To achieve long distance coverage and better resolution, high gain antennas is convenient for airborne radars. So a great deal of attention has been devoted to exploiting new approaches towards the problem. Radar application demands a low profile, minimal weight and high gain antennas. Over the last decade microstrip antennas are used as an alternative element for the bulky and heavy weight reflector antennas. Presently researchers are implementing metasurface antennas and their imitative for the radar applications. A high gain transmitting microstrip lens antenna is presented by putting a layered phase gradient coded metasurface with 0 & 1 elements for 0 and π phase responses. Four types of unit cell with two bits coding elements 00,01,10,11 is implemented for four phase differences. The lens antenna results a gain enhancement of 11.7 dbi and return loss of -34 dB, which is approximately 7 dbi and -17dB in case of a normal microstrip antenna, so the gain is enhanced by 4.7dB and a return loss is reduced by 17 dB at 10.3 MHz frequency.

Codded phase gradient, Lens, Metasurface, Microstrip, X-Band Radar

[1] H. Li, G. Wang, X. He-Xiu, T. Cai, “X-band phase-gradient metasurface for high-gain lens antenna application”, IEEE Transactions on Antennas and Propagation, Vol. 63, Issue.11, pp. 5144-5149,2015.
[2] Y. Zhou, C. Xiang-yu, G. Jun G, "RCS reduction for grazing incidence based on coding metasurface", Electronics Letters, Vol. 53, Issue. 20, pp. 1381-1383, 2017.
[3] X. Li, S. Xiao, B. Cai, H. Qiong, “Flat metasurfaces to focus electromagnetic waves in reflection geometry”, Optics letters, Vol. 37, Issue. 23, pp. 4940-4942, 2012.
[4] B. Rahmati, H. R. Hassani, “Low-profile slot transmit array antenna”, IEEE Transactions on Antennas and Propagation, Vol. 63, Issue.1, pp.174-181, 2015.
[5] Z. Yue-Jun, G. Jun, Z. Yu-Long, "Metamaterial-based patch antenna with wideband RCS reduction and gain enhancement using improved loading method", IET Microwaves, Antennas & Propagation, Vol. 11, Issue. 9, pp. 1183-1189, 2017.
[6] S. Liu, C. Tie, X. Quan, “Anisotropic coding metamaterials and their powerful manipulation of differently polarized terahertz waves”, Light: Science & Applications, Vol. 5, pp. 16076, 2016.
[7] N. Yu, G. Patrice, A. Kats, “Light propagation with phase discontinuities: generalized laws of reflection and refraction”, Science, 6054, pp. 333-337, 2011.
[8] K. S. Beenamole, “Microstrip Antenna Designs for Radar Applications”, DRDO Science Spectrum, pp. 84-86, 2009.
[9] J. Shi, F. Xu, P. Eric, “Coherent control of Snell’s law at metasurfaces”, Optics express, Vol. 22, Issue. 17, pp. 21051-21060, 2014.
[10] W. E. Liu, Z. N. Chen, X. Qing, J. Shi, F.H. Lin, “Miniaturized Wideband Metasurface Antennas,” IEEE Transactions on Antennas and Propagation, Vol. 65, Issue .12, pp.7345-7349, 2017.
[11] X. Liu, J. Gao, L. Xu, X. Cao, Y. Zhao, S. Li, S., “A coding diffuse metasurface for RCS reduction,” IEEE Antennas and Wireless Propagation Letters, Vol.16, pp. 724-727, 2017.
[12] C. L. Holloway, E. F. Kuester, J. A. Gordon, J. O` Hara, J. Booth, D. R. Smith, “An overview of the theory and applications of metasurfaces: The two- dimensional equivalents of metamaterials,” IEEE Antennas and Propagation Magazine, Vol. 54, Issue. 2, pp. 10-35, 2012.
[13] F. Y. Kuo, R. B. Hwang, “High-isolation X-band marine radar antenna design,” IEEE Transactions on Antennas and Propagation, Vol. 62, Issue. 5, pp. 2331-2337, 2014.
[14] J. Li, D. Jiang, “Low-complexity propagator based two dimensional angle estimation for coprime MIMO radar,” IEEE Access, Vol. 4, Issue. 2,2018.