In this paper, a multi-carrier nonlinear frequency modulation system based on pseudo-random frequency offset is designed. The reduction of the main lobe 3\,dB width and the side-lobe peaks cannot be realized simultaneously in conventional beamforming schemes, especially when the number of array elements remains unchanged. The proposed system can reduce the main-lobe 3 dB width and suppressing the side-lobe peaks simultaneously. This is done by adjusting the number of sub-signals, frequency offset coefficient and the inter-element spacing. Then, through time slot processing, signal power is focused on different targets. Numerical simulation experiments are implemented to validate the theoretical analysis of the proposed methodology, and comparisons with other techniques are made.
2. Ren, W., H. Chen, and W. Gao, "On the design of time-domain implementation structure for steerable spherical modal beamformers with arbitrary beampatterns," Applied Acoustics, Vol. 122, 146-151, 2017.
3. Antonik, P., M. C. Wicks, H. D. Griffiths, and C. J. Baker, "Frequency diverse array radars," Proc. IEEE Radar Conf., 215-217, Verona, Italy, Apr. 2006.
4. Antonik, P., M. C. Wicks, H. D. Griffiths, and C. J. Baker, "Range dependent beamforming using element level waveform diversity," Proc. Int. Waveform Diversity Des. Conf., 1-4, Las Vegas, NV, USA, Jan. 2006.
5. Khan, W., I. M. Qureshi, and S. Saeed, "Frequency diverse array radar with logarithmically increasing frequency offset," IEEE Antennas Wireless Propag. Lett., Vol. 14, 499-502, 2015.
6. Khan, W., I. M. Qureshi, A. Basit, and W. Khan, "Range bins based MIMO Frequency diverse array radar with logarithmic frequency offset," IEEE Antennas Wireless Propag. Lett., Vol. 15, 885-888, 2016.
7. Basit, A., et al., "Beam pattern synthesis for an FDA radar with hamming window based non-uniform frequency offset," IEEE Antennas & Wireless Propagation Letters, 2017.
8. Fang, D.-G., A.-M. Yao, and W. Wu, "Synthesis of 4-D beampatterns using 4-D arrays," Proc. IEEE APS/URSI, Fajardo, Puerto Rico, 703-704, Jun. 26–Jul. 1, 2016 (Special session invited paper).
9. Yao, A.-M., W. Wu, and D.-G. Fang, "Frequency diverse array antenna using time-modulated optimized frequency offset to obtain time-invariant spatial fine focusing beampattern," IEEE Trans. Antennas Propag., Vol. 64, No. 10, 4434-4446, Oct. 2016.
10. Rocca, P., L. Manica, L. Poli, and A. Massa, "Synthesis of compromise sum-difference arrays through time-modulation," IET Radar Sonar Navig., Vol. 3, No. 6, 630-637, 2009.
11. Poli, L., Poli, P. Rocca, L. Manica, and A. Massa, "Handling sideband radiations in time-modulated arrays through particle swarm optimization," IEEE Trans. Antennas Propag., Vol. 58, No. 4, 1408-1411, Apr. 2010.
12. Poli, L., P. Rocca, and A. Massa, "Sideband radiation reduction exploiting pattern multiplication in directive time-modulated linear arrays," IET Microw. Antennas Propag., Vol. 6, No. 2, 214-222, 2012.
13. Rocca, P., Q. Zhu, E. T. Bekele, S. Yang, and A. Massa, "4D arrays as enabling technology for cognitive radio systems," IEEE Trans. Antennas Propag., Vol. 62, No. 3, 1102-1106, Mar. 2014.
14. Maneiro-Catoira, R., et al., "Enhanced time-modulated arrays for harmonic beamforming," IEEE Journal of Selected Topics in Signal Processing, Vol. 11, No. 2, 259-270, 2017.
15. Wang, Y., et al., "Time-invariant range-angle dependent beampattern synthesis for FDA radar targets tracking," IEEE Antennas & Wireless Propagation Letters, 2017.
16. Shao, H., J. Dai, J. Xiong, H. Chen, and W.-Q. Wang, "Dot-shaped rangeangle beampattern synthesis for frequency diverse array," IEEE Antennas Wireless Propag. Lett., Vol. 15, 1703-1706, 2016.