Frequency diverse array (FDA) uses a small frequency increment at each antenna element to get a range, angle and time dependent beam pattern. Although linear frequency offset is used in most radar systems, nonlinear frequency offset is also very useful for analyzing FDA radar. A logarithmic frequency offsets based FDA (log-FDA) removes the inherent periodicity of FDA beam pattern to get a single maxima in area of interest. Multiple input multiple output frequency diverse array (MIMO-FDA) radar is also presented recently to provide some improvements compared to FDA radar. In this paper, a new hybrid scheme is proposed in which each subarray of MIMO-FDA uses a variable logarithmic offset. The resultant system, called MIMO-log-FDA, uses not only a different logarithmic offset, but also unique waveform in each subarray. Different logarithmic offsets contributed in terms of getting more control on width of beampattern, while the different waveforms provide diversity, which can be exploited at the receiver of the proposed system. Some improvements in transmit beam patterns have been shown for MIMO-log-FDA, followed by detailed signal model for better estimation of target at the receiving side. Performance analysis is also done in terms of signal to interference plus noise ratio (SINR) and Cramer-Rao lower bound (CRLB). Simulation and results verify the effectiveness of proposed scheme by comparing it with Log-FDA and MIMO-FDA radar.
2. Antonik, P., M. C. Wicks, H. D. Griffiths, and C. J. Baker, "Multimission multi-mode waveform diversity," Proc. IEEE Radar Conf. Dig., 580-582, Verona, NY, USA, Apr. 24-27, 2006.
3. Secmen, M., S. Demir, A. Hizal, and T. Eker, "Frequency diverse array antenna with periodic time modulated pattern in range and angle," IEEE Conference on Radar, 427-430, 2007.
4. Antonik, P. and M. C. Wicks, "Method and apparatus for simultaneous synthetic aperture and moving target indication,", U.S. Patent 20 080 129 584, Jun. 5, 2008.
5. Wicks, M. C. and P. Antonik, "Frequency diverse array with independent modulation of frequency, amplitude, and phase,", U.S. patent 7,319,427, Jan. 15, 2008.
6. Baizert, P., T. B. Hale, M. A. Temple, and M. C. Wicks, "Forwardlooking radar GMTI benefits using a linear frequency diverse array," Electronics Letters, Vol. 42, No. 22, 1311-1312, Oct. 2006.
7. Huang, J., K. F. Tong, and C. J. Baker, "Frequency diverse array with beam scanning feature," Proc. IEEE 2008 Ant. and Prop. Soc. Intl. Symp., 1-4, Jul. 5-11, 2008.
8. Higgins, T. and S. Blunt, "Analysis of range-angle coupled beamforming with frequency diverse chirps," Proceedings of the 4th International Waveform Diversity & Design Conference, 140-144, Orlando, FL, Feb. 2009.
9. Wang, W. Q., H. Shao, and J. Cai, "Range-angle-dependent beamforming by frequency diverse array antenna," International Journal of Antennas and Propagation, 2012.
10. Zhuang, L. and X. Z. Liu, "Precisely beam steering for frequency diverse arrays based on frequency offset selection," Proc. Int. Radar Conf., 1-4, 2009.
11. Chen, Y.-G., Y.-T. Li, Y.-H. Wu, and H. Chen, "Research on the linear frequency diverse array performance," Proc. IEEE 10th Int. Conf. on Signal Processing, 2324-2327, Beijing, Oct. 24-28, 2010.
12. Shao, H., J. Li, H. Chen, and W. Q.Wang, "Adaptive frequency offset selection in frequency diverse array radar," IEEE Antennas and Wireless Propagation Letters, Vol. 13, 1405-1408, 2014.
13. Khan, W. and I. M. Qureshi, "Frequency diverse array radar with time-dependent frequency offset," IEEE Antennas and Wireless Propagation Letters, Vol. 13, 758-761, 2014.
14. Wang, W.-Q., H. C. So, and H. Shao, "Nonuniform frequency diverse array for range-angle imaging of targets," IEEE Sensors Journal, Mar. 2014.
15. Khan, W., I. M. Qureshi, and S. Saeed, "Frequency diverse array radar with logarithmically increasing frequency offset," IEEE Antennas and Wireless Propagation Letters, Vol. 99, 1-5, 2015.
16. Sammartino, P. F., H. D. Griffiths, and C. J. Baker, "Frequency diverse MIMO techniques for radar," IEEE Trans. on Aerospace and Electronic Systems, Vol. 49, No. 1, 201-222, 2013.
17. Wang, W.-Q. and H. C. So, "Transmit subaperturing for range and angle estimation in frequency diverse array radar," IEEE Trans. Signal Process., Vol. 62, No. 8, 2000-2011, 2014.
18. Xu, J., G. Liao, S. Zhu, and H. C. So, "Deceptive jamming suppression with frequency diverse MIMO radar," Signal Processing, Vol. 113, 9-17, 2015.
19. 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 Trans. Signal Process., Vol. 63, No. 13, 3396-3410, 2015.
20. Khan, W., I. Qureshi, A. Basit, and W. Khan, "Range bins based MIMO frequency diverse array radar with logarithmic frequency offset," IEEE Antennas and Wireless Propagation Letters, DOI 10.1109/LAWP.2015.2478964, 2015.
21. Van Trees, H. L., Optimum Array Processing, Wiley, New York, 2002.
22. Renaux, A., P. Forster, E. Chaumette, and P. Larzabal, "On the high SNR conditional maximum-likelihood estimator full statistical characterization," IEEE Trans. Signal Process., Vol. 54, No. 12, 4840-4843, Dec. 2006.
23. Li, J., L. Xu, P. Stoica, K. W. Forsythe, and D. W. Bliss, "Range compression and waveform optimization for MIMO radar: A Cram´er-Rao bound based study," IEEE Trans. Signal Process., Vol. 56, No. 1, 218-232, Jan. 2008.
24. Xu, L., J. Li, and P. Stoica, "Target detection and parameter estimation for MIMO radar systems," IEEE Trans. Aerosp. Electron. Syst., Vol. 44, No. 3, 927-939, Jul. 2008.