture and its application in interferometric ISAR imaging," IEEE Sensors Journal, Vol. 19, No. 19, 8681-8693, 2019.
31. Elad, M., "Optimized projections for compressed sensing," IEEE Transactions on Signal Processing, Vol. 55, No. 12, 5695-5702, 2007.